For Men Daily Multi Vitamin Ingredients & Drug Interactions

Although Panax ginseng has shown antiplatelet effects in the laboratory, it is unlikely to increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
In vitro evidence suggests that ginsenoside constituents in Panax ginseng might decrease platelet aggregation. However, research in humans suggests that ginseng does not affect platelet aggregation. Animal research indicates low oral bioavailability of Rb1 and rapid elimination of Rg1, which might explain the discrepancy between in vitro and human research. Until more is known, use with caution in patients concurrently taking anticoagulant or antiplatelet drugs.

Theoretically, taking Panax ginseng with antidiabetes drugs might increase the risk of hypoglycemia.
Clinical research suggests that Panax ginseng might decrease blood glucose levels. Monitor blood glucose levels closely.

Theoretically, taking Panax ginseng with caffeine might increase the risk of adverse stimulant effects.
Panax ginseng has been shown to have stimulant effects. Theoretically, caffeine might have an additive effect on the stimulant effects of Panax ginseng.

Theoretically, Panax ginseng might increase levels of drugs metabolized by CYP2D6. However, research is conflicting.
There is some evidence that Panax ginseng can inhibit the CYP2D6 enzyme by approximately 6%. In addition, in animal research, Panax ginseng inhibits the metabolism of dextromethorphan, a drug metabolized by CYP2D6, by a small amount. However, contradictory research suggests Panax ginseng might not inhibit CYP2D6. Until more is known, use Panax ginseng cautiously in patients taking drugs metabolized by these enzymes.

Theoretically, Panax ginseng might increase or decrease levels of drugs metabolized by CYP3A4.
Panax ginseng may affect the clearance of drugs metabolized by CYP3A4. One such drug is imatinib. Inhibition of CYP3A4 was believed to be responsible for a case of imatinib-induced hepatotoxicity. In contrast, Panax ginseng has been shown to increase the clearance of midazolam, another drug metabolized by CYP3A4. Clinical research shows that Panax ginseng can reduce midazolam area under the curve by 44%, maximum plasma concentration by 26%, and time to reach maximum plasma concentration by 29%. Midazolam metabolism was also increased in animals given Panax ginseng. Until more is known, use Panax ginseng cautiously in combination with CYP3A4 substrates.

Theoretically, concomitant use of large amounts of Panax ginseng might interfere with hormone replacement therapy.
Laboratory research and some case reports suggest that Panax ginseng can have estrogenic effects due to competition for estrogen receptors. The estrogenic activity is attributed to the ginsenoside constituents of Panax ginseng.

Theoretically, Panax ginseng might reduce the effects of furosemide.
There is some concern that Panax ginseng might contribute to furosemide resistance. There is one case of resistance to furosemide diuresis in a patient taking a germanium-containing ginseng product.

Theoretically, Panax ginseng might increase the effects and adverse effects of imatinib.
A case of imatinib-induced hepatotoxicity has been reported for a 26-year-old male with chronic myelogenous leukemia stabilized on imatinib for 7 years. The patient took imatinib 400 mg along with a Panax ginseng-containing energy drink daily for 3 months. Since imatinib-associated hepatotoxicity typically occurs within 2 years of initiating therapy, it is believed that Panax ginseng affected imatinib toxicity though inhibition of cytochrome P450 3A4. CYP3A4 is the primary enzyme involved in imatinib metabolism.

Theoretically, Panax ginseng use might interfere with immunosuppressive therapy.
Panax ginseng might have immune system stimulating properties.

Theoretically, taking Panax ginseng with insulin might increase the risk of hypoglycemia.
Clinical research suggests that Panax ginseng might decrease blood glucose levels. Insulin dose adjustments might be necessary in patients taking Panax ginseng; use with caution.

Theoretically, Panax ginseng may increase the clearance of midazolam.
Midazolam is metabolized by cytochrome P450 3A4 (CYP3A4). Clinical research suggests that Panax ginseng can reduce midazolam area under the curve by 44%, maximum plasma concentration by 26%, and time to reach maximum plasma concentration by 29%. Midazolam metabolism was also increased in animals given Panax ginseng.

Theoretically, Panax ginseng can interfere with MAOI therapy.
Concomitant use of Panax ginseng with phenelzine (Nardil) is associated with insomnia, headache, tremors, and hypomania.

Theoretically, taking Panax ginseng with nifedipine might increase serum levels of nifedipine and the risk of hypotension.
Preliminary clinical research shows that concomitant use can increase serum levels of nifedipine in healthy volunteers. This might cause the blood pressure lowering effects of nifedipine to be increased when taken concomitantly with Panax ginseng.

Theoretically, Panax ginseng has an additive effect with drugs that prolong the QT interval and potentially increase the risk of ventricular arrhythmias. However, research is conflicting.
Clinical research shows that short-term use of Panax ginseng can increase the QT interval. However, no changes in QT interval have been identified with prolonged use.

Theoretically, taking Panax ginseng with raltegravir might increase the risk of liver toxicity.
A case report suggests that concomitant use of Panax ginseng with raltegravir can increase serum levels of raltegravir, resulting in elevated liver enzymes levels.

Theoretically, Panax ginseng might increase or decrease levels of selegiline, possibly altering the effects and side effects of selegiline.
Animal research shows that taking selegiline with a low dose of Panax ginseng extract (1 gram/kg) reduces selegiline bioavailability, while taking a high dose of Panax ginseng extract (3 grams/kg) increases selegiline bioavailability. More research is needed to confirm these effects.

Theoretically, taking Panax ginseng with stimulant drugs might increase the risk of adverse stimulant effects.
Panax ginseng has been shown to have stimulant effects.

Panax ginseng might affect the clearance of warfarin. However, this interaction appears to be unlikely.
There has been a single case report of decreased effectiveness of warfarin in a patient who also took Panax ginseng. However, it is questionable whether Panax ginseng was the cause of this decrease in warfarin effectiveness. Some research in humans and animals suggests that Panax ginseng does not affect the pharmacokinetics of warfarin. However, other research in humans suggests that Panax ginseng might modestly increase the clearance of the S-warfarin isomer. More evidence is needed to determine whether Panax ginseng causes a significant interaction with warfarin.

