Cat owners are not used to discussing cat contraceptives because it is commonplace to neuter and spay domestic cats. Why aren’t cat contraceptives more popular? It is probably because (1) cats are the patients rather than people and it is easier and more certain to spay female cats than to administer contraceptives and (2) cat contraceptives have side effects which I would argue seriously undermine their use.
Apparently serious attempts have been made to use oral contraceptives to control feral cat populations on a large scale in Israel. It is claimed that 20,000 kittens annually have been prevented using cat contraceptives.
Dr Desmond Morris in his excellent book Cat World published in 1996 refers to 2 different cat contraceptives. At the time there were several kinds of contraceptive pill available. One type was progestogens which have the same effect on the female cat as the natural pregnancy hormone progesterone. The female has a false pregnancy. They could be administered by injection or pill but there were dangers of infection and they appear to have gone out of practice.
A modified treatment using weaker progestogens was tested and a safer pill was made available called Proligestone. However, this drug also had side-effects which it seems were considered to be too severe to make the drug useful.
At that time a different approach was also taken to inhibit the hormone which starts of the female sexual cycle. This hormone is called gonadotrophin. This hormone can be suppressed by certain drugs. I don’t have further information on this.
Nowadays there are some cat birth control options available other than spaying or neutering but they are not commonly used. However sometimes cats are unsuited to spaying because of an allergic reaction to the anesthetic or they’re too small for the surgery (vetinfo.com).
Cat contraceptive drugs do carry the risks of side effects as in the past. One of them is Depo-Provera (medroxyprogesterone acetate). This prevents ovulation. There is a risk that the injection can cause diabetes, mammary tumors and uterine infection. Many cats given the injection gain weight due to lower energy levels and increased appetite.
Another drug is Ovaban. This stops the heat cycle. Breeders use it for their show cats. It is described as safe. However long-term use can cause diabetes, liver disease, mammary gland cancer and uterine disease. Unspayed females who don’t mate have a higher risk of an infection of the uterus (pyometra).
Clearly these drugs have some risks for the female cat.
This method and the above treatments require a veterinarian. In this instance the on-heat female cat is stimulated with a glass rod or a Q-Tip inserted into her vagina. This tricks her into thinking intercourse has occurred to release her eggs. The heat cycle then ends. The eggs she has produced are wasted and contraception is achieved. The cat’s sexual appetite passes and she will be quiet again until her next heat cycle. This would be a phantom pregnancy.
What I take away from my research is that cat contraceptive methods are considered poor alternatives to spaying female cats. Side effects, as far as I can tell, are potentially serious which undermines the process. Let’s remind ourselves that this process is about humans making decisions about cats without consent. Obvious, but it does impact the decision making process. Spaying is more efficient and certain under these circumstances.