BPH Medications, Bethanechol, and Urinary Retention

Benign prostatic hyperplasia is hyperplastic growth of stromal and epithelial cells in the prostate’s transition zone. As this tissue enlarges, it narrows the bladder outlet and increases urethral resistance. The bladder initially compensates by generating stronger contractions, but persistent obstruction can eventually produce incomplete emptying and urinary retention. Lower urinary tract symptoms may be predominantly voiding symptoms—hesitancy, weak stream, intermittency, straining, and incomplete emptying—or storage symptoms such as urgency, frequency, and nocturia. Urinary retention is not a medication choice; it is a clinical state whose cause must be identified. The critical distinction is whether the outlet is blocked or the detrusor is failing. Bethanechol can stimulate a weak bladder muscle, but it cannot open a mechanically narrowed outlet. Giving it to a patient with significant BPH obstruction can increase bladder pressure without producing emptying.