What are the recognized side effects and signs of ivermectin overdose in humans, and when should you seek emergency care?
Executive summary
Ivermectin overdose in humans is associated repeatedly in public-health and clinical sources with gastrointestinal symptoms (nausea, vomiting, diarrhea), cardiovascular effects (hypotension, tachycardia), and a range of neurologic problems from dizziness and ataxia to seizures, coma, and death (FDA, CDC, poison-control reports) [1] [2] [3]. Guidance across clinical and poison-control outlets says call your doctor or poison control for suspected overdose and seek immediate emergency care (911/ER) for severe neurologic or cardiorespiratory signs such as seizures, loss of consciousness, breathing problems, or very low blood pressure [4] [1] [5].
1. What the public-health agencies list as overdose signs — short, plain summary
The U.S. Food and Drug Administration lists nausea, vomiting, diarrhea, hypotension (low blood pressure), allergic reactions (itching/hives), dizziness, ataxia (balance problems), seizures, coma and even death as consequences of ivermectin overdose [1]. The Centers for Disease Control and Prevention and poison‑control summaries add visual and psychiatric symptoms — blurred or altered vision, hallucinations, confusion and loss of coordination — and note that serious cases have required hospitalization [2] [3].
2. Clinical and toxicology perspectives: what clinicians see
Clinical reference sites and toxicology reviews catalog nervous‑system signs such as dizziness, somnolence, tremors, ataxia, mydriasis (dilated pupils), altered mentation, and seizures; other reported problems include hypotension, tachycardia, respiratory depression and, rarely, fatal outcomes after toxic exposures or misuse of veterinary products [6] [7] [3]. Drugs.com and Medical News Today note that overdoses have occurred when people took veterinary formulations or doses far above approved human regimens [8] [4].
3. Why neurologic toxicity can happen — a bit of mechanism and genetics
Ivermectin normally has limited central‑nervous‑system penetration in humans, but at high blood levels it can enter the brain and potentiate GABAergic and other channels causing CNS depression and seizures; rare human cases link severe encephalopathy to loss‑of‑function mutations in the ABCB1 gene (the P‑glycoprotein transporter), which normally helps exclude drugs from the brain [9] [10]. These genetic exceptions help explain why some patients develop severe effects after standard doses [9].
4. When to call poison control or your doctor — the stepped guidance
Authoritative clinical guidance advises: if you think you’ve taken too much ivermectin, call your doctor or America’s Poison Centers at 1‑800‑222‑1222; but if you have severe symptoms — seizures, coma, difficulty breathing, severe hypotension, or loss of consciousness — go to the nearest emergency room or call 911 [4] [3] [1]. Memorial Sloan Kettering and other clinical sources likewise direct patients to seek immediate medical care for suspected overdose [11].
5. Special situations and sources of higher risk
Higher-risk scenarios flagged in the reporting include ingestion of veterinary products formulated for large animals (much higher concentrations), self‑medication for unproven uses (e.g., COVID‑19 or cancer outside trials), drug interactions (e.g., with CYP3A4 substrates or blood thinners), and people with heavy parasitic infections (Loa loa) or genetic transporter defects [2] [1] [6] [9]. Several outlets warn that making ivermectin available without proper medical guidance increases the chance of misuse and overdose [12].
6. What emergency care looks like (what sources describe)
Available reports and reviews describe supportive care as the mainstay: stop the drug, monitor airway/breathing/circulation, treat seizures and hypotension, and provide intensive supportive therapy; in animal literature and some human case reports, lipid emulsion therapy has been used experimentally in severe lipophilic‑drug toxicity, but published human guidance stresses standard emergency management and specialist toxicology input [6] [13]. Specific antidotes for ivermectin are not described in the cited sources (not found in current reporting).
7. Limitations, disagreements, and context
Sources agree on the core overdose signs and the need for emergency care with severe neurologic or respiratory compromise [1] [3]. What’s less uniformly reported is frequency and dose thresholds: severe reactions are described as rare at therapeutic doses but do occur with very high exposures, veterinary formulations, or in rare genetic susceptibility — and available sources do not agree on a single toxic dose that predicts severe outcomes [14] [9]. Also, while some advocates promote ivermectin for off‑label uses, major regulators and medical societies warn against such use outside trials [5] [15].
Bottom line: nausea, vomiting and diarrhea plus dizziness and balance problems can progress to seizures, altered consciousness, coma, very low blood pressure or death in overdose — call poison control or your clinician for any suspected overdose and go to the ER or call 911 for severe neurologic, breathing, or circulatory symptoms [1] [4] [3].