Retrospective Evaluation of Drug-Drug Interactions With Erlotinib and Gefitinib Use in the Military Health System

Thu-Lan T Luong; Chelsea N Powers; Brian J Reinhardt; Michael J McAnulty; Peter J Weina; Karen J Shou; Caban B Ambar

doi:10.12788/fp.0401

Retrospective Evaluation of Drug-Drug Interactions With Erlotinib and Gefitinib Use in the Military Health System

Fed Pract. 2023 Aug;40(Suppl 3):S24-S34. doi: 10.12788/fp.0401. Epub 2023 Aug 15.

Authors

Thu-Lan T Luong¹, Chelsea N Powers¹, Brian J Reinhardt¹, Michael J McAnulty¹, Peter J Weina², Karen J Shou¹, Caban B Ambar¹

Affiliations

¹ Walter Reed National Military Medical Center, Bethesda, Maryland.
² Fort Belvoir Community Hospital, Virginia.

Abstract

Background: Erlotinib and gefitinib are epidermal growth factor receptor-tyrosine kinase inhibitors approved for non-small cell lung cancer treatment by the US Food and Drug Administration. Drug-drug interactions (DDIs) with these agents are vague and poorly understood. Because DDIs can have an effect on clinical outcomes, we aimed to identify drugs that interact with erlotinib or gefitinib and describe their clinical manifestations.

Methods: A retrospective analysis was performed on the health records of patients in the US Department of Defense Cancer Registry (retrieved September 2021), Comprehensive Ambulatory/Professional Encounter Records, and Pharmacy Data Transaction Service database (both retrieved May 2022). Patients' medical history, diagnoses, and demographics were extracted and analyzed for differences in adverse effects when these agents were used alone vs concomitantly with other prescription drugs. Patients' diagnoses and prescription drug use were extracted to compare completed vs discontinued treatment groups, identify medications commonly co-administered with erlotinib or gefitinib, and evaluate DDIs with antidepressants.

Results: Of 387 patients using erlotinib, 264 completed treatments; 28 of 33 patients using gefitinib completed treatment. The P value for erlotinib discontinuation when used alone vs concomitantly was < .001, and the P value for gefitinib discontinuation was .06. Patients who took erlotinib or gefitinib concomitantly with a greater number of prescription drugs had a higher rate of treatment discontinuation than those who received fewer medications. Patients in the completed group received 1 to 75 prescription drugs, and those in the completed group were prescribed 3 to 103. Those who discontinued treatment had more diagnosed medical issues than those who completed treatment.

Conclusions: This review cannot conclude that concomitant use with prescription drug(s) resulted in erlotinib or gefitinib discontinuation. There were no significant DDIs determined between erlotinib or gefitinib and antidepressants.