Which antibiotics increase risk of adverse effects when taken with ivermectin?
Executive summary
Clinical interaction checkers list antibiotics among drugs that can interact with ivermectin; professional sources call out macrolides such as erythromycin and clarithromycin as potentially increasing ivermectin levels or effects (Drugs.com interaction lists and clarithromycin-specific note) [1] [2]. Laboratory binding studies show ivermectin can form measurable physical interactions with several antibiotic molecules in vitro — notably ampicillin and chloramphenicol — but clinical significance of those bindings is not established in available sources [3].
1. What the major drug-checkers say: macrolides flagged
Commercial interaction databases and drug-checking tools enumerate many potential ivermectin interactions and specifically include macrolide antibiotics among the flagged agents; Drugs.com’s ivermectin interaction page lists erythromycin and other interacting medicines, and a dedicated report states that clarithromycin “may increase the blood levels and effects of ivermectin,” advising possible dose adjustment or monitoring [1] [2]. These advisories reflect concern about antibiotic-mediated effects on ivermectin exposure rather than proof that adverse events will occur in every patient [2].
2. Laboratory evidence: molecules can bind, but that’s not the same as clinical harm
A thermodynamic binding study found that ivermectin can physically bind several antibiotics in vitro — about three ampicillin molecules per ivermectin molecule, and roughly a one-to-one binding with chloramphenicol — demonstrating chemical interaction under experimental conditions [3]. Laboratory binding does not automatically translate to altered drug levels, toxicity, or clinical adverse events in patients; available sources do not supply clinical outcome data proving those in vitro bindings produce harm in people [3].
3. Antibiotics that have been co‑administered without recorded interactions: doxycycline and tetracyclines
Clinical trials and reports have combined ivermectin with certain antibiotics without reporting dose changes: for example, a randomized trial that used ivermectin plus doxycycline did not observe known drug–drug interactions and reported no requirement to modify doses in that study [4]. Reviews and narrative papers also discuss co‑use of ivermectin with doxycycline in investigational regimens without flagging safety signals in the cited reports [5] [4].
4. Mechanisms that could plausibly raise risk — P‑gp, CYPs, and pharmacodynamics
Selected drugs can alter ivermectin disposition by modulating transporters or metabolic pathways. Professional monographs note interactions mediated by P‑glycoprotein (MDR1) and point to agents that decrease or increase ivermectin exposure via transporter effects; Medscape specifically highlights drugs that affect P‑gp as changing ivermectin levels [6]. Macrolides can affect metabolic enzymes and transporters that plausibly raise ivermectin blood levels, which is consistent with clarithromycin being singled out for potentially increasing ivermectin’s effects [2] [6].
5. What the clinical guidance and labels emphasize
Prescribing information and major drug references urge clinicians to review all concomitant medicines because ivermectin has documented interactions with many drugs (106 listed in one interaction checker) and because co‑medications such as warfarin have documented interaction concerns [1] [7] [8]. Labeling and drug information sites also warn that alcohol and other agents may increase certain ivermectin side effects like dizziness or sleepiness [7] [8].
6. Conflicting or absent information: limits of the public record
Available sources provide in vitro binding data and interaction warnings from checkers, but do not offer comprehensive, high‑quality clinical trial evidence proving that specific antibiotics (beyond the advisory about macrolides like clarithromycin/erythromycin) consistently cause clinically meaningful adverse events when taken with ivermectin [3] [2]. Systematic reviews and narrative articles discuss ivermectin’s pharmacology and drug‑interaction potential broadly but do not convert all in vitro findings into confirmed clinical risks [9] [10].
7. Practical takeaway for clinicians and patients
Follow trusted interaction tools and product labels: treat macrolides (clarithromycin/erythromycin) as higher‑priority flags that may increase ivermectin levels and warrant monitoring or dose consideration per Drugs.com and related interaction reports [2] [1]. For other antibiotics, note that in vitro binding has been observed (ampicillin, chloramphenicol, tetracycline HCl), but available clinical reports—such as ivermectin plus doxycycline trials—do not show required dose changes [3] [4]. When in doubt, clinicians should check up‑to‑date interaction resources, consider transporter/CYP effects, and monitor patients for increased ivermectin adverse effects [6] [7].
Limitations: this summary relies on interaction checkers, label guidance, a biochemical binding study, and a few clinical reports supplied in the available sources; definitive clinical outcome data tying most antibiotics to increased ivermectin harm are not found in the current reporting [3] [2] [4].