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Key takeaways
• No published human drug-drug interaction study of fisetin exists. Everything below is theoretical, based on in vitro data, or extrapolated from related flavonoids.
• Fisetin is a CYP2C8 substrate and a mild inhibitor of several cytochrome P450 enzymes in vitro — CYP1A2, CYP2C9, CYP3A4 among them (8).
• Warfarin, direct oral anticoagulants (DOACs), and antiplatelet agents warrant particular caution — additive bleeding risk is theoretically possible.
• Tyrosine kinase inhibitors and other CYP2C8-metabolised drugs were explicitly excluded from the Mayo Clinic trial protocols (2,3).
• Fisetin’s poor oral bioavailability limits the plausible magnitude of most interactions — low systemic exposure means smaller interaction potential.
• Any prescription medication should be cleared with your prescriber before starting fisetin. The absence of documented interactions is not documentation of safety.
Quick answer
There is no published human study of fisetin drug-drug interactions. The theoretical concerns are drawn from in vitro cytochrome P450 activity, extrapolation from related flavonoids (particularly quercetin), and the exclusion criteria used in the Mayo Clinic trial protocols. The medications where caution is most warranted are anticoagulants (warfarin, DOACs), antiplatelet agents, tyrosine kinase inhibitors, and other CYP2C8-metabolised drugs. Fisetin’s poor oral bioavailability limits the magnitude of most interactions in practice — low plasma levels mean small effects on drug metabolism — but this is not a guarantee. Any prescription medication should be cleared with the prescriber before starting fisetin. For the general safety picture, see our side effects and safety article.
The cytochrome P450 picture
Fisetin is primarily metabolised by CYP2C8 in the liver, with contributions from CYP1A2 and CYP3A4. In vitro, fisetin is a mild inhibitor of several cytochrome P450 enzymes at concentrations somewhat above those achieved clinically (8). The general flavonoid class — quercetin, kaempferol, myricetin — shares this profile: mild broad-spectrum CYP inhibition at high concentrations, with limited clinical consequence at typical dietary and supplement doses (6).
The Krishnakumar 2022 pharmacokinetic study is important here. It demonstrated that unformulated fisetin produces plasma concentrations approximately 30 to 150 times below the concentrations required for senolytic effects in cell culture. Those same plasma concentrations are also below the concentrations required for meaningful CYP inhibition in most in vitro assays. This means that the theoretical CYP interaction risk from unformulated fisetin capsules is smaller than the in vitro data would suggest — you cannot inhibit an enzyme meaningfully at concentrations well below its Ki.
Bioavailability-enhanced formulations (hydrogel, liposomal) change this calculation. A formulation that produces 20-fold higher plasma concentrations also produces proportionally greater potential for CYP-mediated interactions. Our liposomal fisetin article covers the formulation differences in detail.
Medications requiring particular caution
Warfarin and direct oral anticoagulants (DOACs)
Flavonoids as a class have documented mild antiplatelet activity in vitro and in some animal models (9). Whether this activity is clinically meaningful at typical fisetin supplement doses in a patient already on warfarin, apixaban, rivaroxaban, dabigatran, or edoxaban has not been characterised. The additive bleeding risk is a theoretical concern rather than a documented one, but it is the kind of concern where the consequences of getting it wrong are serious. Patients on any anticoagulant should discuss fisetin with their prescriber before starting, and INR (for warfarin) should be monitored more frequently in the first month after starting fisetin.
Antiplatelet drugs (aspirin, clopidogrel, ticagrelor)
Similar theoretical concern. Aspirin at cardioprotective doses is unlikely to be meaningfully affected by supplement-dose fisetin. Higher-dose aspirin or dual antiplatelet therapy warrants clinician discussion before adding fisetin.
Tyrosine kinase inhibitors
The Mayo Clinic AFFIRM and COVID-FIS protocols explicitly excluded participants on tyrosine kinase inhibitors (2,3). The theoretical basis is that fisetin’s mechanism of senolytic action involves inhibition of tyrosine kinases and other survival pathways — the same pathways targeted by pharmaceutical TKIs. Additive or antagonistic effects are theoretically possible. Patients on imatinib, dasatinib, nilotinib, sunitinib, or other TKIs should not take fisetin without oncology guidance.
CYP2C8 substrates
Because fisetin is a CYP2C8 substrate and mild inhibitor, it may interact with other CYP2C8-metabolised drugs. The clinically important CYP2C8 substrates include repaglinide (a diabetes drug), montelukast (an asthma leukotriene inhibitor), amiodarone (an antiarrhythmic), amodiaquine and chloroquine (antimalarials), and rosiglitazone. Patients on any of these should discuss fisetin with their prescriber.
