Multi Vitamin, Mineral Ingredients & Drug Interactions

Theoretically, taking rhodiola with antidiabetes drugs might increase the risk of hypoglycemia.
In vitro and animal research shows that rhodiola extract can decrease blood glucose due to alpha-glucosidase activity.

Theoretically, taking rhodiola with antihypertensive drugs might increase the risk of hypotension.
In vitro and animal research shows that rhodiola extract inhibits angiotensin-converting enzyme (ACE) and might lower blood pressure.

Theoretically, rhodiola might increase levels of drugs metabolized by CYP2C9.
In vitro research shows that rhodiola inhibits CYP2C9. This effect is highly variable and appears to be dependent on the rhodiola product studied. Also, a clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days reduces the metabolism of losartan, a CYP2C9 substrate, by 21% after 4 hours.

Theoretically, rhodiola use might interfere with immunosuppressive therapy.
In vitro and animal research show that rhodiola has immunostimulatory effects.

Rhodiola might increase the levels and adverse effects of losartan.
A clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days reduces the metabolism of losartan, a CYP2C9 substrate, by 21% after 4 hours.

Theoretically, rhodiola might increase levels of P-glycoprotein substrates.
In vitro research shows that rhodiola inhibits P-glycoprotein. Theoretically, using rhodiola with P-glycoprotein substrates might increase drug levels and potentially increase the risk of adverse effects.

Theoretically, rhodiola might increase the risk of adverse effects when taken with antidepressants.
A review of adverse event reports in Poland identified cases of tachyarrhythmias, myalgia, arthralgia, gum pain, restless leg syndrome, swallowing disorders, and changes in consciousness when rhodiola was taken in combination with paroxetine, escitalopram, fluoxetine, sertraline, trazodone, and/or duloxetine.

Theoretically, rhodiola might increase the risk of adverse effects when taken with CNS depressants.
A review of adverse event reports in Poland identified cases of excessive sedation, myoclonus, hypotension, and hallucinations when rhodiola was taken with haloperidol, diazepam, or alprazolam.

Theoretically, rhodiola might increase levels of drugs metabolized by CYP1A2.
In vitro research shows that rhodiola inhibits CYP1A2. This effect is highly variable and appears to be dependent on the rhodiola product studied. However, a clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days does not inhibit the metabolism of caffeine, a CYP1A2 substrate.

Theoretically, rhodiola might increase levels of drugs metabolized by CYP3A4.
In vitro research shows that rhodiola inhibits CYP3A4. This effect is highly variable and appears to be dependent on the rhodiola product studied. However, a clinical study in healthy young males found that taking rhodiola extract 290 mg daily for 14 days does not inhibit the metabolism of midazolam, a CYP3A4 substrate.

Taking ginkgo with talinolol seems to increase blood levels of talinolol.
There is some evidence that using ginkgo leaf extract 120 mg orally three times daily for 14 days can increase levels of talinolol by 36% in healthy male individuals. However, single doses of ginkgo do not seem to affect talinolol pharmacokinetics.

Theoretically, ginkgo might decrease the levels and clinical effects of alprazolam.
In clinical research, ginkgo extract (Ginkgold) 120 mg twice daily seems to decrease alprazolam levels by about 17%. However, ginkgo does not appear to decrease the elimination half-life of alprazolam. This suggests that ginkgo is more likely to decrease absorption of alprazolam rather than induce hepatic metabolism of alprazolam.

Ginkgo has been shown to increase the risk of bleeding in some people when taken with warfarin. Theoretically, ginkgo might increase the risk of bleeding if used with other anticoagulant or antiplatelet drugs.
Several pharmacodynamic studies suggest that ginkgo inhibits platelet aggregation. It is thought that the ginkgo constituent, ginkgolide B, displaces platelet-activating factor (PAF) from its binding sites, decreasing blood coagulation. Several case reports have documented serious bleeding events in patients taking ginkgo. However, population and clinical studies have produced mixed results. Some evidence shows that short-term use of ginkgo leaf does not significantly reduce platelet aggregation and blood clotting. A study in healthy males who took a specific ginkgo leaf extract (EGb 761) 160 mg twice daily for 7 days found no change in prothrombin time. An analysis of a large medical record database suggests that ginkgo increases the risk of a bleeding adverse event by 38% when taken concurrently with warfarin. It has been suggested that ginkgo has to be taken for at least 2-3 weeks to have a significant effect on platelet aggregation. However, a meta-analysis of 18 studies using standardized ginkgo extracts, 80-480 mg daily for up to 32 weeks, did not find a significant effect on platelet aggregation, fibrinogen concentration, or PT/aPTT. In addition, a single dose of ginkgo plus clopidogrel or ticlopidine does not seem to significantly increase bleeding time or platelet aggregation. Also, taking ginkgo leaf extract daily for 8 days in conjunction with rivaroxaban does not affect anti-factor Xa activity; however, this study did not evaluate bleeding time.

Theoretically, ginkgo might reduce the effectiveness of anticonvulsants.
Ginkgo seeds contain ginkgotoxin. Large amounts of ginkgotoxin can cause neurotoxicity and seizure. Ginkgotoxin is present in much larger amounts in ginkgo seeds than leaves. Ginkgo leaf extract contains trace amounts of ginkgotoxin. The amount of ginkgotoxin in ginkgo leaf and leaf extract seems unlikely to cause toxicity. However, there are anecdotal reports of seizure occurring after use of ginkgo leaf both in patients without a history of seizure disorder and in those with previously well-controlled epilepsy.

Theoretically, taking ginkgo with antidiabetes drugs might alter the response to antidiabetes drugs.
Ginkgo leaf extract seems to alter insulin secretion and metabolism, and might affect blood glucose levels in people with type 2 diabetes. The effect of ginkgo seems to differ depending on the insulin and treatment status of the patient. In diet-controlled diabetes patients with hyperinsulinemia, taking ginkgo does not seem to significantly affect insulin or blood glucose levels. In patients with hyperinsulinemia who are treated with oral hypoglycemic agents, taking ginkgo seems to decrease insulin levels and increase blood glucose following an oral glucose tolerance test. Researchers speculate that this could be due to ginkgo-enhanced hepatic metabolism of insulin. In patients with pancreatic exhaustion, taking ginkgo seems to stimulate pancreatic beta-cells, resulting in increased insulin and C-peptide levels, but with no significant change in blood glucose levels in response to an oral glucose tolerance test.

