Potential Drug-Drug Interactions in Psychiatric Ward of a Tertiary Care Hospital: Prevalence, Levels and Association with Risk Factors

Purpose: To identify the prevalence of potential drug-drug interactions (pDDIs) in a psychiatric ward, their levels and association with risk factors.Methods: This study was conducted in the psychiatric ward of Ayub Teaching Hospital, Abbottabad, Pakistan. Medical records of 415 patients were retrospectively reviewed for pDDIs using Micromedex Drug-Reax software. Logistic regression was applied to determine association of pDDIs with age, gender, hospital stay and number of drugs.Results: In our study, we identified total number of 825 pDDIs of 126 types, with median number of 1 pDDIs per patient. Overall 64.8 % of the patients had at least one pDDI; 27.2 % at least one major pDDI; and 58.5 % patients at least one moderate pDDI. Among 825 identified pDDIs, most were of moderate (75.6 %) or major (20.8 %) severity, good (66.4 %) or fair (29 %) type of scientific evidence; and delayed onset (71 %). The most frequent major and moderate pDDIs included haloperidol + procyclidine (127 cases), haloperidol + olanzapine (49), haloperidol + promethazine (47), haloperidol + fluphenazine (41), diazepam + divalproex sodium (40), haloperidol + trihexyphenidyl (37), lorazepam + divalproex sodium (34), fluphenazine + procyclidine (33) and olanzapine + divalproex sodium (32). There was significant association of occurrence of pDDIs with hospital stay of 7 days or longer (p = 0.005) and taking 7 or more drugs (p < 0.001).                                                       Conclusion: A high prevalence of pDDIs in the psychiatric ward was recorded, a majority of which were of moderate severity. Patients with long hospital stay and increased number of drugs were more exposed to pDDIs.