Potential Drug-Drug Interactions Between Anti-Cancer Drugs and Other Medications in Lung Cancer Patients: A Retrospective Study

Background: Cancer patients are more vulnerable to developing drug-drug interactions as multiple medications are administered concomitantly with cytotoxic agents to treat the underlying comorbidities. These drug-drug interactions often receive less medical attention and consequently are associated with adverse clinical outcomes. Objective: We intended to comprehensively characterize the drug-drug interactions among anticancer drugs and other concomitantly prescribed drugs in hospitalized lung cancer patients. Methods: A retrospective, observational, single-centre study was conducted on lung cancer inpatients from the medical records department of Kasturba Hospital, Manipal, India. Drug-drug interactions were identified using the drug interaction checkers of two drug information databases, Micromedex and Epocrates. These drug-drug interactions were categorized based on the source from which they were identified, mechanism, severity/significance, adverse consequences, and management strategies required. Results: Among 196 patients, 555 drug-drug interactions were identified in 185 patients using Micromedex and Epocrates. Based on the mechanism of action, 74% and 22% of the drug-drug interactions were classified as pharmacodynamic and pharmacokinetic respectively. 112 drug-drug interactions were recorded from Micromedex alone, while 549 interactions were found using Epocrates. The oral chemotherapeutic drug gefitinib was found to be associated with the highest number of drug-drug interactions. Conclusion: Drug-drug interactions were highly prevalent among hospitalized lung cancer patients. Structured screening and monitoring for these potentially clinically relevant drug-drug interactions by oncologists in collaboration with clinical pharmacists should be carried out prior to initiation and during anticancer treatment to prevent adverse clinical outcomes.