Theoretically, ginkgo might decrease the levels and clinical effects of atorvastatin.
In humans, intake of ginkgo extract appears to increase atorvastatin clearance, reducing the area under the curve of atorvastatin by 10% to 14% and the maximum concentration by 29%. However, this interaction does not appear to affect cholesterol synthesis and absorption. Further, a model in rats with hyperlipidemia suggests that administering ginkgo extract does not impact blood levels of atorvastatin and leads to lower total cholesterol, low-density lipoprotein cholesterol, and triglycerides when compared with rats given atorvastatin alone.

Theoretically, ginkgo might increase levels of drugs metabolized by CYP1A2.
Laboratory research suggests that ginkgo leaf extract can mildly inhibit CYP1A2 enzymes. However, clinical research suggests ginkgo might not affect CYP1A2. Until more is known, use ginkgo cautiously in patients taking drugs metabolized by these enzymes.

Theoretically, ginkgo might decrease levels of drugs metabolized by CYP2C19.
Some clinical research shows that a specific ginkgo leaf extract (Remembrance, Herbs Product LTD) 140 mg twice daily can induce CYP2C19 enzymes and potentially decrease levels of drugs metabolized by these enzymes. However, other clinical research shows that taking ginkgo 120 mg twice daily for 12 days has no effect on levels of drugs metabolized by CYP2C19.

Theoretically, ginkgo might increase levels of drugs metabolized by CYP2C9.
In vitro, a specific standardized extract of ginkgo leaf (EGb 761) inhibits CYP2C9 activity . The terpenoid (ginkgolides) and flavonoid (quercetin, kaempferol, etc.) constituents seem to be responsible for this effect. Most ginkgo extracts contain some amount of these constituents. Therefore, other ginkgo leaf extracts might also inhibit the CYP2C9 enzyme. However, clinical research suggests that ginkgo might not have a significant effect on CYP2C9 in humans. Ginkgo does not seem to significantly affect the pharmacokinetics of CYP2C9 substrates diclofenac or tolbutamide.

Theoretically, ginkgo might decrease levels of drugs metabolized by CYP3A4.
There is conflicting evidence about whether ginkgo induces or inhibits CYP3A4. Ginkgo does not appear to affect hepatic CYP3A4. However, it is not known if ginkgo affects intestinal CYP3A4. Preliminary clinical research suggests that taking ginkgo does not significantly affect levels of donepezil, lopinavir, or ritonavir, which are all CYP3A4 substrates. Other clinical research also suggests ginkgo does not significantly affect CYP3A4 activity. However, there are two case reports of decreased efavirenz concentrations and increased viral load in patients taking ginkgo. It is suspected that terpenoids from the ginkgo extract reduced drug levels by inducing cytochrome P450 3A4 (CYP3A4).

Theoretically, ginkgo might decrease the levels and clinical effects of efavirenz.
There are two case reports of decreased efavirenz concentrations and increased viral load in patients taking ginkgo. In one case, an HIV-positive male experienced over a 50% decrease in efavirenz levels over the course of 14 months while taking ginkgo extract. HIV-1 RNA copies also increased substantially, from less than 50 to more than 1500. It is suspected that terpenoids from the ginkgo extract reduced drug levels by inducing cytochrome P450 3A4 (CYP3A4). In another case report, a patient stable on antiviral therapy including efavirenz for 10 years, had an increase in viral load from <50 copies/mL to 1350 copies/mL after 2 months of taking a combination of supplements including ginkgo. After stopping ginkgo, the viral load was again controlled with the same antiviral therapy regimen.

Theoretically, ginkgo might increase the risk of bleeding when used with ibuprofen.
Ginkgo might have antiplatelet effects and has been associated with several case reports of spontaneous bleeding. In one case, a 71-year-old male had taken a specific ginkgo extract (Gingium, Biocur) 40 mg twice daily for 2.5 years. About 4 weeks after starting ibuprofen 600 mg daily he experienced a fatal intracerebral hemorrhage. However, the antiplatelet effects of ginkgo have been questioned. A meta-analysis and other studies have not found a significant antiplatelet effect with standardized ginkgo extracts, 80 mg to 480 mg taken daily for up to 32 weeks.

Theoretically, taking ginkgo with P-glycoprotein substrates might increase the levels and adverse effects of these substrates.
A small clinical study in healthy volunteers shows that using ginkgo leaf extract 120 mg orally three times daily for 14 days can increase levels of the P-glycoprotein substrate, talinolol, by 36% in healthy male individuals. However, single doses of ginkgo do not have the same effect.

Theoretically, taking ginkgo with risperidone might increase the levels and adverse effects of risperidone.
A single case of priapism has been reported for a 26-year-old male with schizophrenia who used risperidone 3 mg daily along with ginkgo extract 160 mg daily. Risperidone is metabolized by cytochrome P450 (CYP) 2D6 and CYP3A4. CYP3A4 activity might be affected by ginkgo. Theoretically, ginkgo may inhibit the metabolism of risperidone and increase the risk of adverse effects.

Theoretically, ginkgo might decrease the levels and clinical effects of rosiglitazone.
Animal research shows that ginkgo leaf extract orally 100 or 200 mg/kg daily for 10 days alters the pharmacodynamics of rosiglitazone in a dose-dependent manner. The 100 mg/kg and 200 mg/kg doses reduce the area under the concentration time curve (AUC) of rosiglitazone by 39% and 52%, respectively, and the half-life by 28% and 39%, respectively. It is hypothesized that these changes may be due to induction of cytochrome P450 2C8 by ginkgo.

Theoretically, taking ginkgo with drugs that lower the seizure threshold might increase the risk for convulsions.
Ginkgo seeds contain ginkgotoxin. Large amounts of ginkgotoxin can cause neurotoxicity and seizure. Ginkgotoxin is present in much larger amounts in ginkgo seeds than leaves. Ginkgo leaf extract contains trace amounts of ginkgotoxin. The amount of ginkgotoxin in ginkgo leaf and leaf extract seems unlikely to cause toxicity. However, there are anecdotal reports of seizure occurring after use of ginkgo leaf both in patients without a history of seizure disorder and in those with previously well-controlled epilepsy.

