Vetdrugs 2.0Methyltestosterone is an orally active synthetic androgen with anabolic and masculinizing activity. Veterinary experience is largely historical and includes selected androgen-replacement and anabolic applications. Additional hormone-responsive disorders have been treated empirically. Its effects arise from androgen-receptor activation and vary with the endocrine state, species and clinical objective.
Group
Androgenic anabolic steroid
Mechanism of Action
Methyltestosterone enters responsive cells and activates androgen receptors, altering transcription of genes involved in reproductive function and protein metabolism. Increased protein synthesis and nitrogen retention provide the basis for proposed anabolic effects. Androgen signaling can also affect libido, hair growth and erythropoietic activity. The balance of these effects depends on the responsive tissue and existing hormone status.
Dose Rates
Dogs
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Androgen replacement or anabolic support | 5–25 mg/animal | PO | Every 24–48 h | |
| Alopecia X | 1 mg/kg | PO | Every 24 h | Maximum 30 mg/dose; When melatonin fails; stop after maximum hair regrowth and monitor liver function. |
| Testosterone-responsive dermatosis — Initial | 1 mg/kg | PO | Every 48 h | Maximum 30 mg/dose |
| Testosterone-responsive dermatosis — Maintenance | 1 mg/kg | PO | Every 96–168 h | Maximum 30 mg/dose; After response; every 4-7 days. |
| Androgenic or anabolic alternative | 0.5 mg/kg | PO | Every 24 h | Do not exceed 1 mg/kg; monitor androgenic and hepatic effects. |
| Historical estrus suppression | Reference only | PO | Greyhound alternative: 5 mg weekly or the weekly total divided twice weekly. Another canine regimen uses 25-50 mg twice weekly; keep the different schedules distinct. |
Cats
| Use / stage | Dose | Route | Schedule | Instructions |
|---|---|---|---|---|
| Androgen replacement or anabolic support | 2.5–5 mg/animal | PO | Every 24–48 h | |
| Androgenic or anabolic alternative | 0.5 mg/kg | PO | Every 24 h | Do not exceed 1 mg/kg; monitor androgenic and hepatic effects. |
Indications
- Selected androgen replacement in animals with clinically supported androgen deficiency, including some libido-associated disorders.
- Historical anabolic support of debilitated or catabolic veterinary patients, with limited evidence of meaningful clinical benefit.
- Historical treatment of selected androgen-responsive alopecias, with limited condition-specific evidence.
Contraindications
- Pregnancy
- Hepatic dysfunction; extreme caution with heart failure and growing animals because of premature epiphyseal closure.
Interactions
- No specific veterinary interaction is established in the supplied material.
Adverse effects
- Prostatic hyperplasia in males
- Masculinization in females
- Hepatopathy, especially with oral methylated androgens
Toxicity
Stop treatment for hepatic injury or excessive androgenic effects.
Preparations
| Preparation | Form | Strength | Route |
|---|---|---|---|
| Methyltestosterone 10 mg tablet | Tablet | 10 mg / tablet | PO |
| Methyltestosterone 25 mg tablet | Tablet | 25 mg / tablet | PO |
Monitoring and Administration
Monitor bilirubin, hepatic enzymes and clinical signs of cholestasis.
Clinical efficacy evidence in veterinary patients is limited; do not confuse this drug with injectable testosterone esters.
For dermatologic treatment obtain baseline hepatic tests and repeat at one and two months; watch for aggression or seborrhoea.