Oral Hormone Tablets for Dogs and Cats

Megestrol acetate is a potent progestagen with marked anti-oestrogenic properties. Progesterones inhibit follicle stimulating hormone (FSH) and luteinising hormone (LH) release; exert a peripheral anti-oestrogenic effect; act as anti-androgens; exert an anti-allergic effect; form a secretory endometrium; maintain pregnancy; help to bring about myometrial relaxation.

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Technical Information

Technical Information

Active Constituent(s)

5 mg and 20 mg Megestrol acetate


Postponement or prevention of oestrus and the treatment of false pregnancy and oestrogen dependent mammary tumours in bitches. Oestrus control and treatment of miliary dermatitis and eosinophilic granuloma (rodent ulcer) in cats. Treatment of behavioural abnormalities such as hypersexuality in male dogs and urine spraying in cats.

Timing of administration is of great importance. In some cases vaginal cytology must be used to determine correct stage of cycle.


Postponement of oestrus: Normal dosage regimen: 0.5 mg/kg daily for maximum period of 40 days. Commence the course preferably 14 days, but at least 7 days, before the effect is required; do not repeat more frequently than once every 6 months.
Extended dosage regimen: 0.1 to 0.2 mg/kg twice weekly for maximum period of 4 months following a 40 day course as described above. Allow bitches to have a normal unmedicated oestrus before this course is repeated.

Suppression (prevention) of oestrus: Commence the course at the onset of pro-oestrus as indicated by the presence of haemorrhage and vulval swelling. The stage of the oestrus cycle may be confirmed by the examination of vaginal smears.
Normal dosage regimen: 2 mg/kg daily for 8 days.
Extended dosage regimen: 2 mg/kg daily for 4 days followed by 0.5 mg/kg daily for 16 days.
The use of this prolonged prevention course may be beneficial in bitches with a history of false pregnancy, in some cases where other abnormalities of the oestrus cycle are known to occur, and in first season bitches and when the animal to be medicated is housed with other bitches.

False pregnancy: 2 mg/kg daily for 5 to 8 days commencing on first signs of false pregnancy. In a small percentage of treated cases the signs of false pregnancy may recur 3 to 6 weeks later. This incidence can be minimised by commencing the treatment immediately the signs are seen.

Oestrogen dependent mammary tumours (bitches): 2 mg/kg daily for 10 days, or 2 mg/kg daily for 5 days; follow by 0.5 to 1 mg/kg daily for further 10 days.

Behavioural abnormalities: Vary the dose to suit individual needs; as a guide: 5 days at 2 mg/kg then, 5 days at 1 mg/kg then, 5 days at 0.5 mg/kg.

Postponement of oestrus: Commence in dioestrus or anoestrus. 2.5 mg daily for 2 months (during breeding season), or 2.5 mg once weekly for up to 18 months (during non-breeding season).

Prevention of oestrus: 5 mg daily for 3 days commencing as soon as signs of calling are seen. Repeat dosage at 21 day intervals at commencement of further calling if necessary.

Miliary dermatitis and eosinophilic granuloma: 2.5 to 5 mg every 2 to 3 days until lesions begin to regress, then once weekly until satisfactory response is obtained. Give maintenance dosage of 2.5 mg weekly or fortnightly if necessary to prevent recurrence.

Behavioural abnormalities: Dosage as for dogs.

The tablets are readily accepted by most animals; give whole or crushed and mixed with food.

Product Codes

Size Code
20 mg 200 tablets 60900
5 mg 200 tablets 60910