Theoretically, ginkgo might decrease the levels and clinical effects of simvastatin.
Clinical research shows that taking ginkgo extract can reduce the area under the curve and maximum concentration of simvastatin by 32% to 39%. However, ginkgo extract does not seem to affect the cholesterol-lowering ability of simvastatin.

Theoretically, ginkgo might increase the levels and clinical effects of sofosbuvir.
Animal research in rats shows that giving a ginkgo extract 25 mg/kg orally daily for 14 days increases the area under the concentration time curve (AUC) after a single sofosbuvir dose of 40 mg/kg by 11%, increases the half-life by 60%, and increases the plasma concentration at 4 hours by 38%. This interaction appears to be related to the inhibition of intestinal P-glycoprotein by ginkgo.

Theoretically, ginkgo might increase the blood levels of tacrolimus.
In vitro evidence suggests that certain biflavonoids in ginkgo leaves (i.e. amentoflavone, ginkgetin, bilobetin) may inhibit the metabolism of tacrolimus by up to 50%. This interaction appears to be time-dependent and due to inhibition of cytochrome P450 (CYP) 3A4 by these bioflavonoids. In rats given tacrolimus 1 mg/kg orally, amentoflavone was shown to increase the area under the concentration time curve (AUC) of tacrolimus by 3.8-fold.

Theoretically, ginkgo might increase the levels and clinical effects of trazodone.
In a case report, an Alzheimer patient taking trazodone 20 mg twice daily and ginkgo leaf extract 80 mg twice daily for four doses became comatose. The coma was reversed by administration of flumazenil (Romazicon). Coma might have been induced by excessive GABA-ergic activity. Ginkgo flavonoids are thought to have GABA-ergic activity and act directly on benzodiazepine receptors. Ginkgo might also increase metabolism of trazodone to active GABA-ergic metabolites, possibly by inducing cytochrome P450 3A4 (CYP3A4) metabolism.

Ginkgo has been shown to increase the risk of bleeding in some people when taken with warfarin.
Several pharmacodynamic studies suggest that ginkgo inhibits platelet aggregation. It is thought that the ginkgo constituent, ginkgolide B, displaces platelet-activating factor (PAF) from its binding sites, decreasing blood coagulation. Several case reports have documented serious bleeding events in patients taking ginkgo. Information from a medical database suggests that when taken concurrently with warfarin, ginkgo increases the risk of a bleeding adverse event by 38%. There is also some evidence that ginkgo leaf extract can inhibit cytochrome P450 2C9, an enzyme that metabolizes warfarin. This could result in increased warfarin levels. However, population and clinical research has produced mixed results. Clinical research in healthy people suggests that ginkgo has no effect on INR, or the pharmacokinetics or pharmacodynamics of warfarin. A meta-analysis of 18 studies using standardized ginkgo extracts, 80 mg to 480 mg daily for up to 32 weeks, did not find a significant effect on platelet aggregation, fibrinogen concentration, or PT/aPTT. There is also some preliminary clinical research that suggests ginkgo might not significantly increase the effects of warfarin in patients that have a stable INR.

Theoretically, taking ginkgo with oral, but not intravenous, nifedipine might increase levels and adverse effects of nifedipine.
Animal research and some clinical evidence suggests that taking ginkgo leaf extract orally in combination with oral nifedipine might increase nifedipine levels and cause increased side effects, such as headaches, dizziness, and hot flushes. However, taking ginkgo orally does not seem to affect the pharmacokinetics of intravenous nifedipine.

Theoretically, taking ginkgo with omeprazole might decrease the levels and clinical effects of omeprazole.
Clinical research shows that a specific ginkgo leaf extract (Remembrance, Herbs Product LTD) 140 mg twice daily can induce cytochrome P450 (CYP) 2C19 enzymes and decrease levels of omeprazole by about 27% to 42%.

Theoretically, concomitant use of quercetin and antidiabetes drugs might increase the risk of hypoglycemia.

Clinical research suggests that a combination of quercetin, myricetin, and chlorogenic acid reduce levels of fasting glucose in patients with type 2 diabetes, including those already taking antidiabetes agents. The effect of quercetin alone is unknown.

Theoretically, taking quercetin with antihypertensive drugs might increase the risk of hypotension.

Quercetin can modestly decrease blood pressure in people with mild hypertension. Theoretically, it might have additive blood pressure lowering effects when used with antihypertensive drugs.

Theoretically, concomitant use might increase the levels and adverse effects of cyclosporine.

A small study in healthy volunteers shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of a single dose of cyclosporine, possibly due to inhibition of p-glycoprotein or cytochrome P450 3A4 (CYP3A4), which metabolizes cyclosporin.

Theoretically, concomitant use might increase the levels and adverse effects of CYP2C8 substrates.

In vitro research shows that quercetin inhibits CYP2C8. Inhibition of paclitaxel (Taxol) metabolism via CYP2C8 has been reported in vitro. However, a small study in humans found no effect of quercetin on rosiglitazone (Avandia), which is also a CYP2C8 substrate.

Theoretically, concomitant use might increase the levels and adverse effects of CYP2C9 substrates.

A small clinical study in healthy volunteers shows that taking quercetin 500 mg twice daily for 10 days prior to taking diclofenac, a CYP2C9 substrate, increases diclofenac plasma levels by 75% and prolongs the half-life by 32.5%. Animal research also shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar), a substrate of CYP2C9. Furthermore, laboratory research shows that quercetin inhibits CYP2C9.

Theoretically, concomitant use might increase the levels and adverse effects of CYP2D6 substrates.

In vitro research show that quercetin inhibits CYP2D6. This effect has not been reported in humans.

Theoretically, concomitant use might alter the effects and adverse effects of CYP3A4 substrates.
A small clinical study in healthy volunteers shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of a single dose of cyclosporine (Neoral, Sandimmune), a substrate of CYP3A4. Animal research also shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar) and quetiapine (Seroquel), substrates of CYP3A4. Other laboratory research also shows that quercetin inhibits CYP3A4. However, one clinical study shows that quercetin can increase the metabolism of midazolam, a substrate of CYP3A4, and decrease serum concentrations of midazolam by about 24% in some healthy individuals, suggesting possible induction of CYP3A4.

Theoretically, concomitant use might increase the levels and adverse effects of diclofenac.

A small clinical study in healthy volunteers shows that taking quercetin 500 mg twice daily for 10 days prior to taking diclofenac increases diclofenac plasma levels by 75% and prolongs the half-life by 32.5%. This is thought to be due to inhibition of CYP2C9 by quercetin.

