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.

Ganirelix

Orgalutran (Organon)
250 microgram/0.5 mL in pre-filled syringes
Approved indication: assisted reproduction
Australian Medicines Handbook Section 10.6.3

Ganirelix is the second member of its class to be approved for use in Australia. The first luteinising hormone releasing hormone (LHRH) antagonist to be approved was cetrorelix (see above).

These drugs are given to prevent premature ovulation when controlled ovarian hyper stimulation is used to assist conception. The patients are given follicle stimulating hormone (FSH) starting on the second or third day of their menstrual cycle. When they have their sixth dose of FSH they start daily subcutaneous injections of ganirelix. By binding to pituitary gonadotrophin receptors, ganirelix inhibits a surge in the concentration of luteinising hormone. By preventing this surge, the timing of ovulation can be controlled. This enables an adequate number of follicles to develop to the required size for collection.

Earlier attempts to create gonadotrophin antagonists had problems because they triggered allergic reactions by releasing histamine. Although this does not appear to occur with ganirelix, it can cause reactions at the injection site in up to 15% of patients. Other adverse effects include headache and nausea.

The efficacy of ganirelix is probably similar to that of the gonadotrophin agonists which have also been used to prevent surges of luteinising hormone. Ganirelix has the advantage of acting more quickly. There is, however, a concern that implantation rates may be reduced for follicles exposed to LHRH antagonists.1

References

  1. Hernandez ER. Embryo implantation and GnRH antagonists. Embryo implantation: the rubicon for GnRH antagonists. Hum Reprod 2000;15:1211-6 .