Megestrol Acetate
Also known as: Ovaban, Megace, Ovarid
Megestrol acetate is a powerful hormone medication. While it can be effective, it carries significant risks, especially in cats. * **Understand the Risks**: This drug can cause serious side effects, including diabetes, severe uterine infections (pyometra), and suppression of the adrenal glands. * **Monitor Closely**: Watch your pet's water intake and urination closely. If they start drinking or urinating excessively, contact your veterinarian immediately, as this could be a sign of diabetes. * **Physical Changes**: Check your pet's mammary glands (belly area) regularly for any swelling, lumps, or discharge. Report any changes to your vet. * **Behavior and Energy**: Note any extreme lethargy, weakness, or sudden changes in behavior. * **Do Not Stop Abruptly**: If your pet has been on this medication long-term, do not stop it suddenly without consulting your veterinarian, as their body may need time to adjust. * **Human Safety**: Pregnant women should avoid handling this medication.
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
What it is used for
- Suppression of estrus (in anestrus)
- Suppression of estrus (in proestrus)
- Suppression of estrus (behavioral estrus)
- Postponement of estrus (started during diestrus)
- Postponement of estrus (started during anestrus)
- Prevention of estrus
- Idiopathic feline miliary dermatitis
- Appetite stimulant
- Alternative treatment for immune-mediated skin diseases
- Adjunctive therapy of eosinophilic granulomas
- Eosinophilic ulcers
- Feline atopy ('last ditch' alternative)
- Feline plasma cell gingivitis
How it is given
Possible side effects
- Profound adrenocortical suppression (especially in cats)
- Transient or permanent diabetes mellitus
- Cystic endometrial hyperplasia (CEH) and pyometra
- Mammary hypertrophy and neoplasia
- Increased appetite and weight gain
- Polydipsia and polyuria (PU/PD)
- Lethargy and personality changes
- Hepatotoxicity (rare)
- Acromegaly (dogs)
- Lactation (rare)
Cautions & contraindications
- Pregnancy
- Uterine disease (e.g., pyometra, endometritis)
- Diabetes mellitus
- Mammary neoplasias
- Prior to the first estrous cycle in dogs
- Anestrus therapy in dogs with abnormal cycles
- During diestrus or in the presence of uterine hemorrhage
- Treatment of pseudopregnancy in bitches (per manufacturer, though off-label protocols exist)
- > **Black Box Warning Equivalent**: Megestrol acetate can induce profound, life-threatening adrenocortical suppression and iatrogenic Addisonian crisis, particularly in cats. * **Adrenal Suppression**: Because of its glucocorticoid activity, patients may require exogenous stress-dose steroids during periods of trauma, surgery, or severe illness. * **Reproductive Risks**: High risk of inducing cystic endometrial hyperplasia (CEH) and pyometra. A thorough reproductive history, physical exam, mammary palpation, and vaginal cytology are strongly recommended before initiating therapy for reproductive control. * **Infection Risk**: May exacerbate latent viral infections (e.g., Feline Herpesvirus-1). * **Human Safety**: Pregnant women should handle this medication with extreme caution (FDA Category X in early pregnancy).
Drug interactions
- Corticosteroids: Concurrent long-term use may exacerbate adrenocortical suppression and increase the risk of diabetes mellitus.
- Rifampin: May decrease progestin activity due to microsomal enzyme induction, resulting in increased progestin metabolism.
Frequently asked questions
What is Megestrol Acetate used for in pets?
Megestrol acetate is a powerful hormone medication. While it can be effective, it carries significant risks, especially in cats. * **Understand the Risks**: This drug can cause serious side effects, including diabetes, severe uterine infections (pyometra), and suppression of the adrenal glands. * **Monitor Closely**: Watch your pet's water intake and urination closely. If they start drinking or urinating excessively, contact your veterinarian immediately, as this could be a sign of diabetes. * **Physical Changes**: Check your pet's mammary glands (belly area) regularly for any swelling, lumps, or discharge. Report any changes to your vet. * **Behavior and Energy**: Note any extreme lethargy, weakness, or sudden changes in behavior. * **Do Not Stop Abruptly**: If your pet has been on this medication long-term, do not stop it suddenly without consulting your veterinarian, as their body may need time to adjust. * **Human Safety**: Pregnant women should avoid handling this medication.
Is Megestrol Acetate safe for my pet?
Dosage must be set by your veterinarian for your specific pet. Never give human medication or another pet’s prescription without veterinary guidance.
This article is for general education and is not a substitute for professional veterinary advice. If your pet is unwell, please consult a veterinarian.
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