Gemtesa (Vibegron) for Overactive Bladder: Mechanism, Dosing, Efficacy & Safety

Gemtesa® (vibegron) is a selective β3-adrenoceptor agonist approved for OAB with urgency, frequency, and urgency incontinence. It offers an alternative to anticholinergics with a favorable side-effect profile.

Mechanism of Action

Vibegron binds β3-receptors on detrusor smooth muscle → activates adenylate cyclase → increases cAMP → smooth muscle relaxation during storage phase → increased bladder capacity, reduced urgency. No significant affinity for β1/β2 receptors → minimal cardiovascular effects.

Dosing & Administration

• Standard dose: 75 mg PO once daily, with or without food
• Renal impairment: No adjustment for mild/moderate (eGFR ≥30); avoid if eGFR <30 (insufficient data)
• Hepatic impairment: No adjustment mild/moderate; avoid severe (Child-Pugh C)
• Swallowing difficulty: Tablet can be crushed, mixed with applesauce/water, administered immediately

Key Clinical Trials

Trial	Design	Key Results (12 weeks)
EMPOWUR (Phase 3)	Vibegron 75 mg vs. tolterodine ER 4 mg vs. placebo (n=1,518)	Vibegron: -1.8 urgency episodes/day, -1.6 UUI episodes/day, -1.4 voids/day vs. placebo (all p<0.001); similar to tolterodine; less dry mouth (1.9% vs. 7.5%)
EMPOWUR Extension	52-week open-label	Sustained efficacy; dry mouth 3.1%, constipation 2.8%, hypertension 2.5%; discontinuation 8.6%
Phase 2b	Dose-ranging (25–150 mg)	75 mg optimal; 150 mg no added benefit, more adverse events

Adverse Events (≥2% & >Placebo)

• Headache (3.4%), nasopharyngitis (2.8%), diarrhea (2.5%), nausea (2.3%), upper respiratory infection (2.1%)
• Dry mouth: 1.9% (vs. 7–20% with anticholinergics)
• Constipation: 1.5% (vs. 5–15% with anticholinergics)
• Hypertension: Monitor BP; exclude uncontrolled HTN
• Urinary retention: Rare; caution with BOO, high PVR, concomitant anticholinergics

Drug Interactions

• Strong CYP3A4 inhibitors (ketoconazole, clarithromycin, itraconazole, HIV protease inhibitors) → increase vibegron exposure; avoid or use 75 mg with monitoring
• Strong CYP3A4 inducers (rifampin, carbamazepine, phenytoin, St. John's wort) → decrease exposure; avoid
• Digoxin: Monitor levels (P-gp substrate)

Contraindications & Precautions

• Hypersensitivity to vibegron or components
• Pregnancy: No human data; animal studies show fetal effects at high doses — use only if benefit > risk
• Lactation: Unknown excretion — advise against
• Severe renal/hepatic impairment: Avoid
• Narrow-angle glaucoma: Theoretical risk (anticholinergic-like); not observed clinically

Positioning in Therapy

First-line for OAB patients who: cannot tolerate anticholinergic side effects (dry mouth, constipation, cognitive burden), have contraindications to anticholinergics (narrow-angle glaucoma, gastric retention, severe constipation), or are elderly/frail (Beers Criteria: avoid anticholinergics). Also used as add-on to anticholinergic if monotherapy insufficient.

Gemtesa provides effective OAB control with a side-effect profile that addresses the main adherence barriers of older therapies.