Adverse drug reaction risk factors in older outpatients

Abstract

Background: Adverse drug reactions (ADRs) are common in older (age ≥65 years) outpatients (prevalence, 5%–35%), but there is no consensus on factors that put these patients at high risk for ADRs. Identifying a uniform set of risk factors would be helpful to develop risk models for ADRs for older outpatients and to implement targeted interventions for those patients at high risk for ADRs. Objective: The aim of this study was to identify potential risk factors for ADRs in older outpatients through a survey of geriatric experts and to determine their prevalence. Methods: A comprehensive literature search was conducted to find published articles on ADRs in older patients. Forty-four potential risk factors were identified through the literature search and 6 additional factors were suggested by the expert panel. Through a modified 2-round survey, based on the Delphi consensus method, of an expert panel of 5 physicians and 5 pharmacists, the probability that each of these 50 potential factors could contribute independently to placing an older outpatient at high risk for an ADR was rated on a 5-point Likert scale. After the survey responses were received, means and 95% Cls were calculated. Consensus was defined as a lower 95% confidence limit ≥4.0. Potential risk factors that reached consensus were then applied to a sample of older outpatients to determine their prevalence. Results: After 2 rounds, the expert panel reached consensus on 21 factors, including 12 medication-related factors and 9 patient characteristics. The most prevalent medication-related risk factors were opioid analgesics; warfarin; non-acetylsalicylic acid, non-cyclooxygenase-2 nonsteroidal anti-inflammatory drugs; anticholinergics; and benzodiazepines. The most prevalent patient characteristics included polypharmacy, multiple chronic medical problems, prior ADR, and dementia. Conclusions: An expert panel was able to reach a consensus on potential risk factors that increase the risk for ADRs in older outpatients. Many risk factors were common in a sample of older outpatients. Future research is needed to determine the predictive validity of these risk factors for ADRs in older outpatients.