Contraceptives for Dogs and Cats

The widespread adoption of contraceptives by women and their high degree of efficacy has stimulated great interest in applying these techniques to controlling reproduction in pets.

One of the problems with this approach is that dogs are not women, and tend to be signficantly more sensitive to adverse effects of steroidal contraceptives. Nonetheless, contraceptive drugs have some utility in pet population control.

Steroidal Contraceptives

Several steroidal contraceptives similar to those used in women have been evaluated in dogs and, to a lesser extent, cats. Many of these treatments are quite effective in preventing conception. The problem is that they also carry a high risk of inducing serious uterine disease in treated bitches, most prominently pyometra (pus-filled uterus). In the United States, two steroidal contraceptives are currently available for dogs:

• Megestrol acetate (Ovaban) is an orally-active progestin. The recommended treatment regimen depends on the stage of the bitch's cycle. Estrus suppression can be attained by initiating treatment with a high dose of drug early in proestrus, and contining for 8 days. Alternatively, treatment with a lower dosage can be started in anestrus and continued for 32 days to achieve estrus postponement. Following treatment, most bitches return to estrus in 4 to 6 months.
• Mibolerone (Cheque): is an androgen that is marketed as a liquid to be added to food. It can be used to suppress the onset of estrus for up to 24 months. After discontinuing treatment, most bitches return to estrus in 2 to 3 months.

There are several important factors to consider before treating a bitch with either megestrol or mibolerone - check the product literature or with your veterinarian first. Neither drug is approved for use in cats.

Long-acting or depot preparations of progestins such as medroxyprogesterone acetate (Depo-Provera) have been widely used in Europe as contraceptives in bitches. Although effective, there is a clear increase in risk of inducing uterine disease associated with these treatments.

Physical Methods for Contraception

Intrauterine devices are not applicable for dogs and cats due to the extreme difficult of passing anything through the cervix. Plastic intravaginal devices, to prevent penetration by the male, were once marketed for contraceptive purposes in bitches, but were poorly retained and of low efficacy.