Theoretically, Panax ginseng might decrease blood levels of oral or intravenous fexofenadine.
Animal research suggests that taking Panax ginseng in combination with oral or intravenous fexofenadine may reduce the bioavailability of fexofenadine. Some scientists have attributed this effect to the ability of Panax ginseng to increase the expression of P-glycoprotein.

Although Panax ginseng has demonstrated variable effects on cytochrome P450 3A4 (CYP3A4), which metabolizes lopinavir, Panax ginseng is unlikely to alter levels of lopinavir/ritonavir.
Lopinavir is metabolized by CYP3A4 and is administered with the CYP3A4 inhibitor ritonavir to increase its plasma concentrations. Panax ginseng has shown variable effects on CYP3A4 activity in humans. However, taking Panax ginseng (Vitamer Laboratories) 500 mg twice daily for 14 days did not alter the pharmacokinetics of lopinavir/ritonavir in 12 healthy volunteers.

Theoretically, licorice might reduce the effects of antihypertensive drugs.
In human research, licorice increases blood pressure in a dose-dependent manner.

Theoretically, licorice might reduce the effects of cisplatin.
In animal research, licorice diminished the therapeutic efficacy of cisplatin.

Theoretically, concomitant use of licorice and corticosteroids might increase the side effects of corticosteroids.
Case reports suggest that concomitant use of licorice and oral corticosteroids, such as hydrocortisone, can potentiate the duration of activity and increase blood levels of corticosteroids. Additionally, in one case report, a patient with neurogenic orthostatic hypertension stabilized on fludrocortisone 0.1 mg twice daily developed pseudohyperaldosteronism after recent consumption of large amounts of black licorice.

Theoretically, licorice might increase levels of drugs metabolized by CYP2B6.
In vitro research shows that licorice extract and glabridin, a licorice constituent, inhibit CYP2B6 isoenzymes. Licorice extract from the species G. uralensis seems to inhibit CYP2B6 isoenzymes to a greater degree than G. glabra extract in vitro. Theoretically, these species of licorice might increase levels of drugs metabolized by CYP2B6; however, these interactions have not yet been reported in humans.

Theoretically, licorice might increase levels of drugs metabolized by CYP2C19.
In vitro, licorice extracts from the species G. glabra and G. uralensis inhibit CYP2C19 isoenzymes in vitro. Theoretically, these species of licorice might increase levels of drugs metabolized by CYP2C19; however, this interaction has not yet been reported in humans.

Theoretically, licorice might increase levels of drugs metabolized by CYP2C8.
In vitro, licorice extract from the species G. glabra and G. uralensis inhibits CYP2C8 isoenzymes. Theoretically, these species of licorice might increase levels of drugs metabolized by CYP2C8; however, this interaction has not yet been reported in humans.

Theoretically, licorice might increase or decrease levels of drugs metabolized by CYP2C9.
There is conflicting evidence about the effect of licorice on CYP2C9 enzyme activity. In vitro research shows that extracts from the licorice species G. glabra and G. uralensis moderately inhibit CYP2C9 isoenzymes. However, evidence from an animal model shows that licorice extract from the species G. uralensis can induce hepatic CYP2C9 activity. Until more is known, licorice should be used cautiously in people taking CYP2C9 substrates.

Theoretically, licorice might increase or decrease levels of drugs metabolized by CYP3A4.
Pharmacokinetic research shows that the licorice constituent glycyrrhizin, taken in a dosage of 150 mg orally twice daily for 14 days, modestly decreases the area under the concentration-time curve of midazolam by about 20%. Midazolam is a substrate of CYP3A4, suggesting that glycyrrhizin modestly induces CYP3A4 activity. Animal research also shows that licorice extract from the species G. uralensis induces CYP3A4 activity. However, licorice extract from G. glabra species appear to inhibit CYP3A4-induced metabolism of testosterone in vitro. It is thought that the G. glabra inhibits CYP3A4 due to its constituent glabridin, which is a moderate CYP3A4 inhibitor in vitro and not present in other licorice species. Until more is known, licorice should be used cautiously in people taking CYP3A4 substrates.

Theoretically, concomitant use of licorice with digoxin might increase the risk of cardiac toxicity.
Overuse or misuse of licorice with cardiac glycoside therapy might increase the risk of cardiac toxicity due to potassium loss.

Theoretically, concomitant use of licorice with diuretic drugs might increase the risk of hypokalemia.
Overuse of licorice might compound diuretic-induced potassium loss. In one case report, a 72-year-old male with a past medical history of hypertension, type 2 diabetes, hyperlipidemia, arrhythmia, stroke, and hepatic dysfunction was hospitalized with severe hypokalemia and uncontrolled hypertension due to pseudohyperaldosteronism. This was thought to be provoked by concomitant daily consumption of a product containing 225 mg of glycyrrhizin, a constituent of licorice, and hydrochlorothiazide 12.5 mg for 1 month.

Theoretically, licorice might increase or decrease the effects of estrogen therapy.
Theoretically, licorice might interfere with estrogen therapy due to estrogenic and anti-estrogenic effects.

Theoretically, loop diuretics might increase the mineralocorticoid effects of licorice.
Theoretically, loop diuretics might enhance the mineralocorticoid effects of licorice by inhibiting the enzyme that converts cortisol to cortisone; however, bumetanide (Bumex) does not appear to have this effect.

Theoretically, licorice might decrease levels of midazolam.
In humans, the licorice constituent glycyrrhizin appears to moderately induce the metabolism of midazolam. This is likely due to induction of cytochrome P450 3A4 by licorice. Until more is known, licorice should be used cautiously in people taking midazolam.

Theoretically, licorice might decrease the absorption of P-glycoprotein substrates.
In vitro research shows that licorice can increase P-glycoprotein activity.

Theoretically, licorice might decrease plasma levels and clinical effects of paclitaxel.
Multiple doses of licorice taken concomitantly with paclitaxel might reduce the effectiveness of paclitaxel. Animal research shows that licorice 3 grams/kg given orally for 14 days before intravenous administration of paclitaxel decreases the exposure to paclitaxel and increases its clearance. Theoretically, this occurs because licorice induces cytochrome P450 3A4 enzymes, which metabolize paclitaxel. Notably, a single dose of licorice did not affect exposure or clearance of paclitaxel.

