Drug-drug interaction potential in men treated with enzalutamide: Mind the gap.

AIMS: Metastatic castration-resistant prostate cancer (mCRPC) patients are generally older patients with several co-morbidities and are therefore at increased risk of complications due to drug-drug interactions (DDIs). We assessed the prevalence of potential DDIs in a cohort of mCRPC patients treated with enzalutamide. METHODS: 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 analysed using two international drug interaction compendia: Lexicomp® and Micromedex® , and the Dutch drug database. Two potential pharmacodynamic DDIs were analysed. RESULTS: A total of 105 records were evaluated for potential DDIs with enzalutamide. Of 205 different co-medications, 56 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. Eighty-five per cent 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. CONCLUSIONS: 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.

An update on extravasation: basic knowledge for clinical pharmacists.

Extravasation is the leakage of intravenously administered solution into surrounding tissues, which can cause serious damage to the patient. The impact of extravasation is mostly determined by the localisation and volume of extravasation, but the physicochemical properties of the drugs are also important. In this paper a stepwise approach to managing an extravasation is described, with recommendations on the role of the pharmacist. Information on osmolality, pH, pKa and the buffering capacity of drugs is given in relation to extravasation, which is summarised in a practical crash card that can be used in clinical practice.