What are symptoms of ivermectin-related neurotoxicity and when to seek emergency care?
Executive summary
Ivermectin neurotoxicity presents primarily with neurologic and central‑nervous‑system signs such as lethargy, ataxia/inability to stand, tremor or seizures, disorientation/encephalopathy and coma; case series of drug misuse during the COVID‑19 pandemic reported neurotoxic effects in the majority of symptomatic patients (30 of 36 cases reported neurotoxicity) [1] [2]. Severe presentations — encephalopathy, coma and respiratory compromise — have been reported after overdoses, use of veterinary or parenteral formulations, or in people with genetic or drug‑interaction vulnerabilities affecting P‑glycoprotein at the blood–brain barrier [3] [4] [5].
1. What the reports say: the core symptoms to watch for
Clinical reviews and pharmacovigilance data list lethargy, drooling, tremors or seizures, inability to stand/ataxia, disorientation or encephalopathy, and coma as characteristic features of ivermectin‑related neurotoxicity [1]. Case series collected by poison centers during the COVID‑19 period found neurologic symptoms to be the dominant clinical effect in people who took high or inappropriate doses — including older men who ingested veterinary or excess human formulations — with neurotoxicity recorded in the majority of symptomatic patients [2].
2. Why some people get severe brain effects: the P‑glycoprotein story
Ivermectin normally has poor brain penetration because ABCB1/MDR1 (P‑glycoprotein) pumps it out of the brain; if those pumps are absent, blocked by other drugs, genetically defective, or overwhelmed by high doses, ivermectin can accumulate and act on GABA and related receptors to produce central nervous system depression, seizures and encephalopathy [5] [6] [1]. Published human case reports have linked severe encephalopathy and coma to ABCB1 (ABCB1/MDR1) mutations, and animal and drug‑interaction studies demonstrate the same mechanism [4] [5].
3. Common contexts that produced harm in recent reports
During the COVID‑19 pandemic, many poison center reports involved people taking veterinary formulations, very large single doses, repeated excessive dosing, or parenteral veterinary products; these contexts were associated with rapid and severe neurologic deterioration [2] [3]. A systematic review and surveillance literature also highlights severe encephalopathy cases in Loa loa coinfection and growing reports outside that classical risk group, driven by misuse or overdose [7] [1].
4. Red flags that should prompt emergency care now
Available sources identify these as emergency signs: new or rapidly worsening decreased consciousness or lethargy, confusion/disorientation or encephalopathy, inability to stand or profound ataxia, tremors evolving into seizures or any seizure activity, respiratory depression or bradypnea, and coma — all required urgent medical evaluation in reported cases [1] [8] [3]. Case reports of intravenous or massive oral overdoses progressed quickly to severe neurotoxicity, underlining the need for immediate ED or emergency medical services if these signs appear after taking ivermectin [3] [2].
5. Who is at higher risk and why clinicians worry
People who accidentally or intentionally take veterinary formulations, receive parenteral ivermectin, ingest doses far above the approved human dose (~≤0.2 mg/kg systemic antiparasitic regimens), take interacting drugs that inhibit P‑glycoprotein (e.g., cyclosporin or some protease inhibitors), or carry ABCB1/ABCB1‑related mutations are at higher risk for severe neurotoxicity [6] [5] [4] [3]. Case series show older adults and those taking veterinary products were prominent among reported intoxications [2] [9].
6. What treatments and outcomes do the reports describe
Reports document supportive care and, in some instances, reversal of neurologic symptoms with appropriate management; however, severe cases have required intensive care and have included encephalopathy and coma with prolonged recovery or fatal outcomes in animal models and isolated human reports [10] [7] [1]. Specific antidotes are not established in routine practice; management focuses on airway, breathing, circulation, seizure control and preventing further drug absorption (available sources do not mention a standardized antidote beyond supportive care and case‑specific measures).
7. Limitations, competing viewpoints and hidden agendas
The literature emphasizes biologic plausibility (P‑glycoprotein role) and case reports/series linking ivermectin misuse to neurotoxicity, but large controlled trials for safety at approved doses are limited in relation to rare genetic susceptibilities [5] [1]. Some systematic reviews and surveillance projects point to Loa loa coinfection as a known cause of severe encephalopathy historically, while more recent reports highlight misuse contexts [7] [1]. Reporting bias from the pandemic period — intense media attention and off‑label use — likely raised detection of harms tied to inappropriate formulations [2] [9].
If you or someone took ivermectin in a way not prescribed and develops confusion, inability to walk, seizures, severe sleepiness, slowed breathing or loss of consciousness, seek emergency care immediately — these are the same red flags repeatedly cited in clinical reviews and case reports [1] [3] [2].