Paediatric post-marketing pharmacovigilance: comparison of the adverse event profile of vigabatrin prescribed to children and adults

Purpose: Post-marketing pharmacovigilance is a cornerstone of monitoring and evaluating the safety of medicines in children and adults. However the methods may require modification to detect paediatric signals. The aim of this study was to compare the adverse event (AE) profile of children and adults taking vigabatrin, using modified signal detection methods (SDMs). Methods: Data from the vigabatrin prescription-event monitoring study an observational cohort study (cohort 10 177 patients), stratified into one paediatric (0–17 years) and one adult (≥18 years) age group were examined using summary statistics for adverse drug reactions (ADRs), reasons for stopping and deaths. Incidence densities of AEs in children and adults in the first month of treatment were compared to months two to six to examine whether the AE rate was different in these two periods. AE rates in children were compared to those in adults (proportional reporting rates; PRRs and incidence rate ratios), to compare the AE profile between these age groups. Results: Abnormal behaviour (PRR 5.3) and hyperactivity (PRR 4.5) were more frequently reported in children; confusion (PRR 25.0) and psychosis (PRR 12.5) more frequently in adults. In children 11.8% of ADRs were reported to the regulatory authority compared to 27.3% in adults. A higher proportion of children stopped treatment due to lack of effectiveness (57.7% vs. 47.5%). No deaths were attributed to vigabatrin. Conclusion: This study demonstrated that modified SDMs can be used to detect differences in the AE profiles between children and adults taking a medicinal product, and also to identify drug safety signals.