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Dietary supplement

Selenium Xtra 200 mcg Ingredients & Drug Interactions

by Sundown Naturals

Selenium Xtra 200 mcg label
See full label image
Tablet Or Pill Category: Other Combinations
Most serious interaction: Major
Clinical methodology reviewed by · Updated Sep 16, 2026 · Label data from the NIH DSLD
What is this page for?

First and foremost: checking Selenium Xtra 200 mcg against your medications. The heart of this page is the interaction checker and the full interaction report — how this product’s ingredients may interact with prescription and over-the-counter medicines you may be taking.

Around that, we add a pharmacist’s high-level view of the product as a whole — what’s inside, the evidence for its stated use, how transparent the label is, and what safety data exists — so you can see the full picture in one place. It’s educational information from our licensed clinical databases and the clinical staff at HelloPharmacist — not medical advice — and we don’t sell or endorse products. Our editorial policy

The interaction bottom line Most serious interaction: Major

Selenium Xtra 200 mcg is a dietary supplement by Sundown Naturals with 3 active ingredients. Its ingredients are commonly taken for thyroid health support, antioxidant support, immune support.Based on those ingredients, 1,443 medications have a known interaction with it, the most serious rated major. The ingredients most likely to interact are Bioflavonoid Complex (Non-Nutrient/Non-Botanical), Selenium, Vitamin C. Use the checker below to test your specific medication, or read the full HelloPharmacist Interaction Report.

Jump to a section

Check Your Meds Against Selenium Xtra 200 mcg by Sundown Naturals

Ask about any prescription or over-the-counter medication and we check it for interactions with Selenium Xtra 200 mcg by Sundown Naturals — and tell you which ingredient is responsible.

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HelloPharmacist Scorecard of Selenium Xtra 200 mcg by Sundown Naturals

Our pharmacy team’s full take, with four database checks built into the cards below — a summary of what is known, not a grade of the product itself.

From our pharmacy team — supplement deep dive

Generated from HelloPharmacist’s pharmacist-curated databases and editorial rules · Last generated Sep 10, 2026

What’s inside

Low disclosure
Ingredient Transparency · database check
Low

Most active ingredients don't disclose an individual amount — you can't tell how much of each you're getting.

Why this rating?
  • The label discloses an exact amount for 2 of its 5 active ingredients.
  • “Bioflavonoid Complex (Non-Nutrient/Non-Botanical)” is a proprietary blend — the label gives one combined amount (398 mg) without saying how much of each component you get.

Selenium Xtra contains 5 active ingredients. The two forms of selenium—mineral selenium and selenium yeast—are the main actives; selenium supports thyroid function and acts as an antioxidant.

Vitamin C (ascorbic acid) aids immune function and collagen formation. Citrus bioflavonoids are plant compounds with antioxidant properties.

Brewer's yeast is a debittered form (mostly flavor removed) that contains B vitamins and may support digestive health. The tablet also contains inactive ingredients: whey and vegetable magnesium stearate (a flow agent).

Does it work?

Strong evidence
Evidence for Intended Use · database check
By FDA rules, dietary supplements can’t claim to treat, cure, or prevent disease — so labels speak in careful marketing language. We discern each product’s intended use from its name, label claims, and label statements, then grade the clinical evidence for that use. How these ratings are computed

This product doesn't appear to be marketed for a specific use, so we graded its ingredients' overall clinical evidence instead.

Strong

Strong clinical evidence supports its ingredients for:

Why this rating?
  • We looked at the product name, claims, and label statements and couldn't find a stated purpose to grade.
  • Since the label doesn't commit to one use, we graded the ingredients' overall clinical evidence instead.
  • On file: Vitamin C deficiency — rated "Effective" (Vitamin C) (Natural Medicines).
  • On file: Selenium deficiency — rated "Likely Effective" (Selenium) (Natural Medicines).
  • On file: Anemia of chronic disease — rated "Possibly Effective" (Vitamin C) (Natural Medicines).
  • On file: Atrial fibrillation — rated "Possibly Effective" (Vitamin C) (Natural Medicines).
  • On file: Cataracts — rated "Possibly Effective" (Vitamin C) (Natural Medicines).

Selenium is likely effective for selenium deficiency and possibly effective for Kashin-Beck disease (a joint and bone condition), pre-eclampsia (high blood pressure in pregnancy), and autoimmune thyroiditis, though it appears ineffective for dyslipidemia (abnormal blood lipid levels). Vitamin C is effective for vitamin C deficiency and possibly effective for anemia of chronic disease, atrial fibrillation, cataracts, and exercise-related respiratory infections.

Citrus bioflavonoids show insufficient reliable evidence for most conditions we have data on—including athletic performance, cognitive decline, hay fever, and asthma—so we cannot confirm they work for these uses. Brewer's yeast is possibly effective for irritable bowel syndrome but insufficient evidence exists for influenza prevention or cholesterol reduction.

