Within Remedies
Natural does not always mean safe
Natural products can have real biological effects, including interactions that weaken or intensify prescribed medicines.
On this page
- Why natural ingredients still need safety checks
- St John's wort as a real world interaction example
- Practical warning signs before combining products
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Introduction
Many people assume that a remedy is safe because it is natural. That assumption is a common logical error. Plants, herbs, teas, and supplements contain biologically active compounds that can affect the body in ways similar to medicines. The fact that a product comes from a plant does not mean it is harmless, and it certainly does not mean it can be combined safely with prescription treatment. In some cases, a natural product can weaken a medicine, making treatment fail. In others, it can intensify a medicine’s effects and increase the risk of side effects or toxicity. Health authorities repeatedly warn that herbal products and supplements can cause clinically significant interactions with prescribed medicines. [NCCIH]nccih.nih.govNCCIHSt. John's Wort: Usefulness and Safety | NCCIHNCCIHSt. John's Wort: Usefulness and Safety | NCCIH
Within discussions of consumer health claims, this issue highlights another fallacy: the belief that “natural” automatically means “safe”. Real-world interaction risks show why safety depends on evidence, dosage, and context rather than origin.
Why Natural Ingredients Still Need Safety Checks
Natural remedies often contain dozens or even hundreds of chemical compounds. Some of these compounds can change how medicines are absorbed, broken down, transported, or eliminated from the body. Researchers have documented interactions involving herbal products, dietary supplements, foods, and conventional medicines through effects on liver enzymes and drug transport systems. [PMC]pmc.ncbi.nlm.nih.govPMCPharmacokinetic Interactions between Drugs and Botanical…by AA Sprouse · 2016 · Cited by 159 — Drug–botanical dietary supplement in…
A key misunderstanding is that safety testing for supplements and herbal products is often less extensive than for prescription medicines. As a result, interaction risks may be less obvious to consumers, particularly when products are sold alongside ordinary health and wellness goods. NHS guidance notes that there is often insufficient evidence to confirm whether many herbal products are safe to use with specific medicines. [nhs.uk]sps.nhs.ukmanaging complementary products and conventional medicinesSPS - Specialist Pharmacy ServiceManaging complementary products and conventional…1 Dec 2025 — Resources for reviewing interactions wi…
The practical consequence is that a person may take:
- A prescribed medicine for a chronic condition.
- A herbal product for mood, sleep, digestion, or energy.
- A vitamin or supplement marketed as supporting general health.
Each product may appear reasonable on its own, yet the combination can create an unexpected interaction. The danger comes not from any single item necessarily being harmful, but from how they affect one another inside the body. [PMC]pmc.ncbi.nlm.nih.govPMCFood–Drug Interactions with Fruit Juicesnih.govFood–Drug Interactions with Fruit Juices - PMC - NIHby Z Petric · 2020 · Cited by 53 — The figure shows the CYP3A4 inhibition by t…
St John’s Wort as a Real-World Interaction Example
Few examples illustrate the problem better than St John’s wort, a herbal remedy commonly used for symptoms of mild to moderate depression. It is also one of the best documented examples of a natural product causing significant medicine interactions. [NCCIH]nccih.nih.govthreatening increase in your body's levels of serotonin, a chemical…Read more…
Research has shown that St John’s wort can increase the activity of enzymes involved in drug metabolism. As a result, some medicines are broken down more quickly, reducing their effectiveness. This interaction has been documented with oral contraceptives, where reduced drug levels can increase the risk of contraceptive failure and unintended pregnancy. [PubMed]pubmed.ncbi.nlm.nih.govPubMedThe interaction between St John's wort and an oral contraceptiveby SD Hall · 2003 · Cited by 361 — The popular herbal remedy St Joh… [GOV.UK]GOV.UKst john s wort interaction with hormonal contraceptives including implantsJohn's wort: interaction with hormonal contraceptives…11 Dec 2014 — St John's wort interacts with hormonal contraceptives reducing th…
The herb has also been linked to interactions with:
- Antidepressants, where combining products may contribute to dangerously high serotonin levels.
- Warfarin and other anticoagulants, where treatment effectiveness can be altered.
- Transplant medicines such as ciclosporin, potentially increasing the risk of organ rejection.
