What are the common side effects of ivermectin overdose?

1. Common, mild-to-moderate effects that present first

The first signs of too much ivermectin are typically gastrointestinal and benign neurological complaints: nausea, vomiting, diarrhea, abdominal discomfort, dizziness, headache, sleepiness and vertigo have all been documented as common adverse effects in human use and in clinical references ^{[1] [3] [5]}. Patient-facing drug descriptions and clinical guidance repeatedly list diarrhea, nausea, dizziness and somnolence among the most frequent complaints after oral ivermectin ^{[1] [3] [6]}.

2. Neurological spectrum: from confusion to coma

When dosing is excessive or confounders exist, ivermectin’s central nervous system impact can escalate: tremor, balance problems, confusion, seizures, loss of consciousness and coma are reported in case series, reviews, and institutional warnings—events attributed to drug penetration into the brain or to compromised blood–brain barrier conditions ^{[7] [2] [5]}. Clinical reviews emphasize that serious neurological adverse events have occurred beyond classical onchocerciasis settings and note symptoms like depressed consciousness, abasia (inability to walk), vomiting and coma in severe intoxication reports ^[7].

3. Cardiovascular, hepatic and dermatologic risks

Less common but serious problems described in reporting include hypotension (low blood pressure), liver injury and severe skin reactions; liver damage and low blood pressure have been specifically linked to higher doses and overdose cases, while severe rashes are documented as an uncommon but important safety concern ^{[2] [3]}. Drug-safety resources caution that hepatic adverse events and circulatory instability can occur and warrant evaluation when overdose is suspected ^{[3] [4]}.

4. Why veterinary products and misinformation raise the stakes

Multiple sources warn that veterinary formulations—especially concentrated pastes intended for large animals—have caused hospitalizations when taken by humans, because concentration and dosing differ markedly from human prescriptions ^{[4] [8]}. Public misinformation about higher-than-recommended dosing regimens has led to harmful self-medication, and guides and clinics have repeatedly urged against using animal ivermectin in people ^{[8] [4]}.

5. Confounders and mechanisms that explain severe toxicity

Investigators point to several amplifiers of severe reactions: co‑administration of drugs that affect the central nervous system, heavy parasitic infections (for example Loa loa coinfection), and conditions that weaken the blood–brain barrier, any of which can allow ivermectin to enter the brain and produce encephalopathy ^{[7] [1]}. Pharmacologic analyses note ivermectin’s action on glutamate-gated chloride channels and GABA systems as explanatory mechanisms for neurological depression and seizures in overdose or unusual host conditions ^{[5] [7]}.

6. Clinical guidance, uncertainty and gaps in reporting

Authoritative patient-education and drug-label sources list common and serious adverse events and instruct seeking emergency help for allergic reactions or severe neurologic signs, while also noting limits in the evidence—such as scarce controlled data on rare encephalopathy outside certain parasitic contexts and limited pediatric dosing studies for small children ^{[6] [1] [7]}. Reporting and online guides converge on practical guidance—avoid self-medication, never use animal formulations, and contact poison control or emergency services for suspected overdose—but acknowledge imperfect data about how often extreme events occur in otherwise healthy people ^{[4] [8]}.

Conclusion

The weight of clinical and academic reporting paints a clear spectrum for ivermectin overdose: common gastrointestinal and mild neurological symptoms at lower excesses; potentially life‑threatening neurologic depression (seizures, coma), hypotension, liver injury and severe skin reactions at high or inappropriate exposures—risks heightened by veterinary products, drug interactions and certain infections or blood–brain‑barrier compromise ^{[1] [2] [7] [4]}. Where evidence is limited, sources explicitly flag uncertainty rather than invent facts, and the consistent public-health message is to follow prescribed, weight‑based dosing and to seek urgent care for severe or progressive symptoms ^{[6] [4] [3]}.