Depo-Promone 3ml (Medroxyprogesterone Acetate 50mg/ml) – Heat Suppression Injection for Dogs & Cats

What Is Depo-Promone?

Depo-Promone is a sterile injectable suspension manufactured by Pfizer Animal Health, containing medroxyprogesterone acetate (MPA) 50mg per ml (44.57mg as the free base per ml). Medroxyprogesterone acetate is a synthetic progestogen — a long-acting progesterone analogue — that suppresses the hormonal cascade responsible for triggering oestrus (heat) in female dogs and cats.

Depo-Promone is available in two vial sizes: 3ml and 5ml. It is administered by subcutaneous (SC) injection and must only be given during the anoestrus phase — the resting period in the second half of the interval between heats. Administration at any other stage of the reproductive cycle can cause serious complications.

How Depo-Promone Works

Medroxyprogesterone acetate suppresses oestrus through multiple hormonal mechanisms:

• Hypothalamic-pituitary suppression: MPA inhibits the release of GnRH (gonadotrophin-releasing hormone) from the hypothalamus and blocks the pituitary secretion of FSH (follicle-stimulating hormone) and LH (luteinising hormone). Without these gonadotrophins, follicle maturation and ovulation cannot proceed.
• Oocyte transport disruption: MPA alters tubal contractility, disrupting the transport and fertilisation of oocytes even if ovulation were to occur.
• Uterine environment modification: MPA changes the uterine lining, making implantation of any fertilised egg impossible.

MPA has no androgenic or oestrogenic effects — it binds selectively to progesterone receptors in target organs (ovary, uterus, udder). It is metabolised in the liver and excreted mainly via the faeces, with a small amount in urine. Because it is a long-acting depot formulation, a single injection maintains suppression for months.

Indications

Depo-Promone is indicated for:

• Prevention of the next oestrus: One injection given 15–21 days before the expected next heat will prevent that cycle
• Long-term suppression of oestrus: Regular injections on a scheduled basis maintain ongoing heat prevention in bitches and queens where spaying is not appropriate or desired

Depo-Promone is specifically indicated for female dogs and cats where pregnancy, whelping/queening, or ovariohysterectomy (spaying) is contraindicated due to health risk, or where litters are undesirable. It is not a first-line alternative to spaying for healthy breeding animals.

Timing — The Most Critical Aspect of Depo-Promone Use

⚠️ Depo-Promone must ONLY be administered during anoestrus — the second half of the resting period between heats (approximately 3 months after the last oestrus ended). Injecting during pro-oestrus, oestrus, or metoestrus dramatically increases the risk of serious uterine disease (pyometra, endometrial hyperplasia) and mammary complications. This is the most common cause of adverse events with MPA in veterinary practice.

• Correct timing: Approximately 3 months after the last heat ended — the mid-to-late anoestrus phase
• Incorrect (dangerous) timing: During or just before heat (pro-oestrus, oestrus, metoestrus)

If there is any doubt about the current stage of the reproductive cycle, do not inject — consult a veterinarian for vaginal cytology or progesterone measurement to confirm anoestrus.

Dosage & Injection Schedule

Administer by subcutaneous (SC) injection only. Do not give intravenously. Shake well before use. Choose an inconspicuous injection site (e.g. flank, lateral neck) as a localised area of hair discolouration or loss may occur at the injection site.

Schedule of Administration

• To prevent the next heat cycle: Give 1 injection, 15–21 days before the expected date of the next heat
• For ongoing (permanent) heat suppression in bitches: Repeat every 6 months during anoestrus
• For ongoing (permanent) heat suppression in cats: Repeat every 4–6 months during anoestrus

Return of Fertility After Stopping Treatment

If injections are discontinued, the oestrous cycle will return — but this can take considerable time. The interval between the last injection and the first reappearance of oestrus is typically 6 months but may extend to 2 years or longer in some animals. Owners should be clearly informed of this before treatment begins.

If breeding is intended after discontinuing treatment, do not attempt mating until at least the second heat following the last injection to ensure the uterus has fully recovered to a normal state.