- Certain antiviral, anticonvulsant, and cardiovascular medicines. [BNF]bnf.nice.org.ukBNFSt John's wort | InteractionsJohn's wort | Interactions - BNF - NICESee the list of drugs that interact with St John's wort. Includes… St John's wort decreases the… [3NCCIH 3Mayo Clinic]mayoclinic.orgart 20362212St. John's wort21 Mar 2025 — Antidepressants. If you take St. John's wort with antidepressants, it might raise the risk of a buildup of h…
The importance of this example extends beyond the herb itself. St John’s wort demonstrates that a product can be both natural and pharmacologically powerful. The logical mistake occurs when consumers assume that a traditional or plant-based origin eliminates the need for the same caution applied to prescription drugs.
Interactions Are Not Limited to Herbal Remedies
Consumers often think of interactions as a problem involving exotic supplements, yet ordinary foods and beverages can also affect medicines.
Grapefruit is a well-known example. The U.S. Food and Drug Administration warns that grapefruit and grapefruit juice can alter how certain medicines are processed, leading to unexpectedly high drug levels and potentially dangerous side effects. This interaction has been documented across multiple classes of medicines. [U.S. Food and Drug Administration]fda.govgrapefruit juice and some drugs dont mixU.S. Food and Drug AdministrationGrapefruit Juice and Some Drugs Don't MixJul 1, 2021 — Grapefruit juice and grapefruit can affect the wa… [2U.S. Food and Drug Administration]fda.govgrapefruit juice and some drugs dont mixU.S. Food and Drug AdministrationGrapefruit Juice and Some Drugs Don't MixJul 1, 2021 — Grapefruit juice and grapefruit can affect the wa…
Similarly, people taking warfarin may encounter interaction concerns involving herbal products, supplements, and foods that influence blood clotting or vitamin K levels. Reviews have identified potential concerns involving products such as St John’s wort, ginkgo, ginger, chamomile tea, cranberry products, and others, although the strength of evidence varies by product. [Medicines Resources]medicinesresources.nhs.ukMedicines ResourcesWarfarin and food, herbal or dietary supplement interactionsReview concluded that healthcare staff should be aware of…
These examples matter because they challenge another common assumption: that interaction risks are confined to prescription medicines. In reality, foods, supplements, and herbal remedies can all contribute to clinically important effects. [U.S. Food and Drug Administration]fda.govgrapefruit juice and some drugs dont mixU.S. Food and Drug AdministrationGrapefruit Juice and Some Drugs Don't MixJul 1, 2021 — Grapefruit juice and grapefruit can affect the wa…
Practical Warning Signs Before Combining Products
The safest approach is not to assume compatibility simply because two products are sold separately or because neither requires a prescription. Several warning signs should prompt extra caution.
When a Product Claims to Affect Mood, Sleep, Energy, or Hormones
Products marketed for depression, anxiety, sleep, concentration, weight loss, or hormonal balance often contain biologically active ingredients. These are precisely the kinds of products most likely to interact with medicines because they are intended to change body function. [NCCIH]nccih.nih.govJohn's Wort | NCCIHQ&A on Clinically Relevant Herb-Drug Interactions · Other Online Resources for Clinically Relevant Herb-Drug Interacti…
When Taking Medicines With a Narrow Safety Margin
Medicines such as anticoagulants, transplant medicines, certain heart medicines, seizure medicines, and some psychiatric drugs can be particularly sensitive to interactions. Even relatively small changes in drug levels may have significant consequences. [PMC]pmc.ncbi.nlm.nih.govPMCCo-ingestion of herbal medicines and warfarinIn our opinion…Read more… [Mayo Clinic]mayoclinic.orgart 20362212St. John's wort21 Mar 2025 — Antidepressants. If you take St. John's wort with antidepressants, it might raise the risk of a buildup of h…
When a Supplement Promises Powerful Effects
Claims that a natural product can dramatically boost immunity, detoxify the body, balance hormones, improve mood, or replace medicines should encourage scepticism. A product cannot simultaneously be powerful enough to transform health and too weak to interact with other treatments. The two claims are logically inconsistent.
When the Label Omits Interaction Information
The absence of a warning is not proof of safety. Many interactions are discovered only after products have been widely used, and evidence may remain incomplete for years. NHS and other health organisations advise discussing herbal and supplement use with healthcare professionals, particularly when prescription medicines are involved. [nhs.uk]nhs.ukTaking rivaroxaban with other medicines and herbal…Do not take St John's wort, the herbal remedy for depression, while you're taking r…
What This Reveals About Health Reasoning
Interaction risks expose a recurring flaw in consumer health reasoning: treating “natural” as a safety guarantee rather than a description of origin. A plant-derived product can help, harm, or interact with medicines depending on its chemical properties. Evidence, not marketing language, determines safety.