The evidence, ingredient by ingredient Selenium Vitamin C Quercetin Brewer's Yeast

How safe is it?

Well-documented data
Safety Information · database check
Well characterized

Adverse-effect, pregnancy, and general safety data are on file for most of these ingredients.

Why this rating?
  • We hold adverse-effect (side-effect) data for 4 of the 4 matched ingredients.
  • Pregnancy & breastfeeding safety ratings cover 4 of 4.
  • General safety write-ups exist for 4 of 4.
  • Remember: this measures how much safety information exists. Thin data is not the same as being safe.

Selenium at 200 mcg daily falls within the tolerable upper limit of 400 mcg daily and is generally well tolerated, though gastric discomfort, headache, and rash can occur at recommended doses. Excess selenium is toxic and can cause hair loss, nail damage, fatigue, and at very high levels, organ failure.

Vitamin C at supplement doses is well tolerated orally; side effects like stomach cramps, heartburn, and diarrhea are more likely above 2 grams daily. Citrus bioflavonoids (quercetin) are generally well tolerated at typical amounts, though high-dose safety is not well studied.

Brewer's yeast commonly causes gas and may trigger migraine-like headaches in sensitive people; rarely, anaphylaxis is possible. The safety data for citrus bioflavonoids during pregnancy and breastfeeding shows not enough information exists—avoid supplemental doses and check with your doctor or pharmacist.

Side effects, ingredient by ingredient Selenium Vitamin C Quercetin Brewer's Yeast

Meds to double-check

Major interaction found
Known Interaction Concern · database check
Major identified

At least one ingredient has a documented Major-severity interaction. Check your medications for a personalized result.

Why this rating?
  • 4 of the 4 matched ingredients can interact with medications — Quercetin, Brewer's Yeast, Vitamin C, Selenium.
  • The most serious interaction on file is rated Major.
  • Some involve high-stakes drug classes: anticoagulant / antiplatelet drugs; immunosuppressants / transplant drugs; cancer treatments; diabetes medications; lithium.
  • For scale: 1,444 individual medications appear in the full list. A big number alone doesn't make a product dangerous — what matters is whether YOUR medication is on it, so run yours through the interaction checker on this page.

Before taking this product, check with your doctor or pharmacist if you take monoamine oxidase inhibitors (a Major-severity risk for dangerous blood pressure spike from brewer's yeast). Also double-check Moderate-severity interactions: blood thinners or antiplatelet drugs like warfarin, immunosuppressants, barbiturate sedatives, chemotherapy drugs (alkylating agents and antitumor antibiotics), statin cholesterol medications, blood pressure drugs like losartan, cyclosporine, sulfasalazine, mitoxantrone, quinolone antibiotics, aluminum supplements, levothyroxine (thyroid medication), the antipsychotic fluphenazine, and the antiviral indinavir.

Diabetes medications also require review due to brewer's yeast's potential to lower blood sugar.

Check your own medication Run your meds through the checker above

The bottom line

Scorecard at a glanceFormula with limited ingredient disclosure with strong clinical evidence behind its ingredients' uses. Major medication interactions have been identified, and safety information is well characterized.

This product may help if you have a selenium deficiency or are looking to support thyroid and antioxidant health, though the full benefit of all ingredients is not established. If you take any blood thinners, diabetes medications, MAOIs (older antidepressants), immunosuppressants, chemotherapy, or thyroid medication, you need to check your specific drugs against the interaction tool below before starting.

Talk with your doctor or pharmacist about whether this supplement fits your medication regimen and health needs.

Educational only — not medical advice; always confirm with your pharmacist. Our editorial policy · How we use AI

Assessment coverage: 5 of 5 active ingredients matched to our full ingredient reviews (monographs). Based on the product label dated Feb 23, 2012.

This Scorecard evaluates available label information, ingredient evidence, and known medication-safety considerations. It does not independently verify product identity, purity, potency, contamination, or manufacturing quality. How these ratings are computed

At a glance

General information

Key facts about Selenium Xtra 200 mcg, straight from the product label.

Brand Sundown Naturals
Barcode (UPC) 030768008840
Net contents 60 Tablet(s)
Market status On market
Date entered into DSLD Feb 23, 2012
DSLD ID 5848
Product type Other Combinations
Supplement form Tablet Or Pill
Dietary claims / uses All Other, Qualified Health, Structure/Function
Intended target group(s) Vegetarian, Women (not pregnant or lactating), Adult Male (18-50 Years)
From the label
Everything in this section is reproduced from the manufacturer’s own product label — it’s the label speaking, not HelloPharmacist. We show it so you can see exactly what the maker states; we don’t verify or endorse those statements.

Supplement Facts

The label details for Selenium Xtra 200 mcg by Sundown Naturals, sourced from the NIH Dietary Supplement Label Database.

