Why does vesicare (solifenacin) take so long to work?

Ought be in few days: Possible that your dose is too low, some respond to 5mg/day, others 10mg or more/day. Discuss with your Dr., she/he may advise increasing dose if no effect after 10-14 days. You might possibly be a non responder to Vesicare (solifenacin) but may respond to Oxybutynin ER 10, 15, 20 or 30mg/day. Dry mouth, common side effect of all anticholinergic medications, would indicate that you are on enough medication.