Megestrol acetate, the active ingredient of Ovarid (now discontinued), has been used by breeders for postponement and prevention of oestrus (calling) in queens for many years. Used correctly at the lowest possible dose for short/medium term oestrus control side effects should not be a problem. However use of progestogens can be associated with adverse effects such as chronic endometrial hyperplasia (thickening of the uterine lining), pyometra and Diabetes mellitus. Breeders should discuss the risks/ benefits of using megestrol in their particular situation with their vets as alternative options may be more suitable depending on their circumstances.
Most breeders find that 1.25mg (1/4 Ovarid) given in anoestrus ( ie when the queen is not calling) will postpone the next oestrus for 2-4 weeks. Individual queens vary in this respect and a few may require a higher dose of 2.5mg.
This is a safer way of using megestrol than giving it when the queen is actually calling when higher doses over 3 consecutive days are required to prevent the call.
Megestrol acetate, can now be made by a licensed UK laboratory (The Specials Laboratory) in 1.25mg capsules equivalent to 1/4 of a 5mg Ovarid tablet.
Unfortunately, as this medicine is made in small batches by a specialist laboratory, the price for direct order by vets in small quantities for individual clients is very expensive so we have negotiated with an approved online pharmacy (Vet Medic) who have agreed to buy in bulk when they receive enough prescriptions. The cost will be approximately £5 per capsule but might be slightly less if enough orders are received.
The procedure for obtaining megestrol from Vet-Medic is detailed below – the shelf life is only 90 days so only order what you can use in that period
The procedure is as follows:
1. Please obtain a prescription from your veterinary surgeon for the number of capsules and dose schedule you require. Please remember the shelf life of the capsules is 90 days
2. The prescription can be sent by email ( scanned copy is acceptable) to
or by post to: Vet-Medic Pharmacy Manor House
Derbyshire DE7 4RA
3. Please title your email:
PRESCRIPTION MEGESTROL (FAO: A WALTON)
4. Please include your contact details so that the company can get in touch to collect payment when the order is ready.
You can copy and paste the following text into your email if easier:
Attached is a prescription for 1.25mg megestrol capsules as discussed with Mr Walton. Please contact me when you require payment.
My email address is:
My telephone/mobile numbers are:”
Please order as quickly as possible so that you get the maximum shelf life for the capsule.