How does ivermectin interact with other medications and supplements?
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Executive summary
Ivermectin has documented interactions with many drugs — drugs checkers list about 106 possible interactions (1 major, 75 moderate, 30 minor) and authoritative advisories flag specific concerns with blood thinners and central‑nervous‑system depressants [1] [2] [3] [4]. Key mechanisms reported include modified metabolism via CYP3A4 inhibitors (which can raise ivermectin levels) and clinically observed potentiation of warfarin and sedatives [5] [6] [4].
1. Broad inventory: "More than a handful" — the scope of interactions
Clinical drug‑interaction databases and patient resources consistently show ivermectin interacts with many medicines: Drugs.com and its Stromectol checker list roughly 106 potential interacting drugs — categorized as 1 major, 75 moderate, and 30 minor interactions — underscoring that combinations are common enough to require review before prescribing [1] [2]. Independent summaries from WebMD, Drugs.com and Medscape reiterate that other prescription, OTC, herbal and supplemental products can matter and that patients should disclose all of them to clinicians [7] [8] [6].
2. Most consequential interactions: blood thinners and antifungals
Multiple sources single out interactions with warfarin (a vitamin K antagonist) and with certain antifungals. Medscape and WebMD say ivermectin can increase the effect of warfarin — a clinically important interaction that requires monitoring — and drugmonographs and hospital resources flag antifungals like ketoconazole as relevant because they alter ivermectin metabolism [6] [7] [5] [9].
3. The likely mechanism: CYP3A4 inhibition and altered ivermectin levels
Pharmacology summaries and clinical medicine sites point to CYP3A4 inhibition as a mechanism by which drugs such as ketoconazole and erythromycin can boost circulating ivermectin concentrations, raising the chance of adverse effects [5] [10]. Drug interaction checkers and the DrugBank profile note ivermectin’s metabolism and pharmacokinetics are complex and that co‑administered inhibitors of drug‑metabolizing enzymes can change exposure [1] [10] [11].
4. Central nervous system (CNS) potentiation: benzodiazepines, barbiturates and alcohol
Public health advisories warn that ivermectin may enhance the effects of CNS depressants. The CDC advisory cited by a medical board reports ivermectin can increase potency of benzodiazepines and barbiturates — heightening risks like sedation or respiratory depression — and sources also caution that alcohol may worsen dizziness or sleepiness while on ivermectin [4] [7] [8].
5. Supplements, cannabis and over‑the‑counter products: sparse but cautious guidance
MedicalNewsToday and patient resources say there are no well‑documented specific interactions between ivermectin and many supplements (for example, cannabis/CBD), but they advise clinical discussion because evidence is limited and interactions could be indirect (adherence, sedation) or mediated by shared metabolic pathways [9] [7]. Optim and other consumer sites vary — some report no known alcohol interaction while also warning alcohol can worsen side effects — reflecting inconsistent public‑facing guidance [12].
6. What this means for patients: monitoring and disclosure
Regulatory and clinical sources converge on practical advice: tell your clinician about every prescription, OTC, herb, vitamin and supplement before taking ivermectin; clinicians should monitor INR if patients take warfarin and watch for excessive sedation if patients use sedatives or alcohol [7] [6] [3]. Drug checkers permit individualized screening because the generic “106 interactions” list includes a range of severities and mechanisms [1] [2].
7. Limits of current reporting and where uncertainties remain
Published reviews note that human pharmacokinetic and interaction data are more limited than veterinary data and that some mechanistic claims are inferred rather than proven in large human trials [11]. Sources largely rely on case reports, pharmacology knowledge of CYP3A4 and regulatory advisories; therefore, exact risks for particular supplements or rarer drug combinations are not well quantified in current reporting [11] [10].
8. Bottom line — a practical checklist for clinicians and patients
Treat ivermectin like any drug with multiple potential interactions: disclose all medicines and supplements, check warfarin INR and consider dose timing or avoidance with strong CYP3A4 inhibitors (eg, ketoconazole, erythromycin), avoid heavy alcohol or concomitant sedatives without medical advice, and use interaction‑checking tools for individualized assessment [5] [6] [7] [1]. Available sources do not mention definitive interaction guidance for many specific supplements beyond general caution [9] [12].