Theoretically, concomitant use might increase the effects and adverse effects of losartan and decrease the effects of its active metabolite.

Animal research shows that pretreatment with quercetin increases plasma levels and prolongs the half-life of losartan (Cozaar) while decreasing plasma levels of losartan's active metabolite. This metabolite, which is around 10-fold more potent than losartan, is the result of cytochrome P450 (CYP) 2C9- and CYP3A4-mediated transformation of losartan. Additionally, in vitro research shows that quercetin may inhibit P-glycoprotein-mediated efflux of losartan from the intestines, resulting in increased absorption of losartan. These results suggest that concomitant use of quercetin and losartan might increase systemic exposure to losartan while also decreasing plasma concentrations of losartan's active and more potent metabolite.

Theoretically, concomitant use might decrease the levels and effects of midazolam.

A small clinical study in healthy volunteers shows that quercetin can increase the metabolism of midazolam, with a decrease in AUC of about 24%.

Theoretically, quercetin might increase the effects and adverse effects of mitoxantrone.
In vitro research shows that quercetin increases the intracellular accumulation and cytotoxicity of mitoxantrone, possibly through inhibition of breast cancer resistance protein (BCRP), of which mitoxantrone is a substrate. So far, this interaction has not been reported in humans.

Theoretically, concomitant use might increase the effects and adverse effects of OAT1 substrates.

In vitro research shows that quercetin is a strong non-competitive inhibitor of OAT1, with half-maximal inhibitory concentration (IC50) values less than 10 mcM. So far, this interaction has not been reported in humans.

Theoretically, concomitant use might increase the effects and adverse effects of OAT3 substrates.

In vitro research shows that quercetin is a strong non-competitive inhibitor of OAT3, with half-maximal inhibitory concentration (IC50) values as low as 0.75 mcM. So far, this interaction has not been reported in humans.

Theoretically, concomitant use might increase the effects and adverse effects of OATP substrates.

In vitro evidence shows that quercetin can inhibit organic anion-transporting peptide (OATP) 1B1-mediated uptake of estrone-3-sulfate and pravastatin. Furthermore, clinical research in healthy males shows that intake of quercetin along with pravastatin increases the AUC of pravastatin by 24%, prolongs its half-life by 14%, and decreases its apparent clearance by 18%, suggesting that quercetin modestly inhibits the uptake of pravastatin in hepatic cells.

Theoretically, concomitant use might alter the effects and adverse effects of P-glycoprotein substrates.

There is preliminary evidence that quercetin inhibits the gastrointestinal P-glycoprotein efflux pump, which might increase the bioavailability and serum levels of drugs transported by the pump. A small study in healthy volunteers reported that pretreatment with quercetin increased bioavailability and plasma levels after a single dose of cyclosporine (Neoral, Sandimmune). Also, two small studies have shown that quercetin might decrease the absorption of talinolol, a substrate transported by the gastrointestinal P-glycoprotein efflux pump. However, in another small study, several days of quercetin treatment did not significantly affect the pharmacokinetics of saquinavir (Invirase). The reason for these discrepancies is not entirely clear. Until more is known, use quercetin cautiously in combination with P-glycoprotein substrates.

Theoretically, concomitant use might increase the effects and adverse effects of pravastatin.
In vitro evidence shows that quercetin can inhibit OATP 1B1-mediated uptake of pravastatin. Also, preliminary clinical research in healthy males shows that intake of quercetin along with pravastatin increases the maximum concentration of pravastatin by 24%, prolongs its half-life by 14%, and decreases its apparent clearance by 18%, suggesting that quercetin modestly inhibits the uptake of pravastatin in hepatic cells.

Theoretically, quercetin might increase the effects and adverse effects of prazosin.
In vitro research shows that quercetin inhibits the transcellular efflux of prazosin, possibly through inhibition of breast cancer resistance protein (BCRP), of which prazosin is a substrate. BCRP is an ATP-binding cassette efflux transporter in the intestines, kidneys, and liver. So far, this interaction has not been reported in humans.

Theoretically, concomitant use might increase the effects and adverse effects of quetiapine.
Animal research shows that pretreatment with quercetin can increase plasma levels of quetiapine and prolong its clearance, possibly due to inhibition of cytochrome P450 3A4 (CYP3A4) by quercetin. Additionally, the brain-to-plasma ratio of quetiapine concentrations increased, possibly due to inhibition of P-glycoprotein at the blood-brain barrier. This interaction has not been reported in humans.

Theoretically, concomitant use might inhibit the effects of quinolone antibiotics.
In vitro, quercetin binds to the DNA gyrase site on bacteria, which may interfere with the activity of quinolone antibiotics.

Theoretically, quercetin might increase the effects and adverse effects of sulfasalazine.
Animal research shows that quercetin increases the maximum serum concentration (Cmax) and area under the curve (AUC) of sulfasalazine, possibly through inhibition of breast cancer resistance protein (BCRP), of which sulfasalazine is a substrate. So far, this interaction has not been reported in humans.

Theoretically, quercetin may increase the risk of bleeding if used with warfarin.
Animal and in vitro studies show that quercetin might increase serum levels of warfarin. Quercetin and warfarin have the same human serum albumin (HSA) binding site, and in vitro research shows that quercetin has stronger affinity for the HSA binding site and can theoretically displace warfarin, causing higher serum levels of warfarin. Animal research shows that taking quercetin for 2 weeks before initiating warfarin increases the maximum serum level of warfarin by 30%, the half-life by 10%, and the overall exposure by 63% when compared with control. Concomitant administration of quercetin and warfarin, without quercetin pre-treatment, also increased these measures, but to a lesser degree. Researchers theorize that inhibition of CYP3A4 by quercetin may explain these effects. So far, this interaction has not been reported in humans.

Turmeric has antioxidant effects. Theoretically, this may reduce the activity of chemotherapy drugs that generate free radicals. However, research is conflicting.
In vitro research suggests that curcumin, a constituent of turmeric, inhibits mechlorethamine-induced apoptosis of breast cancer cells by up to 70%. Also, animal research shows that curcumin inhibits cyclophosphamide-induced tumor regression. However, some in vitro research shows that curcumin does not affect the apoptosis capacity of etoposide. Also, other laboratory research suggests that curcumin might augment the cytotoxic effects of alkylating agents. Reasons for the discrepancies may relate to the dose of curcumin and the specific chemotherapeutic agent. Lower doses of curcumin might have antioxidant effects while higher doses might have pro-oxidant effects. More evidence is needed to determine what effect, if any, turmeric might have on alkylating agents.

