Urinary retention is defined as the inability to empty the bladder completely and may present acutely, with painful suprapubic distension, or chronically, with more subtle lower urinary tract symptoms. It is a clinically significant condition that can lead to complications such as recurrent urinary tract infections, bladder dysfunction, hydronephrosis, and renal impairment if left untreated. While urinary retention may arise from neurological, pharmacological, infective, or obstructive causes, in older men the most common underlying aetiology is Benign prostatic hyperplasia (BPH). BPH is characterised by non-malignant enlargement of the prostate gland, which surrounds the proximal urethra. As the prostate increases in size, it narrows the urethral lumen and impedes urinary flow, resulting in bladder outlet obstruction. This mechanical and functional obstruction contributes to symptoms such as hesitancy, weak stream, intermittency, incomplete emptying, frequency, and nocturia. Over time, chronic obstruction may impair detrusor muscle function and predispose to acute urinary retention. Adobe stock Fig 1: Benign prostatic hyperplasia (BPH). Comparison between normal prostate and enlarged prostate. Pathophysiology Two major components contribute to obstruction in BPH: Static component: Enlarged prostate compresses the urethra. Dynamic component: Increased alpha1-adrenoceptor–mediated tone in the prostate and bladder neck. Pharmacological Management The primary pharmacological classes for managing urinary retention and BPH are: 1. Alpha1-Adrenoceptor Blockers Examples: Tamsulosin, Alfuzosin, Doxazosin, Terazosin These agents act by relaxing smooth muscle in the prostate and bladder neck through antagonism of α₁-adrenoceptors, thereby reducing the dynamic component of obstruction. They provide relatively rapid symptomatic relief, often within days to weeks, but do not reduce prostate size. Common adverse effects include postural hypotension, dizziness, and ejaculatory disturbance. 2. 5α-Reductase Inhibitors Examples: Finasteride, Dutasteride These drugs inhibit the conversion of testosterone to dihydrotestosterone (DHT), a key driver of prostatic growth. By lowering intraprostatic DHT levels, they gradually reduce prostate volume and address the static component of obstruction. Clinical benefit may take several months to become apparent. 3. Phosphodiesterase Type 5 (PDE5) Inhibitors Example: Tadalafil may be considered when erectile dysfunction coexists. PDE5 inhibition enhances nitric oxide-mediated smooth muscle relaxation in the lower urinary tract, improving urinary symptoms while simultaneously treating erectile dysfunction. Summary Urinary retention, particularly in older men, is most commonly attributable to benign prostatic hyperplasia, a condition characterised by both mechanical and functional obstruction of the bladder outlet. Recognition of the static and dynamic components of BPH has guided the development of effective pharmacological therapies that target smooth muscle tone, prostate size, or both. Alpha₁-adrenoceptor blockers offer rapid symptomatic relief, 5α-reductase inhibitors provide long-term disease modification, and PDE5 inhibitors may offer dual benefit in selected patients. A tailored approach based on symptom severity, prostate size, comorbidities, and patient preference is essential to optimise outcomes. Early recognition and appropriate management not only improve quality of life but also reduce the risk of complications such as acute urinary retention and progressive bladder dysfunction. Rate This Article