How long do prescription pills for painful urination take to start working?

Quickly. Such medications as Pyridium (phenazopyridine) usually kick in within a few hours.
Few hours, 1-3 days. Pain relievers like Phenazopyridine (pyridium), acetomenophen (tylenol), work within hours – as soon as they are absorbed and reach the site of the pain in the bladder. Antibiotics that treat and eliminate the usual source of the pain (urine infection with bacteria from the bowel) work within 1-3 days in 2/3rds of patients with infection sensitive to the antibiotic used.