Results of a systematic adverse drug reaction (ADR)-screening concerning bradycardia caused by drug interactions in departments of internal medicine in Rostock.

OBJECTIVES

The concomitant intake of drugs, which is frequently needed, may be associated with drug interactions. We report results on the screening of ADRs responsible for hospital admissions involving bradycardia. This investigation was part of a BfArM pilot project with the objective of monitoring and reporting ADRs.

METHOD: Beginning in 1997, a trained medical staff member of the Pharmacovigilance Center, Rostock, prospectively screened all hospital admissions to the Departments of Internal Medicine of the 2 hospitals in Rostock (40,000 hospital admissions). ADRs leading to hospital admission were registered, evaluated and reported.

RESULTS

A total of 1,441 ADRs were recorded by the Pharmacovigilance Center Rostock in the period up to December 2000. 12% (n = 173) of all ADRs involve the cardiovascular system; 83 patients (5.7% of all ADRs) suffered from bradycardia. Bradycardia was the most frequent cardiovascular ADR observed. Of these patients, 88% were receiving 3 - 10 different drugs. Drugs suspected of causing bradycardia were: digitalis (n = 62), beta-blockers (n = 47), calcium channel blockers with negative chronotropic effect (n = 45), and antiarrhythmic drugs (n = 3). 54 patients had received more than I of these drugs concomitantly as outpatients, increasing the risk of drug interactions: 18 patients received digitalis + calcium channel blocker; 14 patients digitalis + beta-blocker; 7 patients beta-blocker + calcium channel blocker; 12 cases digitalis + beta-blocker + calcium channel blocker.

CONCLUSION

The results show that special attention should be given to patients who receive more than 1 drug when there is a high risk of bradycardia. Drug combinations which may cause drug interactions should be avoided, especially when other equivalent therapeutic options are available.