Ivermectin toxicity in humans and animals: clinical spectrum, mechanisms, and management
A 2026 review of how ivermectin poisons the nervous system: usually safe at approved doses, but encephalopathy, seizures, coma and death have followed high doses, and the pump that keeps it out of the brain is the key factor.
Overview
The review integrates controlled human trials, pharmacovigilance, case reports and animal studies, and finds that early placebo-controlled studies in healthy volunteers showed ivermectin well tolerated even at doses well above approved levels, while post-marketing surveillance has identified rare but severe neurotoxic events, including encephalopathy, seizures, coma and death, after supratherapeutic exposure and, in susceptible people, at standard doses (Yilmaz toxicity review 2026). It identifies impairment or saturation of P-glycoprotein-mediated efflux at the blood-brain barrier as the central determinant of neurotoxicity, and records that the COVID-19 pandemic brought a substantial increase in toxic exposures, especially to veterinary formulations, without demonstrated clinical benefit (Yilmaz toxicity review 2026).
- Severe neurotoxicity follows high or cumulative dosing and, in susceptible people, standard doses.
- P-glycoprotein efflux at the blood-brain barrier is the central determinant; drugs that block it raise the risk.
- Pandemic-era off-label use, especially of veterinary products, increased toxic exposures without demonstrated benefit.
Explains why a patient on cancer drugs that inhibit P-glycoprotein or CYP3A4 is at higher risk from ivermectin than a healthy volunteer, and why veterinary doses are dangerous.
- A review; the human neurotoxicity data are case reports and surveillance rather than controlled studies.
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