Theoretically, licorice might decrease plasma levels and clinical effects of warfarin.
Licorice seems to increase metabolism and decrease levels of warfarin in animal models. This is likely due to induction of cytochrome P450 2C9 (CYP2C9) metabolism by licorice. Advise patients taking warfarin to avoid taking licorice.

Theoretically, licorice might decrease the levels and clinical effects of CYP1A2 substrates.
In vitro research shows that licorice induces CYP1A2 enzymes.

Theoretically, licorice might increase levels of methotrexate.
Animal research suggests that intravenous administration of glycyrrhizin, a licorice constituent, and high-dose methotrexate may delay methotrexate excretion and increase systemic exposure, leading to transient elevations in liver enzymes and total bilirubin. This interaction has not yet been reported in humans.

Theoretically, antioxidant effects of vitamin E might reduce the effectiveness of alkylating agents.
There's concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa. However, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that might interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effect, if any, antioxidants such as vitamin E have on chemotherapy. Advise patients to consult their oncologist before using vitamin E supplements, especially in high doses.

Concomitant use of vitamin E and anticoagulant or antiplatelet agents might increase the risk of bleeding.
Vitamin E seems to inhibit of platelet aggregation and antagonize the effects of vitamin K-dependent clotting factors. These effects appear to be dose-dependent, and are probably only likely to be clinically significant with doses of at least 800 units daily. Mixed tocopherols, such as those found in food, might have a greater antiplatelet effect than alpha-tocopherol. RRR alpha-tocopherol (natural vitamin E) 1000 IU daily antagonizes vitamin K-dependent clotting factors. Advise patients to avoid high doses of vitamin E, especially in people with low vitamin K intake or other risk factors for bleeding.

Theoretically, antioxidant effects of vitamin E might reduce the effectiveness of antitumor antibiotics.
There's concern that antioxidants could reduce the activity of antitumor antibiotic drugs such as doxorubicin, which generate free radicals. However, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that might interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effect, if any, antioxidants such as vitamin E have on chemotherapy involving antitumor antibiotics. Advise patients to consult their oncologist before using vitamin E supplements, especially in high doses.

A specific form of vitamin E might increase absorption and levels of cyclosporine.
There is some evidence that one specific formulation of vitamin E (D-alpha-tocopheryl-polyethylene glycol-1000 succinate, TPGS, tocophersolan, Liqui-E) might increase absorption of cyclosporine. This vitamin E formulation forms micelles which seems to increase absorption of cyclosporine by 40% to 72% in some patients. However, this interaction is unlikely to occur with the usual forms of vitamin E.

Theoretically, vitamin E might induce metabolism of CYP3A4, possibly reducing the levels CYP3A4 substrates.
Vitamin E appears to bind with the nuclear receptor, pregnane X receptor (PXR), which results in increased expression of CYP3A4. Although the clinical significance of this is not known, use caution when considering concomitant use of vitamin E and other drugs affected by these enzymes.

Taking selumetinib with vitamin E can result in a total daily dose of vitamin E that exceeds safe limits and therefore might increase the risk of bleeding.
Selumetinib contains 48-54 IU vitamin E per capsule. The increased risk of bleeding with vitamin E appears to be dose-dependent. Be cautious when using selumetinib in combination with supplemental vitamin E, especially in patients at higher risk of bleed, such as those with chronic conditions and those taking antiplatelet drugs.

Using vitamin E with warfarin might increase the risk of bleeding.
Due to interference with production of vitamin K-dependent clotting factors, use of more than 400 IU of vitamin E daily with warfarin might increase prothrombin time (PT), INR, and the risk of bleeding,. At a dose of 1000 IU per day, vitamin E can antagonize vitamin K-dependent clotting factors even in people not taking warfarin. Limited clinical evidence suggests that doses up to 1200 IU daily may be used safely by patients taking warfarin, but this may not be applicable in all patient populations.

Vitamin E might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.
A combination of niacin and simvastatin (Zocor) effectively raises high-density lipoprotein (HDL) cholesterol levels in people with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50%. Vitamin E alone combined with a statin does not seem to decrease HDL levels. It is not known whether the adverse effect on HDL is due to one of the other antioxidants or to the combination. It also is not known whether it will occur in other patient populations.

Concomitant use of alcohol and niacin might increase the risk of flushing and hepatotoxicity.
Alcohol can exacerbate the flushing and pruritus associated with niacin. Large doses of niacin might also exacerbate liver dysfunction associated with chronic alcohol use. A case report describes delirium and lactic acidosis in a patient taking niacin 3 grams daily who ingested 1 liter of wine. Advise patients to avoid large amounts of alcohol while taking niacin.

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as allopurinol.
Large doses of niacin can reduce urinary excretion of uric acid, potentially resulting in hyperuricemia. Doses of uricosurics such as allopurinol might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Theoretically, niacin may have additive effects when used with anticoagulant or antiplatelet drugs.
Several cases of clotting factor synthesis deficiency and coagulopathy have been reported in patients taking sustained-release niacin. Also, thrombocytopenia has been reported in patients treated with niacin or niacin plus lovastatin.

Niacin can increase blood glucose levels and may diminish the effects of antidiabetes drugs.
Niacin impairs glucose tolerance in a dose-dependent manner, probably by causing or aggravating insulin resistance and increasing hepatic production of glucose. In diabetes patients, niacin 4.5 grams daily for 5 weeks can increase plasma glucose by an average of 16% and glycated hemoglobin (HbA1c) by 21%. However, lower doses of 1.5 grams daily or less appear to have minimal effects on blood glucose. In some patients, glucose levels increase when niacin is started, but then return to baseline when a stable dose is reached. Up to 35% of patients with diabetes may need adjustments in hypoglycemic therapy when niacin is added.

Theoretically, niacin may increase the risk of hypotension when used with antihypertensive drugs.
The vasodilating effects of niacin can cause hypotension. Furthermore, some clinical evidence suggests that a one-hour infusion of niacin can reduce systolic, diastolic, and mean blood pressure in hypertensive patients. This effect is not observed in normotensive patients.

