Tolterodine use for symptoms of overactive bladder

OBJECTIVE: To describe the pharmacology, pharmacokinetics, clinical efficacy, and safety of tolterodine for the treatment of overactive bladder. DATA SOURCES: Published articles and abstracts were identified from a MEDLINE search (January 1980-October 1998) using the terms tolterodine, PNU-200583E, urge incontinence, overactive bladder, detrusor instability, detrusor overactivity, and antimuscarinic. Pertinent articles written in English were considered for review. Additional articles were identified from the bibliographies of retrieved articles. Data from the Food and Drug Administration-approved product labeling and the manufacturer were also used in the absence of published data. STUDY SELECTION AND DATA EXTRACTION: Clinical studies of tolterodine involving human subjects were evaluated. DATA SYNTHESIS: Tolterodine is a competitive muscarinic receptor antagonist with relative functional selectivity for bladder muscarinic receptors. It is metabolized in the liver by CYP2D6 to an active metabolite (DD 01), which is partially responsible for its pharmacologic activity. Those who are genetically devoid of CYP2D6 will have higher concentrations of the parent compound and virtually undetectable concentrations of DD 01; however, the clinical efficacy does not appear to be altered. In dosages of 2 mg twice daily, tolterodine has shown consistent reductions in the number of micturitions per 24 hours and less consistently decreased incontinence episodes in patients with detrusor overactivity. The functional selectivity of tolterodine for bladder muscarinic receptors results in fewer systemic adverse effects, such as dry mouth, than occur with comparable nonselective antimuscarinic agents. CONCLUSIONS: Clinical studies have shown that the effectiveness of tolterodine for symptoms of overactive bladder is similar to that of oxybutynin. The adverse effect profiles of tolterodine and oxybutynin are similar; however, comparative clinical trials have shown significantly fewer patients taking tolterodine require dosage reductions or discontinue therapy due to antimuscarinic adverse effects such as dry mouth. Although more costly than oxybutynin, tolterodine represents a modest improvement over oxybutynin with respect to adverse effect profile, which may allow more patients with incontinence to tolerate therapeutic doses. Further research is necessary to determine whether tolterodine has clinical advantages over similar agents in patients with other muscarinic adverse effects, such as constipation or cognitive impairment.