Drug use survey to identify significant drug-drug interactions and assess clinical importance in the outpatient setting of a tertiary care hospital.

Objectives: Drug-drug interactions (DDIs) are a common problem in pharmacotherapy, particularly in situations where multiple disorders must be treated at the same time. We conducted a drug use survey in the general medicine outpatient department of a tertiary care hospital with the objective of assessing the potential for DDI in individual prescriptions for adult patients.

Materials and methods: Drugs prescribed in the current physician-patient encounter were considered in conjunction with medicines already being received by the patient as well as those discontinued in the past 1 month. Free online DDI checkers (available at https://www.drugs.com/drug_interactions.html and https://reference.medscape.com/) were used to identify potential DDI and categorize them into mild, moderate, and severe categories. We did not consider food, alcohol, or smoking-related interactions.

Results: A total of 153 prescriptions, having two or more drugs, were collected, and they accounted for 1052 prescribed drugs. Among them, 613 (58.27%) were prescribed in index visits, and the rest 438 (41.63%) were preexisting medication. The number of drugs prescribed in index visits ranged from 1 to 9 (mean ± standard deviation [SD] 4.0 ± 1.86; median 4). Potential DDIs were identified in 103 (67.32%) instances. The total number of interactions identified was 412. Of these, 19.66% had minor, 77.67% moderate, and 7.19% major clinical implications. Potential DDI count in each prescription was found from 0 to 13 in number (mean ± SD 2.7 ± 3.12; median 2.0). This number correlated strongly with the number of drugs being received by individual subjects (Rho 0.744; P < 0.001).

Conclusions: Potential DDIs are a reality in day to day prescribing practice. Substantial proportion of these DDIs may have significant clinical implications. Prescribers need to be sensitized to this issue. Combining human expertise with technological solutions such as automated drug interaction alerts can help rectify the situation. Similar surveys are needed on a periodic basis to improve medication safety for patients.