Bile acid sequestrants can bind niacin and decrease absorption. Separate administration by 4-6 hours to avoid an interaction.
In vitro studies show that colestipol (Colestid) binds about 98% of available niacin and cholestyramine (Questran) binds 10% to 30%.

Theoretically, concomitant use of niacin and gemfibrozil might increase the risk of myopathy in some patients.
A case of myopathy from concomitant use of niacin and gemfibrozil has been reported. Niacin alone has also been associated with cases of myopathy. Using gemfibrozil with niacin might further increase the risk of developing myopathy.

Theoretically, concomitant use of niacin and hepatotoxic drugs might increase the risk of hepatotoxicity.
Niacin has been associated with cases of liver toxicity, especially when used in pharmacologic doses. Sustained-release niacin preparations appear to be associated with a higher risk of hepatotoxicity than immediate-release niacin.

Theoretically, concomitant use of niacin and statins might increase the risk of myopathy and rhabdomyolysis in some patients.
Some case reports have raised concerns that niacin might increase the risk of myopathy and rhabdomyolysis when combined with statins. However, a significantly increased risk of myopathy has not been demonstrated in clinical trials, including those using an FDA-approved combination of lovastatin and niacin (Advicor).

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as probenecid.
Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia. Doses of uricosurics such as probenecid might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Theoretically, niacin might antagonize the therapeutic effects of uricosurics such as sulfinpyrazone.
Large doses of niacin reduce urinary excretion of uric acid, potentially causing hyperuricemia. Doses of uricosurics such as sulfinpyrazone might need to be increased to maintain control of gout in patients who start taking niacin. People who have frequent attacks of gout despite uricosuric therapy should avoid niacin.

Theoretically, niacin might antagonize the therapeutic effects of thyroid hormones.
Clinical research and case reports suggests that taking niacin can reduce serum levels of thyroxine-binding globulin by up to 25% and moderately reduce levels of thyroxine (T4). Patients taking thyroid hormone for hypothyroidism might need dose adjustments when using niacin.

Theoretically, concomitant use of niacin and transdermal nicotine might increase the risk of flushing and dizziness.
Niacin and nicotine can both cause flushing and dizziness.

There is limited evidence that niacin may increase the anticoagulant effects of warfarin.
In a case report, a patient on warfarin developed an elevated international normalized ratio (INR) of 3.9 after taking niacin for two weeks. The patient's INR was previously stable, ranging between 2 and 3 in recent months, and no other medication changes were identified. The elevated INR returned to therapeutic range within 4 days following the discontinuation of niacin.

Large doses of aspirin might alter the clearance of niacin.
Aspirin is often used with niacin to reduce niacin-induced flushing. Doses of 80-975 mg aspirin have been used, but 325 mg appears to be optimal. Aspirin also seems to reduce the clearance of niacin by competing for glycine conjugation. Taking aspirin 1 gram seems to reduce niacin clearance by 45%. This is probably a dose-related effect and not clinically significant with the more common aspirin dose of 325 mg.

Vitamin D might increase aluminum absorption and toxicity, but this has only been reported in people with renal failure.
The protein that transports calcium across the intestinal wall can also bind and transport aluminum. This protein is stimulated by vitamin D, which may therefore increase aluminum absorption. This mechanism may contribute to increased aluminum levels and toxicity in people with renal failure, when they take vitamin D and aluminum-containing phosphate binders chronically.

Vitamin D might reduce absorption of atorvastatin.
A small, low-quality clinical study shows that taking vitamin D reduces levels of atorvastatin and its active metabolites by up to 55%. However, while atorvastatin levels decreased, total cholesterol, low-density lipoprotein (LDL) cholesterol, and high-density lipoprotein (HDL) cholesterol levels did not substantially change. Atorvastatin is metabolized in the gut by CYP3A4 enzymes, and researchers theorized that vitamin D might induce CYP3A4, causing reduced levels of atorvastatin. However, this proposed mechanism was not specifically studied.

Taking calcipotriene with vitamin D increases the risk for hypercalcemia.
Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia. Theoretically, combining calcipotriene with vitamin D supplements might increase the risk of hypercalcemia.

Theoretically, hypercalcemia induced by high-dose vitamin D can increase the risk of arrhythmia from digoxin.
High doses of vitamin D can cause hypercalcemia. Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin. Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and digoxin concurrently.

Theoretically, hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of diltiazem for arrhythmia.
High doses of vitamin D can cause hypercalcemia. Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically this could also occur with diltiazem. Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and diltiazem concurrently.

Theoretically, taking thiazide diuretics and high-dose vitamin D can increase the risk of hypercalcemia.
Thiazide diuretics decrease urinary calcium excretion, which could lead to hypercalcemia if vitamin D supplements are taken concurrently. This has been reported in people being treated with vitamin D for hypoparathyroidism, and also in elderly people with normal parathyroid function who were taking a thiazide, vitamin D, and calcium-containing antacids daily.

Hypercalcemia induced by high-dose vitamin D can reduce the therapeutic effects of verapamil for arrhythmia.
Hypercalcemia due to high doses of vitamin D can reduce the effectiveness of verapamil in atrial fibrillation. Avoid vitamin D doses above the tolerable upper intake level (4000 IU daily for adults) and monitor serum calcium levels in people taking vitamin D and verapamil concurrently.

Vitamin D might induce CYP3A4 enzymes and reduce the bioavailability of CYP3A4 substrates.
There is some concern that vitamin D might induce CYP3A4. In vitro research suggests that vitamin D induces CYP3A4 transcription. Additionally, observational research has found that increased UV light exposure and serum vitamin D levels are associated with decreased serum levels of CYP3A4 substrates such as tacrolimus and sirolimus, while no association between UV light exposure or vitamin D levels and levels of mycophenolic acid, a non-CYP3A4 substrate, was found. A small, low-quality clinical study shows that taking vitamin D reduces levels of the CYP3A4 substrate atorvastatin and its active metabolites by up to 55%; however, the clinical effects of atorvastatin were not reduced. While researchers theorized that vitamin D might induce CYP3A4, this proposed mechanism was not specifically studied.

