There has been followed up the risk of drug interactions (DI) which the insured at the Škoda Employee Insurance Co. (SEI) had been exposed to. The follow-up was carried out in the data base of prescriptions (July 1, 2001 – June 30, 2004) settled by the SEI. It has been found that 1 š of the prescriptions had been prescribed for a drug that posed a serious DI with one that had been already prescribed previously. At an average, 243 insured at the SEI were threatened by a serious DI within a period of six months, that being 0.39% of all insured that were prescribed a remedy over the given period. Of the very serious DI the most frequently encountered were interactions of warfarin, statins, drugs prolonging the QT interval, and antidepressants. Drugs interacting with already introduced therapy had been prescribed at out-patient wards of hospitals, by out-patient specialists, and by general practitioners. In agreement with sources abroad the authors recommend that physicians be informed of the DI occurring in their prescriptions and be speciafically trained so that the risk of threat to the patient be minimized.

        Key words: drug interactions – quality of healthcare – Škoda Employee Insurance Co. – prescription analyses