Drugs causing adverse events in patients aged 45 or older: a randomised survey of Australian general practice patients

OBJECTIVE: To determine prevalence of adverse drug events (ADEs) in patients aged 45 years or older presenting to Australian general practitioners (GPs) and identify drug groups related to ADEs, their severity and manifestation. DESIGN: Substudy of the Bettering the Evaluation and Care of Health continuous survey of Australian GP clinical activity in which randomly selected GPs collected survey data from patients. Data are reported with 95% CIs. SETTING: General practice in Australia. MAIN OUTCOME MEASURES: Prevalence in the preceding 6 months, type, implicated drugs, severity (including hospitalisation) and manifestation of ADEs. PARTICIPANTS: From three survey samples, January–October 2007, and two samples, January–March 2010, responses were received from 482 GPs about 7561 patients aged 45 years or older. RESULTS: Of a final sample of 7518 patients (after duplicate patients removed), 871 (11.6%) reported ADEs in the previous 6 months. The type of ADE was recognised side effect (75.8%, 95% CI 72.0 to 79.7), drug sensitivity (9.9%, 95% CI 7.2 to 12.7) and drug allergy (7.4%, 95% CI 4.7 to 10.1). Drug interaction (1.0%, 95% CI 0.1 to 1.8), overdose (0.8%, 95% CI 0.0 to 1.5) and contraindications (0.2%, 95% CI 0.0 to 0.6) were very infrequent. A severity rating was provided for 846 patients. Almost half (45.9%, 95% CI 42.0 to 49.7) were rated as ‘mild’ events, 42.2% (95% CI 38.8 to 45.6) ‘moderate’, 11.8% (95% CI 9.5 to 14.1) severe and 5.4% (95% CI 3.8 to 7.0) had been hospitalised as a result of the most recent ADE. Thirteen commonly prescribed drug groups accounted for 58% of all ADEs, opioids being the group most often implicated. CONCLUSION: ADEs in patients aged 45 or older are frequent and are associated with significant morbidity. Most of ADEs result from commonly prescribed drugs at therapeutic dosage. The list of causative agents bears little relationship to published lists of ‘inappropriate medications’.