A study of drug-drug interactions in cancer patients of a south Indian tertiary care teaching hospital

Background: Drug interactions in oncology are of particular importance owing to the narrow therapeutic index and the inherent toxicity of anticancer agents. Interactions with other medications can cause small change in pharmacokinetics or pharmacodynamics of chemotherapeutic agents that could significantly alter their safety and efficacy. Aim: To identify and document the potential drug-drug interactions in prescriptions of patients receiving cancer chemotherapy. Settings and Design: A tertiary care teaching hospital based prospective study. Materials and Methods: Patients admitted in the medical oncology wards with different types of malignancies and receiving cancer chemotherapy during the period of June 2009 to November 2009 were included in the study. A detailed data collection was done in a specially designed proforma with ethical approval and consent of patients and their prescriptions were subjected to drug-drug interaction screening using Drug Interaction Fact Software Version-4 and standard references. Incidence of drug-drug interactions, their types, correlation between age, cancer type, number of drugs prescribed and incidence of drug interactions were analyzed. Statistical Analysis: Logistic regression analysis and Odds ratio were performed to identify the incidence of drug-drug interactions and their correlation with the factors above mentioned. Results: A total of 75 patients (32 males and 43 females; median age 56 years, age range 23-74) were enrolled in the study and their prescriptions were screened. 213 interactions were identified of which, 21 were major, 121 were moderate and 71 were minor. There were 13 (6.1%) clinically significant interactions between anticancer drugs and 14 (6.5%) drug-drug interactions between anticancer drugs and other drugs prescribed for co-morbidities. There was a positive correlation between number of drugs prescribed and drug interactions (P=0.011; OR 0.903). Conclusion: Though there was not any life threatening interactions, the potential interactions were brought to the oncologist purview for ensuring patients safety and to avoid undesirable effects.