Supplement Facts

Daily Value (DV) Target Group(s):
Adults and children 4 or more years of age
Minimum serving Sizes:
1 Tablet(s)
Maximum serving Sizes:
1 Tablet(s)
UPC/BARCODE
030768008840
IngredientAmount% DV
Selenium200 mcg286%
Vitamin C60 mg100%
Citrus Bioflavonoids0 NP--
Selenium Yeast0 NP--
Bioflavonoid Complex (Non-Nutrient/Non-Botanical)398 mg--
Brewer’s Yeast Debittered0 NP--

Other ingredients: Whey, Vegetable Magnesium Stearate

Tap any ingredient to jump to its full detail below.

Label statements
These statements are the manufacturer’s wording, reproduced from the product label — the label is saying it, not HelloPharmacist. We don’t verify or endorse them.
FDA Statement of Identity

DIETARY SUPPLEMENT

Suggested/Recommended/Usage/Directions

DIRECTIONS: FOR ADULTS, TAKE ONE (1) TABLET PER DAY, PREFERABLY WITH A MEAL. As a reminder, discuss the supplements and medications you take with your health care providers.

Precautions

KEEP OUT OF REACH OF CHILDREN.

WARNING: Not intended for use by pregnant or nursing women.

Avoid this product if you are allergic to yeast.

Contains milk and wheat ingredients.

Discontinue use and consult your doctor if any adverse reactions occur.

If you are taking any medications, consult your doctor before use.

TAMPER RESISTANT: DO NOT USE IF SEAL UNDER CAP IS BROKEN OR MISSING.

FDA Disclaimer Statement

*This statement has not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease.

Storage

STORE IN A DRY PLACE AND AVOID EXCESSIVE HEAT.

Formula

HIGH SELENIUM YEAST

General

Prod. No. 44629 03D B44629 EAZ

General Statements

Clinically Studied Dosage

Smart Facts Selenium is an essential mineral important for life.* Some scientific evidence suggests that consumption of selenium may reduce the risk of certain forms of cancer. However, the FDA has determined that this evidence is limited and not conclusive. Vitamin C and Bioflavonoids round out this premium formula.

Brand IP Statement(s)

2010

Formulation

VEGETARIAN FORMULA

No Artificial Color, Flavor or Sweetener, No Preservatives, No Sugar, No Starch, No Soy, No Fish.

Sodium Free.

Seals/Symbols

GUARANTEED QUALITY LABORATORY TESTED

PLEASE RECYCLE

Is this label outdated? Report a formula or label change and our pharmacy team will review it.

See for yourself

Selenium Xtra 200 mcg by Sundown Naturals label

The label scan from the NIH Dietary Supplement Label Database. Tap to enlarge.

Selenium Xtra 200 mcg label

Label images are published by the NIH Dietary Supplement Label Database for the version of this product on file. Always read your actual product label.

View the full label (PDF)
What’s inside

The Ingredients in Selenium Xtra 200 mcg by Sundown Naturals

These are the 3 active ingredients this product is made of. Select any to open its full monograph.

Serving size1 Tablet(s) Dosage formTablet Or Pill Amounts shown are per serving.

Most supplement products combine several ingredients, and a medication can interact with the product through any one of them. Each ingredient below shows whether it has known drug interactions.

Selenium

Interacts with
321 drugs
200 mcg per serving Form: Selenium Yeast

Selenium is an essential trace mineral your body needs in small amounts for thyroid function, antioxidant defense, and immune health. Most people who...

Selenium monograph & interactions

Vitamin C

Interacts with
207 drugs
60 mg per serving Form: Ascorbic Acid

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for im...

Vitamin C monograph & interactions

Bioflavonoid Complex (Non-Nutrient/Non-Botanical)

Interacts with
1,169 drugs
398 mg per serving

Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties found in many common foods and sold as a supplement. While early rese...

Bioflavonoid Complex (Non-Nutrient/Non-Botanical) monograph & interactions

Other (inactive) ingredients: Whey, Vegetable Magnesium Stearate. These complete the product’s ingredient list but are not active constituents.

Interaction report

Selenium Xtra 200 mcg by Sundown Naturals Drug Interactions

Want to check YOUR meds against Selenium Xtra 200 mcg?

Ask about interactions with your drugs in plain English — “Can I take it with lisinopril?” — and we find you the answer in seconds, ingredient by ingredient.

 Go to the checker
1,443Drugs
9 Major 1,370 Moderate 64 Minor

Ingredients driving the most interactions

Bioflavonoid Complex (Non-Nutrient/Non-Botanical) 1,169
Selenium 321
Vitamin C 207

Individual Drug Interactions

The ingredients in Selenium Xtra 200 mcg interact with 1,443 drugs. Click any drug to see the details.

3 of the 3 ingredients in Selenium Xtra 200 mcg interact with drugs. Each result below shows which ingredient is responsible. Bioflavonoid Complex (Non-Nutrient/Non-Botanical) Selenium Vitamin C

Each ingredient & the kinds of drugs it affects

For each ingredient in Selenium Xtra 200 mcg with known interactions, here are the types of medications they can affect. Open any type for the detail — or search your exact drug in the checker above.

