Praziquantel and risk of visual disorders: Case series assessment

Introduction: 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. Methods: 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. Results: 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. Conclusion: The strength, temporal plausibility, consistency and specificity of the association are suggestive of a causal association between praziquantel and visual disorders. Author summary: The Eritrean Pharmacovigilance centre, since its integration in Mass Drug Administration in 2017, has been receiving large proportion of reports of adverse drug reactions associated with the drug praziquantel administered in mass drug campaigns. Of note were reports of the visual abnormalities namely blurred vision and visual impairment which are not known to be related to the drug. On a probability assessment, the series of 61 cases seems to show a reasonable link between the reported adverse reactions and praziquantel but not an absolute cause and effect relationship. This study suggests inaccuracies in the dose of praziquantel, in reference to some African studies, as a possible root cause, that might have led to overdosing of some subjects and hence the occurrence of the reported reactions in noticeable rates. It also addresses primarily a public health issue, rendering the findings interesting to both the scientific and non-scientific communities in general and disease control programs in particular. It is a driving force to conduct further research, improve our understanding of praziquantel and its safety profile, and the use of the drug in better ways.