Abstract

Closantel is a broad-spectrum antihelminthic agent. It is a veterinary drug used only in animals—usually cattle, sheep and goats. A man in his 60s accidentally ingested approximately 1500 mg closantel. His visual acuity deteriorated. Optical coherence tomography (OCT) showed disruption of the outer retinal layers. Electroretinography identified abnormalities in macula and inner retinal function. He received methylprednisolone 1 g daily intravenously for 3 days. Improvements in both his visual acuity and OCT appearance followed. This case illustrates the profoundly destructive effect of this drug on humans even when consumed in low dose. We provide a concise summary of the small number of cases of closantel toxicity in humans, previously reported, for future reference as needed by others.