Multiple drug exposure as a risk factor for the seriousness of adverse drug reactions

Abstract

The aim of the present study was to validate the hypothesis that multiple drug exposure is an independent risk factor for serious adverse drug reactions (ADRs). Adverse drug reactions (ADRs) are an important cause of iatrogenic disease, the majority being preventable. Multiple drug exposure, ageing and female gender have been identified as important risk factors for an increased incidence of ADRs. ADR reports received by the central Portugal Regional Pharmacovigilance Unit, between January 2001 and December 2009, were studied. Nearly half (47.4%) of ADRs reports were considered serious, from which 66.7% reported multiple drug exposure (mean 3.07 ± 2.2; maximum 13). After adjusting for gender, simultaneous exposure to three or more drugs was significantly associated with an increased risk of serious ADRs [odds ratio (OR) 1.23; 95% confidence interval (CI) 1.02-1.51]. The present results support that multiple drug exposure is an independent risk factor for serious ADRs. Such findings are of importance in both medicines benefit/risk ratio evaluations and patient safety monitoring. A new level of nursing involvement is needed in both the detection of ADRs and prevention of serious outcomes, particularly in high-risk patients.