The practical lesson is straightforward. Whenever a natural remedy has enough biological activity to produce noticeable effects, it may also have enough biological activity to alter the effects of prescribed medicines. That possibility deserves the same careful scrutiny applied to any other health intervention. [NCCIH]nccih.nih.govNCCIHSt. John's Wort: Usefulness and Safety | NCCIHNCCIHSt. John's Wort: Usefulness and Safety | NCCIH [PMC]pmc.ncbi.nlm.nih.govPMCPharmacokinetic Interactions between Drugs and Botanical…by AA Sprouse · 2016 · Cited by 159 — Drug–botanical dietary supplement in…
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Further Reading
Books and field guides related to Natural does not always mean safe. Use these as the next step if you want deeper reading beyond the article.
The Essential Guide to Herbal Safety
Directly addresses risks, adverse effects, and interactions involving herbal remedies.
The Complete Guide To Herbal Medicines
Covers herbal products, evidence, precautions, and interaction concerns.
Trick Or Treatment?
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Challenges the belief that natural treatments are automatically safe or effective.
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Endnotes
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Source: nccih.nih.gov
Title: NCCIHSt. John’s Wort: Usefulness and Safety | NCCIH
Link: https://www.nccih.nih.gov/health/st-johns-wort -
Source: sps.nhs.uk
Title: managing complementary products and conventional medicines
Link: https://www.sps.nhs.uk/articles/managing-complementary-products-and-conventional-medicines/Source snippet
SPS - Specialist Pharmacy ServiceManaging complementary products and conventional...1 Dec 2025 — Resources for reviewing interactions wi...
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Source: pmc.ncbi.nlm.nih.gov
Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC4727115/Source snippet
PMCPharmacokinetic Interactions between Drugs and Botanical...by AA Sprouse · 2016 · Cited by 159 — Drug–botanical dietary supplement in...
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Source: fda.gov
Link: https://www.fda.gov/drugs/drug-interactions-labeling/healthcare-professionals-fdas-examples-drugs-interact-cyp-enzymes-and-transporter-systemsSource snippet
Food and Drug AdministrationFDA's Examples of Drugs that Interact with CYP Enzymes...John's wort (a dietary supplement), curcumin (a sup...
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Source: nhs.uk
Link: https://www.nhs.uk/medicines/rivaroxaban/taking-rivaroxaban-with-other-medicines-and-herbal-supplements/Source snippet
Taking rivaroxaban with other medicines and herbal...Do not take St John's wort, the herbal remedy for depression, while you're taking r...
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Source: fda.gov
Title: preventable adverse drug reactions focus drug interactions
Link: https://www.fda.gov/drugs/drug-interactions-labeling/preventable-adverse-drug-reactions-focus-drug-interactionsSource snippet
Food and Drug AdministrationPreventable Adverse Drug Reactions: A Focus on Drug...6 Mar 2018 — We will then examine several well-recogni...
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Source: nccih.nih.gov
Link: https://www.nccih.nih.gov/health/st-johns-wort-and-depression-in-depthSource snippet
threatening increase in your body's levels of serotonin, a chemical...Read more...
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Source: GOV.UK
Title: st john s wort interaction with hormonal contraceptives including implants
Link: https://www.gov.uk/drug-safety-update/st-john-s-wort-interaction-with-hormonal-contraceptives-including-implantsSource snippet
John's wort: interaction with hormonal contraceptives...11 Dec 2014 — St John's wort interacts with hormonal contraceptives reducing th...
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Source: sps.nhs.uk
Link: https://www.sps.nhs.uk/articles/advising-on-complementary-products-and-conventional-medicines/Source snippet
SPS - Specialist Pharmacy ServiceAdvising on complementary products and conventional...Dec 1, 2025 — St John's Wort (SJW) reduces the ef...
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Source: bnf.nice.org.uk
Title: BNFSt John’s wort | Interactions
Link: https://bnf.nice.org.uk/interactions/st-johns-wort/Source snippet
John's wort | Interactions - BNF - NICESee the list of drugs that interact with St John's wort. Includes... St John's wort decreases the...
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Source: fda.gov
Title: 5 medication safety tips older adults
Link: https://www.fda.gov/consumers/consumer-updates/5-medication-safety-tips-older-adultsSource snippet
Food and Drug Administration5 Medication Safety Tips for Older Adults15 Feb 2024 — Even common foods and drinks can cause serious interac...
