How does ivermectin interact with other common medications and supplements?
Executive summary
Ivermectin’s interactions are driven mainly by effects on drug metabolism, transport proteins, and additive side-effect profiles, meaning it can both raise or lower levels of co‑administered drugs and magnify shared toxicities (e.g., CNS depression, bleeding, muscle injury) [1] [2] [3]. Clinical guidance is to disclose all prescription, over‑the‑counter, herbals and supplements to the prescriber because hundreds of potential interactions have been documented—most moderate, a few major—and some common remedies (warfarin, certain antifungals, macrolide antibiotics, alcohol) are repeatedly flagged [4] [5] [6] [7].
1. How ivermectin physiologically interacts with other medicines
Ivermectin’s interaction profile reflects two pharmacologic realities: it is highly protein‑bound in plasma, so changes in albumin or competing drugs can alter its free fraction, and it is handled by hepatic metabolic enzymes and membrane transporters (including CYP-mediated routes and ABC/MRP transporters), so inhibitors or inducers of those systems can increase or decrease ivermectin exposure [1] [2]. Several clinical and review sources explain that drugs which inhibit CYP3A4 or related pathways (for example, some macrolide antibiotics and azole antifungals) can slow ivermectin clearance and raise blood levels, increasing adverse‑effect risk [8] [9]. Conversely, drugs that up‑regulate metabolism may reduce ivermectin exposure and potentially blunt efficacy [3].
2. Common prescription drugs clinicians single out
Anticoagulants such as warfarin are repeatedly flagged—case reports and interaction checkers raise concern that ivermectin can alter bleeding risk or INR control, so clinicians typically recommend monitoring when both are used [4] [6] [9]. Antifungals (ketoconazole, others) and some antibiotics (erythromycin) are notable because they inhibit CYP3A4 and may increase ivermectin blood concentrations [4] [8] [9]. Reviews and interaction databases also list statins, fibrates, certain antivirals and CNS agents among drugs that can either potentiate muscle toxicity or share overlapping adverse effects; some combinations have been discussed in literature as raising risks of myopathy or rhabdomyolysis [3] [2]. Interaction checkers enumerate dozens more: of the interactions cataloged, most are moderate in severity though one is classified as major and clinical relevance depends on dose, duration and patient factors [5] [4].
3. Supplements, alcohol, foods and the murky areas
Alcohol is a recognized interaction: ethanol can increase ivermectin levels or add to CNS side effects such as dizziness and sleepiness, and many authorities recommend caution or avoidance during treatment [6] [7]. Supplements and herbal products are more incompletely characterized; mainstream patient guidance emphasizes declaring vitamins, herbs and CBD because formal interaction data are sparse—Medical News Today notes cannabis/CBD has not been specifically reported to interact but advises consultation before combining them [8]. Grapefruit juice and other dietary inhibitors of CYP3A4 are mentioned in consumer guidance as potential concerns even if direct clinical reports are limited, reflecting a precautionary approach in many online drug‑interaction summaries [10] [7].
4. Who is most vulnerable and why monitoring matters
Patients with low albumin, liver or kidney impairment, older adults on polypharmacy, or those on narrow‑therapeutic‑index drugs like warfarin have the highest potential for clinically meaningful interactions because altered protein binding and impaired clearance magnify exposure and side effects [1] [11]. Professional sources and drug databases stress that real-world interaction risk depends on specific combinations and clinical context—many listed interactions are theoretical or moderate, but individual susceptibility can convert a theoretical risk into a harmful event, so clinicians often recommend lab monitoring or dose adjustments when needed [5] [11].
5. Practical takeaways, reporting gaps and competing narratives
The pragmatic bottom line in clinical guidance and interaction databases is consistent: disclose everything a patient takes, avoid or monitor known offenders (warfarin, strong CYP3A4 inhibitors like ketoconazole/erythromycin), be cautious with alcohol, and recognize that many interactions are moderate rather than prohibitive [4] [6] [7]. Review articles and drug‑interaction sites expand the list to dozens of drugs—including statins, antivirals, and CNS depressants—while admitting not all listed interactions are equally proven, exposing a tension between comprehensive caution and evidence of clinical harm [3] [9]. Reporting agendas vary: consumer sites emphasize safety and avoidance, clinical reviews highlight mechanisms and theoretical risks, and regulators warn against non‑prescribed veterinary use—reading across these sources shows robust reasons for clinician oversight but also gaps where high‑quality clinical interaction studies are limited [12] [13] [1].