How does ivermectin interact with other medications and what drug interactions increase side effect risk?
Executive summary
Ivermectin has documented interactions with many prescription, OTC and herbal products — one interaction checker lists 106 drugs and one alcohol/food interaction [1] [2]. Clinically important concerns reported in recent references include rare increases in INR with warfarin (post‑marketing reports) and potentiation of central nervous system (CNS) depression when given with benzodiazepines or barbiturates; several P‑glycoprotein (P‑gp) modulators (for example, fostamatinib, eliglustat) can raise ivermectin exposure [3] [4] [5].
1. A wide net: how many drugs and what kinds of interactions are reported
Ivermectin’s interaction profile is broad: consumer and professional checkers count well over a hundred potential drug interactions and flag alcohol/food effects as well — Drugs.com reports 106 interacting medicines plus one alcohol/food interaction [1] [2]. Sources classify interactions into pharmacokinetic mechanisms (changes in absorption, metabolism or efflux) and pharmacodynamic effects (additive side effects such as sedation or altered coagulation) [6] [7].
2. Warfarin and coagulation: rare but monitored
Post‑marketing surveillance has recorded rare cases of increased International Normalized Ratio (INR) when ivermectin was co‑administered with warfarin, prompting labels and drug monographs to advise clinicians to monitor coagulation parameters when both drugs are used together [3]. Professional resources (WebMD, Mayo Clinic) also single out warfarin as an agent deserving discussion with your prescriber [8] [9].
3. CNS depression and alcohol: additive risks and public warnings
Multiple sources warn that ivermectin can potentiate central nervous system depression from other agents and substances. The CDC advisory and clinical references note that ivermectin may increase the effects of benzodiazepines and barbiturates and that alcohol can raise risk of sleepiness, dizziness and more severe neurologic signs [4] [8] [2]. Emergency departments have seen rises in ivermectin‑related toxicity tied to inappropriate use or combination with other depressants [4].
4. Transporter and metabolic interactions: P‑glycoprotein and CYP concerns
Pharmacology summaries and prescribing monographs highlight that drugs affecting P‑glycoprotein (MDR1) can alter ivermectin levels. Medscape cites fostamatinib and eliglustat as agents likely to increase ivermectin exposure by inhibiting P‑gp, recommending close monitoring or dose adjustment [5]. Reviews also emphasize that ivermectin’s pharmacokinetics are not fully characterised in humans and that co‑administration with other agents may change absorption or metabolism [6].
5. Antimalarials, statins and other flagged combinations — evolving evidence
Research into co‑administration of ivermectin with antimalarial drugs (for mass drug administration or chemoprevention) indicates potential for altered ivermectin exposure, with laboratory and trial data prompting investigation of CYP‑mediated changes [10]. Consumer‑facing interaction sites and drug databases list additional potential interactions such as with atorvastatin (possible increased rhabdomyolysis risk) and protease inhibitors like atazanavir that may decrease ivermectin metabolism; however, reporting sources vary in completeness and many are based on theoretical or limited data [11] [12].
6. Practical risks: what increases side‑effect likelihood
Sources converge on three practical risk scenarios: concurrent use of CNS depressants or alcohol (increases sedation, dizziness, risk of severe neurologic effects) [4] [8] [2]; co‑use with P‑gp inhibitors or modulators (raises ivermectin blood levels and toxicity risk) [5]; and interaction with anticoagulants such as warfarin (rare reports of increased INR requiring monitoring) [3]. Many interaction checkers also flag herbals, supplements and OTCs as possible contributors [7] [2].
7. Limitations, disagreements and hidden agendas in reporting
Available sources differ in scope and evidence strength: consumer sites and interaction checkers (Drugs.com, WebMD) emphasize quantity of flagged interactions [1] [8], drug monographs and Medscape focus on mechanistic concerns and specific flagged drugs like fostamatinib [5], while the CDC frames risks in a public‑health advisory context tied to misuse [4]. Some online lists (e.g., DrugBank or MedIndia) enumerate many theoretical interactions without consistently citing clinical outcome data [12] [11]. Reporting may be driven by safety vigilance, medico‑legal caution and the need to discourage off‑label or veterinary use — an implicit agenda that amplifies warnings even where clinical evidence is limited [4] [1].
8. Bottom line for clinicians and patients
Tell your clinician or pharmacist about every prescription, OTC, supplement and alcohol use before taking ivermectin; monitor INR if on warfarin, avoid combining with other sedatives or alcohol, and be cautious when P‑gp inhibitors or certain antimalarials are co‑prescribed [3] [4] [5]. For many listed interactions, available sources do not provide high‑quality clinical trial evidence of harm and instead rely on pharmacologic rationale, case reports or post‑marketing surveillance [6] [12].