Results of the experience with the use of varenicline in daily practice using intensive monitoring

Background: Although a concise overview of Adverse Drug Reactions (ADRs) of varenicline is known, little is known about the time related information about ADRs of varenicline such as for example latencies. Objectives: To gain insight in the experience and safety of varenicline in daily practice as reported by patients through web-based questionnaires using an intensive monitoring system. Methods: Design A prospective, observational, non-interventional cohort study. Setting: First-time users of varenicline were defined as patients who have not filled in a prescription of varenicline in the previous 12 months using the first prescription signal in that particular pharmacy. Participants: All first-time users of varenicline in participating pharmacies between 1 December 2008 and 31 March 2012 were invited for the study. Patients could sign up for the study on a dedicated website. Electronic questionnaires were sent after 1, 2 and 6 weeks, 3 months and 4 months after they started to use varenicline. In these questionnaires questions about drug use and ADRs were asked for. Main outcome measurements: Information about the ADR, seriousness, and action taken when experiencing an ADR. Statistical analysis: Descriptive analysis was done using Microsoft Access. Results: About 1,418 patients signed up for the study. Response rates for the various questionnaires vary from 31.3% to 62.5%. 58.8% of the patients reported at least one ADR. The most frequently reported ADRs were nausea (30.8%), abdominal pain (11.2%) and abnormal dreaming (10.3%) which are listed in the Summary of Product Characteristics (SmPC) of varenicline. Median latency times were 3-7 days, with exception for depressed mood (10 days). The number of ADRs did not abate over time. No signals were detected. During treatment 43.9% of the patients stopped using varenicline. The main reasons for stopping were the occurrence of ADRs (42.2%) and other (40%) unspecified reasons. Conclusions: This study indicates that varenicline is a relatively safe drug. The reported ADRs correspond with the ADRs mentioned in the SmPC of varenicline with a median latency of 3-7 days. The number of ADRs do not abate over time.