Snapshot A 52-year-old man presents to his primary care physician for a routine visit. On further questioning, the patient reports increased daytime urinary frequency, nocturia, slow urinary stream, and terminal dribbling. On digital rectal exam there is an enlarged prostate. The patient was started on finasteride. (Benign prostatic hyperplasia) Finasteride Mechanism of action 5α-reductase inhibitor resulting in ↓ conversion of testosterone to dihydrotestosterone Clinical use benign prostatic hyperplasia (BPH) androgenetic alopecia (in men only) also known as male pattern baldness Toxicity dizziness Flutamide Mechanism of action testosterone receptor blocker Clinical use prostate cancer Toxicity hot flashes decreased libido Ketoconazole Mechanism of action multiple mechanisms inhibits cytochrome P450 (14α-demethylase) login to view 1 more bullet inhibits fungal biosynthesis of triglycerides and phospholipids impairs androgen synthesis login to view 1 more bullet Clinical use prostate cancer Toxicity gynecomastia amenorrhea Spironolactone Mechanism of action potassium sparing diuretic competitive aldosterone receptor inhibitor in the cortical collecting tubule login to view 1 more bullet Clinical use hirsutism acne vulgaris (in women) Toxicity gynecomastia amenorrhea