Osaterone acetate

Introduction

Name

• Osaterone acetate.

Class of drug

• Steroidal androgen antagonist.

Uses

Action

• 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.

Indications

• 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).

Adverse reactions

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)).