Theoretically, hesperidin may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Animal research suggests that hesperetin, a bioflavonoid aglycone derivative of hesperidin, may have antiplatelet activity.

Theoretically, taking hesperidin with antihypertensive drugs might increase the risk of hypotension.
Some clinical and animal research shows that hesperidin can decrease blood pressure. However, other clinical research shows that hesperidin does not affect blood pressure.

Theoretically, hesperidin may decrease the levels and clinical effects of celiprolol.
Animal research shows that concomitant use of hesperidin may reduce the plasma area under the curve of celiprolol by up to 75%. This effect has not been reported in humans.

Theoretically, concomitant use with CNS depressants may cause additive sedative effects.
Animal studies show that hesperidin has sedative effects, due to opioid receptor activity and can increase sedation when used with diazepam. This effect has not been reported in humans.

Theoretically, hesperidin may increase the levels and clinical effects of diltiazem.
Animal research suggests that hesperidin may enhance the bioavailability of diltiazem, increasing the plasma area under the curve of diltiazem by up to 65.3%. This effect has not been reported in humans.

Theoretically, hesperidin might inhibit P-glycoprotein-mediated drug efflux and potentially increase levels of drugs that are substrates of P-glycoprotein.
In vitro research shows that hesperidin can inhibit P-glycoprotein efflux. This effect has not been reported in humans.

Theoretically, hesperidin might increase the levels and clinical effects of verapamil.
Animal research suggests that hesperidin may enhance the bioavailability of verapamil, increasing the plasma area under the curve of verapamil by 96.8%. This effect has not been reported in humans

Theoretically, antibiotics might interfere with the metabolism of flaxseed constituents, which could potentially alter the effects of flaxseed.
Some potential benefits of flaxseed are thought to be due to its lignan content. Secoisolariciresinol diglucoside (SDG), a major lignan precursor, is found in high concentrations in flaxseed. SDG is converted by bacteria in the colon to the lignans enterolactone and enterodiol. Antibiotics alter the flora of the colon, which could theoretically alter the metabolism of flaxseed.

Theoretically, using flaxseed in combination with anticoagulant or antiplatelet drugs might have additive effects and increase the risk of bleeding.
Some clinical evidence suggests that the oil contained in flaxseed can decrease platelet aggregation.

Theoretically, flaxseed might have additive effects when used with antidiabetes drugs and increase the risk for hypoglycemia.
Some clinical research suggests that flaxseed can lower blood glucose levels.

Theoretically, flaxseed might have additive effects when used with antihypertensive drugs and increase the risk of hypotension.
Clinical research shows that daily flaxseed consumption, especially for longer than 12 weeks, modestly reduces blood pressure.

Theoretically, taking flaxseed might decrease the effects of estrogens.
Flaxseed contains lignans with mild estrogenic and possible antiestrogenic effects. The lignans seem to compete with circulating endogenous estrogen and might reduce estrogen binding to estrogen receptors, resulting in an anti-estrogen effect. It is unclear if this effect transfers to exogenously administered estrogens.

Theoretically, taking dandelion root along with anticoagulant or antiplatelet drugs might increase the risk of bruising and bleeding.
In vitro research suggests that dandelion root inhibits platelet aggregation.

Theoretically, dandelion might increase the risk for hypoglycemia when used with antidiabetes drugs.
Laboratory research suggests that dandelion extract may have moderate alpha-glucosidase inhibitor activity and might also increase insulin secretion. Also, in a case report, a 58-year-old woman with type 2 diabetes who was being treated with insulin developed hypoglycemia 2 weeks after beginning to eat salads containing dandelion.

Theoretically, dandelion might increase levels of drugs metabolized by CYP1A2.
Laboratory research suggests that dandelion might inhibit CYP1A2. So far, this interaction has not been reported in humans. However, until more is known, watch for an increase in the levels of drugs metabolized by CYP1A2 in patients taking dandelion.

Theoretically, dandelion might increase the clearance of drugs that are UDP-glucuronosyltransferase substrates.
There is some preliminary evidence that dandelion might induce UDP-glucuronosyltransferase, a phase II enzyme.

Theoretically, through diuretic effects, dandelion might reduce excretion and increase levels of lithium.
Animal research suggests that dandelion has diuretic properties. As diuretics can increase serum lithium levels, the dose of lithium might need to be decreased when taken with dandelion.

Theoretically, dandelion might increase the risk of hyperkalemia when taken with potassium-sparing diuretics.
Dandelion contains significant amounts of potassium.

Theoretically, dandelion might lower fluoroquinolone levels.
Animal research shows that dandelion reduces absorption of ciprofloxacin and can lower levels by 73%. However, this effect has not been reported in humans.

Theoretically, parsley might increase the risk of bleeding when taken with anticoagulant or antiplatelet drugs.
Animal research suggests that parsley has antiplatelet effects.

Theoretically, parsley might increase the risk of hypoglycemia when taken with antidiabetes drugs.
Animal research suggests that parsley might decrease blood glucose. Monitor blood glucose levels closely. Dose adjustments might be necessary.

Theoretically, parsley might increase serum levels of CYP1A2 substrates.
Laboratory research suggests that parsley can inhibit CYP1A2.

Theoretically, parsley might enhance or interfere with the effects of diuretic drugs.
Animal research suggests that parsley seed extract increases urine elimination. Parsley leaf and root might also interfere with diuretic therapy due their purported aquaretic effects.

Theoretically, parsley might increase the duration of pentobarbital effects.
Animal research suggests that parsley juice prolongs the action of pentobarbital, perhaps by decreasing cytochrome P450 levels. It is not known if this occurs in humans or if this applies to other barbiturates or sedatives.

Theoretically, large quantities of parsley might increase sirolimus levels.
In one case report, an adult female with a history of kidney transplant presented with elevated blood sirolimus levels, approximately 4-7 times greater than previous measures, after daily consumption of a juice containing approximately 30 grams of parsley for 7 days. Sirolimus levels returned to normal a week after the parsley juice was discontinued.

Theoretically, large amounts of parsley leaf and root might decrease the effects of warfarin.
Parlsey contains vitamin K.

