Tizanidine as an Adjunct to Alpha-Blockers in Adults With Dysfunctional Voiding/Poor Relaxation of the External Sphincter: A Retrospective Review.

BACKGROUND

Skeletal muscle relaxants (SMR), particularly baclofen, have been used in patients with dysfunctional voiding (DV) and poor relaxation of the external sphincter (PRES) with variable efficacy and notable side effects. Tizanidine, a centrally acting α2-adrenergic agonist, may offer comparable benefits with a more favorable tolerability profile. However, data regarding its use in DV remain limited.

METHODS

This retrospective analysis included adults diagnosed with DV/PRES between July 2017 and January 2025. Data comprised demographics, lower urinary tract symptoms (LUTS), urodynamic parameters, pre, and posttreatment uroflowmetry values, and subjective response to alpha-blockers with pelvic floor relaxation exercises, and subsequent addition of tizanidine. Uroflowmetry indices included Qmax, Qave, and volume-normalized flow indices (VQImax, VQIave). Clinical outcomes were assessed via patient-reported symptom improvement.

RESULTS

Of 114 patients, 62.2% showed no response to alpha-blockers alone. Following addition of tizanidine (median dose 6 mg/day), 69.3% reported symptomatic improvement (45% ≥ 50% improvement, 24.6% < 50% improvement; p < 0.00001). VQImax improved by ≥ 50% in 52% of patients, and clinical improvement significantly correlated with changes in VQImax (p = 0.004) and VQIave (p = 0.009). Women demonstrated greater improvement in flow parameters than men (p < 0.05), although symptom relief was similar across sexes. Tizanidine was generally well tolerated, with sedation being the most common dose-limiting side effect (25%). Median follow up duration was 12 months (IQR 9-22).

CONCLUSIONS

Addition of tizanidine to alpha-blocker and pelvic relaxation is associated with clinically significant improvement in LUTS and uroflometry parameters in adults with pelvic floor dysfunction. We acknowledge that causal inference is limited by the study design and randomized placebo-controlled studies are required for deriving stronger conclusions.