Adverse drug reactions in older Australians, 1981-2002

Objective: To examine trends in adverse drug reactions (ADRs) in people aged 60 years or over causing admission to or an extended stay in Western Australian hospitals between 1981 and 2002. Design and setting: Secondary data analysis of case series. Patients: 43 380 patients admitted to WA public and private hospitals with an (International Classification of Diseases) ICD external cause code for an ADR, identified by the population-based WA Hospital Morbidity Data System. Main outcome measures: Age-specific, age-standardised and drug-specific rates of ADR-related hospital stays. Results: The age-standardised rate of ADR-related hospital stays increased from 2.5 per 1000 person-years (py) in 1981 to 12.9 per 1000 py in 2002. The largest increases occurred in those aged 80+ years (tenfold in men and sevenfold in women). The most common drug group involved was cardiovascular agents (17.5%), while anticoagulants (7.5%), cytotoxics (7.4%) and antirheumatics (6.8%) were the more specific drug classes most often implicated. ADRs from the last three classes of drugs were still rising at the end of the study, whereas ADRs from corticosteroids and antihypertensives peaked in 1996 and from opioids in 2000. Conclusions: Increases in hospital admissions or extended lengths of stay due to ADRs in WA have continued despite programs to promote rational and safer use of medicines. The sharp increase in ADRs from anticoagulants warrants attention to revised clinical guidelines.