Irish Medicines Board safety warnings: do they affect prescribing rates in primary care?

To examine the impact of safety warnings issued between 2005 and 2007 by the Irish Medicines Board (IMB) on the rate of prescribing of clopidogrel, co-amoxiclav, celecoxib and haloperidol by primary care physicians in the General Medical Services (GMS) scheme across Ireland.

This study was performed using the Irish Health Service Executive-Primary Care Reimbursement Services national prescribing database. Rate of prescribing per 1000 GMS population was calculated for each of the 12 months before and after the IMB warnings were issued to physicians. A segmented regression analysis was used to examine the change in level and trend in prescribing rates before and after the IMB warnings. Regression coefficients are presented with SEs. Significance at p < 0.05 was assumed. SPSS 16 and SAS were used for statistical analysis.

Prescribing of clopidogrel continued to rise in both genders following the warning. This increase was slightly higher in male patients. The prescribing of co-amoxiclav showed seasonal variation with significant autocorrelation. The rate of prescribing of celecoxib declined approximately 4  months prior to the IMB warning. A significant decrease in the level and trend of the rate of prescribing of celecoxib was observed with evident discontinuity. The IMB warning had no significant effect on the level of trend in the prescribing of haloperidol, suggesting no discontinuity.

Results indicate that the IMB safety warnings had inconsistent effects on the rate of prescribing of drugs considered.