Tolterodine, a new antimuscarinic drug for treatment of bladder overactivity

Tolterodine is a nonsubtype selective antimuscarinic agent recently approved as therapy in patients with overactive bladder with symptoms of urinary frequency, urgency, or urge incontinence. It acts by muscarinic receptor blockade in the bladder wall and detrusor muscle. Despite short terminal disposition half-lives of 2-3 and 3-4 hours for tolterodine and its active 5-hydroxy metabolite, respectively, twice/day dosing is effective due to the drug's prolonged pharmacodynamic effects. Dosage adjustment is recommended in the presence of hepatic impairment and during concurrent therapy with drugs that inhibit cytochrome P450 2D6 and 3A4 isozymes. Tolterodine significantly reduces clinically relevant end points such as number of micturitions and number of incontinence episodes/day. In general, it is superior to placebo and equivalent to oxybutynin in this regard. As might be expected from its pharmacologic profile, the principal adverse effects of the drug are anticholinergic. In clinical trials, tolterodine was tolerated significantly better than oxybutynin. Its relative merits as a first- or second-line agent for patients intolerant of oxybutynin are unclear. Until pharmacoeconomic analyses are conducted that clearly justify use of this more expensive agent, tolterodine is perhaps best reserved for patients who are intolerant of or fail oxybutynin therapy.