Medroxyprogesterone
Medroxyprogesterone acetate is a long-acting progestin used for reproductive manipulation; behavioural and dermatologic use is discouraged because of adverse effects.
Group
Progestin
Mechanism of Action
Activates progesterone receptors, with additional androgenic and glucocorticoid activity.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical systemic progestin treatment | 1.1–2.2 mg/kg | IM | Every 168 h | Indication-specific benefit must justify the endocrine risks. |
| Prostatic disease | 3–5 mg/kg | IM, SC | Every 504–672 h | Acetate formulation; every 3-4 weeks. |
| Luteal-insufficiency pregnancy support | Reference only | PO | 0.1 mg/kg daily only for confirmed apparent luteal insufficiency; stop several days before expected parturition. Maternal/fetal risks include reported malformations. This exceptional reproductive indication does not override the pregnancy contraindication for non-reproductive uses. | |
| Benign prostatic enlargement | 0.3 mg/kg | SC | Once | Historical short-term preservation-of-breeding alternative; effects may persist around 10 months. |
| Long-term reproductive control | Reference only | IM | 2.5-3 mg/kg every five calendar months; substantial endocrine and reproductive risks. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Historical systemic progestin treatment | 1.1–2.2 mg/kg | IM | Every 168 h | Indication-specific benefit must justify the endocrine risks. |
| Estrus suppression | 0.05 mg/kg | PO | Every 24 h | May impair subsequent fertility and kitten viability. |
| Estrus suppression depot | Reference only | IM | 2-2.5 mg/kg repeated every 4-6 calendar months; a month-based depot schedule is not a fixed hour interval. | |
| Progesterone-deficiency abortion prevention | Reference only | IM | 1-2 mg/kg weekly, stopped 7-10 days before parturition; confirm the endocrine diagnosis and monitor maternal/fetal risk. | |
| Long-term reproductive control | Reference only | PO | 2.5-5 mg/cat weekly; alternative IM 2 mg/kg every five months. An unspecified-route 25 mg every six months entry is not assigned a route. |
Horses
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Estrus suppression | 250–500 mg/animal | IM | No repeat schedule is supplied; clinical efficacy requires assessment. |
Indications
- Selected estrus suppression
- Historical prostatic and behavioural uses
Contraindications
- Pregnancy
- High risk of diabetes
- Avoid behavioural or dermatologic use in male cats.
Interactions
- Hepatic enzyme inducers may increase clearance.
Adverse effects
- Polyphagia, polydipsia and adrenal suppression
- Diabetes, pyometra and mammary hyperplasia
- Possible neoplastic and reproductive effects
Toxicity
Depot exposure cannot be withdrawn after injection; monitor endocrine, uterine and mammary complications.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Medroxyprogesterone 2.5 mg tablet | Tablet | 2.5 mg / tablet | PO |
| Medroxyprogesterone 5 mg tablet | Tablet | 5 mg / tablet | PO |
| Medroxyprogesterone 10 mg tablet | Tablet | 10 mg / tablet | PO |
| Medroxyprogesterone 150 mg/mL injection Medroxyprogesterone acetate depot suspension; not for IV use. | Injection | 150 mg / mL | IM |
| Medroxyprogesterone 400 mg/mL injection Medroxyprogesterone acetate depot suspension; not for IV use. | Injection | 400 mg / mL | IM |
Monitoring and Administration
Evaluate reproductive status, glucose and mammary health before treatment.
Adverse fertility and kitten viability effects have followed feline estrus suppression.
Monitor liver enzymes and cholesterol when treatment is sustained.
Historical canine behavioural treatment is 5 mg/dog daily as needed, without a route stated in that entry. Behavioural use is discouraged because of endocrine risks.
Historical behavioural/dermatologic MPA protocols are not preferred: canine aggression 10 mg/kg IM/SC as needed, maximum three yearly treatments for inter-male aggression; canine dermatitis 20 mg/kg IM repeated after 3-6 months. Feline marking 5-20 mg/kg IM/SC 3-4 times yearly, psychogenic alopecia 75-150 mg IM/SC no more often than 2-3 months, or progestin-responsive dermatitis 50-100 mg IM at 3-6-month intervals. These high-exposure depot courses carry serious mammary, uterine and metabolic risks.
Pituitary-dwarf dogs were treated at 2.5-5 mg/kg every 3 weeks then every 6 weeks, but the administration route is not supplied. Equine MPA 500-800 mg IM has variable 2-3-month effects and does not reliably stop cyclicity or prevent pregnancy loss. Bird ovulation/pruritus guidance pairs 3 mg/100 g with an unbound 0.025-1 mL volume range; no concentration-based avian calculator is inferred.