What are the most common ivermectin side effects reported in adults versus children?
Executive summary
Adults most commonly report mild nervous‑system and gastrointestinal effects from oral ivermectin — dizziness, headache, fatigue/somnolence, nausea and diarrhea — with occasional serious neurologic events reported in special contexts (eg, Loa loa coinfection or overdose) [1] [2]. Pediatric data are more limited: regulatory pages and reviews note dosing is weight‑based and that studies in children under ~15 kg were limited, but pooled data in children <15 kg showed low rates (1.4%) of mostly mild, self‑limited adverse events in one meta‑analysis [3] [4] [5].
1. What adults most often report: common, mostly mild complaints
Clinical summaries and drug‑information sites list dizziness, headache, somnolence (fatigue), tremor or vertigo and gastrointestinal complaints such as nausea and diarrhea as the most frequently observed side effects in adults taking oral ivermectin [1] [6]. These sources also stress that most adverse events are mild to moderate and resolve without intervention, but they record rare severe neurological reactions — confusion, ataxia, seizures, hypotension — in cases of toxicity, misuse (including veterinary product ingestion), or when interacting conditions such as heavy Loa loa infection are present [1] [2] [7].
2. Children: limited direct data, weight‑based dosing, and mostly mild events in studies
Authoritative drug pages state that ivermectin dosing for children is determined by body weight and that safety in very small children has not been well studied or was previously contraindicated under certain weight cutoffs (commonly <15 kg) [3] [8]. A systematic review and individual‑patient meta‑analysis of children under 15 kg found that only 1.4% (15 of 1,088) experienced adverse events — 18 events total — and all were mild and self‑limiting; no serious adverse events were reported in that pooled dataset [4]. The European Medicines Agency also reported that, in trials of an ivermectin/albendazole combination in children ≥5 years, most side effects were mild or moderate and resolved without medical intervention [5].
3. Serious events are rare but documented — context matters
Case reports and journal correspondence have documented severe toxic effects — confusion, ataxia, seizures, and hypotension — typically in the setting of inappropriate use, overdose, or drug interactions and sometimes in patients with heavy filarial coinfection (Loa loa) [2] [1]. Regulatory and clinical sources warn that veterinary formulations, which are much more concentrated, have caused overdoses when taken by people, and that older adults or those with impaired liver function may be at higher risk because the drug can persist longer in the body [7] [9].
4. Why adult and pediatric profiles look similar but reporting differs
Available sources indicate the types of adverse effects (nervous system and GI symptoms) are broadly the same across ages where ivermectin is used, but pediatric safety data are sparser, especially for children under 15 kg — a gap reflected in labeling and in calls to re‑examine contraindications based on limited evidence [3] [4]. The EMA’s evaluation of orodispersible combination tablets and pooled pediatric trials suggests most observed side effects in children are mild and transient, but larger, age‑stratified surveillance is still limited [5].
5. Practical takeaways for clinicians and families
Clinicians should dose ivermectin by weight and counsel patients that common side effects are mild (dizziness, headache, somnolence, nausea, diarrhea) and usually self‑limited [1] [6]. Families of young children should know that formal studies are limited for very low weights and that regulators historically imposed weight thresholds (eg, ~15 kg) because of sparse trial data, even though pooled analyses have suggested low rates of mild events in smaller children [3] [4]. Providers must also warn against using veterinary products and watch for drug interactions or conditions that raise risk [7] [10].
6. Limitations, disagreements and what’s not in the reporting
Sources disagree on how definitive pediatric safety is: labeling still notes insufficient studies for very small children [3], while a meta‑analysis argues adverse events were rare and mild in children <15 kg [4]. Available sources do not mention long‑term comparative frequency percentages for each specific side effect split by narrow pediatric age bands versus adults (not found in current reporting). Surveillance for rare severe neurologic events relies largely on case reports and poison‑center/clinical alerts, not large randomized comparisons [2] [1].
If you want, I can extract the explicit lists of "common" versus "serious" side effects from specific patient‑leaflet style sources (Mayo Clinic, WebMD, Drugs.com) and put them side‑by‑side for adults and children with direct quotes and exact wording from each source [3] [11] [7].