Reversible blindness in a patient with closantel toxicity

Abstract

To describe the optical coherence tomography (OCT) and electrophysiological changes in a case of closantel toxicity. A 25-year-old patient presented with sudden painless defective vision following intake of closantel. Visual acuity (VA) was counting fingers at 5 m in both eyes (BE). OCT revealed disruption of outer retinal layers and electroretinogram (ERG) and visual evoked potential (VEP) were subnormal in BE. The patient was treated with systemic corticosteroids, after which his VA improved to 6/9, OCT revealed preservation of central outer retinal layers, and ERG and VEP responses improved in BE. This is the first case report of successful treatment with systemic steroids for closantel-related reversible blindness.

Closantel retinal toxicity: Recovery from severe vision loss after corticosteroid therapy

“…Two recent case reports, also treated acute Closantel toxicity with intravenous injection of methyl prednisolone, one report with 1 gram daily for 3 days followed by oral prednisolone 40 mg and the other case with a single 250 mg dose. 12,13 Similar to our case they observed significant visual recovery in both eyes. Early initiation of steroid treatment may have limited the toxic effects of this drug to retinal cells, although vision improvement due to the normal course of poisoning cannot be excluded.…”

“…7 They observed partial improvement in visual acuity and irregular retinal thinning on OCT. Aside from this early report, there have been 6 cases of Closantel toxicity reported around the world. [8][9][10][11][12][13] A case report from Morocco describes a 5-year old girl who was mistakenly given Closantel 500 mg daily for 8 days. She had bilateral pre-atrophic disc edema with significantly decreased ERG.…”

Closantel toxicity

“…Better visual outcome after treatment with systemic steroids has also been reported 17 19 21. Inflammation likely mediates, to some degree, the toxic effects of closantel.…”

“…In Lithuania, in 1993, donated closantel was mistakenly given to 11 women to treat endometritis 14 15. A summary of those cases of closantel poisoning in humans previously described is given in table 1 3 8 9 15–21…”

“…Poorer outcomes in other cases treated similarly3 18 have been ascribed to late patient presentation and in turn the late commencement of steroid treatment. Unfortunately, there is no evidence beyond that provided by case reports17 19 21 to support the use of systemic steroids in human closantel toxicity.…”