Fact check: What are the common symptoms of ivermectin overdose?

Executive summary — Clear answers up front: The analyses consistently identify neurotoxicity (altered mental status, hallucinations, decreased sensorium, restlessness) as the most commonly reported manifestation of ivermectin overdose, often accompanied by gastrointestinal symptoms and musculoskeletal complaints; these patterns appear in individual case reports and retrospective poison center data from 2022–2023 ^{[1] [2] [3]}. Reports flag higher risk when people ingest supratherapeutic doses, veterinary formulations, or self-medicate for COVID-19, and they emphasize caution because evidence supporting such use is lacking ^{[4] [5] [2]}.

1. Shocking neurological effects that clinicians keep seeing: Multiple case reports from July 2023 document striking neurological signs after high-dose ivermectin exposure — decreased consciousness, restlessness, and complex visual hallucinations — with symptom onset after supratherapeutic ingestion and improvement after decontamination and supportive care ^{[1] [2]}. Poison center analyses echo this picture: older males ingesting higher-than-recommended doses frequently present with altered mental status and neurotoxic features, a finding that is consistent across both individual case narratives and a 37-case series analyzed in 2022 ^[3]. These consistent neurological findings underscore that central nervous system toxicity is the dominant clinical concern in overdose.

2. Gastrointestinal and musculoskeletal complaints aren’t rare — they matter clinically: Retrospective poison center reviews and pharmacovigilance analyses report gastrointestinal upset (diarrhea, nausea), abdominal pain, and musculoskeletal symptoms alongside neurotoxicity, suggesting a multisystem toxidrome in many patients ^{[6] [4] [3]}. The WHO-sourced adverse event review found a notable rise in gastrointestinal and neurological reports after 2020, coinciding with off-label ivermectin use during the COVID-19 pandemic, which complicates interpretation because some symptoms may reflect disease, co-ingestants, or reactions to dying parasites ^{[4] [6]}. Clinicians should therefore expect combination presentations rather than isolated findings.

3. Veterinary products and dosing errors amplify risk: Multiple analyses identify a consistent pattern: people who ingest veterinary ivermectin or self-administer higher-than-prescribed dosages have worse outcomes and more frequent altered mental status than those taking prescription human tablets ^{[3] [5]}. Poison center data indicate that veterinary formulations lead to higher ingested doses and more severe neurotoxicity, likely because concentrations and excipients differ and because lay dosing calculations are error-prone. This suggests that the source and formulation of ivermectin are key determinants of overdose severity and clinical trajectory.

4. Laboratory abnormalities and systemic markers appear in some overdoses: Case reports note metabolic perturbations such as hyperglycemia, mild hyponatremia, and inflammatory marker elevation accompanying neurobehavioral symptoms in at least one documented overdose, suggesting systemic stress or secondary effects rather than a uniform biochemical signature of toxicity ^[1]. These lab findings are not reported uniformly across datasets, so they cannot be used alone to diagnose ivermectin overdose; instead, they provide supportive context in patients with compatible exposure histories, and they inform monitoring and supportive management decisions.

5. The public health signal: more reports since COVID-19 and reporting biases: Analyses of pharmacovigilance databases show a substantial increase in ivermectin-related adverse event reports since May 2020, coinciding with off-label promotion for COVID-19; this temporal clustering raises concerns about exposure frequency, misuse, and reporting bias ^[4]. Poison center demographics skew toward older males in several reports, but that may reflect help-seeking behaviors, exposure patterns, or sampling bias in regional centers ^[3]. These trends highlight the interplay of public messaging, self-medication, and surveillance artifacts in shaping the observed clinical picture.

6. Treatment patterns and outcomes described in the literature: Case reports document symptomatic improvement after activated charcoal, supportive care, and monitoring, with some patients also receiving antibiotics when secondary infections or other complicating diagnoses were considered ^{[1] [2]}. Retrospective series indicate that chronic lower-dose exposures produced milder symptoms than acute high-dose ingestions, suggesting a dose–response relationship that clinicians can use to stratify risk ^[3]. There are no standardized antidotes, so management is largely supportive and exposure-dependent.

7. What the datasets omit and what uncertainty remains: The available analyses lack systematic prospective data, standardized dosing histories, and long-term follow-up, limiting precise estimates of incidence, dose thresholds for toxicity, and vulnerable populations ^{[1] [4] [3]}. Many reports focus on symptomatic clusters without ruling out co-ingestants or preexisting neurologic disease, so causality is inferred but not uniformly proven. Surveillance increases since 2020 may reflect both true rises in misuse and enhanced reporting, meaning the absolute risk per exposure remains uncertain.

8. Bottom line for clinicians and the public: Taken together, the evidence from 2021–2023 converges on a clear pattern: ivermectin overdose most commonly produces neurotoxicity (altered mental status, hallucinations, decreased sensorium), often with GI and musculoskeletal symptoms, and risk is heightened by veterinary formulations and supratherapeutic dosing ^{[1] [2] [3] [4]}. Given reporting biases and gaps in prospective data, clinicians should focus on exposure history, supportive care, and avoidance of nonprescription veterinary products, while public health messaging should discourage self-medication for unproven indications.