Comorbidity of chronic disease and potential treatment conflicts in older people dispensed antidepressants

Objectives: the study aimed to examine the prevalence of comorbidity, the prescribing of potentially inappropriate medications and treatment conflicts in a large sample of older people who have been dispensed an antidepressant medicine. Methods: a cross-sectional study of administrative claims data from the Department of Veterans' Affairs, Australia, 1 April-31 July 2007, of veterans aged ≥65 years was conducted. Comorbidities determined using the pharmaceutical-based comorbidity index, Rx-Risk-V. Concomitant medicines that may be potentially inappropriate for patients with depression and areas of treatment conflicts were determined from Australian clinical guidelines or reference compendia. Results: a total of 39,695 subjects were included, with a median of 5 comorbid conditions (inter-quartile range 3-6). Ninety percent of medicine use was attributed to the treatment of comorbid conditions. Eighty-seven percent of the study cohort was identified as having at least one comorbid condition that may cause a potential treatment conflict when an antidepressant is used. Those conditions of most concern included cardiovascular diseases, anxiety disorders, arthritis or pain management and osteoporosis. Conclusion: we observed a high level of potentially inappropriate prescribing and treatment conflicts that may arise when caring for older patients dispensed an antidepressant with comorbidity. These have the potential to place a large number of older people with depression at increased risk for adverse events.