Bioflavonoid Complex (Non-Nutrient/Non-Botanical)21 drug types · 1,169 drugs

Antidiabetes Drugs

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.

Likelihood Possible Evidence B
Antihypertensive Drugs

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.

Likelihood Possible Evidence B
Cyclosporine (Neoral, Sandimmune)

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.

Likelihood Possible Evidence B
Cytochrome P450 2C8 (Cyp2C8) Substrates

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.

Likelihood Possible Evidence D
Cytochrome P450 2C9 (Cyp2C9) Substrates

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.

Likelihood Possible Evidence B
Cytochrome P450 2D6 (Cyp2D6) Substrates

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.

Likelihood Possible Evidence D
Cytochrome P450 3A4 (Cyp3A4) Substrates

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.

Likelihood Possible Evidence D
Diclofenac (Voltaren, Others)

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.

Likelihood Probable Evidence B
Losartan (Cozaar)

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.

Likelihood Possible Evidence D
Midazolam (Versed)

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%.

Likelihood Possible Evidence B
Mitoxantrone

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.

Likelihood Possible Evidence D
Organic Anion Transporter 1 (Oat1) Substrates

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.

Likelihood Possible Evidence D
Organic Anion Transporter 3 (Oat3) Substrates

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.

Likelihood Possible Evidence D
Organic Anion-Transporting Polypeptide Substrates (Oatp)

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.

Likelihood Possible Evidence B
P-Glycoprotein Substrates

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.

Likelihood Possible Evidence B
Pravastatin (Pravachol)

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.

Likelihood Possible Evidence B
Prazosin (Minipress)

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.

Likelihood Possible Evidence D
Quetiapine (Seroquel)

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.

Likelihood Possible Evidence D
Quinolone Antibiotics

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.

Likelihood Possible Evidence B
Sulfasalazine (Azulfidine)

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.

Likelihood Possible Evidence D
Warfarin (Coumadin)

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.

Likelihood Possible Evidence D
Bioflavonoid Complex (Non-Nutrient/Non-Botanical) full monograph & interactions

Selenium6 drug types · 321 drugs

Anticoagulant/Antiplatelet Drugs

Selenium may have antiplatelet effects and may increase the risk of bleeding if used with anticoagulant or antiplatelet drugs.
Clinical research suggests that taking selenium 10 mcg/kg/day can increase bleeding times by increasing prostacyclin production, which inhibits platelet activity. Other clinical research suggests that taking selenium 75 mcg daily, in combination with ascorbic acid 600 mg, alpha-tocopherol 300 mg, and beta-carotene 27 mg, reduces platelet aggregation.

Likelihood Possible Evidence D
Barbiturates

Theoretically, selenium might prolong the sedating effects of barbiturates.
Laboratory research suggests that selenium can inhibit the hepatic metabolism of barbiturates. Selenium seems to prolong the sedative effect of pentobarbital in animal models.

Likelihood Possible Evidence D
Immunosuppressants

Theoretically, selenium supplementation may reduce the effectiveness of immunosuppressant therapy.
In vitro research and preliminary clinical evidence suggests that selenium may stimulate the immune system.

Likelihood Possible Evidence D
Warfarin (Coumadin)

Theoretically, selenium might interfere with warfarin activity.
Animal research suggests that selenium can increase warfarin activity. Selenium might interact with warfarin by displacing it from albumin binding sites, reducing its metabolism in the liver, or by decreasing production of vitamin K-dependent clotting factors. Selenium can also prolong bleeding times in humans by increasing prostacyclin production, which inhibits platelet activity.

Likelihood Possible Evidence D
Contraceptive Drugs

Contraceptive drugs might increase levels of selenium, although the clinical significance of this effect is unclear.
Some research suggests that oral contraceptives increase serum selenium levels in women taking oral contraceptives; however, other research shows no change in selenium levels. It is suggested that an increase could be due to increased carrier proteins, indicating a redistribution of selenium rather than a change in total body selenium.

Likelihood Possible Evidence B
Niacin

Selenium might reduce the beneficial effects of niacin on high-density lipoprotein (HDL) 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 selenium, or to the combination. It also is not known whether it will occur in other patient populations.

Likelihood Possible Evidence A
Selenium full monograph & interactions

Vitamin C13 drug types · 207 drugs

Alkylating Agents

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.

Likelihood Possible Evidence D
Aluminum

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.

Likelihood Probable Evidence B
Antitumor Antibiotics

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.

Likelihood Possible Evidence D
Estrogens

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.

Likelihood Probable Evidence B
Fluphenazine (Prolixin)

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.

Likelihood Possible Evidence D
Indinavir (Crixivan)

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.

Likelihood Probable Evidence B
Levothyroxine (Synthroid, Others)

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.

Likelihood Probable Evidence B
Warfarin (Coumadin)

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.

Likelihood Possible Evidence D
Acetaminophen (Tylenol, Others)

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.

