Potential drug-drug interactions among hospitalized patients in a developing country.

Background: Drug-drug interactions (DDIs) may often lead to preventable adverse drug events and health damage. Particularly in hospitals, this might be an important factor as multiple drug therapies are common. The objective of this study was to identify the frequency and levels of potential DDIs in internal medicine wards in an Iranian university hospital.

Methods: A cross-sectional study was conducted by reviewing charts of 448 hospitalized patients in internal medicine wards of a teaching hospital, from November 2014 to May 2015. "Lexicomp drug interaction software" and Micromedex Drug-Reax system were used for screening the potential DDIs. The identified DDIs were categorized by level of severity. Logistic regression was applied to determine the odds ratio for specific risk factors of potential DDIs e.g., age, gender, hospital stay and number of medications.

Results: The mean age of patients was 61 years, the length of hospital stay for patients was 9 days and the number of drugs per patient was 9. Potential interactions were detected in 386 patients. The most common types of interactions were type C (78.6%), moderate (60.9%) and delayed onset (56.5%). There was a significant association of the occurrence of potential DDIs with seven or more numbers of prescribed medications (OR: 0.048, 95% CI:0.02-0.12, p<0.0001).

Conclusion: The present study has recorded a high prevalence of potential DDIs in internal medicine wards. Patients with polypharmacy were at high risk for DDIs. Education, computerized prescribing systems, drug information, and pharmaceutical care are important measures that were recommended to minimize harm associated with DDIs.