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.
Synarel Nasal Spray (Syntex)
200 micrograms per actuation in a 10 mL spray pump
Nafarelin is an analogue of gonadotrophin releasing hormone (GnRH). While a single dose stimulates gonadotrophin release, regular doses gradually reduce gonadotrophin secretion. This results in suppression of ovarian function. The reduced secretion of oestrogens may heal endometriosis.
At the recommended dose, nafarelin is sprayed into one nostril in the morning and into the other in the evening. The drug is rapidly absorbed, but the bioavailability of an intranasal dose averages 3% and can be affected by rhinitis. Nafarelin is metabolised and has a half-life of 3 hours.
Treatment begins at the start (days 2-4) of the menstrual cycle and continues for 6 months. This regimen is as effective as a course of danazol.1 A higher dose can be considered in patients who have persistent symptoms of endometriosis and do not develop amenorrhoea. If the woman's symptoms recur after therapy, a second course of treatment is not recommended as safety data are lacking.
Nafarelin does not have the same androgenic adverse effects as danazol, but it can cause menopausal symptoms. The most commonly reported symptoms are hot flushes, vaginal dryness, altered libido and headaches. Treatment for 6 months results in a loss of bone density. The vertebral trabecular bone density falls by nearly 9% and may not return to normal after treatment. Nafarelin also has a similar effect to oestrogen deficiency on blood lipids e.g. concentrations of total cholesterol and triglycerides may increase.
As nafarelin is likely to be expensive, it may be reserved for women with endometriosis who do not respond to or cannot tolerate other treatments.
- Henzl MR, Corson SL, Moghissi K, Buttram VC, Berqvist C, Jacobson J. Administration of nasal nafarelin as compared with oral danazol for endometriosis. A multi center double-blind comparative clinical trial. N Engl J Med 1988;318:485-9.