My female dog was spayed at two years of age.  When she sleeps or rests, she leaks urine. I give her hormone pills, called phenylpropanolamine, and was told these would not hurt her. Why does she leak urine? Are these pills safe?

A common problem with several different causes.

Urinary incontinence, or leakage of urine, is commonly seen in middle-aged and older spayed females or neutered male dogs. Many veterinarians believe that a lack of hormones causes the urethral sphincter muscle to lose tone, therefore allowing urine to leak. However, there are several causes of urinary leakage. Hormone-responsive urinary incontinence is diagnosed after first ruling out a urinary tract infection and other urination problems.

Phenylpropanolamine is a medication that increases the tone of the urethral sphincter muscle, which helps to hold urine in the bladder. It is a relatively safe and effective medication that is one of the drugs of choice for urinary incontinence in older spayed female dogs. It is not a hormone, but an alpha-adrenergic drug.

Many experts now recommend the use of hormone replacement with a drug called diethylstilbestrol, or DES, in spayed female dogs. DES is typically given once a day for three to five days, then only once every seven to 15 days as needed to control the incontinence. Some dogs only need one pill every three weeks to prevent the leaking of urine. DES in high dosages can cause estrus, or heat-like signs, as well as bone marrow toxicity. However, in low dosages, this is usually not a problem. Male dogs can be given testosterone hormone replacement.

The phenylpropanolamine may be used instead of, or in addition to, DES or testosterone. Side effects of phenylpropanolamine can include hyperexcitability, panting, and decreased appetite. It also increases heart rate and blood pressure, so it should not be given with drugs such as ephedrine that may have similar effects. Hypertension, or high blood pressure, may develop when phenylpropanolamine is given with aspirin and other non-steroidal anti-inflammatory agents. When these drugs are used in combination, careful veterinary monitoring is required. This drug may need to be given one to three times a day to control incontinence.

Your veterinarian will be able to determine the best treatment protocol for your dog as well as the best dosage for these medications. The best treatment is the one that works, that does not cause your dog any problems, and that is easy to administer.

05/04/06