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Next Course 23-24 May 2012
Staying Current and in Control in the Constantly Changing Global Regulatory Pharmacovigilance Environment

Safety profile of Orlistat: Results of a prescription-event monitoring study

Background

Orlistat, the first of a new type of medicine for the treatment of obesity, was launched in the UK in December 1998. The prescribing information recommends that treatment with orlistat should be discontinued after 12 weeks if the patient has not lost weight. The objective of this study was to monitor the safety of orlistat in the primary care setting in England using prescription-event monitoring (PEM).

Methods

Patients were identified from prescriptions for orlistat issued by GPs between December 1998 and November 1999. The outcome data were reports of subsequent events. These were obtained by sending green form questionnaires to the prescribing doctor at least 6 months after the first prescription for an individual patient. The rates at which events occurred in the first month of treatment were compared with the second and third months combined. Differences between these rates were regarded as potential signals that an event was related to treatment. The reasons for stopping orlistat were also analysed. Follow-up information was requested for selected events and used to assess whether or not orlistat might have caused these events.

Results

Green forms containing clinically useful information were received for 16,021 patients. The average age was 45 years and 80% were female. The adverse events reported most frequently during the first month of treatment were ‘not effective’ (in 4% of patients), diarrhoea (2%) and weight loss (1%). Twelve clinical adverse events were identified for which the rate in the first month of treatment was significantly greater than in months two and three combined. These included intolerance of orlistat, malaise, lassitude, weight loss and inflammation of the vagina or vulva. The remaining events affected the abdomen and included diarrhoea, abdominal pain, flatulence, nausea/vomiting, rectal discharge and faecal incontinence. A similar pattern of events was seen when examining the reasons for stopping orlistat and events which were suspected by the doctor to be related to the drug. Review of possible cause and effect in individual cases revealed 45 events which were thought to be possibly or probably related to orlistat.

Conclusion

This study shows that orlistat is fairly well-tolerated. The safety profile of orlistat was similar to what was expected from the prescribing information and experience reported in the medical literature.