Is the antiparasitic drug ivermectin a suitable candidate for the treatment of epilepsy?

There are only a few drugs that can seriously lay claim to the title of "wonder drug" and ivermectin, the world's first endectocide and forerunner of a completely new class of antiparasitic agents, is among them. Ivermectin, a mixture of two macrolytic lactone derivatives (avermectin B 1a and B 1b in a ratio of 80:20), exerts its highly potent antiparasitic effect by activating the glutamate-gated chloride channel that is absent in vertebrate species. However, in mammals, ivermectin activates several other Cys-loop receptors, including the inhibitory GABA A and glycine receptors and the excitatory nicotinic acetylcholine receptor of brain neurons. Based on these effects on vertebrate receptors, ivermectin has recently been proposed to constitute a multifaceted wonder drug for various novel neurological indications, including alcohol use disorders, motor neuron diseases, and epilepsy. This review critically discusses the preclinical and clinical evidence of anti-seizure effects of ivermectin and provides several arguments why ivermectin is not a suitable candidate drug for the treatment of epilepsy. First, ivermectin penetrates the mammalian brain poorly, so it does not exert any pharmacological effects via mammalian ligand-gated ion channels in the brain unless it is used in high, potentially toxic doses or the blood-brain barrier is functionally impaired. Second, ivermectin is not selective but activates numerous inhibitory and excitatory receptors. Third, the preclinical evidence for anti-seizure effects of ivermectin is equivocal and, at least in part, ED 50 s in seizure models are in the range of the LD 50 . Fourth, the only robust clinical evidence of anti-seizure effects stems from the treatment of patients with onchocerciasis in which the reduction of seizures is due to a reduction in microfilariae densities but not a direct anti-seizure effect of ivermectin. We hope that this critical analysis of available data will avert that the unjustified hype associated with the recent use of ivermectin to control COVID-19 recurs also in neurological diseases such as epilepsy.