Taking turmeric with amlodipine may increase levels of amlodipine.
Animal research shows that giving amlodipine 1 mg/kg as a single dose following the use of turmeric extract 200 mg/kg daily for 2 weeks increases the maximum concentration and area under the curve by 53% and 56%, respectively, when compared with amlodipine alone. Additional animal research shows that taking amlodipine 1 mg/kg with a curcumin 2 mg/kg pretreatment for 10 days increases the maximum concentration and area under the curve by about 2-fold when compared with amlodipine alone.

Turmeric may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs. However, research is conflicting.
Curcumin, a constituent of turmeric, has demonstrated antiplatelet effects in vitro. Furthermore, two case reports have found that taking turmeric along with warfarin or fluindione was associated with an increased international normalized ratio (INR). However, one clinical study in healthy volunteers shows that taking curcumin 500 mg daily for 3 weeks, alone or with aspirin 100 mg, does not increase antiplatelet effects or bleeding risk. It is possible that the dose of turmeric used in this study was too low to produce a notable effect.

Theoretically, taking turmeric with antidiabetes drugs might increase the risk of hypoglycemia.
Animal research and case reports suggest that curcumin, a turmeric constituent, can reduce blood glucose levels in patients with diabetes. Furthermore, clinical research in adults with type 2 diabetes shows that taking curcumin 475 mg daily for 10 days prior to taking glyburide 5 mg decreased postprandial glucose levels for up to 24 hours when compared with glyburide alone, despite the lack of a significant pharmacokinetic interaction. Other clinical studies in patients with diabetes show that taking curcumin daily can reduce blood glucose levels when compared with placebo.

Turmeric has antioxidant effects. Theoretically, this may reduce the activity of chemotherapy drugs that generate free radicals. However, research is conflicting.
In vitro and animal research shows that curcumin, a constituent of turmeric, inhibits doxorubicin-induced apoptosis of breast cancer cells by up to 65%. However, curcumin does not seem to affect the apoptosis capacity of daunorubicin. In fact, some research shows that curcumin might augment the cytotoxic effects of antitumor antibiotics, increasing their effectiveness. Reasons for the discrepancies may relate to the dose of curcumin and the chemotherapeutic agent. Lower doses of curcumin might have antioxidant effects while higher doses might have pro-oxidant effects. More evidence is needed to determine what effects, if any, antioxidants such as turmeric have on antitumor antibiotics.

Turmeric might increase or decrease levels of drugs metabolized by CYP3A4.
In vitro and animal research show that turmeric and its constituents curcumin and curcuminoids inhibit CYP3A4. Also, 8 case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking turmeric and cancer medications that are CYP3A4 substrates, including everolimus, ruxolitinib, ibrutinib, and palbociclib, and bortezomib. In another case report, a transplant patient presented with acute nephrotoxicity and elevated tacrolimus levels after consuming turmeric powder at a dose of 15 or more spoonfuls daily for ten days prior. It was thought that turmeric increased levels of tacrolimus due to CYP3A4 inhibition.
Conversely, other in vitro research suggests that turmeric induces CYP3A4 activity, leading to reduced levels of CYP3A4 substrates. An animal model suggests that induction of CYP3A4 occurs after daily curcumin use for 1 week. However, the induction of CYP3A4 by turmeric has not been reported in humans.

Theoretically, turmeric might increase the risk of liver damage when taken with hepatotoxic drugs.
There is concern that turmeric might cause hepatotoxicity, especially when highly bioavailable formulations are used in high doses.

Theoretically, turmeric might have additive effects when used with hepatotoxic drugs such as methotrexate.
In one case report, a 39-year-old female taking methotrexate, turmeric, and linseed oil developed hepatotoxicity.

Theoretically, turmeric might increase blood levels of OATP4C1 substrates.
In vitro research shows that the turmeric constituent curcumin competitively inhibits OATP4C1 transport. This transporter is expressed in the kidney and facilitates the renal excretion of certain drugs. Theoretically, taking turmeric might decrease renal excretion of OATP substrates.

Turmeric might increase the effects and adverse effects of sulfasalazine.
Clinical research shows that taking the turmeric constituent, curcumin, can increase blood levels of sulfasalazine by 3.2-fold.

Turmeric might increase the effects and adverse effects of tacrolimus.
In one case report, a transplant patient presented with acute nephrotoxicity and elevated tacrolimus levels of 29 ng/mL. The patient previously had tacrolimus levels within the therapeutic range at 9.7 ng/mL. Ten days prior to presenting at the emergency room the patient started consumption of turmeric powder at a dose of 15 or more spoonfuls daily. It was thought that turmeric increased levels of tacrolimus due to cytochrome P450 3A4 (CYP3A4) inhibition. In vitro and animal research show that turmeric and its constituent curcumin inhibit CYP3A4.

Turmeric may reduce the absorption of talinolol in some situations.
Clinical research shows that taking curcumin for 6 days decreases the bioavailability of talinolol when taken together on the seventh day. The clinical significance of this effect is unclear.

Theoretically, turmeric might reduce the levels and clinical effects of tamoxifen.
In a small clinical trial in patients with breast cancer taking tamoxifen 20-30 mg daily, adding curcumin 1200 mg plus piperine 10 mg three times daily reduces the 24-hour area under the curve of tamoxifen and the active metabolite endoxifen by 12.8% and 12.4%, respectively, as well as the maximum concentrations of tamoxifen, when compared with tamoxifen alone. However, in the absence of piperine, the area under the curve for endoxifen and the maximum concentration of tamoxifen were not significantly reduced. Effects were most pronounced in patients who were extensive cytochrome P450 (CYP) 2D6 metabolizers.

Turmeric has antioxidant effects. There is some concern that this may reduce the activity of chemotherapy drugs that generate free radicals. However, research is conflicting.
In vitro research shows that curcumin, a constituent of turmeric, inhibits camptothecin-induced apoptosis of breast cancer cells by up to 71%. However, other in vitro research shows that curcumin augments the cytotoxic effects of camptothecin. Reasons for the discrepancies may relate to the dose of curcumin and the chemotherapeutic agents. Lower doses of curcumin might have antioxidant effects while higher doses might have pro-oxidant effects. More evidence is needed to determine what effect, if any, turmeric might have.

