What are common side effects, contraindications, and drug interactions for therapeutic ivermectin use?

1. Common side effects: GI upset, dizziness and skin reactions — what clinicians list first

Drug information sources and consumer health sites consistently list nausea, diarrhea, abdominal pain, dizziness, headache, somnolence, and skin rash among the most frequent adverse effects of oral ivermectin ^{[1] [2] [3]}. Drugs.com and Healthline group these as the typical, usually transient complaints patients report after a single therapeutic dose ^{[7] [1]}. DrugBank and veterinary-poisoning reports add edema, asthenia and vomiting when larger or inappropriate exposures occur ^[8].

2. Serious but rare neurologic and hepatic events — recognized red flags

Multiple clinical and case-report sources warn of rare but serious neurologic events including severe confusion, ataxia, seizures and encephalopathy, and of occasional hepatic injury; these have been reported in contexts of heavy parasitic infection, overdose, or inappropriate use ^{[5] [3] [1]}. The New England Journal of Medicine case series highlighted severe confusion, ataxia, seizures and hypotension associated with toxic or inappropriate use—underscoring that neurologic toxicity is an established, though uncommon, hazard ^[5].

3. Contraindications and populations needing caution

Labels and reviews identify absolute hypersensitivity to ivermectin or formulation components as a contraindication ^[4]. Many regulatory and clinical sources historically contraindicate routine use in children under 15 kg because of limited safety data, though systematic reviews have examined whether that restriction should be revisited; current practice in many places still treats low body weight/young age as a caution ^{[9] [10]}. Pregnancy and breastfeeding concerns and teratogenic findings in animal studies are noted in product monographs and specialist summaries ^[6], and sources advise discussing risks with clinicians for these groups ^[11].

4. Drug interactions — P‑glycoprotein and enzyme modulators matter

Ivermectin’s pharmacokinetics are influenced by P‑glycoprotein (MDR1) transport and hepatic metabolism; drugs that inhibit P‑glycoprotein or relevant liver enzymes can raise ivermectin exposure. Reference tools list dozens of potential interactions (Drugs.com cites ~106 interacting drugs), with examples including ketoconazole, erythromycin, and warfarin among reported interactors ^{[12] [13]}. Medscape flags specific P‑glycoprotein-related interactions (e.g., erdafitinib, lasmiditan) that could increase ivermectin levels and suggests avoidance or alternatives ^[14]. Reviews note that clinical interaction data are limited but point to plausible increases in exposure when co‑administered with enzyme or transporter inhibitors ^{[15] [16]}.

5. Alcohol and CNS depressants — additive risks

Clinical interaction warnings call out alcohol as an agent that can increase ivermectin blood levels or add to side effects such as dizziness, weakness, nausea and, in extreme cases, seizures and respiratory depression; concomitant use with other central‑nervous‑system depressants (benzodiazepines, barbiturates) may increase sedation or overdose risk ^{[13] [17]}. The CDC and clinical advisories have reported emergency visits tied to inappropriate use often involving other sedating substances ^[17].

6. Overdose, veterinary products, and misuse — a public‑health angle

Sources repeatedly caution that veterinary formulations differ from human products and have produced severe toxicity when ingested by people; overdose syndromes reported include hypotension, altered consciousness, seizures, coma, and death ^{[8] [17]}. The NEJM and public‑health outlets emphasize that many serious cases come from inappropriate self‑medication for conditions such as COVID‑19, a use not supported by the evidence base in available reporting ^{[5] [17]}.

7. Practical guidance and limits of the record

For individual patients, clinicians and pharmacists should review current drug lists, liver function, and weight/age prior to dosing, and counsel about signs of serious reactions ^{[7] [1] [14]}. Available sources do not provide a single exhaustive, universally applicable list of all interactions or absolute incidence rates for each side effect; rather, clinicians rely on interaction databases (e.g., Drugs.com, Medscape) and product monographs to tailor decisions ^{[12] [14]}. If you want, I can extract a shortlist of the highest‑risk interacting drugs mentioned across databases (e.g., strong P‑gp or CYP inhibitors) with exact citations for each.