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Antiandrogens are very powerful drugs which act on the androgen receptor and are used to treat metastatic prostate carcinoma.

We can distinguish two categories of anti-androgens:

Progestative drugs

They are represented by cyproterone acetate. They possess a double effect:

• by their action on the hypothalamus, they down-regulate the secretion of androgens by the testis (castration),
  
• by their effect on the androgen receptor of the tumour cells, they block the development of this hormone-dependant cells.

 

Mechanisms of action of cyproterone

The side effects of this product are either related to hormonal deficiency (loss of libido, impotence, asthenia, moderate gynaecomastia) or to vascular disorders (venous thrombosis) or, more rarely, liver toxicity (cytolysis).

Nonsteroidal antiandrogens

These antiandrogens inhibit the translocation of protein cytoplasmic receptors towards the nucleus after fixation to the hormone.

There is no testosterone concentration diminution: thus no hot flushes, no or limited loss of libido and a variable diminution of sexual potency.

Mechanisms of action of nonsteroidal antiandrogens

The most toxic side effect is gynaecomastia (which may be painful) in approximately 60% of patients, diarrhoea, vomiting, modification of liver enzymes and visual disorders for one drug (nilutamide).

A relatively high number of molecules are available:

• nilutamide,
• bicalutamide,
• flutamide.