The market lifecycle of duloxetine for urinary incontinence in Norway

Objective. To investigate the epidemiology of prescriptions for duloxetine for the treatment of stress urinary incontinence during its entire lifecycle in Norway (October 2004-May 2007), including the persistence of use of the drug and the prescribers. Design and setting. Observational study in Norway. Sample. All prescriptions on duloxetine filled in Norwegian pharmacies. Methods. Data from the Norwegian Prescription Database. Main outcome measure. Patient's age, unique identification, date of dispensing, data on specialty of the prescribing doctor, and number of packages purchased. Persistence of use of duloxetine was analyzed by grouping the months of first prescription filled into quarters of a year, from the fourth quarter of 2004 to the third quarter of 2007. Results. A total of 3,024 filled prescriptions were recorded of which 2,903 (96%) could be further analyzed, corresponding to 37 users per 100,000 women in the population. Each patient filled a mean of 3.4 prescriptions. The persistence of use was very low from the second quarter itself, and after 1 year only 12.5% of the patients still purchased the drug. Most prescriptions were written by GPs and gynecologists. A prescription database like ours consists of dispensed prescriptions and not drugs taken. We believe that these biases are of little importance for the main results. Conclusions. Analyses from the national prescription database show that duloxetine had a low uptake on the market and a low persistence rate among the patients during its full lifecycle on the Norwegian market.