Recruitment of a cohort of lamotrigine users through community pharmacists: differences between patients who gave informed consent and those who did not.

OBJECTIVE: Community pharmacists may function as intermediaries in the recruitment of a population-based cohort of patients using specific drugs. In this study, baseline characteristics and the retention rate of patients that gave informed consent, refused and did not answer were compared.
METHODS: A total of 1819 patients using the new antiepileptic drug (AED) lamotrigine were asked to provide informed consent for a retrospective chart study via their individual pharmacist. Four possible reactions resulted from the consent question: active consent, active refusal, passive refusal and non-informed. Patient characteristics and lamotrigine retention rate of the different groups were compared.
RESULTS: Pharmacists did not inform a total of 183 patients (10%). Of the remaining patients, a total of 968 (59%) gave consent; 101 (6%) actively refused and 567 (35%) did not respond. Age, burden of illness, psychotropic co-medication and continuation of lamotrigine therapy were related to active consent. Lamotrigine retention rate in patients that gave consent was higher than in other patients.
CONCLUSIONS: Patient recruitment with community pharmacists as intermediaries for observational studies on the effects of (new) drugs is feasible, and allows access to a broad population of patients. The recruitment procedure, however, may lead to selection bias.