Review Question - QID 215029

This elderly man with nocturia, slow urine stream, and straining to void with an unremarkable urinalysis has typical features of benign prostatic hyperplasia (BPH). Alpha-1-adrenergic antagonists, such as tamsulosin or doxazosin, provide immediate symptomatic relief but can cause orthostatic hypotension as a side effect.

BPH is caused by the proliferation of prostatic stromal and epithelial cells in the periurethral zone, leading to urinary outflow obstruction. Alpha-1-adrenergic receptors are found in smooth muscle cells in the vasculature, bladder, prostate, and urethra. When stimulated, these G protein-coupled receptors initiate a signaling cascade that ultimately results in the activation of protein kinase C (PKC), which mediates downstream effects including vasoconstriction in the vasculature and constriction of smooth muscle in the bladder neck, prostate, and urethra. Alpha-1-adrenergic blockade reverses these effects, leading to relaxation of smooth muscle lining the urethra which relieves urinary outflow obstruction. However, since alpha-1-adrenergic receptors are also found in blood vessels, the side effects of alpha-1-adrenergic antagonists include hypotension due to vasodilation and reflex tachycardia as a compensatory response to hypotension.

Incorrect Answers:
Answer 1: Achilles tendinopathy is a side effect of fluoroquinolones (e.g., ciprofloxacin) which can rarely cause tendon rupture. Fluoroquinolones may be used in the treatment of urinary tract infections, which would be expected to manifest with dysuria and positive leukocyte esterase and/or nitrites on urinalysis.

Answer 2: Bradycardia is a side effect of beta-blockers, which are not used in the treatment of BPH. Instead, BPH causes a reflex tachycardia due to hypotension.

Answer 3: Gynecomastia is a side effect of finasteride, which is a 5-alpha-reductase inhibitor used in the long-term treatment of BPH. Finasteride does not provide immediate symptomatic relief and requires long-term treatment (6-12 months) for symptom improvement.

Answer 4: Lactic acidosis is a potential side effect of metformin, especially in patients with underlying renal insufficiency. Metformin is a first-line agent used for the treatment of diabetes mellitus, which could present with nocturia but would not cause a slow urine stream or straining to void. Metformin also does not provide rapid relief of urinary symptoms.

Bullet Summary:
Alpha-1-adrenergic antagonists such as tamsulosin and doxazosin provide immediate relief of urinary outflow obstruction in benign prostatic hyperplasia (BPH) but can cause hypotension as a side effect.