Likelihood Probable Evidence B
Aspirin

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.

Likelihood Possible Evidence B
Choline Magnesium Trisalicylate (Trilisate)

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.

Likelihood Possible Evidence B
Niacin

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.

Likelihood Possible Evidence A
Salsalate (Disalcid)

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.

Likelihood Possible Evidence B
Vitamin C full monograph & interactions
The maker

Brand information

Manufacturer and brand details for Selenium Xtra 200 mcg, from the product label.

Sundown Naturals

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Web Address
www.sundownnaturals.com
Pharmacist Counseling Corner

Selenium Xtra 200 mcg by Sundown Naturals: Common Questions

Does Selenium Xtra 200 mcg by Sundown Naturals interact with any medications?
Yes. Based on its ingredients, Selenium Xtra 200 mcg has a known interaction with 1,443 medications, including 9 rated major. Use the checker to see how it interacts with a specific drug.
How can one product interact with so many drugs?
Selenium Xtra 200 mcg contains 3 active ingredients, and an interaction can come from any of them. We check every ingredient, combine the results into one list per medication, and show which ingredient and mechanism is responsible.
Where does this information come from?
The product label data comes from the NIH Dietary Supplement Label Database (DSLD); the interaction data is built on the Natural Medicines database and reviewed by HelloPharmacist pharmacists.
Is this safe to take if I'm on blood thinners like warfarin?
No—not without checking first. Both the selenium and vitamin C in this product can interfere with warfarin's effectiveness and increase bleeding risk. Talk to your doctor or pharmacist before starting; they may need to adjust your dose or monitor you more closely.
Can I take this if I'm on an older antidepressant like phenelzine (Nardil)?
You need to check with your doctor first. The brewer's yeast in this product contains tyramine, which can cause a dangerous spike in blood pressure when mixed with MAOIs. This is a serious interaction, so do not start without clearance from your healthcare provider.
Will this help with thyroid health?
Selenium is possibly effective for autoimmune thyroiditis, an autoimmune condition affecting the thyroid. However, vitamin C in this product can also increase how much levothyroxine (thyroid medication) your body absorbs, so if you take thyroid medication, discuss this with your doctor or pharmacist before starting.
What are the most common side effects?
At the recommended 200 mcg selenium dose, gastric discomfort, headache, and rash can happen. Brewer's yeast commonly causes gas and may trigger migraine-like headaches in sensitive people. Vitamin C at these levels rarely causes side effects, but stomach upset and diarrhea are possible at higher doses.
Is it safe during pregnancy?
Selenium is rated possibly safe and possibly unsafe during pregnancy—the data is mixed. Vitamin C is likely safe in normal amounts, though the facts advise against high-dose supplements in pregnancy. Citrus bioflavonoids have insufficient safety information, so avoid supplemental doses. Talk with your doctor or pharmacist about whether this product is right for you during pregnancy.
What if I'm diabetic and on blood sugar medication?
Brewer's yeast in this product may lower blood sugar when combined with diabetes drugs, raising the risk of low blood sugar (hypoglycemia). Check with your doctor or pharmacist before taking it; they may want to monitor your blood sugar more closely.

Written and reviewed by the HelloPharmacist editorial staff. Our editorial policy

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Selenium Xtra 200 mcg label
Go deeper

The Full Monographs Behind Selenium Xtra 200 mcg’s Ingredients

Every ingredient we hold a full HelloPharmacist monograph for — uses, evidence, safety, and the complete interaction list.

Herb & supplement monograph

Selenium

Interacts with 321 drugs

Selenium is an essential trace mineral your body needs in small amounts for thyroid function, antioxidant defense, and immune health. Most people who eat a varied diet get enough, and supple...

Read the full Selenium monograph → Herb & supplement monograph

Vitamin C

Interacts with 207 drugs

Vitamin C (ascorbic acid) is an essential nutrient your body needs but cannot make, so you must get it from food or supplements. It's important for immune function, collagen, and acts as an...

Read the full Vitamin C monograph → Herb & supplement monograph

Quercetin

Interacts with 1,169 drugs

Quercetin is a plant flavonoid with antioxidant and anti-inflammatory properties found in many common foods and sold as a supplement. While early research is interesting for allergies, blood...

Read the full Quercetin monograph → Herb & supplement monograph

Brewer's Yeast

Interacts with 136 drugs

Brewer's yeast is a nutrient-rich fungus that provides B vitamins, protein, and minerals, and a related yeast product (S. boulardii) is used for some types of diarrhea. Most other health cla...

Read the full Brewer's Yeast monograph →
Sources

Sources & How We Checked

Selenium Xtra 200 mcg's label data comes from the NIH Dietary Supplement Label Database; the ingredient interaction data is from the Natural Medicines database, reviewed by our pharmacists.

Content is written and reviewed by licensed HelloPharmacist pharmacists. See our data sources and editorial standards for how this information is built and checked.

