Objectives: The study aimed to determine the prevalence of documented side effects and drug–drug interactions in older adults using antidepressants and their implications for adherence.
Design: Data were from the MarketScan Medicare Database,which comprises insurance claims from retirees with employer-sponsored Medicare supplemental insurance. Subjects were aged 65 years or older, new antidepressant users, and had a depression diagnosis between July 1, 2001, and December 31, 2006.Twelve commonly reported antidepressant side effects were identified in the month after drug initiation through International Classification of Diseases, Ninth Revision,Clinical Modification diagnoses. Potential drug- drug interactions involving an antidepressant and another drug were identified during the 1 year after antidepressant initiation using MicroMedex DRUG-REAX software. Multinomial logistic regression was used to determine the association of side effects and potential interactions with refills rates, switching, and discontinuation.
Results: The presence of a side effect was associated with a 4.7 percentage point increase in the probability of switching (from 16.5% to 21.7%) and a 3.7 percentage point increase in the discontinuation rate (from 22% to 25.7%). Among the 39,512 treatment-naive antidepressants users, 25.4% hadpotential contraindicated or major interactions, 36.1% had moderate interactions,and 38.5% had minor or no interactions. The presence of potential contraindicated or potential major interactions increased the probability of switching by 19.5 percentage points and had a minimal effect on discontinuation.
Conclusion: Although antidepressant medications have been demonstrated to be effective in treatment of geriatric depression, this study highlights the complexity of antidepressant prescribing in this population and the need for clinicians to be aware of potential drug- drug interactions and side effects.