- Osaterone acetate.
Class of drug
- Steroidal androgen antagonist.
- Osaterone is a derivative of chlormadinone acetate and is a steroid chemically related to progesterone. It is a potent progestagen and a potent anti-androgen and also has some glucocorticoid effects.
- Both osaterone and its major metabolite (15²-hydroxylated osaterone acetate) are pharmacologically active.
- Osaterone acetate competitively prevents the binding of androgens to their prostatic receptors and blocks the transport of testosterone into the prostate. The effects are dose-dependent.
- For the treatment of benign prostatic hypertrophy (BPH ) in male dogs.
- BPH is an increase in size or non-malignant hypertrophy of the prostate and is the most common disease of the prostate in entire male dogs.
- The increase in prostate size is caused by changes in the ratio of androgens, like testosterone and estrogens.
- Many dogs are asymptomatic but clinical signs can result when there is a large degree of prostate hyperplasia.
- Treatment aims to decrease the size of the prostate gland and thus alleviate clinical signs (such as constipation and difficulty in urinating).
Effects of overdosage
- At dose rates <10 mg/kg bodyweight:
- Reduced food intake.
- Reduced bodyweight gain
- At dose rates >10 mg/kg:
- Ataxia and tremors
Other reported reactions
- Mainly associated with progestational effects of osaterone acetate:
- A transient increase in appetite occurs very commonly.
- Transient behavioral changes such as increased or decreased activity, or more sociable behavior, are common.
- Other adverse reactions, including transient vomiting and/or diarrhea, polyuria/polydipsia, lethargy or feminization syndrome including mammary gland hyperplasia occur uncommonly.
- A transient reduction in plasma cortisol occurs in most treated animals.
- Treatment does not usually need to be discontinued. In clinical trials, all dogs recovered without any specific therapy.
- Mammary gland hyperplasia was seen as a very rare adverse effect of osaterone during a laboratory study.
- NOEL for mammary gland proliferation of 100 mg/kg/day was calculated for male dogs (in female dogs this is 0.1 mg/kg/day (1 month)).