Mibolerone
dimethyl-nortestosterone
Also known as: Cheque Drops · dimethyl-nortestosterone · NSC-72260 · U-10997 · 19-nor-steroid
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Suppression of estrus | 0.5-11 kg: 30 micrograms (0.3 mL) PO per day; 12-22 kg: 60 micrograms (0.6 mL) PO per day; 23-45 kg: 120 micrograms (1.2 mL) PO per day; >45 kg: 180 micrograms (1.8 mL) PO per day. German shepherds or German shepherd crosses: 180 micrograms (1.8 mL) PO per day; regardless of weight | PO | q24h | Treatment must begin at least 30 days prior to proestrus | 🌎 NA |
| Pseudocyesis (false pregnancy) | 10 times the dosage listed above for suppression of estrus | PO | q24h | 5 days | 🌎 NA |
| Pseudocyesis (false pregnancy) | 16 micrograms/kg | PO | q24h | 5 days | 🌎 NA |
| Cystic endometrial hyperplasia (CEH) | 30 micrograms/25lb. body weight | PO | q24h | 6 months | 🌎 NA |
| Treatment of severe galactorrhea | 8-18 micrograms/kg | PO | q24h | 5 days | 🌎 NA |
- Suppression of estrus: If dog comes into estrus after receiving the drug for 30 or more days, stop drug and determine that the dog is not pregnant before resuming therapy. If owner compliance has been determined, increase dosage by 20-50%.
- Treatment of severe galactorrhea: Once discontinued, prolactin may surge and galactorrhea resume.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Mibolerone is a potent androgenic, anabolic, and antigonadotropic 19-nor-steroid.
- Historically marketed as Cheque® Drops, commercial availability is now an issue, and it is primarily obtained through compounding pharmacies. It is classified as a Schedule III controlled substance in the USA.
- Clinical uses include the suppression of estrus, treatment of pseudocyesis (false pregnancy), and severe galactorrhea in female dogs.
Warning: Mibolerone has a very narrow therapeutic index in felines and is highly toxic to cats. It should never be used in feline patients.
Mechanism of action
Mibolerone exerts its effects via a negative feedback mechanism on the anterior pituitary gland.
- Blocks luteinizing hormone (LH) release → prevents follicular maturation → inhibits ovulation and corpus luteum development.
- The net result is the suppression of the estrous cycle if administered prior to (up to 30 days) the onset of proestrus.
- After discontinuation, the next estrus typically occurs within 7-200 days (average 70 days).
Safety & warnings
Contraindications
- Perianal adenoma or perianal adenocarcinoma
- Other androgen-dependent neoplasias
- Pregnant or lactating bitches
- Patients with ongoing or a history of liver or kidney disease
- Bedlington Terriers
- Cats
Adverse effects
- Premature epiphyseal closure (in prepuberal females)
- Clitoral enlargement / hypertrophy
- Vaginitis / Vulvovaginitis
- Increased body odor
- Abnormal behavior (e.g., riding/mounting behavior)
- Urinary incontinence
- Voice deepening
- Enhanced clinical signs of seborrhea oleosa
- Epiphora (tearing)
- Hepatic changes (intranuclear hyaline bodies) and rare hepatic dysfunction
- Increased kidney weight
- Fatalities, thyroid dysfunction, and pancreatic dysfunction (in cats)
Precautions
Mibolerone should not be used in pregnant bitches as masculinization of female fetuses will occur (changes in vagina patency, phallus-like structure, testes-like structures). It inhibits lactation and should not be used in nursing bitches. The manufacturer recommends discontinuing the product after 24 months of use. Do not use to abbreviate an estrous period or in bitches prior to their first estrous period. Extremely toxic to cats.
Drug interactions
Increased seizure activity has been reported in a dog previously controlled on phenytoin.
Should generally not be used concurrently.
Should generally not be used concurrently.
Monitoring
- Clinical signs of estrus
- Liver function tests (baseline, annual, or as needed)
- Physical examination of genitalia
Pharmacokinetics
Absorption
Well absorbed from the intestine after oral administration.
Metabolism
Rapidly metabolized in the liver to over 10 separate metabolites.
Elimination
Excretion is apparently equally divided between the urine and feces.
Overdose
In dogs, the drug did not cause death in doses up to 30,000 micrograms/kg/day when administered to beagles for 28 days. In cats, dosages as low as 120 micrograms/day have resulted in fatalities.
Available products
Formulations
- Oral drops (compounded)
Veterinary
- Commercially prepared mibolerone preparations are apparently no longer being marketed. Available from compounding pharmacies. Class-III controlled substance in the USA.
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
The original manufacturer states that the compound is stable under ordinary conditions and temperatures. If using a compounded preparation, follow specific instructions from the pharmacy.
Client information
- Strict Compliance: Give this medication exactly as prescribed. Missing doses can result in treatment failure (e.g., the dog coming into heat).
- Behavioral Changes: You may notice changes such as increased mounting/riding behavior, voice deepening, or increased body odor.
- Physical Changes: Mild enlargement of the clitoris or vaginal discharge may occur. Contact your veterinarian if these become severe.
- Handling Precautions: Because this is an anabolic steroid, wear gloves when handling the medication, especially if you are pregnant.
Do not give to cats! This medication is highly toxic and potentially fatal to cats.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.