Theoretically, turmeric might increase or decrease levels of tramadol.
Animal research suggests that a single dose of curcumin, a constituent of turmeric, may increase tramadol's maximum concentration (Cmax) by inhibiting metabolism, while continued daily use for 7 days may reduce the area under the curve (AUC) due to the induction of drug-metabolizing enzymes such as cytochrome P450 3A4 (CYP3A4). However, this interaction has not been reported in humans.

Turmeric might increase the risk of bleeding with warfarin.
One case of increased international normalized ratio (INR) has been reported for a patient taking warfarin who began taking turmeric. Prior to taking turmeric, the patient had stable INR measurements. Within a few weeks of starting turmeric supplementation, the patient's INR increased to 10. Additionally, curcumin, the active constituent in turmeric, has demonstrated antiplatelet effects in vitro, which may produce additive effects when taken with warfarin.

Theoretically, turmeric might increase levels of drugs metabolized by CYP1A2. However, research is conflicting.
In vitro and animal research show that the turmeric constituent, curcumin, inhibits CYP1A2. However, other in vitro research suggests that curcumin does not significantly affect CYP1A2.

Theoretically, turmeric might increase blood levels of oral docetaxel.
Animal research suggests that the turmeric constituent, curcumin, enhances the oral bioavailability of docetaxel. However, the significance of this interaction is unclear, as this drug is typically administered intravenously in clinical settings.

Theoretically, large amounts of turmeric might interfere with hormone replacement therapy through competition for estrogen receptors.
In vitro research shows that curcumin, a constituent of turmeric, displaces the binding of estrogen to its receptors.

Theoretically, taking turmeric and glyburide in combination might increase the risk of hypoglycemia.
Clinical research shows that taking curcumin 475 mg daily for 10 days prior to taking glyburide 5 mg increases blood levels of glyburide by 12% at 2 hours after the dose in patients with type 2 diabetes. While maximal blood concentrations of glyburide were not affected, turmeric modestly decreased postprandial glucose levels for up to 24 hours when compared to glyburide alone, possibly due to the hypoglycemic effect of turmeric demonstrated in animal research.

Theoretically, turmeric might increase the effects of losartan.
Research in hypertensive rats shows that taking turmeric can increase the hypotensive effects of losartan.

Theoretically, turmeric might increase the effects and adverse effects of norfloxacin.
Animal research shows that taking curcumin, a turmeric constituent, can increase blood levels of orally administered norfloxacin.

Theoretically, turmeric might increase the absorption of P-glycoprotein substrates.
In vitro and animal research shows that curcuminoids and other constituents found in turmeric can inhibit P-glycoprotein expression and activity.

Theoretically, turmeric might alter blood levels of paclitaxel, although any effect may not be clinically relevant.
Clinical research in adults with breast cancer receiving intravenous paclitaxel suggests that taking turmeric may modestly alter paclitaxel pharmacokinetics. Patients received paclitaxel on day 1, followed by either no treatment or turmeric 2 grams daily from days 2-22. Pharmacokinetic modeling suggests that turmeric reduces the maximum concentration and area under the curve of paclitaxel by 12.1% and 7.7%, respectively. However, these changes are not likely to be considered clinically relevant. Conversely, animal research suggests that curcumin, a constituent of turmeric, enhances the oral bioavailability of paclitaxel. However, the significance of this interaction is unclear, as this drug is typically administered intravenously in clinical settings.

Theoretically, black pepper might increase the risk of bleeding when taken with antiplatelet or anticoagulant drugs.
In vitro research shows that piperine, a constituent of black pepper, seems to inhibit platelet aggregation. This has not been reported in humans.

Theoretically, black pepper might increase the risk of hypoglycemia when taken with antidiabetes drugs.
Animal research shows that piperine, a constituent of black pepper, can reduce blood glucose levels. Monitor blood glucose levels closely. Dose adjustments might be necessary.

Theoretically, black pepper might increase blood levels of atorvastatin.
Animal research shows that taking piperine, a constituent of black pepper, 35 mg/kg can increase the maximum serum concentration of atorvastatin three-fold. This has not been reported in humans.

Theoretically, black pepper might increase the effects and side effects of cyclosporine.
In vitro research shows that piperine, a constituent of black pepper, increases the bioavailability of cyclosporine. This has not been reported in humans.

Theoretically, black pepper might increase levels of drugs metabolized by CYP2D6.
In vitro research suggests that some constituents of black pepper inhibit CYP2D6. This has not been reported in humans.

Theoretically, black pepper might increase levels of drugs metabolized by CYP3A4.
In vitro research and pharmacokinetic simulation data suggest that piperine, a constituent of black pepper, as well as the pepper fruit seem to inhibit CYP3A4. This has not been reported in humans.

Theoretically, black pepper might increase blood levels of lithium due to its diuretic effects. The dose of lithium might need to be reduced.
Black pepper is thought to have diuretic properties.

Black pepper might increase blood levels of nevirapine.
Clinical research shows that piperine, a constituent of black pepper, increases the plasma concentration of nevirapine. However, no adverse effects were observed in this study.

Theoretically, black pepper might increase levels of P-glycoprotein substrates.
In vitro research shows that piperine, a constituent of black pepper, seems to inhibit P-glycoprotein.

Theoretically, black pepper might increase the sedative effects of pentobarbital.
Animal research shows that piperine, a constituent of black pepper, increases pentobarbital-induced sleeping time.

Black pepper might increase blood levels of phenytoin.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption, slow elimination, and increase levels of phenytoin. Taking a single dose of black pepper 1 gram along with phenytoin seems to double the serum concentration of phenytoin. Consuming a soup with black pepper providing piperine 44 mg/200 mL of soup along with phenytoin also seems to increase phenytoin levels when compared with consuming the same soup without black pepper.

Black pepper might increase blood levels of propranolol.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of propranolol.

Black pepper might increase blood levels of rifampin.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and serum levels of rifampin.

Black pepper might increase blood levels of theophylline.
Clinical research shows that piperine, a constituent of black pepper, seems to increase absorption and slow elimination of theophylline.

