Research| Spay/Neuter, Trap-Neuter-Return, Veterinarian Awareness

Cat Contraception Megestrol Acetate (MA) A Useful Tool During COVID-19 Pandemic

For several months in 2020 during the COVID-19 pandemic, a significant number of spay and neuter clinics closed their doors. Even today, appointments for spay and neuter surgery—especially low-cost—remain extremely limited. In many cases, the wait is months long.

Fortunately, there is another option: Megestrol Acetate (MA). If securing a spay appointment is not possible, you can buy time until an appointment is made. Alley Cat Allies recommends an immediate, short-term oral contraceptive, a form of birth control that ‘halts’ estrus in cats.

Megestrol Acetate, when given in the proper low dosage, prevents female cats from going into heat and becoming pregnant. MA has long been prescribed by American veterinarians to treat various medical conditions in both male and female cats with minimal side effects. But before now, it has not been widely used in the United States as a contraceptive.

The use of MA for other purposes, and its use for cat contraception overseas, have led veterinarians to recommend MA as a short-term contraceptive for female cats through the challenges of the COVID-19 pandemic. Whether it’s a cat you are fostering or a community cat, many of us experience the uncomfortable position of having an unspayed female cat in our lives when access to surgical spay is limited. Given this reality, MA is a welcome addition for many.

What is Megestrol Acetate (MA)?

Megestrol Acetate is a progestin hormone, or a manmade chemical that mimics the female naturally-occurring hormone progesterone. As a progestin, MA prevents pregnancy by inhibiting ovulation. In female cats, it has been shown to halt estrus, or heat.

How Much & How to Give Megestrol Acetate

What cats can be given Megestrol Acetate?

  • MA should be given to unspayed female cats only.
  • MA provides no contraceptive benefit to male cats.
  • MA can be given to both owned and community cats.

 How do you give Megestrol Acetate to cats?

  • MA is available from a veterinarian prescription, in tablet or liquid form, though  liquid compound version is recommended.
  • MA dosage should be given orally, or mixed into food as a liquid.
  • When given in liquid form and mixed into food, do not serve the food on paper plates or bowls. The MA may be absorbed by the paper. Plastic or ceramic plates or bowls should be used.
  • MA should be given in such a way as to prevent cats from accidentally consuming all or part of another cat’s dose. This ensures appropriate contraceptive protection for the target cat, and that other cats do not receive unintended doses.

How long can cats be given Megestrol Acetate?

  • It is recommended that cats be given MA for no more than 30 weeks (or about 7 months).

What is the proper treatment and dosage of Megestrol Acetate for cats?

  • Experts recommend that one 2.5 mg dose of MA be given orally to each unspayed female cat once a week for up to 30 weeks (or about 7 months). The simple guideline is “one cat – one dose – once a week.”
  • For female cats already showing signs of heat, the dose should be given at 5 mg per cat per day for three days only. After that, it should be given in a 2.5 mg dose once a week for up to 30 weeks (or about 7 months).

Can I give Megestrol Acetate to community cats?

  • Yes, MA can be given to community cats. However, doing so requires a commitment on the part of the caregiver to give the medicine each week in the right dosage to each female cat, without another cat consuming all or part of the medication.
  • For this reason, providing the proper dosage of MA is most easily accomplished with only one cat, and more difficult in scenarios in which there are multiple cats.
  • If you are giving MA to more than one cat, each cat must be watched carefully to ensure she doesn’t eat her own food with its dose and then wander over to eat another cat’s dose as well.
  • If you are familiar with your community cats and know that a female cat tends to approach you or an area alone at a certain time, take advantage of that time to provide her with her dosage of MA.

 Megestrol Acetate (MA) is Safe and Effective

MA is recommended for contraception by veterinarians when used at the proper low dosage. MA is already used safely in cats to treat other medical conditions with minimal side effects.

Does Megestrol Acetate have side effects for cats?

  • Yes, but they are minimal and health risk is low. The most common, though still rare, side effects are weight gain at the lowest dosage (2.5 mg) and diabetes at the higher dosage (5 mg).

Is Megestrol Acetate approved for cats?

  • The use of MA for fertility control in female cats is “off-label” in the United States. This means that the FDA has yet to approve MA specifically for the use of fertility control in female cats.
  • However, know that many drugs are used off-label in veterinary medicine, usually after experts have weighed in and made recommendations on safe and effective dosage. This is the case with MA as a contraceptive for female cats.

Do veterinarians recommend Megestrol Acetate for cats?

Cost and Availability of Megestrol Acetate (MA)

  • A veterinarian prescription is required for MA and MA must be compounded, meaning tailored to the needs of a particular patient by a compounding pharmacy. You can obtain a prescription from your veterinarian for MA suspended in a liquid compound and flavored in a way that is appealing to a cat, such as tuna or chicken.
  • In turn, your veterinarian must obtain MA from a compounding pharmacy. Please speak with your veterinarian about availability of medicines from compounders, as rules vary from state to state.
  • MA has a shelf life of 180 days.

 Is Megestrol Acetate expensive?

  • Cost and availability of MA will vary, but back-of-the-envelope calculations based on discussions with compounders put the cost of an eight-week course of MA in the range of $3.00 – $5.00 per cat.

Conclusion

In situations where there is low access to spay and neuter, as we’ve experienced during the on-going COVID-19 crisis, MA can be a useful tool in providing short-term, non-surgical contraception in female cats.

We each make the best decisions we can with the information we have, and we must recognize that both action and inaction carry risks. Pregnancy and birth carry risks, surgical spaying carries risks, and oral contraception carries risks. Only you and your veterinarian can assess your comfort level with the course of action you choose regarding the health of your cats.

At the doses being recommended, veterinarians indicate that the health risks of MA as a contraceptive are low. Experts feel the health risks to non-target cats who accidentally ingest some MA are also low. It is worth discussing MA with your veterinarian.