Potential Drug–Drug Interactions and Adverse Drug Reactions Among Elderly Psychiatric Outpatients Receiving Antipsychotics: A Cross-Sectional Study

Abstract

Background: Older adults with psychiatric illness often take long-term antipsychotics along with medicines for chronic diseases, increasing the risk of potential drug–drug interactions (pDDIs) and adverse drug reactions (ADRs). Indian outpatient data are limited. The main objective of this study was to describe pDDIs involving antipsychotics and assess associated ADRs in elderly psychiatric outpatients (frequency, mechanism, severity). Methodology: The present study was a cross-sectional study, in which 105 elderly psychiatric outpatients who were on stable antipsychotics plus chronic disease therapy were enrolled. Prescriptions were screened for pDDIs using Epocrates and Medscape and classified by mechanism (pharmacodynamic, pharmacokinetic, or mixed) and severity. ADRs were documented using ICSR, with causality assessed by the Naranjo algorithm and severity by the Hartwig–Siegel scale. Ethical approval was obtained from the Institute Ethical Committee. Descriptive and bivariate analyses (chi-square, Welch’s t-test) were performed. Results: Mean age was 69.0 ± 4.7 years; 54.3% were male, and patients used a mean of 2.18 medications. Depressive (27.6%) and anxiety disorders (25.7%) were most common; hypertension (29.5%) and diabetes (18.1%) were leading comorbidities. Ninety-nine drug pairs were evaluated, predominantly pharmacodynamic (72.7%). Most were rated “no interaction” (63.6–70.7%), while 27.3% required “monitor closely.” ADRs occurred in 52.4% (n=55), mainly mild (41.8%) or moderate (47.3%); 10.9% were severe. ADRs were more frequent in older patients (mean difference 1.96 years; p=0.034) and males (OR 3.65; p=0.0027). Conclusion: pDDIs are common in elderly psychiatric outpatients and often warrant close monitoring to reduce ADRs. Routine screening and multidisciplinary medication review may improve safety.