A 64-year-old man comes to the office due to urinary frequency, hesitancy, and dribbling. His symptoms began insidiously 5 years ago and have progressively worsened. He has to get up 2 or 3 times each night to urinate. Vital signs are normal. Examination shows a smooth, symmetrically enlarged prostate without nodules or tenderness. There is no suprapubic tenderness. Prostate-specific antigen level is 3.5 ng/mL, creatinine is 1.2 mg/dL, and urinalysis is normal. The patient is started on a new medication. After 6 months of therapy, his urinary symptoms improve and prostate volume decreases by 20%. Which of the following medications is most likely responsible for the decreased prostate volume in this patient?
Medical therapy for benign prostatic hyperplasia | |
α-Adrenergic antagonists |
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5-α Reductase inhibitors |
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Antimuscarinics |
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This patient has benign prostatic hyperplasia (BPH). BPH is due to the effects of dihydrotestosterone on prostatic epithelial cells and is characterized by progressive prostatic enlargement with age, leading to bladder outlet obstruction and incomplete bladder emptying. Typical symptoms include urinary frequency, nocturia, hesitancy, and weak urinary stream. The bladder outlet obstruction is made up of a dynamic component (smooth muscle tone in the bladder neck, prostate capsule, and prostatic urethra) and a fixed component (structural effects of the enlarged prostate).
Alpha adrenergic antagonists (eg, terazosin, tamsulosin) are smooth muscle relaxants that work on the dynamic component of bladder outlet obstruction. They work within days to weeks. However, these drugs do not significantly affect prostate volume (Choice D). 5-alpha reductase inhibitors (eg, finasteride, dutasteride) inhibit the conversion of testosterone to dihydrotestosterone and address the fixed component of bladder outlet obstruction. Over time, they reduce prostate volume but can take up to 6-12 months to achieve maximal effect.
(Choice B) Phenazopyridine is a urinary analgesic that provides symptomatic relief of dysuria in urinary tract infections. It is not effective for BPH and does not affect prostate volume.
(Choice C) Tadalafil is a phosphodiesterase-5 inhibitor that is primarily used to treat erectile dysfunction. Although some studies have shown symptom improvement in BPH, tadalafil does not significantly decrease prostate volume.
(Choice E) Antimuscarinics (eg, tolterodine) are used to treat overactive bladder symptoms (eg, urinary frequency, urgency, incontinence). They can cause urine retention and are normally used in BPH only once another drug has addressed the bladder outlet obstruction. They do not affect prostate volume.
Educational objective:
5-alpha reductase inhibitors (eg, finasteride, dutasteride) block the conversion of testosterone to dihydrotestosterone in the prostate. These drugs reduce prostate volume in patients with benign prostatic hyperplasia and relieve the fixed component of bladder outlet obstruction.