Urinary incontinence (enuresis) has been reported in between 1% and 20% of patients taking clozapine. It usually occurs at night during the first three months of treatment. A number of mechanisms have been proposed, including sedation or α-adrenergic blockade. Initial management options include limiting fluid intake during the evening, voiding at bedtime, and scheduling a middle-of-the-night awakening to empty the bladder. Enuresis alarms can also be used. There is limited research or consensus regarding pharmacological approaches to management of this side effect of incontinence. There is some evidence supporting desmopressin, oxybutynin, and pseudoephedrine. Serum sodium should be assessed if using desmopressin. The use of a second antipsychotic medication increases the risk for enuresis, so there should be consideration of tapering off non-clozapine antipsychotic medications.
Urinary retention is a relatively rare problem in isolation with clozapine, but has been reported. Urinary retention can present as lessening of urinary output, bladder sensations, abnormal urinary flow, straining to void, and discomfort or pain. If urinary retention is suspected, the patient should be promptly evaluated with consideration for emergent drainage. Imaging via a bladder scan or point of care ultrasound can help to evaluate the presence or degree of urinary retention. Other potential causes of urinary retention should be considered, including neurological conditions, post-operative complications, diabetes, prostatic hypertrophy, other medications, and obstructions. Benign prostatic hypertrophy (BPH) is one of the most common causes of urinary retention in men. Consultation with urology might be helpful to evaluate for other medical causes of urinary retention. Clinicians should minimize the amount of other anticholinergic medications prescribed. There have been some non-pharmacologic strategies proposed for urinary retention such as physical therapy (pelvic floor exercises), timed voiding (urinating at scheduled times) and double voiding (waiting a short time after voiding then trying again).