Mibolerone

Androgen Synthetic anabolic steroid

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 30-60 mcg/kg (0.03-0.06 mg/kg) Once daily Duration: Administer daily for up to 2 years; discontinue if breeding is desired
Notes: Start treatment at least 30 days before expected estrus. Dose may be adjusted based on body weight and response.

Clinical Indications & Species Uses

General Indications
  • Prevention of estrus in intact female dogs
Dog (Canine)
  • Prevention of estrus (heat) in female dogs

Pharmacology & Mechanism of Action

Drug Class: Androgen | Pharmacological Group: Synthetic anabolic steroid

Mechanism of Action: Mibolerone is a synthetic androgen that binds to androgen receptors, leading to inhibition of pituitary gonadotropin release (LH and FSH). This suppresses ovarian function and estrus in female dogs. It also has anabolic effects and may influence sebaceous gland activity.

Pharmacodynamics: Mibolerone suppresses the release of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) from the anterior pituitary, thereby preventing follicular development and ovulation. It also has direct effects on the reproductive tract, causing atrophy of the endometrium and preventing implantation. Its androgenic activity is about 10 times that of testosterone, but it has minimal anabolic effects.

⚡ Pharmacokinetics Summary

Absorption: Rapidly absorbed after oral administration in dogs, with peak plasma concentrations occurring within 1-2 hours.
Distribution: Widely distributed in tissues, with high concentrations in reproductive organs and sebaceous glands. Crosses the blood-brain barrier.
Metabolism: Extensively metabolized in the liver, primarily via reduction and conjugation.
Excretion: Excreted primarily in urine and feces as metabolites.
Half-Life: Approximately 8 hours in dogs.
Bioavailability: Oral bioavailability is approximately 60-70% in dogs.
Protein Binding: Approximately 90% bound to plasma proteins.

Available Formulations & Strengths

Oral Tablet 50 mcg, 100 mcg, 200 mcg (PO)

Contraindications & Clinical Warnings

Contraindications:
  • Pregnancy
  • Lactation
  • Female dogs intended for breeding
  • Hypersensitivity to androgens
  • Use in cats (due to potential toxicity)
Warnings & Clinical Precautions:
  • Use with caution in dogs with hepatic or renal disease
  • May cause clitoral hypertrophy in female dogs
  • May cause behavioral changes (increased aggression)
  • Not for use in pregnant or lactating bitches
  • Avoid in dogs with a history of seizures
  • Use with caution in dogs with diabetes mellitus (may alter glucose tolerance)

Adverse Effects & Reactions

Common:

  • Clitoral hypertrophy
  • Vaginal discharge
  • Increased aggression
  • Weight gain
  • Polyuria and polydipsia
  • Elevated liver enzymes

Serious / Severe:

  • Hepatotoxicity
  • Bone marrow suppression
  • Diabetes mellitus exacerbation
  • Adrenal suppression

Rare:

  • Cholestatic jaundice
  • Behavioral changes
  • Feminization of male fetuses if used during pregnancy

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Corticosteroids May increase risk of edema and hyperglycemia Moderate
Anticoagulants (e.g., warfarin) May enhance anticoagulant effect Moderate
Insulin or oral hypoglycemics May alter glucose tolerance, requiring dose adjustment Moderate
Hepatotoxic drugs (e.g., NSAIDs, anticonvulsants) Increased risk of hepatotoxicity High

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • Restlessness
  • Aggression
  • Tremors
  • Seizures
  • Hepatotoxicity

Emergency Treatment Protocol: Induce emesis if recent ingestion, administer activated charcoal, and provide symptomatic and supportive care. Monitor liver function and treat seizures if they occur.

Food Animal Withdrawal Times

Not approved for use in food animals; no withdrawal times established.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F)

Handling & Special Conditions: Protect from moisture; keep container tightly closed.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved by FDA for use in dogs for estrus prevention (e.g., Cheque Drops, no longer marketed).

Extra-Label (Off-Label) Use: Extra-label use in food animals is prohibited due to lack of withdrawal times and potential for residues. In the US, use in dogs is regulated under the Animal Medicinal Drug Use Clarification Act (AMDUCA) for non-food animals.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Mibolerone is primarily used for estrus prevention in intact female dogs. It is not recommended for use in cats due to potential toxicity. Treatment should be initiated at least 30 days before the expected estrus and continued daily. Adverse effects such as clitoral hypertrophy and behavioral changes may occur. Liver function should be monitored periodically during long-term therapy. Due to the availability of safer alternatives (e.g., GnRH agonists, progestins), mibolerone is less commonly used today.

References & Literature

  • 📚 Plumb's Veterinary Drug Handbook
  • 📚 Papich Veterinary Pharmacology and Therapeutics
  • 📚 Compendium of Veterinary Products (CVP)