What are reported cases and regulatory responses to ivermectin overdose or misuse in recent years?

1. Reported case volume and surveillance signals

Multiple surveillance streams documented a marked rise in reports of ivermectin exposure beginning in mid‑2020 and peaking in 2021: the WHO pharmacovigilance database shows reporting increases from pre‑pandemic baselines to a sizable jump after May 2020 ^[5], U.S. poison centers recorded spikes—from 0.25 calls per month in 2020 to 21 calls in August 2021 at one center—and national reporting rose dramatically between 2020 and 2021 ^{[1] [2] [4]}.

2. Clinical presentations documented in reports

Clinical descriptions across case series and reviews emphasize gastrointestinal symptoms such as nausea, vomiting and diarrhea as common, while serious overdoses produce hypotension, depressed consciousness, seizures, coma and sometimes death; neurologic complaints were a dominant feature among serious cases reported to WHO and in regional case series ^{[8] [5] [3] [9]}.

3. Role of formulation and dosing errors in harm

A consistent pattern in the literature is harm linked to misuse of veterinary formulations or grossly excessive dosing: patients who ingested veterinary ivermectin often took single extremely large doses or prolonged high‑dose regimens and developed rapid neurologic decline, whereas most human‑label exposures adhered to approved doses and were less severe ^{[3] [2] [4]}.

4. Notable severe and fatal case reports

Clinical vignettes underscore worst‑case outcomes: a rare fatal transdermal poisoning was described with documented blood concentrations and extensive dermatologic injury ^[7], and other case reports include status epilepticus and prolonged intensive care admissions after ingestion of veterinary products intended for horses ^{[10] [11]}.

5. Biological and individual susceptibility factors

Toxicity mechanisms draw on ivermectin’s CNS effects at high concentrations and vulnerability when blood‑brain‑barrier efflux is impaired; reports note that genetic ABCB1 (MDR1) mutations can allow central penetration and severe neurotoxicity even at standard doses, and some serious adverse events have occurred without clear overdose but with possible blood‑brain‑barrier compromise or drug interactions ^{[12] [6]}.

6. Regulatory and professional responses

Regulators and professional bodies issued layered responses: FDA, CDC and state health advisories warned the public about veterinary‑product risks and urged clinicians to avoid prescribing ivermectin for COVID‑19 outside trials ^[4]; the American College of Medical Toxicology and the American Medical Association publicly summarized toxicity reports and opposed non‑trial use ^{[11] [9]}. Poison centers, toxicology consortia and journals published data highlighting the increased ingestion rates and clinical patterns to inform clinicians and the public ^{[1] [13]}.

7. Gaps, caveats and competing narratives

Available reporting combines passive pharmacovigilance, poison‑center call data and case series, each with biases—underreporting, variable documentation of dose and source, and confounding by co‑medications or underlying infections—so population‑level rates and causal attribution beyond temporal association are imperfectly quantified ^{[5] [6]}. Alternative viewpoints persist: proponents cite in‑vitro antiviral activity and selective studies, while major systematic reviews and regulatory analyses find no reliable clinical benefit for COVID‑19 and emphasize safety risks when misused ^{[2] [9]}.

8. Bottom line

Surveillance and clinical reports converge on a clear pattern: inappropriate ivermectin use—especially ingestion of veterinary formulations or supratherapeutic dosing—led to a demonstrable rise in toxic exposures, sometimes causing severe neurologic injury and rare deaths, and prompted explicit regulatory advisories and professional warnings against off‑label use for COVID‑19 outside clinical trials ^{[1] [3] [4] [11]}.