The 119 references behind this product’s interaction data

Every citation that drives the interaction findings for this product’s ingredients, from the evidence-graded Natural Medicines (TRC Healthcare) database. Open an ingredient to browse its citations — links open the study on PubMed or the publisher’s site.

Selenium 36 references
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  2. Brown BG, Zhao XQ, Chait A, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med 2001;345:1583-93. DOI
  3. Trafikowska U, Zachara BA, Wiacek M, et al. Selenium supply and glutathione peroxidase activity in breastfed Polish infants. Acta Paediatr 1996;85:1143-5. PubMed
  4. Duffield-Lillico AJ, Slate EH, Reid ME, et al. Selenium supplementation and secondary prevention of nonmelanoma skin cancer in a randomized trial. J Natl Cancer Inst 2003;95:1477-81.. PubMed
  5. Cheung MC, Zhao XQ, Chait A, et al. Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL. Arterioscler Thromb Vasc Biol 2001;21:1320-6. PubMed
  6. Schiavon R, Freeman GE, Guidi GC, et al. Selenium enhances prostacyclin production by cultured endothelial cells: possible explanation for increased bleeding times in volunteers taking selenium as a dietary supplement. Thromb Res 1984;34:389-96. PubMed
  7. Davila JC, Edds GT, Osuna O, Simpson CF. Modification of the effects of aflatoxin B1 and warfarin in young pigs given selenium. Am J Vet Res 1983;44:1877-83. DOI
  8. Heese HD, Lawrence MA, Dempster WS, Pocock F. Reference concentrations of serum selenium and manganese in healthy nulliparas. S Afr Med J 1988;73:163-5.
  9. Lloyd B, Lloyd RS, Clayton BE. Effect of smoking, alcohol and other factors on the selenium status of a healthy population. J Epidemiol Commun Health 1983;37:213-7. PubMed
  10. Capel ID, Jenner M, Williams DC, et al. The effect of prolonged oral contraceptive steroid use on erythrocyte glutathione peroxidase activity. J Steroid Biochem 1981;14:729-32. PubMed
  11. Contempre B, Dumont JE, Ngo B, et al. Effect of selenium supplementation in hypothyroid subjects of an iodine and selenium deficient area: the possible danger of indiscriminate supplementation of iodine-deficient subjects with selenium. J Clin Endocrinol PubMed
  12. Hofbauer LC, Spitzweg C, Magerstadt RA, Heufelder AE. Selenium-induced thyroid dysfunction. Postgrad Med J 1997;73:103-4. PubMed
  13. Debski B, Milner JA. Dietary selenium supplementation prolongs pentobarbital induced hypnosis. J Nutr Biochem 2004;15:548-53. PubMed
  14. Ishikawa M, Sasaki M, Koiwai K, et al. Inhibition of hepatic mixed-function oxidase enzymes in mice by acute and chronic treatment with selenium. J Pharmacobiodyn 1992;15:377-85. PubMed
  15. Lippmann SM, Klein EA, Goodman PJ, et al. Effect of selenium and vitamin E on risk of prostate cancer and other cancers: the selenium and vitamin E cancer prevention trial (SELECT). JAMA 2009;301:39-51. DOI
  16. Reid SM, Middleton P, Cossich MC, Crowther CA. Interventions for clinical and subclinical hypothyroidism in pregnancy. Cochrane Database Syst Rev 2010;(7):CD007752. PubMed
  17. Vinceti, M., Wei, E. T., Malagoli, C., Bergomi, M., and Vivoli, G. Adverse health effects of selenium in humans. Rev.Environ.Health 2001;16(4):233-251. PubMed
  18. Abrams, C. K., Siram, S. M., Galsim, C., Johnson-Hamilton, H., Munford, F. L., and Mezghebe, H. Selenium deficiency in long-term total parenteral nutrition. Nutr Clin Pract 1992;7(4):175-178. PubMed
  19. Spiller, H. A. and Pfiefer, E. Two fatal cases of selenium toxicity. Forensic Sci Int 8-24-2007;171(1):67-72. PubMed
  20. Negro, R., Greco, G., Mangieri, T., Pezzarossa, A., Dazzi, D., and Hassan, H. The influence of selenium supplementation on postpartum thyroid status in pregnant women with thyroid peroxidase autoantibodies. J Clin Endocrinol.Metab 2007;92(4):1263-1268. PubMed
  21. Alexander, J. Selenium. Novartis.Found.Symp 2007;282:143-149.
  22. Salonen, J. T., Salonen, R., Seppanen, K., Rinta-Kiikka, S., Kuukka, M., Korpela, H., Alfthan, G., Kantola, M., and Schalch, W. Effects of antioxidant supplementation on platelet function: a randomized pair-matched, placebo-controlled, double-blind trial
  23. Kupka, R., Mugusi, F., Aboud, S., Msamanga, G. I., Finkelstein, J. L., Spiegelman, D., and Fawzi, W. W. Randomized, double-blind, placebo-controlled trial of selenium supplements among HIV-infected pregnant women in Tanzania: effects on maternal and chil
  24. Kamble, P., Mohsin, N., Jha, A., Date, A., Upadhaya, A., Mohammad, E., Khalil, M., Pakkyara, A., and Budruddin, M. Selenium intoxication with selenite broth resulting in acute renal failure and severe gastritis. Saudi.J Kidney Dis.Transpl. 2009;20(1):106
  25. Peretz, A., Neve, J., Desmedt, J., Duchateau, J., Dramaix, M., and Famaey, J. P. Lymphocyte response is enhanced by supplementation of elderly subjects with selenium-enriched yeast. Am.J Clin.Nutr. 1991;53(5):1323-1328. PubMed
  26. Kumpulainen, J., Salmenpera, L., Siimes, M. A., Koivistoinen, P., and Perheentupa, J. Selenium status of exclusively breast-fed infants as influenced by maternal organic or inorganic selenium supplementation. Am.J Clin.Nutr. 1985;42(5):829-835. PubMed
  27. Han, L. and Zhou, S. M. Selenium supplement in the prevention of pregnancy induced hypertension. Chin Med J (Engl) 1994;107(11):870-871.
  28. Kiremidjian-Schumacher, L., Roy, M., Wishe, H. I., Cohen, M. W., and Stotzky, G. Supplementation with selenium and human immune cell functions. II. Effect on cytotoxic lymphocytes and natural killer cells. Biol.Trace Elem.Res. 1994;41(1-2):115-127. PubMed
  29. Srivastava, A. K., Gupta, B. N., Bihari, V., and Gaur, J. S. Generalized hair loss and selenium exposure. Vet.Hum.Toxicol. 1995;37(5):468-469.
  30. Sudfeld CR, Aboud S, Kupka R, et al. Effect of selenium supplementation on HIV-1 RNA detection in breast milk of Tanzanian women. Nutrition 2014;30(9):1081-4. PubMed
  31. Rees K, Hartley L, Day C, et al. Selenium supplementation for the primary prevention of cardiovascular disease. Cochrane Database Syst Rev 2013;1:CD009671. PubMed
  32. Thompson PA, Ashbeck EL, Roe DJ, et al. Selenium Supplementation for Prevention of Colorectal Adenomas and Risk of Associated Type 2 Diabetes. J Natl Cancer Inst. 2016;108(12). PubMed
  33. Wichman J, Winther KH, Bonnema SJ, Hegedüs L. Selenium supplementation significantly reduces thyroid autoantibody levels in patients with chronic autoimmune thyroiditis: a systematic review and meta-analysis. Thyroid 2016;26(12):1681-92. PubMed
  34. Vinceti M, Filippini T, Rothman KJ. Selenium exposure and the risk of type 2 diabetes: a systematic review and meta-analysis. Eur J Epidemiol. 2018 Sep;33(9):789-810. Epub 2018 Jul 5. Review. PubMed
  35. Fallah S, Sani FV, Firoozrai M. Effect of contraceptive pill on the selenium and zinc status of healthy subjects. Contraception. 2009;80(1):40-3. PubMed
  36. Malpas CB, Vivash L, Genc S, et al. A Phase IIa Randomized Control Trial of VEL015 (Sodium Selenate) in Mild-Moderate Alzheimer's Disease. J Alzheimers Dis. 2016;54(1):223-232. PubMed

