Introduction

An 'overactive bladder' is a common complaint among adults - about one in 6 people will experience what is called urgency (a sudden, compelling desire to urinate, which is difficult to postpone), urge incontinence (associated leakage of urine), and increased frequency of urination (more than 7 times a day). These symptoms get worse with age, and can affect the 'quality-of-life'.

There are two main ways to tackle this problem: bladder retraining, and the use of anticholinergic drugs, such as Detrol® (tolterodine). New Zealand scientists have evaluated the actual effectiveness of anticholinergic drugs, based on published reports of over 30 clinical studies comparing them to placebo, or 'sugar' pills. Here's what they found.

What was done

All randomized controlled trials on men and women diagnosed as having overactive bladder were included, if they compared the active drug with an inactive placebo. They collected information on the patient's observations of cure or improvement in symptoms, number of urine leakages, and frequency of urination (number of voids). Side effects, quality-of-life scores, and some lab measures (volume of the bladder at first contraction, maximum bladder capacity, and residual urine volume after voiding) were also analyzed.

What was found

The scientists identified 64 studies in the medical literature, but of these, only 32 qualified for further analysis; the rest were too small, or had serious problems with data collection, etc. In these double-blind studies¹ there were a total of 6,800 patients, however; 22.5% were men and 58% were women (gender wasn't reported in some studies).

The drugs studied were tolterodine, oxybutynin chloride, trospium chloride, propiverine, empronium bromide, and propatheline. In 28 of the studies the drugs were given orally, and in the other four they were given 'into the bladder'. Length of treatment ranged from 2 to 12 weeks.

At the end of treatment, those taking the active anticholinergic drug:

• were roughly 1½ times as likely to have their symptoms improved than those on placebo.
• had, on average, one leakage episode less in 48 hours than the placebo subjects.
• had about one fewer urinations in 24 hours than placebo subjects.
• had an increased bladder volume at the first contraction, and the maximum bladder capacity was greater, but the residual urine volume was slightly greater than in the placebo control subjects.

The most frequently reported side effect was dry mouth, which occurred about three times more often in the drug-treated subjects than in the controls. However, there was no difference between the two groups in the numbers of people who dropped out of the trial because of side effects.

All these effects of anticholinergic drugs were significant (in the statistical sense), and didn't differ depending on age, sex, or the type of drug used.

Comment

The results of this large analysis were instructive. Most people in the studies showed a large improvement in their symptoms, but this was the case for both the drug-treated and the placebo subjects. The differences in favor of drug treatment were small, but statistically significant; they were less than those expected from clinical experience with these drugs.

Overactive bladder can also be treated by bladder retraining; the results with this form of treatment are about the same as for anticholinergic drugs. It seems clear that there is room for improvement in the treatment of this disorder, and future research will certainly provide this, whether it takes the form of physical therapy, behavioral therapy, or a new drug.