Contraindications — Do Not Use In:

• Animals in pro-oestrus, oestrus or metoestrus — only use during anoestrus
• Prepubescent animals that have not yet had their first heat
• Animals intended for breeding in the near future
• Animals with mammary tumours (existing or suspected) — MPA stimulates mammary tissue proliferation
• Pregnant females
• Animals with diabetes mellitus — MPA has an anti-insulin effect and will worsen diabetic control
• Animals with uterine infections, endometritis, pyometra, or other gynaecological conditions
• Animals with a history of abnormal or irregular heat cycles, nymphomania, or false pregnancy
• Greyhounds — continuous treatment is not recommended in this breed

Side Effects & Risks

Depo-Promone is a potent hormonal treatment with a significant side effect profile. These risks increase with repeated use, high doses, or incorrect timing of administration:

• Uterine disease: Endometrial hyperplasia, pyometra (life-threatening uterine infection), and uterine tumours have been reported after single or repeated use
• Mammary complications: Mammary gland hypertrophy, mammary tumours, and abnormal milk production
• Diabetes mellitus: MPA has an anti-insulin effect; it can precipitate or worsen diabetes
• Behavioural changes: Polyphagia (increased appetite), weight gain, lethargy, aggression, or apathy
• Local injection site reaction: Hair discolouration or permanent localised alopecia at the SC injection site — use an inconspicuous location
• Growth hormone stimulation: MPA stimulates growth hormone release from the mammary gland, which can cause acromegaly-like signs in some dogs
• Adrenal suppression: At high doses, MPA can suppress cortisol production due to glucocorticoid-like activity

Because of this side effect profile, many veterinary guidelines now recommend spaying (ovariohysterectomy) as the preferred long-term solution for oestrus suppression in dogs and cats where breeding is not intended, reserving MPA products for cases where spaying carries unacceptable anaesthetic or surgical risk.

Drug Interactions

• Corticosteroids: Combination with corticosteroids can aggravate or precipitate diabetes mellitus — avoid concurrent use
• Insulin therapy: Do not use alongside insulin — MPA’s anti-insulin effect makes glycaemic control impossible

Storage

• Store in a cool, dry place protected from light at 5–25°C
• Do not freeze
• Shake well before each use
• Shelf life: 3 years from date of manufacture

Depo-Promone vs Other Heat Suppression Options

Frequently Asked Questions

When is the right time to give Depo-Promone to my dog?

Depo-Promone must only be given during anoestrus — the resting phase, approximately 3 months after the last heat ended. If you want to prevent the next heat, give the injection 15–21 days before the expected heat date. Never inject during or just before a heat cycle (pro-oestrus, oestrus, or metoestrus) as this dramatically increases the risk of pyometra and mammary disease.

How long does one Depo-Promone injection last in dogs?

A single injection suppresses oestrus for approximately 6 months in bitches. For long-term suppression, injections are repeated every 6 months during the anoestrus period. If injections are stopped, the heat cycle typically returns within 6 months but can take up to 2 years or more.

Can Depo-Promone be used in cats?

Yes. Cats receive 1ml (50mg MPA) by subcutaneous injection during anoestrus. For long-term suppression, repeat every 4–6 months. The same contraindications apply as in dogs — never inject during or close to a heat cycle, and do not use in cats with mammary or uterine disease, diabetes, or pregnancy.

What are the main risks of Depo-Promone?

The most serious risks are pyometra (life-threatening uterine infection), mammary tumours, and precipitation or worsening of diabetes mellitus. These risks increase with repeated injections and incorrect timing. For healthy animals where breeding is not planned, spaying is generally a safer long-term solution than repeated MPA injections.

Can I breed my dog after stopping Depo-Promone?

Yes, but not immediately. You should wait until at least the second heat cycle following the last injection before attempting mating. This allows the uterus time to fully return to a normal, healthy state. The first heat after stopping treatment may be irregular.

What should I do if I accidentally inject myself with Depo-Promone?

Seek medical advice immediately and take the package leaflet or product label to show the doctor. MPA is a potent hormone and accidental self-injection requires prompt medical evaluation.

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