RESUMEN
OBJECTIVE: To determine the frequency of concurrent use of cisapride, astemizole and terfenadine with macrolides and azole antimitotics, drug combinations that have been reported in the literature as producing a pharmacological interaction associated with potentially fatal ventricular arrhythmias. MATERIAL AND METHODS: A retrospective analysis of a total of 72,444 prescriptions generated by 611 physicians during a 6 months period for ambulatory patients, was performed. The database included a register of automatic alerts produced every time a predetermined drug combination was detected. RESULTS: 145 potentially risk situations were detected, with an incidence rate to 2.1 cases per 1,000 prescriptions, which increases to 6.2 when prescriptions for terfenadine, astemizole, and cisapride were included, with 12, 9 y 5, respectively. Only 36 physicians (6) wrote prescriptions producing alerts, and about half (45) were pediatricians. The same physician prescribed both drugs in 31 of the cases. CONCLUSION: The use of drug combinations associated with a high risk of potentially fatal ventricular arrhythmias is relatively high in Mexico. An electronic online detecting system showed to be useful in preventing this kind of potential pharmacological interactions.