Statins
Most statins (atorvastatin, simvastatin, lovastatin) are CYP3A4-metabolised. Fisetin’s CYP3A4 inhibition in vitro is mild and at typical unformulated capsule doses is unlikely to produce clinically meaningful changes in statin plasma levels. High-dose or bioavailability-enhanced fisetin combined with high-dose statin therapy warrants clinician discussion.
Diabetes medications
Fisetin has preclinical evidence for mild hypoglycaemic effects. Patients on insulin, sulfonylureas, meglitinides, or repaglinide (also a CYP2C8 substrate) should be aware that fisetin may modestly potentiate blood-sugar-lowering effects. Metformin has been used alongside fisetin in some longevity practice without documented interaction concerns. Blood glucose monitoring after starting fisetin is a sensible precaution for diabetic patients.
Chemotherapy and targeted anti-cancer therapy
This is the most cautious category. Fisetin has documented preclinical activity against many cancer cell lines, and some studies have described chemosensitising effects — fisetin amplifying the anti-tumour effects of concurrent chemotherapy (8). Whether this is beneficial or harmful depends on the specific regimen and cancer type, and is not established for any human protocol. Patients with active malignancy should not take fisetin without explicit oncology guidance.
Immunosuppressants
Tacrolimus, ciclosporin, and mTOR inhibitors (sirolimus, everolimus) are CYP3A4-metabolised. Theoretical interactions with fisetin have not been characterised. Patients on immunosuppression (post-transplant, autoimmune therapy) should not start fisetin without transplant or rheumatology guidance.
Antidepressants
SSRIs and SNRIs are primarily metabolised by CYP2D6, which is not the primary fisetin pathway. Interaction potential is small. Patients on MAO inhibitors should be aware that flavonoids as a class have mild MAO-inhibiting activity in vitro; this is unlikely to be clinically consequential at supplement doses but is worth naming.
Supplement-supplement interactions
Concurrent supplementation with other polyphenols and flavonoids is common in longevity practice. Most combinations are pharmacologically benign but a few points are worth noting.
Fisetin plus quercetin
Same pharmacological class, overlapping mechanisms. No known negative interaction. Additive effects on CYP inhibition are theoretically possible at very high combined doses but not clinically documented. Our fisetin vs quercetin article covers the combination case.
Fisetin plus curcumin
Both are polyphenols with mild CYP inhibitory activity. Additive effects are theoretically possible. Curcumin is often taken with piperine to enhance its own bioavailability; piperine is a broader-spectrum CYP inhibitor that may modestly enhance fisetin plasma concentrations too. Not clinically consequential in most cases.
Fisetin plus resveratrol
Different metabolic pathways (resveratrol is primarily metabolised by sulphation and glucuronidation, less through CYP). No known interaction. Our fisetin vs resveratrol article compares the mechanisms.
Fisetin plus spermidine, NMN, or urolithin A
Different pharmacological classes and mechanisms. No known interactions. Commonly co-administered in longevity practice.
Food and drink interactions
Grapefruit juice. Grapefruit is a potent inhibitor of intestinal CYP3A4 and can substantially increase plasma concentrations of many drugs. It also modestly affects flavonoid bioavailability. High grapefruit juice intake alongside fisetin has not been formally studied but is unlikely to cause clinically meaningful interaction problems.
Alcohol. Moderate alcohol consumption is not known to interact with fisetin. Very high alcohol intake combined with high-dose fisetin has not been studied. Both are metabolised by the liver and impose modest hepatic load; concurrent very heavy use is not recommended.
Coffee and tea. Neither has documented interaction with fisetin. Very high green tea catechin intake might compete with flavonol absorption at extreme levels but is not clinically consequential at typical intakes.
What we still don't know
• Whether any of the theoretical CYP-mediated interactions produce measurable clinical effects at typical fisetin supplement doses in humans. No human drug-drug interaction study exists.
• Whether bioavailability-enhanced fisetin formulations (liposomal, hydrogel) meaningfully change the interaction profile — higher plasma levels increase theoretical interaction potential.
• Whether specific patient subgroups (older adults, poor CYP2C8 metabolisers) are at elevated interaction risk. Not studied.
• How fisetin interacts with common polypharmacy patterns (e.g., the typical 65-year-old on a statin, an ACE inhibitor, aspirin, and a PPI). Not characterised.
• Whether interactions differ between pulsed and continuous dosing regimens. Pulsed dosing produces higher plasma peaks but only briefly; continuous dosing produces sustained lower plasma levels. The interaction profiles may differ.
