Metastatic castration resistant prostate cancer (mCRPC) patients are generally older patients with several co-morbidities and are therefore more at risk for complications due to drug-drug interactions(DDIs). We assessed the prevalence of potential DDIs in a cohort of mCRPC patients treated with enzalutamide.
We conducted a retrospective review of pharmacy records to retrieve individual drug histories of mCRPC patients who started enzalutamide therapy in a tertiary care setting. Potential DDIs were analyzed using two international drug interaction compendia: Lexicomp® and Micromedex®, and the Dutch drug database. Two potential pharmacodynamic DDIs were analyzed.
105 records were evaluated for potential DDIs with enzalutamide, 56 out of 205 different co-medications were flagged by at least one of the three compendia. Lexicomp, Micromedex and the Dutch drug database flagged for potential DDIs in 85%, 54% and 32%, respectively. 85% of DDIs were classified as major. The median number of co-medications per patient was 11(range 1-26). The median (range) number of interactions per patient was 4(0-10),1(0-5) and 0(0-2) for Lexicomp, Micromedex and the Dutch drug database, respectively. In 23% and 45% of all patients a potential DDI was found with PPIs and CNS depressants, respectively.
A high prevalence of potential DDIs was found. The inclusion and grading of potential DDIs was highly variable between the three drug interaction compendia. Physicians, nurses and pharmacists should be aware of this potential problem, which might require intensive monitoring or alternative treatment strategies to prevent suboptimal treatment of the co-morbidities in patients treated with enzalutamide.
British journal of clinical pharmacology. 2017 Sep 07 [Epub ahead of print]
G E Benoist, I M van Oort, S Smeenk, A Javad, D M Somford, D M Burger, N Mehra, N P van Erp
Department of Pharmacy, Radboud University Medical Center, Nijmegen, The Netherlands., Department of Urology, Radboud University Medical Center, Nijmegen, The Netherlands., Department of Medical Oncology, Radboud University Medical Center, Nijmegen, The Netherlands., Department of Urology, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands.