Evaluation of a drug-drug interaction alert structure through the retrospective analysis of statins-macrolides co-prescriptions.

The aim of this work was the evaluation of the existent drug interaction alert structure in Spain, which is based on yellow cards notifications and circulation of drug alert letters, through the retrospective analysis of CYP3A-metabolized statins and macrolides co-prescriptions in the Spanish province of Badajoz between May and September 2001. The period of study was planned to include the release of 2 drug alert letters released by the Spanish Drug Agency in June and July, addressed to all healthcare professionals, which warned against the concomitant prescription of statins and inhibitors of their metabolism, e.g. macrolides antibacterials. 4,600,764 prescriptions were examined, 664 of which corresponded to combinations of statins and macrolides. Although a decrease was detected in the number of these co-prescriptions throughout the study, 80 of these corresponding to 67 patients were still being prescribed in September, after the warnings by the Spanish Drug Agency had been released. 431 physicians prescribed these drugs simultaneously, with 22.9% of them having more than one patient at potential risk. Doctors working at rural healthcare centres or not directly attached to any healthcare facility were more prone to prescribe unsafe coprescriptions than those working at urban health centre. This study shows that the present drug alert system is not fully efficient when facing a situation like the one retrospectively reviewed in this study, in which a prompt action, in this case termination of potentially hazardous coprescriptions, was required. New systems developed to improve prescribing, including a new method based on personal contact between Drug Surveillance Centres and general practitioners, are discussed.