See these in context on the Selenium monograph →

Vitamin C 51 references
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  5. Dwyer JH, Merz NB, Shirocre AM, et al. Progression of early atherosclerosis and intake of vitamin C and vitamin E from supplements and food. The Los Angeles Atherosclerosis Study. 41st Annual Conference on Cardiovascular Disease Epidemiology and Prevent
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  9. Food and Nutrition Board, Institute of Medicine. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press, 2000. Available at: http://www.nap.edu/books/0309069351/html/.
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  11. Brown BG, Zhao XQ, Chait A, et al. Simvastatin and niacin, antioxidant vitamins, or the combination for the prevention of coronary disease. N Engl J Med 2001;345:1583-93. DOI
  12. Rosenthal G. Interaction of ascorbic acid and warfarin. JAMA 1971;215:1671. DOI
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  15. Traxer O, Huet B, Poindexter J, et al. Effect of ascorbic acid consumption on urinary stone risk factors. J Urol 2003;170:397-401.. PubMed
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  17. Domingo JL, Gomez M, Llobet JM, Corbella J. Influence of some dietary constituents on aluminum absorption and retention in rats. Kidney Int 1991;39:598-601. PubMed
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  24. Cheung MC, Zhao XQ, Chait A, et al. Antioxidant supplements block the response of HDL to simvastatin-niacin therapy in patients with coronary artery disease and low HDL. Arterioscler Thromb Vasc Biol 2001;21:1320-6. PubMed
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See these in context on the Vitamin C monograph →

