Androgens

By | 2011-08-18

Testosterone esters and methyltestosterone promote and maintain primary and secondary anatomical, physiological, and psychological male sexual characteristics. Anabolic steroids are synthetic derivatives of testosterone. In the female, they can be used to exert a negative feedback effect on the hypothalamic-pituitary axis thereby reducing gonadotrophin secretion.

Although androgens are used in the treatment of deficient libido in males, they are generally unreliable and may result in depression of spermatogenesis. Androgens are administered for the treatment of hormonal alopecia in dogs and cats and for mammary tumours and pseudopregnancy with lactation in bitches. These drugs may also be used for suppression of oestrus.

Care should be taken to avoid inducing excess virilism. Androgen therapy should not be given to animals suffering from conditions known to be aggravated by testosterone, such as prostatic hypertrophy in dogs. The effects of oral methyltestosterone last for 1 to 3 days, while oily injections of testosterone phenylpropionate are effective for 14 days.

Mibolerone is an orally active synthetic androgen-derived anabolic steroid with no progestogenic or oestrogenic activity. It inhibits luteinising hormone secretion, thereby preventing oestrus. It will not postpone pro-oestrus or oestrus once these have begun and it will not abort a pregnancy. If administered to pregnant bitches, it causes gross masculini-sation of female fetuses. It should not be used for more than 2 years.

MESTEROLONE

Indications.

Dose: See Prescribing for pigeons

Prescription-only medicine:® Pro-Viron (Schering Health) UK

Tablets, scored, mesterolone 25 mg

METHYLTESTOSTERONE

Indications. See notes above and under Dose

Contra-indications. Pregnant animals, hepatic impairment, congestive heart failure

Side-effects. Virilisation and aggression with overdosage; cessation of spermatogenesis; masculisation in female animals

Warnings. Use with caution in female animals intended for breeding, early epiphyseal closure may occur with prolonged treatment in young animals resulting in stunted growth

Dose: Treat according to individual response with gradual reduction of dose rather than abrupt cessation of treatment. By mouth.

Dogs. Females: treatment of oestrogen-dependent mammary tumours, suppression of oestrus, pseudopregnancy, certain hormonal alopecias, 500 micrograms/kg daily

Males: deficient libido, reversion of feminisation after removal of testicular tumour, certain hormonal alopecias, 500 micrograms/kg (0.5 mg/kg) daily

Cats. Females: certain hormonal alopecias, 500 micrograms/kg (0.5 mg/kg) daily

Males: deficient libido, certain hormonal alopecias, 500 micrograms/kg (0.5 mg/kg) daily

Prescription-only medicine: Orandrone (Intervet) UK

Tablets, methyltestosterone 5 mg, for dogs, cats

TESTOSTERONE ESTERS

Indications. See notes above and preparation details

Contra-indications. Pregnant animals, hepatic impairment, renal impairment, congestive heart failure, dogs with prostatic hypertrophy or androgen-dependent neoplasia

Side-effects. Virilisation in females with overdosage; possible spraying in male cats

Warnings. Early epiphyseal closure may occur in young animals

Dose: See preparation details

Prescription-only medicine: Durateston (Intervet) UK

Depot injection (oily), testosterone decanoate 20 mg, testosterone isocaproate 12 mg, testosterone phenylpropionate 12 mg, testosterone propionate 6 mg/mL, for dogs, cats

Dose: By subcutaneous or intramuscular injection. Repeat dose after 28 days, if required

Dogs. Females: suppression of oestrus, pseudopregnancy, 0.05-0.1 mL/kg

Males: reversion of feminisation due to Sertoli cell tumour, certain hormonal alopecias, 0.05-0.1 mL/kg

Cats: skin conditions, 0.05-0.1 mL/kg