Channelling of controlled release formulation of ketoprofen (Oscorel) in patients with history of gastrointestinal problems.

The aim was to determine if a new controlled release formulation (Oscorel) of the non-steroidal anti-inflammatory drug (NSAID) ketoprofen has been preferentially prescribed in patients with prior history of gastro-intestinal disturbances. The study was a pharmacy records based comparison of the rates of prior prescribing of drugs indicated for peptic ulcer treatment in first recipients of Oscorel in 1989 versus recipients of other NSAID products. A representative panel of Dutch community pharmacies serving approximately 425,000 people was used. Oscorel was launched in January 1989. Data on prescriptions dispensed in 1987-1988 to a total of 837 first users of Oscorel were analysed and compared with the dispensing history of a reference population including 30,787 patients who did not receive a prescription for Oscorel during 1989. Compared to the reference population, first users of Oscorel included a greater proportion of females, of patients 75 years and older, of heavy users of NSAIDs, and of patients switching among different NSAIDs. A total of 24.1% of first users of Oscorel had received peptic ulcer therapy in 1987-1988, versus 15.7% of the reference population. The rate ratio was 1.54, with 95% confidence interval of 1.36-1.74. Adjustment for stratifying variables caused only minor changes in the rate ratio, which remained stable on 1.5. Oscorel appears to have been channelled into use in patients with recognised risk factors for gastrointestinal toxicity. This preferential prescribing probably resulted from expectations and claims that this product has a lower risk of such toxicity.