Quercetin 26 references
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  7. DiCenzo R, Frerichs V, Larppanichpoonphol P, et al. Effect of quercetin on the plasma and intracellular concentrations of saquinavir in healthy adults. Pharmacotherapy 2006;26:1255-61. PubMed
  8. Choi JS, Choi BC, Choi KE. Effect of quercetin on the pharmacokinetics of oral cyclosporine. Am J Health Syst Pharm 2004;61:2406-9. PubMed
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  16. Wu LX, Guo CX, Chen WQ, et al. Inhibition of the organic anion-transporting polypeptide 1B1 by quercetin: an in vitro and in vivo assessment. Br J Clin Pharmacol 2012;73(5):750-7.
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  18. Larson A, Witman MA, Guo Y, et al. Acute, quercetin-induced reductions in blood pressure in hypertensive individuals are not secondary to lower plasma angiotensin-converting enzyme activity or endothelin-1: nitric oxide. Nutr Res. 2012;32(8):557-64. PubMed
  19. Bedada SK, Neerati P. Evaluation of the effect of quercetin treatment on CYP2C9 enzyme activity of diclofenac in healthy human volunteers. Phytother Res. 2018 Feb;32(2):305-311. doi: 10.1002/ptr.5978. PubMed
  20. Zhao Q, Wei J, Zhang H. Effects of quercetin on the pharmacokinetics of losartan and its metabolite EXP3174 in rats. Xenobiotica 2019;49(5):563-8. PubMed
  21. Bhutani P, Rajanna PK, Paul AT. Impact of quercetin on pharmacokinetics of quetiapine: insights from in-vivo studies in wistar rats. Xenobiotica. 2020:1-7.
  22. Li C, Wang X, Bi Y, et al. Potent Inhibitors of Organic Anion Transporters 1 and 3 From Natural Compounds and Their Protective Effect on Aristolochic Acid Nephropathy. Toxicol Sci. 2020;175(2):279-291. PubMed
  23. Ni Y, Duan Z, Zhou D, et al. Identification of Structural Features for the Inhibition of OAT3-Mediated Uptake of Enalaprilat by Selected Drugs and Flavonoids. Front Pharmacol. 2020;11:802. PubMed
  24. Song YK, Yoon JH, Woo JK, et al. Quercetin is a flavonoid breast cancer resistance protein inhibitor with an impact on the oral pharmacokinetics of sulfasalazine in rats. Pharmaceutics 2020;12(5):397. PubMed
  25. Ahmad E, Jahangir M, Ismail MA, et al. Influence of quercetin pretreatment on pharmacokinetics of warfarin in rats. Curr Drug Saf 2022. PubMed
  26. Nambiar A, Kellogg D 3rd, Justice J, et al. Senolytics dasatinib and quercetin in idiopathic pulmonary fibrosis: results of a phase I, single-blind, single-center, randomized, placebo-controlled pilot trial on feasibility and tolerability. EBioMedicine 20 PubMed

See these in context on the Quercetin monograph →

Brewer's Yeast 6 references
  1. Blumenthal M, ed. The Complete German Commission E Monographs: Therapeutic Guide to Herbal Medicines. Trans. S. Klein. Boston, MA: American Botanical Council, 1998.
  2. Lewis SJ, Freedman AR. Review article: the use of biotherapeutic agents in the prevention and treatment of gastrointestinal disease. Aliment Pharmacol Ther 1998;12:807-22. PubMed
  3. Bahijiri, S. M., Mira, S. A., Mufti, A. M., and Ajabnoor, M. A. The effects of inorganic chromium and brewer's yeast supplementation on glucose tolerance, serum lipids and drug dosage in individuals with type 2 diabetes. Saudi.Med.J. 2000;21(9):831-837. DOI
  4. Schrauzer, G. N. and de, Vroey E. Effects of nutritional lithium supplementation on mood. A placebo-controlled study with former drug users. Biol.Trace Elem.Res. 1994;40(1):89-101. PubMed
  5. Gayathri R, Aruna T, Malar S, Shilpa B, Dhanasekar KR. Efficacy of Saccharomyces cerevisiae CNCM I-3856 as an add-on therapy for irritable bowel syndrome. Int J Colorectal Dis. 2020;35(1):139-145. PubMed
  6. Mourey F, Decherf A, Jeanne JF, et al. Saccharomyces cerevisiae I-3856 in irritable bowel syndrome with predominant constipation. World J Gastroenterol 2022;28(22):2509-2522.

See these in context on the Brewer's Yeast monograph →

Parts of this content are provided by the Therapeutic Research Center, LLC.

DISCLAIMER: Currently this does not check for drug-drug interactions. This is not an all-inclusive comprehensive list of potential interactions and is for informational purposes only. Not all interactions are known or well-reported in the scientific literature, and new interactions are continually being reported. Input is needed from a qualified healthcare provider including a pharmacist before starting any therapy. Application of clinical judgment is necessary.

© 2021 Therapeutic Research Center, LLC

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