Abstract
Background: Drug-drug interactions (DDIs) often pose a greatest challenge to health-care providers in patient care, hence their prediction, identification, and prevention are of prime importance.

Aims and Objectives: The aims of the study were to evaluate the potential DDIs (pDDI) and factors influencing clinically relevant pDDI in ischemic heart disease (IHD) patients.

Materials and Methods: An analytical cross-sectional study conducted from April to September 2018 to analyze the pDDIs among the outpatients of the Cardiology Department at Bangalore Medical College and Research Institute. All patients with a history of IHD on at least two drugs were included in the study. Patient demographic data and prescription details (drugs prescribed, duration of therapy, and number of drugs) were collected in a case record form. Drug data were analyzed for interactions using a drug interaction software (Lexicomp version 4.1.1) by risk rating scale (category A, B, C, D, or X).

Results: Of 520 IHD patients, 489 had 3217 pDDIs. The average number of drugs prescribed per patient was 6.4±1.6 and most commonly prescribed drugs were aspirin (93%), atorvastatin (88%), clopidogrel (60%), metoprolol (57%), and ramipril (43%). Aspirin and clopidogrel (54%), aspirin and ramipril (40%) were the most commonly interacting pairs. The majority of the interactions were of category C, i.e. which requires monitoring of therapy. Number of drugs prescribed and hypertension was found to be the factors significantly influencing clinically relevant pDDIs.

Conclusion: Antiplatelets and statins were the most commonly prescribed drugs in IHD and contributed to most of the pDDIs in particular categories C and D. In addition to number of drugs, comorbidity also influences pDDIs. Awareness regarding DDIs should be raised among prescribers which will enable them to recognize potentially harmful drug combinations and avoid them or to monitor therapy if such drugs are deemed essential.

Key words: Aspirin, Clopidogrel, Ischemic heart disease, Potential drug-drug interactions