Purpose: To evaluate the incidence of serious adverse drug events (ADEs) caused by cardiovascular drugs during hospitalization in a department of internal medicine, and to identify patients at highest risk.
Patients and methods: All the patients treated with cardiovascular drugs and/or anticoagulants in the department between November 1999 and January 2000 were recruited into the study. During hospitalization the patients' charts were reviewed by a pharmacist and a clinician, and the occurrence of serious ADEs was assessed using the Naranjo algorithm. 'Possible' and 'doubtful' ADEs were not counted.
Results: Of 496 patients who were enrolled in the study, 20 (4%) had serious ADEs. Compared to patients without ADEs, patients in the ADE group were older (72 +/- 12.6 years (mean +/- SD) vs. 65 +/- 13 years, p = 0.048), their average stay in hospital was longer (7.3 +/- 5.5 days vs. 5.2 +/- 3.7 days, p = 0.018) and their mean urea levels were higher (10.8 +/- 9.3 mmol/l vs. 7.8 +/- 5.3 mmol/l, p = 0.027). The most frequent background pathologies of the 20 patients with ADEs were hypertension (in 18 (90%)) and atrial fibrillation (in nine (45%)). In 50% of the the ADE group there was a history of drug allergies. The ADEs recorded were bleeding in four (20%), arrhythmias in six (30%), orthostatic hypotension in six (30%) and skin necrosis, paranoid reaction, acute hepatitis and acute renal failure in four (20%). The causative drugs were warfarin (which accounted for 25% of the ADEs), beta-blockers (15%), propafenone (5%), amiodarone (5%), and Ca(2+)-channel blockers, nitrates and diuretics (together accounting for 50% of ADEs). Drug combinations were implicated in 50% of ADE.
Conclusions: Serious ADEs were developed by 4% of hospitalized patients taking cardiovascular drugs. Those at highest risk were older, were receiving multiple drug therapy and had higher urea levels. Warfarin and beta-blockers were the drugs causing the largest number of adverse effects. ADEs are an important cause of preventable morbidity, often with serious economic implications and special attention should be given to their prevention.