Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.
Dimetriose (Roussel Uclaf)
2.5 mg capsules
Gestrinone is a synthetic steroid hormone which inhibits the release of pituitary gonadotrophins. The effect on ovarian secretion results in the atrophy of endometrial tissue, including regression of endometriosis. Gestrinone is structurally related to norgestrel and has some androgenic and progestogenic activity. However, the drug has an antiprogesterone effect on endometrial tissue.
The half life is approximately 27 hours and a steady state is achieved if a second capsule is taken 3 days after the first dose. The drug is metabolised and the metabolites are excreted in the urine and faeces.
Treatment begins on the first day of a period and continues for 6 months. Most women develop amenorrhoea within two months. If spotting occurs, the dose can be increased to one capsule 3 times a week for a few weeks. Repeat courses of gestrinone are not recommended.
Although gestrinone is effective in relieving the symptoms of endometriosis, its effect on infertility is not clear. The efficacy of the drug is probably similar to danazol.
Like danazol, many of gestrinone's adverse effects are due to its androgenic activity. These include acne, seborrhoea, hirsutism, weight gain and changes to the voice. Most patients will have at least one adverse event. Although gestrinone inhibits ovulation, patients need to use barrier contraception while taking the drug. This is because the drug is embryotoxic in some animals and can cause masculinisation of a female fetus. Gestrinone also significantly reduces HDL concentrations.