Solifenacin shows advantage in several OAB outcome measures

Two newer-generation antimuscarinic agents - solifenacin succinate (Vesicare) and tolterodine tartrate extended-release (Detrol LA) - improve symptoms of overactive bladder, but solifenacin appears to provide superior outcomes, partly because it offers a flexible dosing regimen, researchers say.

As part of the prospective, double-blind solifenacin versus tolterodine multinational trial (STAR), 1,117 patients with overactive bladder entered a 2-week single-blind placebo period to establish baseline scores, followed by randomization to treatment with solifenacin, 5 mg, or tolterodine, 4 mg. After 4 weeks, patients had the option to increase their drug dosage. Patients choosing to increase their dose in the solifenacin arm went up to 10 mg of the drug; those in the tolterodine arm added a placebo to their 4-mg dose, since tolterodine is only recommended for use in doses of 4 mg, while solifenacin is recommended in doses of 5 and 10 mg.

"Being that the solifenacin regime has got two dosages means that it does address a population of patients that the tolterodine can't," said senior author John Bolodeoku, MB, senior director of medical affairs and health economics at Astellas Pharma Europe, Ltd., the maker of solifenacin.

After a total trial period of 12 weeks, both drugs improved symptoms, based on the Perception of Bladder Condition measure. Solifenacin, however, was associated with significantly greater improvement. Solifenacin also fared better on objective analyses, including decrease in urge incontinence (p=.001), number of urgency episodes (p=.035), number of incontinence episodes (p=.005), and incontinence pad use (p=.002).

Both drugs were associated with antimuscarinic side effects, including dry mouth, constipation, and blurred vision, at similar rates. Patients receiving the higher dose of solifenacin did show higher rates of side effects but not higher rates of discontinuation due to side effects.

"We've been long waiting to see a comparison between these two new-generation antimuscarinics," said Dr. Bolodeoku. "The solifenacin-treated patients fared better than the treatment regime of tolterodine ER."