Were there increased ivermectin side effects during COVID-19 off-label use?
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Executive summary
Off-label use of ivermectin for COVID‑19 was followed by a measurable rise in adverse-event reports and poison‑center calls, including a subset classified as serious — hospitalizations, life‑threatening events and deaths — though causality and reporting bias limit firm numerical attribution to the drug itself [1] [2] [3]. Regulatory and toxicology groups warned against use outside trials because randomized trials showed no clinical benefit while surveillance documented increased harms and healthcare encounters [4] [5].
1. Reported adverse events rose sharply as off‑label use expanded
Global pharmacovigilance databases and published analyses documented a marked increase in ivermectin adverse drug reaction (ADR) reports after the drug was promoted for COVID‑19: reports rose from hundreds annually pre‑pandemic to 1,418 in 2020 and 1,252 in 2021 in one WHO‑based analysis, with 1,777 cases explicitly listing COVID‑19 as the indication between May 2020 and December 2021 [1]. Another synthesis noted a 2.5‑fold jump in reports between 2019 and 2020 and called attention to serious ADRs affecting neurological, gastrointestinal and respiratory systems [6].
2. Serious outcomes — hospitalizations, life‑threatening events and deaths — were documented
Pharmacovigilance summaries and New England Journal of Medicine letters reported that among nearly 3,000 ivermectin‑linked adverse reactions captured in VigiBase between May 2020 and April 2022, 167 (5.7%) were coded as severe with 46 deaths or life‑threatening conditions and 67 hospitalizations, underscoring that a subset of reports involved clinically significant harm [2]. Poison control centers also recorded sudden surges in calls — for example, an increase from 0.25 calls/month in 2020 to 21 calls in August 2021 at one center — tied to self‑treatment and veterinary product exposures [3].
3. The clinical literature links ivermectin’s known toxicology to observed events but notes sparse controlled data on neuropsychiatric risk
Reviews of ivermectin’s pharmacology and case reports highlight plausible mechanisms for neurological adverse events — the drug acts on chloride channels and has documented neurotoxic effects in animals and occasional serious neurologic events in humans at therapeutic and higher doses (ataxia, tremor, encephalopathy, seizures) — and several COVID‑era case series raised concerns about neuropsychiatric effects, while stressing that literature remains limited and heterogenous [7] [8]. Authors caution that pre‑existing infections or co‑medications can complicate attribution and that systematic evidence of neuropsychiatric risk in COVID‑treated populations is sparse [7].
4. Increased use — and misuse — explains much of the signal but surveillance has inherent limitations
Multiple sources link the rise in ADRs to expanded prescriptions, self‑medication and even veterinary product ingestion rather than to a new pharmacology of ivermectin: U.S. human prescriptions increased dramatically and poison centers saw spikes coincident with popularization of ivermectin for COVID‑19, including use of animal formulations, which can produce overdoses [3] [9] [10]. However, spontaneous reporting systems are subject to reporting bias, duplicate reports, variable case quality and lack of denominators for exposed populations, so signal magnitude cannot be interpreted as precise incidence without controlled studies [1] [6].
5. Regulatory stance and clinical trials converge: no proven benefit and avoid off‑label use outside trials
Large randomized trials and systematic reviews failed to show clinical benefit for COVID‑19, leading regulators and toxicologists to advise against off‑label ivermectin use and to warn of toxic effects and hospitalizations associated with misuse, recommendations grounded both in negative efficacy data and the accumulating safety signals from surveillance and poison centers [4] [5] [2]. Some commentators and clinicians have urged bans on off‑label repurposing unless efficacy is proven, citing the combination of absent benefit and rising reports of harm [11].