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Source: pmc.ncbi.nlm.nih.gov
Title: PMCFood–Drug Interactions with Fruit Juices
Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC7823305/Source snippet
nih.govFood–Drug Interactions with Fruit Juices - PMC - NIHby Z Petric · 2020 · Cited by 53 — The figure shows the CYP3A4 inhibition by t...
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Source: medicinesresources.nhs.uk
Link: https://www.medicinesresources.nhs.uk/warfarin-and-food-herbal-or-dietary-supplement-interactions-a-systematic-review.htmlSource snippet
Medicines ResourcesWarfarin and food, herbal or dietary supplement interactionsReview concluded that healthcare staff should be aware of...
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Source: pmc.ncbi.nlm.nih.gov
Title: PMCCo-ingestion of herbal medicines and warfarin
Link: https://pmc.ncbi.nlm.nih.gov/articles/PMC1266203/Source snippet
In our opinion...Read more...
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Source: drugs.com
Title: Can You Take St. john’s wort with Warfarin?
Link: https://www.drugs.com/drug-interactions/st-john-s-wort-with-warfarin-2106-0-2311-0.htmlSource snippet
InteractionsAsk your doctor before using warfarin together with St. John's wort. This combination may reduce the effects of warfarin.Read...
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Source: drugs.com
Title: Interactions between St
Link: https://www.drugs.com/drug-interactions/st-john-s-wort-with-warfarin-2106-0-2311-0.html?professional=1Source snippet
john's wort and WarfarinGENERALLY AVOID: Limited clinical data suggest that St. John's wort may reduce the plasma concentrations and/or h...
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Source: drugs.com
Title: Drug Interaction Report: st
Link: https://www.drugs.com/interactions-check.php?drug_list=2106-0%2C2311-0&professional=1Source snippet
john's wort, warfarinGENERALLY AVOID: Limited clinical data suggest that St. John's wort may reduce the plasma concentrations and/or hypo...
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Source: drugs.com
Title: grapefruit drug interactions
Link: https://www.drugs.com/article/grapefruit-drug-interactions.htmlSource snippet
Medicines that can interact include certain cholesterol medicines, antihistamines, migraine...Read more...
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Source: sps.nhs.uk
Title: complementary products resources to support answering questions
Link: https://www.sps.nhs.uk/articles/complementary-products-resources-to-support-answering-questions/Source snippet
Complementary products: resources to support answering...1 Dec 2025 — Evidence based guidance on the interactions of herbal ingredients...
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Source: nhs.uk
Link: https://www.nhs.uk/medicines/edoxaban/taking-edoxaban-with-other-medicines-and-herbal-supplements/Source snippet
edoxaban with other medicines and herbal...Do not take St John's wort, the herbal remedy for depression, while you're taking edoxaban...
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Source: standrewsmc-southborough.nhs.uk
Link: https://www.standrewsmc-southborough.nhs.uk/warfarin-advice-leafletSource snippet
Warfarin Advice LeafletThere are also certain foods, herbal medicines and vitamin supplements that may affect your INR level...
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Source: tga.gov.au
Link: https://www.tga.gov.au/safety/safety-monitoring-and-information/safety-alerts/st-johns-wort-important-interactions-between-st-johns-wort-hypericum-perforatum-preparations-and-prescription-medicinesSource snippet
St John's Wort: Important interactions between St...15 Mar 2001 — Oral Contraceptives ("the pill") may be affected by the enzyme inducti...
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Source: pubmed.ncbi.nlm.nih.gov
Link: https://pubmed.ncbi.nlm.nih.gov/14663455/Source snippet
PubMedThe interaction between St John's wort and an oral contraceptiveby SD Hall · 2003 · Cited by 361 — The popular herbal remedy St Joh...
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Source: mayoclinic.org
Title: art 20362212
Link: https://www.mayoclinic.org/drugs-supplements-st-johns-wort/art-20362212Source snippet
St. John's wort21 Mar 2025 — Antidepressants. If you take St. John's wort with antidepressants, it might raise the risk of a buildup of h...
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Source: mayoclinic.org
Link: https://www.mayoclinic.org/healthy-lifestyle/consumer-health/in-depth/herbal-supplements/art-20046488Source snippet
John's wort if you take blood thinners. It also may keep some medicines from working as well as they should, such as: Calcium...Read more...
