Oxybutynin Patches (OXYTROL): A Grossly Overpriced Product For Overactive Bladder

In February of this year the Food and Drug Administration (FDA) approved a transdermal or patch form of the old drug oxybutynin (OXYTROL) for the treatment of overactive bladder. The drug is applied to the skin every three to four days. Oxybutynin has been available in the U.S. since 1976 and there are many less expensive generic versions of the tablet form of the drug on the market.

Transdermal oxybutynin is marketed by Watson Pharma, Inc. of Corona CA. The most common brand name for oral oxybutynin is DITROPAN.

Oxybutynin is referred to as an anticholinergic drug. Anticholinergic drugs block the effects of acetylcholine, a substance produced by the body that is responsible for certain nervous system activities. Drugs with anticholinergic effects (including some antidepressants, antihistamines, antipsychotics, drugs for intestinal problems, antiparkinsonians) inhibit the secretion of acid in the stomach, slow the passage of food through the digestive system, inhibit the production of saliva, sweat, and bronchial secretions, and increase the heart rate and blood pressure. Adverse effects of these drugs include dry mouth, constipation, difficulty urinating, confusion, worsening of glaucoma, blurred vision, and short-term memory problems.

The editors of The Medical Letter on Drugs and Therapeutics, a respected independent source of drug information written for physicians and pharmacists, reviewed transdermal oxybutynin in their May 12, 2003 issue and concluded:

Oxybutynin delivered transdermally may cause less dry mouth than when it is taken orally, but it may also be less effective for incontinence, and itching at the application site can be a problem. As the Medical Letter has said before, none of these drugs are as effective as advertisements to the public have suggested.

We agree with the Medical Letter editors on their assessment of transdermal oxybutynin’s effectiveness and we would characterize this drug’s effectiveness as only marginal. In the first of two clinical trials described in the drug’s professional product labeling or package insert, transdermal oxybutynin was compared to a placebo. At the end of the 12 week study there was an average reduction in incontinence episodes of 21 per week in patients using transdermal oxybutynin. For those patients given the placebo the average reduction was 19.2 per week. This is an average difference of 1.8 episodes of incontinence per week.

When daily urinary frequency was measured the average reduction seen in patients receiving the transdermal oxybutynin was two per day; with the placebo it was one.

In the second clinical trial described in the package insert, patients who had previously responded to an anticholinergic drug for the urinary symptoms were studied for 12 weeks. The average daily reduction in incontinence episodes was 2.9 in the transdermal oxybutynin treated patients. In the placebo group, the average reduction was 2.1 episodes. This is a difference of less than one episode per day on average.

A similar result was found when daily urinary frequency was studied. On average there was only a difference of 0.5 episodes of urinary frequency per day between the transdermal oxybutynin and the placebo.

In the area of retail cost, the difference between transdermal oxybutynin and generic oxybutynin is not marginal, it is significant by almost a factor of ten. A one month supply of eight transdermal oxybutynin patches is $146.99 at a Washington, DC chain pharmacy. At the same pharmacy a one month supply, 90 tablets, of generic oral oxybutynin is $15.09 at the maximum recommended dose of five milligrams, three times a day.

One cause of loss of bladder control is drugs. There are a number of prescription and non-prescription drugs that have been associated with bladder control problems. These drugs are listed in the table on these pages. DO NOT stop taking any of these drugs without first consulting your physician. The drugs are arranged by their family and then in alphabetical order by the most common brand name. This table was constructed from various sources including the medical literature, Side Effects of Drugs Annual 25, 2002, and the Textbook of Adverse Drug Reactions.

What You Can Do

You should check the list of drugs that can cause loss of bladder control before starting drug treatment for this condition. You may be able to change from a drug that causes loss of bladder control to a drug that does not or alter the dose. This may be enough to solve the problem. DO NOT stop taking any of the drugs in the list without consulting your physician.

You should try a low dose of generic oxybutynin tablets before using oxybutynin patches. Neither form of the drug is particularly effective but you can save a significant amount of money by using the generic tablets.