Bottom line
Fisetin has a theoretical interaction profile drawn from in vitro CYP data and extrapolation from related flavonoids, but no published human drug-drug interaction study exists. The medications requiring most caution are anticoagulants, antiplatelet agents, tyrosine kinase inhibitors, and other CYP2C8-metabolised drugs. Fisetin’s poor oral bioavailability limits the magnitude of most interactions in practice, but this is not a guarantee. Any prescription medication should be cleared with the prescriber before starting fisetin. Bioavailability-enhanced formulations warrant more caution than unformulated capsules. Fisetin is not a substitute for prescribed pharmacotherapy in any serious condition. For the broader safety picture, see our side effects and safety article. For the general clinical context, see our complete clinician’s guide.
Frequently asked questions
Is fisetin a blood thinner?
It has mild antiplatelet activity in vitro, consistent with the general flavonoid class (9). Whether this translates to a clinically meaningful blood-thinning effect at supplement doses in humans is not established. Discuss with your prescriber if you are on anticoagulation or antiplatelet therapy.
Can I take fisetin with warfarin?
Discuss with your prescriber before starting. Increase INR monitoring frequency in the first month. If INR becomes labile after starting fisetin, discontinue and inform your clinician.
Does fisetin interact with birth control?
Combined oral contraceptives are primarily CYP3A4-metabolised. Fisetin’s CYP3A4 inhibition is mild and at supplement doses is unlikely to compromise contraceptive efficacy meaningfully. No documented failures. Discuss with your prescriber if you rely on hormonal contraception.
Can I take fisetin with metformin?
No documented interaction. Combination has been used in longevity practice without concerning reports. Monitor blood glucose in the first weeks after starting fisetin if you are diabetic.
Can I take fisetin with rapamycin?
Not formally studied. Both are being explored in longevity practice; the combination has been used empirically without documented interactions. Rapamycin is CYP3A4-metabolised; theoretical mild interaction with fisetin exists but is unlikely to be clinically significant at typical fisetin supplement doses.
Should I stop other supplements when taking fisetin?
Generally, no. Fisetin is co-administered with quercetin, spermidine, NMN, urolithin A, resveratrol, and other longevity supplements without documented interactions. If you experience new side effects after starting fisetin alongside multiple other supplements, isolating the cause requires stopping one at a time.
References
1. Kandemir K, Tomas M, McClements DJ, Capanoglu E. Recent advances on the improvement of quercetin bioavailability. Trends Food Sci Technol. 2022;119:192-200. https://www.sciencedirect.com/science/article/pii/S092422442100781X
2. AFFIRM: Alleviation by Fisetin of Frailty, Inflammation, and Related Measures in Older Women (NCT03430037). ClinicalTrials.gov. https://clinicaltrials.gov/study/NCT03430037
3. Verdoorn BP, Evans TK, Hanson GJ, et al. Fisetin for COVID-19 in skilled nursing facilities: senolytic trials in the COVID era. J Am Geriatr Soc. 2021;69(11):3023-3033. https://pmc.ncbi.nlm.nih.gov/articles/PMC8447437/
4. Piver B, Fer M, Vitrac X, et al. Involvement of cytochrome P450 1A2 in the biotransformation of trans-resveratrol in human liver microsomes. Biochem Pharmacol. 2004;68(4):773-782. https://pubmed.ncbi.nlm.nih.gov/15276085/
5. Shia CS, Tsai SY, Kuo SC, Hou YC, Chao PD. Metabolism and pharmacokinetics of 3,3′,4′,7-tetrahydroxyflavone (fisetin) and antihemolysis effects of fisetin and its serum metabolites. J Agric Food Chem. 2009;57(1):83-89. https://pubmed.ncbi.nlm.nih.gov/19090758/
6. Choi JS, Piao YJ, Kang KW. Effects of quercetin on the bioavailability of doxorubicin in rats: role of CYP3A4 and P-gp inhibition by quercetin. Arch Pharm Res. 2011;34(4):607-613. https://pubmed.ncbi.nlm.nih.gov/21544726/
7. Wong CC, Botting NP, Orfila C, Al-Maharik N, Williamson G. Flavonoid conjugates interact with organic anion transporters (OATs) and attenuate cytotoxicity of adefovir mediated by organic anion transporter 1. Biochem Pharmacol. 2011;81(7):942-949. https://pubmed.ncbi.nlm.nih.gov/21296309/
8. Pal HC, Pearlman RL, Afaq F. Fisetin and its role in chronic diseases. Adv Exp Med Biol. 2016;928:213-244. https://pubmed.ncbi.nlm.nih.gov/27671818/
9. Ravishankar D, Salamah M, Attina A, et al. Ruthenium-conjugated chrysin analogues modulate platelet activity, thrombus formation and haemostasis. Sci Rep. 2017;7:5738. https://pubmed.ncbi.nlm.nih.gov/28720781/