Introduction:
Monitoring was required for the introduction of non-chlorofluorocarbon (CFC) propellants in metered dose inhalers (MDIs) to ensure that there were no unexpected adverse events due to the new products. A postmarketing surveillance study has been conducted to evaluate the introduction of the MDI Seretide Evohaler^TM (hydrofluoroalkane-134a inhaler containing salmeterol and fluticasone propionate).

Objectives:
To summarise the modified prescription-event monitoring (PEM) study conducted to evaluate the introduction of Seretide Evohaler^TM and discuss the relevance of this type of study towards pharmacovigilance risk-management planning.

Methods:
Modified PEM methodology was used to examine the introduction of Seretide Evohaler^TM into general practice in England. Patients were identified from the first National Health Service prescriptions dispensed in England for Seretide Evohaler^TM. One postal questionnaire was sent to the prescribing doctor, requesting demographic information, severity of the indication, concomitant medication for this condition, smoking history, event data 3 months prior to and 3 months after the first prescription for Seretide Evohaler^TM and also reason for stopping if it had been stopped. Pregnancies, deaths and selected events were followed up. Incidence density ratios were calculated to compare event rates 3 months prior to and 3 months after the introduction of Seretide Evohaler^TM. A matched cohort analysis examined oral corticosteroid use and hospital admissions between the pre- and post-exposure periods.

Results:
The cohort comprised 13 464 patients prescribed Seretide Evohaler^TM, with a response rate of 62%. There was no significant difference in the length of courses of oral corticosteroid use when the pre-and post-exposure periods were compared. A matched cohort analysis showed there was no increase in the use of oral corticosteroids (relative risk [RR] 0.95; 95% CI 0.90, 0.99) or hospital admissions in the post-exposure period (RR 0.87; 95% CI 0.73, 1.04). When the number of patients with events were compared for the periods 3 months before and 3 months after exposure, fewer events were reported in the post-exposure period. There were 64 patients who experienced adverse events within an hour of using Seretide Evohaler^TM, including one report of paradoxical bronchospasm and one of myocardial infarction with fatal outcome that were both assessed as possibly related to treatment.

Discussion:
The results of the study suggest that the introduction of Seretide Evohaler^TM was generally well tolerated. The modified methodology has allowed a comparison of the event rates before and after the introduction of this CFC-free inhaler into general practice.