Atypical presentation of urinary retention induced by low-dose venlafaxine

Abstract: Venlafaxine, a serotonin–norepinephrine reuptake inhibitor, is commonly prescribed for depressive disorders and is usually well tolerated. However, urinary retention has been reported as a rare but clinically significant adverse effect. We describe the case of a 59-year-old male with major depressive disorder who developed acute urinary retention 1 week after initiating venlafaxine 37.5 mg/day. Clinical evaluation revealed prostatomegaly and evidence of bladder outlet obstruction. Venlafaxine was discontinued, and the patient underwent catheterization followed by the initiation of tamsulosin and dutasteride therapy, resulting in symptomatic improvement and successful recovery. The likely mechanism is related to venlafaxine’s enhanced noradrenergic and serotonergic activity, which may impair detrusor muscle function and exacerbate preexisting prostatic obstruction. This case highlights the need for clinicians to remain vigilant for urinary complications when prescribing venlafaxine, especially in patients with known risk factors such as benign prostatic hyperplasia. Prompt recognition and drug withdrawal are crucial, and alternative antidepressants such as mirtazapine may be considered in susceptible individuals.