Potential negative pharmacodynamic interaction of spironolactone and abiraterone in two prostate cancer patients

INTRODUCTION: Spironolactone when combined with abiraterone in metastatic castration-resistant prostate cancer (mCRPC) may theoretically exert androgenic properties, thereby compromising the therapeutic effectiveness of abiraterone. CASE REPORT: Two patients with a medical history of cardiovascular disease and mCRPC combined spironolactone within the course of abiraterone regimen. The abiraterone-spironolactone interaction was identified using the Lexicomp® interaction tool (classified as risk C). MANAGEMENT & OUTCOME: Spironolactone treatment was maintained as it was considered beneficial due to the cardiac condition. The prostate-specific antigen (PSA) levels started to rise when these two drugs were used together. Eventually, tumour progression was observed. DISCUSSION: There is increasing evidence that spironolactone behaves as a selective androgen receptor modulator. Strategies to overcome abiraterone-spironolactone interaction could involve the use of eplerenone, although this drug is also controversial. The best strategy should imply a multidisciplinary evaluation by cardiologists and oncologists.