Overactive Bladder: When You Have to Go, Go, Go
The study was funded by Alza Corporation, of Mountain View, Calif., which manufactures Ditropan. Appell is head of the corporation's scientific advisory board. He is also the F. Brantley Scott Professor of Urology at Baylor College of Medicine in Houston.
Ditropan XL is a new version of a drug long used for overactive bladder -- but the older version was associated with significant side effects, including dry mouth and blurred vision. As Appell explains, enzymes in the stomach and the small intestine break down the active agent in the older form of Ditropan into a metabolite, which gets into the bloodstream and causes the side effects.
But the new drug employs an ingenious system to bypass the stomach and small intestine and deliver the drug to the large intestine, which is free of the enzymes. "It's a capsule with a tiny hole in it," Appell says. "As it goes through the intestinal system it sucks in water, which pushes out the medication. That delays the delivery of the drug until it gets into the large intestine."
The drug appears to act by inhibiting release of acetylcholine, a chemical in the central nervous system that causes the bladder to contract. "In patients with an overactive bladder, the main problem is over-stimulation of the bladder muscle and the nerves going to the bladder," says Elliott, who wrote an editorial accompanying the report. "The medications are designed to blunt or lower the response of those muscles and help the bladder relax."
Elliott says both drugs are expensive, costing about $74 per month. The high price of the treatment makes it necessary to know which is the one that gives patients "the best bang for the buck," he says.
Alan Wein, MD, professor and chair of urology at the University of Pennsylvania School of Medicine, took issue with some aspects of the trial, though. The difference in effectiveness of the two drugs, while statistically significant, was not great, he tells WebMD.
The difference in average number of incontinence episodes per week for the two drugs, for instance, was about two, Wein notes.
And he is critical of the study because it did not include a placebo to determine how much of the effects of either drug could be merely random. Finally, Wein says that a new version of Detrol, called Detrol LA -- which, like Ditropan XL, is taken once a day -- has since been developed and been shown to have even lower side effects than what was reported for Detrol.
As for all incontinence medications, Appell says most patients will need to be on medication for an indefinite period of time. But some -- perhaps 30% -- will be able to quit the medication after a short period of treatment, he tells WebMD.