Theoretically, aspirin might increase the severity of allergic reactions to parsley.
In one case, severe urticaria and swelling were reported after taking aspirin with parsley in an individual with a known mild parsley allergy.

Concomitant use of retinoids with vitamin A supplements might produce supratherapeutic vitamin A levels.
Retinoids, which are vitamin A derivatives, could have additive toxic effects when taken with vitamin A supplements.

Theoretically, taking high doses of vitamin A in combination with other potentially hepatotoxic drugs might increase the risk of liver disease.
The tolerable upper intake level (UL) is the highest level of intake that is likely to pose no risk of adverse effects. Doses of vitamin A above the UL can cause hepatotoxicity, ranging from elevated liver enzymes to liver failure.

Theoretically, taking tetracycline antibiotics with high doses of vitamin A can increase the risk of pseudotumor cerebri.
Benign intracranial hypertension (pseudotumor cerebri) can occur with tetracyclines and with acute or chronic vitamin A toxicity. Case reports suggest that taking tetracyclines and vitamin A concurrently can increase the risk of this condition. Avoid high doses of vitamin A in people taking tetracyclines chronically.

Theoretically, high doses of vitamin A could increase the risk of bleeding with warfarin.
Vitamin A toxicity is associated with hemorrhage and hypoprothrombinemia, possibly due to vitamin K antagonism. Advise patients taking warfarin to avoid doses of vitamin A above the tolerable upper intake level of 10,000 IU/day for adults.

Theoretically, vitamin B6 might increase the photosensitivity caused by amiodarone.
Despite initial case reports suggesting that pyridoxine may have a protective effect against amiodarone-induced photosensitivity, preliminary clinical research suggests that pyridoxine may actually exacerbate this adverse effect.

Theoretically, vitamin B6 may have additive effects when used with antihypertensive drugs.
Research in hypertensive rats shows that vitamin B6 can decrease systolic blood pressure. Similarly, clinical research in patients with hypertension shows that taking high doses of vitamin B6 may reduce systolic and diastolic blood pressure, possibly by reducing plasma levels of epinephrine and norepinephrine.

High doses of vitamin B6 may reduce the levels and clinical effects of phenobarbital.
Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenobarbital, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenobarbital to avoid high doses of vitamin B6.

High doses of vitamin B6 may reduce the levels and clinical effects of phenytoin.
Preliminary clinical evidence suggests that vitamin B6 200 mg daily can reduce plasma levels of phenytoin, possibly by increasing metabolism. It is not known whether lower doses have any effect. Advise people taking phenytoin to avoid high doses of vitamin B6.

Vitamin B6 may increase the metabolism of levodopa when taken alone, but not when taken in conjunction with carbidopa.
Vitamin B6 (pyridoxine) enhances the metabolism of levodopa, reducing its clinical effects. However, this interaction does not occur when carbidopa is used concurrently with levodopa (Sinemet). Therefore, it is not likely to be a problem in most people.

Theoretically, antioxidant effects of vitamin C might reduce the effectiveness of alkylating agents.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs that generate free radicals, such as cyclophosphamide, chlorambucil, carmustine, busulfan, and thiotepa. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effect, if any, antioxidants such as vitamin C have on chemotherapy.

Vitamin C can increase the amount of aluminum absorbed from aluminum compounds.
Research in animals and humans shows that vitamin C increases aluminum absorption, theoretically by chelating aluminum and keeping it in solution where it is available for absorption. In people with normal renal function, urinary excretion of aluminum will likely increase, making aluminum retention and toxicity unlikely. Patients with renal failure who take aluminum-containing compounds such as phosphate binders should avoid vitamin C supplements in doses above the recommended dietary allowances.

Theoretically, the antioxidant effects of vitamin C might reduce the effectiveness of antitumor antibiotics.
The use of antioxidants like vitamin C during chemotherapy is controversial. There is concern that antioxidants could reduce the activity of chemotherapy drugs which generate free radicals, such as doxorubicin. In contrast, some researchers theorize that antioxidants might make chemotherapy more effective by reducing oxidative stress that could interfere with apoptosis (cell death) of cancer cells. More evidence is needed to determine what effects, if any, antioxidants such as vitamin C have on chemotherapy.

Vitamin C might increase blood levels of estrogens.
Increases in plasma estrogen levels of up to 55% occur under some circumstances when vitamin C is taken concurrently with oral contraceptives or hormone replacement therapy, including topical products. It is suggested that vitamin C prevents oxidation of estrogen in the tissues, regenerates oxidized estrogen, and reduces sulfate conjugation of estrogen in the gut wall. When tissue levels of vitamin C are high, these processes are already maximized and supplemental vitamin C does not have any effect on estrogen levels. Increases in plasma estrogen levels may occur when patients who are deficient in vitamin C take supplements. Monitor these patients for estrogen-related side effects.

Theoretically, vitamin C might decrease levels of fluphenazine.
In one patient there was a clinically significant decrease in fluphenazine levels when vitamin C (500 mg twice daily) was started. The mechanism is not known, and there is no further data to confirm this interaction.

Vitamin C can modestly reduce indinavir levels.
One pharmacokinetic study shows that taking vitamin C 1 gram orally once daily along with indinavir 800 mg orally three times daily reduces the area under the concentration-time curve of indinavir by 14%. The mechanism of this interaction is unknown, but it is unlikely to be clinically significant in most patients. The effect of higher doses of vitamin C on indinavir levels is unknown.

Vitamin C can increase levothyroxine absorption.
Two clinical studies in adults with poorly controlled hypothyroidism show that swallowing levothyroxine with a glass of water containing vitamin C 500-1000 mg in solution reduces thyroid stimulating hormone (TSH) levels and increases thyroxine (T4) levels when compared with taking levothyroxine alone. This suggests that vitamin C increases the oral absorption of levothyroxine, possibly due to a reduction in pH.

