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.

Cetrorelix acetate

Cetrotide (Serono)
vials containing 250 microgram or 3 mg as powder for reconstitution
Approved indication: assisted reproduction
Australian Medicines Handbook Section 10.6.3

Luteinising hormone has an important role in the menstrual cycle. In assisted reproduction programs a premature surge in luteinising hormone can cause ovulation, and therefore disrupt the collection of oocytes. This surge can be prevented by antagonising luteinising hormone releasing hormone (LHRH).

Cetrorelix competes with LHRH for binding sites in the pituitary gland. This reduces the secretion of luteinising hormone and follicle stimulating hormone. A 250 microgram dose is injected every day starting five or six days after ovarian stimulation is begun. These injections continue until the day before ovulation is induced. A single large dose (300 mg) can be used to suppress ovulation for at least four days.

Analogues of gonadotrophin-releasing hormones have also been used to prevent surges of luteinising hormone. (Prolonged administration of an analogue agonist eventually reduces gonadotrophin production.) Cetrorelix has therefore been compared with the LHRH agonists such as triptorelin and buserelin. While cetrorelix was as efficacious as the agonists it has the advantage of a more immediate action.

The most frequent adverse effects of cetrorelix are injection site reactions. Ovarian hyper stimulation can occur, but it is uncertain if this is caused by cetrorelix rather than the hormones used to promote follicular development. Compared to patients given LHRH agonists there are fewer cases of ovarian hyper stimulation.

While cetrorelix has been approved for use by specialists in the management of female infertility, researchers are studying other possible uses of LHR Hantagonists.