Drug update: overactive bladder.(Gynecology)

Health professionals increasingly recognize that an overactive bladder (OAB) presents significant quality-of-life problems for patients and warrants aggressive treatment. More medications are now available for treatment, including a trans-dermal patch that received Food and Drug Administration approval this year, and still more medications are on the way.

Only 20% of the estimated 17-20 million Americans who suffer from OAB seek help from a physician for their condition, which highlights the sensitive nature of the disorder. Many of those who do not seek help cope by "toilet mapping": memorizing the bathroom locations in places that they frequent. A more medically sound, nondrug therapy is bladder training with timed voiding. Bladder training uses biofeedback and Kegel exercises to help patients resist their sense of urgency and to urinate according to a timetable that's based on their personal voiding diary.

Antimuscarinics, the medication of choice for treating OAB, relax the bladder and reduce contractions of the detrusor muscle. The popularity of extended-release antimuscarinics reflect an effort to eliminate peaks and valleys in frequency, urgency, and urge incontinence. Most patients on OAB medication typically report symptom relief within 2 weeks, with a reduced incidence of frequency and urgency.

The newer drugs and formulations are also better tolerated, with adverse effects mostly limited to dry mouth and upset stomach. A common adverse effect with the older agents is a more severe dry mouth that many patients find intolerable. There are no human pregnancy data for oxybutynin or tolterodine. Animal reproduction studies with oxybutynin suggest that the pregnancy risk from this agent is probably low. The data are less convincing for tolterodine, so it is best avoided in the first trimester. Imipramine does not appear to cause birth defects, but long-term use during pregnancy may cause neonatal withdrawal. Imipramine is excreted in breast milk and no adverse effects have been reported, but there is concern that long-term exposure could potentially cause infant neurobehavior toxicity. It is not known if oxybutynin or tolterodine is excreted in milk, but nursing infants should be observed for constipation and urinary retention.

Three new medications aimed at OAB sufferers, darifenacin, solifenacin, and trospium, are awaiting FDA approval. These drugs are also antimuscarinics, intended to relax the smooth muscle of the bladder. Trospium is purported not to cross the blood-brain barrier, is minimally metabolized, has low serum protein binding, and therefore may have fewer adverse effects than the other medications.

 
Drug               Dosage           Cast/Day 
 
oxybutynin         5-15 mg/day,     $3.05 * 
(Ditropan XL)      once daily       (10 mg/day) 
 
tolterodine        2-4 mg/day,      $2.95 * 
(petrol LA)        once daily       (4 mg/day) 
 
oxybutynin         3.9 mg/day       $2.34 ** 
transdermal 
system (Oxytrol) 
 
oxybutynin         5 mg, three to   $1.38 * 
                   four times       (15 mg/day) 
                   daily 
 
imipramine         10-150           $1.74 * 
                   mg/day, three    (75 mg/day) 
                   times daily 
 
Drug               Comment[dagger] 
 
oxybutynin         Extended-release formulation. Start at 10 mg daily, 
(Ditropan XL)      equivalent to 4 mg of ...