High-dose vitamin C might reduce the levels and effectiveness of warfarin.
Vitamin C in high doses may cause diarrhea and possibly reduce warfarin absorption. There are reports of two people who took up to 16 grams daily of vitamin C and had a reduction in prothrombin time. Lower doses of 5-10 grams daily can also reduce warfarin absorption. In many cases, this does not seem to be clinically significant. However, a case of warfarin resistance has been reported for a patient who took vitamin C 500 mg twice daily. Cessation of vitamin C supplementation resulted in a rapid increase in international normalized ratio (INR). Tell patients taking warfarin to avoid taking vitamin C in excessively high doses (greater than 10 grams daily). Lower doses may be safe, but the anticoagulation activity of warfarin should be monitored. Patients who are stabilized on warfarin while taking vitamin C should avoid adjusting vitamin C dosage to prevent the possibility of warfarin resistance.

High-dose vitamin C might slightly prolong the clearance of acetaminophen.
A small pharmacokinetic study in healthy volunteers shows that taking high-dose vitamin C (3 grams) 1.5 hours after taking acetaminophen 1 gram slightly increases the apparent half-life of acetaminophen from around 2.3 hours to 3.1 hours. Ascorbic acid competitively inhibits sulfate conjugation of acetaminophen. However, to compensate, elimination of acetaminophen glucuronide and unconjugated acetaminophen increases. This effect is not likely to be clinically significant.

Acidification of the urine by vitamin C might increase aspirin levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction is not clinically significant.

Acidification of the urine by vitamin C might increase choline magnesium trisalicylate levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams daily of vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction probably is not clinically significant.

Vitamin C might decrease the beneficial effects of niacin on high-density lipoprotein (HDL) cholesterol levels.
A combination of niacin and simvastatin (Zocor) effectively raises HDL cholesterol levels in patients with coronary disease and low HDL levels. Clinical research shows that taking a combination of antioxidants (vitamin C, vitamin E, beta-carotene, and selenium) along with niacin and simvastatin (Zocor) attenuates this rise in HDL, specifically the HDL-2 and apolipoprotein A1 fractions, by more than 50% in patients with coronary disease. It is not known whether this adverse effect is due to a single antioxidant such as vitamin C, or to the combination. It also is not known whether it will occur in other patient populations.

Acidification of the urine by vitamin C might increase salsalate levels.
It has been suggested that acidification of the urine by vitamin C could increase reabsorption of salicylates by the renal tubules, and increase plasma salicylate levels. However, short-term use of up to 6 grams/day vitamin C does not seem to affect urinary pH or salicylate excretion, suggesting this interaction probably is not clinically significant.

Saw palmetto might increase the risk of bleeding with anticoagulant or antiplatelet drugs.
Saw palmetto is reported to prolong bleeding time. Theoretically, it might increase the risk of bleeding when used concomitantly with anticoagulant or antiplatelet drugs.

Saw palmetto might reduce the effectiveness of contraceptive drugs.
Saw palmetto might have antiestrogenic effects. Theoretically, it might interfere with contraceptive drugs taken concomitantly.

Saw palmetto might reduce the effectiveness of estrogens.
Saw palmetto might have antiestrogenic effects. Theoretically, it might interfere with estrogens taken concomitantly.

Co-administration of intravenous calcium and ceftriaxone can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys.
Avoid administering intravenous calcium in any form, such as parenteral nutrition or Lactated Ringers, within 48 hours of intravenous ceftriaxone. Case reports in neonates show that administering intravenous ceftriaxone and calcium can result in precipitation of a ceftriaxone-calcium salt in the lungs and kidneys. In several cases, neonates have died as a result of this interaction. So far there are no reports in adults; however, there is still concern that this interaction might occur in adults.

Calcium seems to reduce levels of dolutegravir.
Advise patients to take dolutegravir either 2 hours before or 6 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium carbonate 1200 mg concomitantly with dolutegravir 50 mg reduces plasma levels of dolutegravir by almost 40%. Calcium appears to decrease levels of dolutegravir through chelation.

Calcium seems to reduce levels of elvitegravir.
Advise patients to take elvitegravir either 2 hours before or 2 hours after taking calcium supplements. Pharmacokinetic research suggests that taking calcium along with elvitegravir can reduce blood levels of elvitegravir through chelation.

Calcium citrate might increase aluminum absorption and toxicity. Other types of calcium do not increase aluminum absorption.
Calcium citrate can increase the absorption of aluminum when taken with aluminum hydroxide. The increase in aluminum levels may become toxic, particularly in individuals with kidney disease. However, the effect of calcium citrate on aluminum absorption is due to the citrate anion rather than calcium cation. Calcium acetate does not appear to increase aluminum absorption.

Calcium might decrease levels of bictegravir/emtricitabine/tenofovir alafenamide by reducing its absorption when taken in a fasting state.
Advise patients that bictegravir/emtricitabine/tenofovir alafenamide and calcium can be taken together if taken with food. However, if taken on an empty stomach, bictegravir/emtricitabine/tenofovir alafenamide should not be taken with, or 2 hours after, calcium containing products.

Calcium reduces the absorption of bisphosphonates.
Advise patients to take bisphosphonates at least 30 minutes before calcium, but preferably at a different time of day. Calcium supplements decrease absorption of bisphosphonates.

Taking calcipotriene with calcium might increase the risk for hypercalcemia.
Calcipotriene is a vitamin D analog used topically for psoriasis. It can be absorbed in sufficient amounts to cause systemic effects, including hypercalcemia. Theoretically, combining calcipotriene with calcium supplements might increase the risk of hypercalcemia.

Using intravenous calcium with digoxin might increase the risk of fatal cardiac arrhythmias.
Hypercalcemia increases the risk of fatal cardiac arrhythmias with digoxin. However, one retrospective analysis of clinical data suggests that intravenous calcium does not increase the risk of dysrhythmias or mortality in patients receiving digoxin.

Theoretically, calcium may reduce the therapeutic effects of diltiazem.
Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically, calcium might increase this risk of hypercalcemia and reduce the effectiveness of diltiazem.

Calcium seems to reduce the absorption and effectiveness of levothyroxine.
Advise patients to take levothyroxine and calcium supplements at least 4 hours apart. Calcium reduces levothyroxine absorption, probably by forming insoluble complexes. Calcium carbonate supplements reduce effectiveness of levothyroxine in patients with hypothyroidism.

