Source: Am J Med Genet  |  Posted 7 years ago

By Ed Susman

ORLANDO, FL -- October 15, 2004 -- The incidence of dry mouth -- the most annoying of adverse side effects associated with overactive bladder treatments -- appears to be lower with the investigative, M3 selective receptor antagonist darifenacin than with the less selective antimuscarinic agent oxybutynin.

"We were specifically looking at the side effect profile of these drugs in this particular study," said Ursula Ebinger, MD, Urologist, Medical Director for Darifenacin, Novartis Pharmaceuticals Corporation, East Hanover, New Jersey.

Dr. Ebinger presenter her study during a poster session at the 17[^]th[] World Conference of Family Doctors, being held in conjunction with the American Academy of Family Physicians Scientific Assembly.

In the trial, four men and four women were given darifenacin 2.5 mg and three women and five men were given oxybutynin 2.5 mg for a week. Patients' mean salivary flow was measured. In this low dose group, the researchers found no significant differences between the two groups.

In a second, larger study group, four women and eight men received 15 mg daily of darifenacin, and five women and seven men received oxybutynin 5 mg taken 3 times a day. In this group, Dr. Ebinger and her colleagues measured differences in salivary flow. All the patients in both studies had been diagnosed with overactive bladder.

The 5 mg oxybutynin resulted in a 1.55 mL/min decrease in salivary flow compared to a 0.9 mL/min decrease among those on darifenacin 15 mg, she reported.

"Dry mouth was consistently reported more often among those receiving oxybutynin," Dr. Ebinger said. However, one patient taking darifenacin 15 mg discontinued treatment due to severe dry mouth.

"These results suggest that up to 15 mg a day of darifenacin has the potential for less dry mouth compared with oxybutynin 15 mg [taken in three 5 mg doses] a day," she said. "This may be explained by the M1-sparing properties of darifenacin, reducing the overall occupancy of muscarinic receptor subtypes in the salivary glands."

Darifenacin, being developed by Novartis, the sponsor of the study, is now in phase 3 trials, Dr. Ebinger said, and the company is planning to more forward with a 15 mg dose.

[Presentation title: "Darifenacin Versus Oxybutynin for Overactive Bladder." Poster 4029]