Case report: restored vision after ocular Closantel intoxication and blindness

Closantel is the best-known anti-parasitic medicine for veterinarians, which is contraindicated in humans. After reviewing the literature on ocular toxicity following mistaken usage of Closantel in humans, this report was found as the first complete restoration of visual function after Closantel intoxication. This report could be useful in anticipating the possibility of a further improvement based on a dose-response relationship. An important point of this report is the apparent reversibility of the vision and Electrophysiological parameters after Closantel intoxication and blindness. To conclude, the present case report demonstrates the importance of immediate referral and management in Closantel intoxication to avoid the long-term adverse effects of drug on visual function.

A 47-year-old man mistakenly took about 20 cc of Closantel 5% (15.87 mg/kg). Four hours after mistaken usage of Closantel, he was transferred to the district hospital due to dizziness and nausea. His stomach was washed out immediately after hospital arrival. He was being hospitalized in that hospital for 3 days. Then, he was referred to our clinic due to progressive vision loss. Methylprednisolone acetate 250 mg was injected once on 5th day after taking Closantel. His vision was reducing gradually so low that he could only detect hand motion (HM) on the 14th day after taking Closantel. ERG test was requested. It showed an exclusive reduction in b-wave amplitude under photopic and scotopic conditions. Later, his vision surprisingly improved gradually and his visual acuity was fully restored on the 28th day after the incident. After 3 years, we checked him again. His visual acuity was 20/20 in both eyes and the patient did not have any problem and his ERG report was completely normal.

In low dose of Closantel and immediate referral, ocular toxicity could be resolved.