Praziquantel and risk of visual disorders: Case series assessment

Praziquantel has been in use by helminthiasis and schistosomiasis control programs for about 30 years. Although deemed to be safe with regard to its adverse drug reaction profile in reference to the product information of Biltricide, the Eritrean Pharmacovigilance Center received reports of visual abnormalities related to the drug. This is a case series assessment of unusual cases of visual abnormalities associated with praziquantel.

Search was made in VigiBase by setting praziquantel as a drug substance, Eritrea as the reporting country and all eye disorders, high level term (HLT) to capture all visual disorders associated with Praziquantel. The retrieved dataset was exported into an Excel spreadsheet for descriptive analysis and causality was assessed using Austin Bradford-Hill criteria.

There are a total of 2579 Individual Case Safety Reports (ICSRs) of various Adverse Drug Reactions (ADRs) of praziquantel reported from Eritrea in VigiBase. The 61 reports of visual abnormalities that arose within the first 24 hours of praziquantel administration are of note. With a strong association as evidenced by the positive IC025 value, the association of praziquantel and blurred vision was consistently reported from different health facilities over a period of three years. It is a specific association in terms of both the exposure (only praziquantel) and the outcome (blurred vision) as reported in majority of the cases. However, experimental evidences for the association are lacking, the underweight profile of the Eritrean population suggests overdosing as a possible risk factor for the occurrence of these reactions.

The strength, temporal plausibility, consistency and specificity of the association are suggestive of a causal association between praziquantel and visual disorders.