Theoretically, black pepper might increase the effects and side effects of amoxicillin.
Animal research shows that taking piperine, a constituent of black pepper, with amoxicillin increases plasma levels of amoxicillin. This has not been reported in humans.

Theoretically, black pepper might increase blood levels of carbamazepine, potentially increasing the effects and side effects of carbamazepine.
One clinical study in patients taking carbamazepine 300 mg or 500 mg twice daily shows that taking a single 20 mg dose of purified piperine, a constituent of black pepper, increases carbamazepine levels. Piperine may increase carbamazepine absorption by increasing blood flow to the GI tract, increasing the surface area of the small intestine, or inhibiting cytochrome P450 3A4 (CYP3A4) in the gut wall. Absorption was significantly increased by 7-10 mcg/mL/hour. The time to eliminate carbamazepine was also increased by 4-8 hours. Although carbamazepine levels were increased, this did not appear to increase side effects. In vitro research also shows that piperine can increase carbamazepine levels by 11% in a time-dependent manner.

Theoretically, black pepper might decrease levels and clinical effects of drugs metabolized by CYP1A2.
In vitro research suggests that black pepper induces CYP1A2. This has not been reported in humans.

Ginger may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs. However, research is conflicting.
Laboratory research suggests that ginger inhibits thromboxane synthetase and decreases platelet aggregation. However, this has not been demonstrated unequivocally in humans, with mixed results from clinical trials. Theoretically, excessive amounts of ginger might increase the risk of bleeding when used with anticoagulant/antiplatelet drugs.

Theoretically, taking ginger with antidiabetes drugs might increase the risk of hypoglycemia.
Animal and human research suggests that ginger might increase insulin levels and/or decrease blood glucose levels.

Ginger might increase or decrease the levels of CYP3A4 substrates.
In vitro research and some case reports suggest that ginger inhibits CYP3A4 activity. Three case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking ginger and cancer medications that are CYP3A4 substrates (imatinib, dabrafenib, and crizotinib). However, the causality of this interaction is unclear due to the presence of multiple interacting drugs and routes of administration.
Conversely, other in vitro research suggests that ginger induces CYP3A4 activity, leading to reduced levels of CYP3A4 substrates. However, this interaction has not been reported in humans.

Theoretically, ginger might increase levels of losartan and the risk of hypotension.
In animal research, ginger increased the levels and hypotensive effects of a single dose of losartan. It is not clear if ginger alters the concentration or effects of losartan when taken continuously. Additionally, this interaction has not been shown in humans.

Ginger may have antiplatelet effects and increase the risk of bleeding if used with nifedipine.
Clinical research shows that combined treatment with ginger 1 gram plus nifedipine 10 mg significantly inhibits platelet aggregation when compared to nifedipine or ginger alone.

Ginger might increase the absorption and blood levels of P-glycoprotein (P-gp) substrates.
In vitro research and case reports suggest that ginger inhibits drug efflux by P-gp, potentially increasing absorption and serum levels of P-gp substrates. Two case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking ginger and cancer medications that are P-gp substrates (trametinib, crizotinib). However, the causality of this interaction is unclear due to the presence of multiple interacting drugs and routes of administration.

Ginger might increase the risk of bleeding with phenprocoumon.
Phenprocoumon, a warfarin-related anticoagulant, might increase the international normalized ratio (INR) when taken with ginger. There is one case report of a 76-year-old woman with a stable INR on phenprocoumon that increased to greater than 10 when she began consuming dried ginger and ginger tea.

Ginger might increase the risk of bleeding with warfarin.
Laboratory research suggests that ginger might inhibit thromboxane synthetase and decrease platelet aggregation. In one case report, ginger increased the INR when taken with phenprocoumon, which has similar pharmacological effects as warfarin. In another case report, ginger increased the INR when taken with a combination of warfarin, hydrochlorothiazide, and acetaminophen. A longitudinal analysis suggests that taking ginger increases the risk of bleeding in patients taking warfarin for at least 4 months. However, research in healthy people suggests that ginger has no effect on INR, or the pharmacokinetics or pharmacodynamics of warfarin. Until more is known, monitor INRs closely in patients taking large amounts of ginger.

Theoretically, taking ginger with calcium channel blockers might increase the risk of hypotension.
Some animal and in vitro research suggests that ginger has hypotensive and calcium channel-blocking effects. Another animal study shows that concomitant administration of ginger and the calcium channel blocker amlodipine leads to greater reductions in blood pressure when compared with amlodipine alone.

Theoretically, when taken prior to cyclosporine, ginger might decrease cyclosporine levels.
In an animal model, ginger juice taken 2 hours prior to cyclosporine administration reduced the maximum concentration and area under the curve of cyclosporine by 51% and 40%, respectively. This effect was not observed when ginger juice and cyclosporine were administered at the same time.

Theoretically, ginger might increase the levels of CYP1A2 substrates.
In vitro research shows that ginger inhibits CYP1A2 activity. However, this interaction has not been reported in humans.

Theoretically, ginger might increase the levels of CYP2B6 substrates.
In vitro research shows that ginger inhibits CYP2B6 activity. However, this interaction has not been reported in humans.

Theoretically, ginger might increase the levels of CYP2C9 substrates.
In vitro research shows that ginger inhibits CYP2C9 activity. However, this interaction has not been reported in humans.

Theoretically, ginger might increase levels of metronidazole.
In an animal model, ginger increased the absorption and plasma half-life of metronidazole. In addition, the elimination rate and clearance of metronidazole was significantly reduced.

Theoretically, concomitant use of clove extracts with antidiabetes drugs might increase the risk of hypoglycemia.
Clinical and laboratory research suggest that polyphenol extracts from clove flower buds might lower blood glucose levels. Dosing adjustments for insulin or oral hypoglycemic agents may be necessary when taken with clove. Monitor blood glucose levels closely.

Theoretically, concomitant use of clove may increase levels of drugs metabolized by CYP1A2.
In vitro research shows that eugenol, the principal constituent of clove, can inhibit CYP1A2 in a dose-dependent manner,. This effect has not been reported in humans.

Theoretically, concomitant use of clove may increase levels of drugs metabolized by CYP2C9.
In vitro research shows that eugenol, the principal constituent of clove, inhibits CYP2C9 in a dose-dependent manner. This effect has not been reported in humans.