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Source: fda.gov
Title: grapefruit juice and some drugs dont mix
Link: https://www.fda.gov/consumers/consumer-updates/grapefruit-juice-and-some-drugs-dont-mixSource snippet
U.S. Food and Drug AdministrationGrapefruit Juice and Some Drugs Don't MixJul 1, 2021 — Grapefruit juice and grapefruit can affect the wa...
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Source: nccih.nih.gov
Link: https://www.nccih.nih.gov/training/videolectures/14/6Source snippet
John's Wort | NCCIHQ&A on Clinically Relevant Herb-Drug Interactions · Other Online Resources for Clinically Relevant Herb-Drug Interacti...
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Source: Wikipedia
Link: https://en.wikipedia.org/wiki/GrapefruitSource snippet
GrapefruitThe grapefruit (Citrus × paradisi) is a subtropical citrus tree known for its relatively large, sour to semi-sweet, somewhat...
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Source: mayoclinic.org
Title: Grapefruit: Beware of dangerous medication interactions Yes
Link: https://www.mayoclinic.org/healthy-lifestyle/consumer-health/expert-answers/food-and-nutrition/faq-20057918Source snippet
Grapefruit can get in the way of several kinds of prescription medicines. So can other citrus fruits, such as pomelos, tangelos and Sevil...
Additional References
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Source: researchgate.net
Link: https://www.researchgate.net/publication/8897011_Drug_interactions_with_herbal_products_and_grapefruit_juice_A_conference_reportSource snippet
Drug interactions with herbal products and grapefruit juiceSt John's wort, for example, induces the expression of p-glycoprotein and CYP3...
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Source: researchgate.net
Link: https://www.researchgate.net/publication/8363845_Drug_Interactions_with_St_John%27s_Wort_Mechanisms_and_Clinical_ImplicationsSource snippet
(PDF) Drug Interactions with St John's WortOct 29, 2015 — Combinations of St John's wort with serotonergic agents and other antidepressan...
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Source: facebook.com
Title: grapefruit juice and grapefruit can affect the way your medicines work and that
Link: https://www.facebook.com/FDA/posts/grapefruit-juice-and-grapefruit-can-affect-the-way-your-medicines-work-and-that-/10159569589427299/Source snippet
Grapefruit juice and grapefruit can affect the way your...Jul 1, 2021 — Grapefruit juice inhibits a major liver enzyme that breaks down...
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Source: accessdata.fda.gov
Link: https://www.accessdata.fda.gov/drugsatfda_docs/nda/2022/213312Orig1s000IntegratedR.pdfSource snippet
fda.gov213312Orig1s000 INTEGRATED REVIEW - accessdata.fda.gov22 Nov 2021 — Therefore, grapefruit juice must not be taken with ABI-009 tre...
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Source: youtube.com
Link: https://www.youtube.com/watch?v=aj8KKItAp-ISource snippet
Grapefruit Juice and Some Drugs Don't MixBy blocking transporters that help us absorb some drugs, grapefruit juice can decrease the amoun...
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Link: https://www.fda.gov/files/food/published/Evaluation-and-Definition-of-Potentially-Hazardous-Foods.pdfSource snippet
Evaluation and Definition of Potentially Hazardous FoodsIf an uncontrolled food safety hazard exists, the food is not potentially hazardo...
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Source: patient.info
Title: Learn why you should avoid this herbal remedy
Link: https://patient.info/medication-interactions/st-john-s-wort-and-contraceptive-pill-interactionSource snippet
Can I take St John's wort and Contraceptive pill together?24 Jan 2026 — St John's Wort can make the contraceptive pill less effective, in...
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Title: Interactions (7.3)]. Drug-Herb Interactions.Read more
Link: https://www.accessdata.fda.gov/drugsatfda_docs/label/2013/021083s053%2C021110s067lbl.pdfSource snippet
fda.gov3272763 This label may not be the latest approved by FDA...Grapefruit juice must not be taken with or used for dilution of Rapamu...
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Link: https://www.accessdata.fda.gov/drugsatfda_docs/label/2018/021083s061%2C021110s080lbl.pdfSource snippet
For current...Grapefruit juice must not be taken with or used for dilution of Rapamune [see Dosage and Administration (2.9), Drug Intera...
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Link: https://www.accessdata.fda.gov/spl/data/01dc7bb5-0901-c8fe-e063-6394a90a7d3e/01dc7bb5-0901-c8fe-e063-6394a90a7d3e.xmlSource snippet
fda.gov01dc7bb5-0901-c8fe-e063-6394a90a7d3e.xml... drug-drug interactions were not observed in studies of drugs listed below.... medicin...
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