Theoretically, concomitant use of calcium and lithium may increase this risk of hypercalcemia.
Clinical research suggests that long-term use of lithium may cause hypercalcemia in 10% to 60% of patients. Theoretically, concomitant use of lithium and calcium supplements may further increase this risk.

Calcium seems to reduce the absorption of quinolone antibiotics.
Advise patients to take oral quinolones at least 2 hours before or 4-6 hours after calcium supplements or calcium-fortified foods. Taking calcium at the same time as oral quinolones can reduce quinolone absorption. Calcium binds to quinolones in the gut.

Calcium may reduce levels of raltegravir.
Pharmacokinetic research shows that taking a single dose of calcium carbonate 3000 mg along with raltegravir 400 mg twice daily modestly decreases the mean area under the curve of raltegravir, but the decrease does not necessitate a dose adjustment of raltegravir. However, a case of elevated HIV-1 RNA levels and documented resistance to raltegravir has been reported for a patient taking calcium carbonate 1 gram three times daily plus vitamin D3 (cholecalciferol) 400 IU three times daily in combination with raltegravir 400 mg twice daily for 11 months. It is thought that calcium reduced raltegravir levels by chelation, leading to treatment failure.

Calcium seems to reduce the absorption of sotalol.
Advise patients to separate doses by at least 2 hours before or 4-6 hours after calcium. Calcium appears to reduce the absorption of sotalol, probably by forming insoluble complexes.

Calcium seems to reduce the absorption of tetracycline antibiotics.
Advise patients to take oral tetracyclines at least 2 hours before, or 4-6 hours after calcium supplements. Taking calcium at the same time as oral tetracyclines can reduce tetracycline absorption. Calcium binds to tetracyclines in the gut.

Taking calcium along with thiazides might increase the risk of hypercalcemia and renal failure.
Thiazides reduce calcium excretion by the kidneys. Using thiazides along with moderately large amounts of calcium carbonate increases the risk of milk-alkali syndrome (hypercalcemia, metabolic alkalosis, renal failure). Patients may need to have their serum calcium levels and/or parathyroid function monitored regularly.

Theoretically, calcium may reduce the therapeutic effects of verapamil.
Hypercalcemia can reduce the effectiveness of verapamil in atrial fibrillation. Theoretically, use of calcium supplements may increase this risk of hypercalcemia and reduce the effectiveness of verapamil.

Intravenous calcium may decrease the effects of calcium channel blockers; oral calcium is unlikely to have this effect.
Intravenous calcium is used to decrease the effects of calcium channel blockers in the management of overdose. Intravenous calcium gluconate has been used before intravenous verapamil (Isoptin) to prevent or reduce the hypotensive effects without affecting the antiarrhythmic effects. But there is no evidence that dietary or supplemental calcium when taken orally interacts with calcium channel blockers.

Theoretically, taking inositol with antidiabetes drugs might increase the risk of hypoglycemia.
Clinical research shows that inositol lowers blood glucose levels and glycated hemoglobin (HbA1c) levels in patients with diabetes.

Theoretically, taking rutin with antidiabetes drugs might increase the risk of hypoglycemia.
Animal research suggests that rutin has hypoglycemic effects.

Theoretically, taking damiana with antidiabetes drugs might increase the risk of hypoglycemia.
Animal research shows that taking damiana lowers blood glucose level.

Betaine hydrochloride increases stomach acidity and could decrease the effects of antacids.
In human research, betaine hydrochloride increases stomach acidity. Antacids are taken to decrease stomach acidity. Theoretically, taking betaine hydrochloride along with antacids might decrease the effects of the antacids.

Betaine hydrochloride increases stomach acidity and could decrease the effects of H2-blockers.
In human research, betaine hydrochloride increases stomach acidity. H2-blockers are used to decrease stomach acidity. Theoretically, taking betaine hydrochloride along with H2-blockers might decrease the effects of H2-blockers.

Betaine hydrochloride increases stomach acidity and could decrease the effects of PPIs.
In human research, betaine hydrochloride increases stomach acidity. PPIs are used to decrease stomach acidity. Theoretically, taking betaine hydrochloride along with PPIs might decrease the effects of PPIs

Theoretically, taking riboflavin with tetracycline antibiotics may decrease the potency of these antibiotics.
In vitro research suggests that riboflavin may inhibit the potency of tetracycline antibiotics. It is not clear if this effect is clinically significant, as this interaction has not been reported in humans.

Metformin, a common medication used to manage type 2 diabetes, has been associated with lower vitamin B12 levels in some individuals. Prolonged use of metformin can interfere with the absorption of B12 in the digestive system, potentially leading to a deficiency in this essential vitamin.

Theoretically, choline might decrease the effects of atropine in the brain.
Animal research shows that administering choline one hour before administering atropine can attenuate atropine-induced decreases in brain levels of acetylcholine. Theoretically, concomitant use of choline and atropine may decrease the effects of atropine.

Combining iodine with amiodarone might cause excessively high iodine levels.
Amiodarone contains 37.3% iodine and can increase iodine levels. Concomitant use with iodine might increase the risk of having excessive iodine levels and adversely affecting thyroid function. Monitor thyroid function.

Iodine might alter the effects of antithyroid drugs.
Iodine in high doses has been reported to cause both hyperthyroidism and hypothyroidism, depending on the individual's past medical history. Taking iodine while using antithyroid drugs could alter the effects of the antithyroid drugs.

Combining iodine with lithium might have additive hypothyroid effects.
Lithium can inhibit thyroid function. Several case reports suggest that concomitant use of lithium and potassium iodide can reduce thyroid function in otherwise healthy adults. Monitor thyroid function.

Trimethoprim might increase blood levels of thiamine.
In vitro, animal, and clinical research suggest that trimethoprim inhibits intestinal thiamine transporter ThTR-2, hepatic transporter OCT1, and renal transporters OCT2, MATE1, and MATE2, resulting in paradoxically increased thiamine plasma concentrations.

Pumpkin might reduce excretion and increase levels of lithium.
Pumpkin is thought to have diuretic properties. Theoretically, this might reduce excretion and increase levels of lithium. The dose of lithium might need to be decreased.