Theoretically, concomitant use of clove may increase levels of drugs metabolized by CYP2D6.
In vitro research shows that eugenol, the principal constituent of clove, can inhibit CYP2D6 in a dose-dependent manner. This effect has not been reported in humans.

Theoretically, concomitant use of clove may increase levels of drugs metabolized by CYP3A4.
In vitro research shows that eugenol, the principal constituent of clove, can inhibit CYP3A4 in a dose-dependent manner. This effect has not been reported in humans.

Theoretically, clove oil may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Laboratory research suggests that eugenol, a constituent of clove, has antiplatelet activity. This interaction has not been reported in humans.

Theoretically, topical application of clove oil with ibuprofen might increase the absorption and side effects of topical ibuprofen.
Laboratory research shows that topical application of clove oil increases the absorption of topical ibuprofen. This interaction has not been reported in humans.

Taking milk thistle with antidiabetes drugs may increase the risk of hypoglycemia.
Clinical research shows that milk thistle extract, alone or along with tree turmeric extract, can lower blood glucose levels and glycated hemoglobin (HbA1c) in patients with type 2 diabetes, including those already taking antidiabetes drugs. Additionally, animal research shows that milk thistle extract increases the metformin maximum plasma concentration and area under the curve and decreases the renal clearance of metformin, due to inhibition of the multi-drug and toxin extrusion protein 1 (MATE1) renal tubular transport protein.

Theoretically, milk thistle might inhibit CYP2B6.
An in vitro study shows that silybin, a constituent of milk thistle, binds to and noncompetitively inhibits CYP2B6. Additionally, silybin might downregulate the expression of CYP2B6 by decreasing mRNA and protein levels.

Theoretically, milk thistle might affect the clearance of drugs that undergo glucuronidation.
Laboratory research shows that milk thistle constituents inhibit uridine diphosphoglucuronosyl transferase (UGT), the major phase 2 enzyme that is responsible for glucuronidation. Theoretically, this could decrease the clearance and increase levels of glucuronidated drugs. Other laboratory research suggests that a milk thistle extract of silymarin might inhibit beta-glucuronidase, although the significance of this effect is unclear.

Theoretically, milk thistle might increase the levels and clinical effects of ledipasvir.
Animal research in rats shows that milk thistle increases the area under the curve (AUC) for ledipasvir and slows its elimination.

Theoretically, concomitant use of milk thistle with morphine might affect serum levels of morphine and either increase or decrease its effects.
Animal research shows that milk thistle reduces serum levels of morphine by up to 66%. In contrast, laboratory research shows that milk thistle constituents inhibit uridine diphosphoglucuronosyl transferase (UGT), the major phase 2 enzyme that is responsible for glucuronidation. Theoretically, this could decrease the clearance and increase morphine levels. The effect of taking milk thistle on morphine metabolism in humans is not known.

Theoretically, milk thistle might decrease the clearance and increase levels of raloxifene.
Laboratory research suggests that the milk thistle constituents silibinin and silymarin inhibit the glucuronidation of raloxifene in the intestines.

Milk thistle might decrease the clearance of sirolimus.
Pharmacokinetic research shows that a milk thistle extract of silymarin decreases the apparent clearance of sirolimus in hepatically impaired renal transplant patients. It is unclear if this interaction occurs in patients without hepatic impairment.

Theoretically, milk thistle might decrease the levels and clinical effects of sofosbuvir.
Animal research in rats shows that milk thistle reduces the metabolism of sofosbuvir, as well as the hepatic uptake of its active metabolite.

Theoretically, the milk thistle constituent silibinin might increase tamoxifen levels and interfere with its conversion to an active metabolite.
Animal research suggests that the milk thistle constituent silibinin might increase plasma levels of tamoxifen and alter its conversion to an active metabolite. The mechanism appears to involve inhibition of pre-systemic metabolism of tamoxifen by cytochrome P450 (CYP) 2C9 and CYP3A4, and inhibition of P-glycoprotein-mediated efflux of tamoxifen into the intestine for excretion. Whether this interaction occurs in humans is not known.

Theoretically, milk thistle might increase the effects of warfarin.
In one case report, a man stabilized on warfarin experienced an increase in INR from 2.64 to 4.12 after taking a combination product containing milk thistle 200 mg daily, as well as dandelion, wild yam, niacinamide, and vitamin B12. Levels returned to normal after stopping the supplement. Although a direct correlation between milk thistle and the change in INR cannot be confirmed, some in vitro research suggests that milk thistle might inhibit cytochrome P450 2C9 (CYP2C9), an enzyme involved in the metabolism of various drugs, including warfarin.

It is unclear if milk thistle inhibits CYP2C9; research is conflicting.
In vitro research suggests that milk thistle might inhibit CYP2C9. Additionally, 3 case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking milk thistle and cancer medications that are CYP2C9 substrates, including imatinib and capecitabine. However, contradictory clinical research shows that milk thistle extract does not inhibit CYP2C9 or significantly affect levels of the CYP2C9 substrate tolbutamide. Differences in results could be due to differences in dosages or formulations utilized.

It is unclear if milk thistle inhibits CYP3A4; research is conflicting.
While laboratory research shows conflicting results, pharmacokinetic research shows that taking milk thistle extract 420-1350 mg daily does not significantly affect the metabolism of the CYP3A4 substrates irinotecan, midazolam, or indinavir. However, 8 case reports from the World Health Organization (WHO) adverse drug reaction database describe increased toxicity in patients taking milk thistle and cancer medications that are CYP3A4 substrates, including gefitinib, sorafenib, doxorubicin, and vincristine.

Theoretically, milk thistle might interfere with estrogen therapy through competition for estrogen receptors.
Animal research suggests that a milk thistle extract of silymarin binds to estrogen receptor beta.

Theoretically, milk thistle might interfere with statin therapy by decreasing the activity of organic anion transporting polypeptide 1B1 (OATB1B1) and inhibiting breast cancer resistance protein (BCRP).
Preliminary evidence suggests that a milk thistle extract of silymarin can decrease the activity of the OATP1B1, which transports HMG-CoA reductase inhibitors into the liver to their site of action, and animal research shows this increases the maximum plasma concentration of pitavastatin and pravastatin. The silibinin component also inhibits BCRP, which transports statins from the liver into the bile for excretion. However, in a preliminary study in healthy males, silymarin 140 mg three times daily had no effect on the pharmacokinetics of a single 10 mg dose of rosuvastatin.