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.
Implanon (Organon)
68 mg implants
Approved indication: contraception
Australian Medicines Handbook Section 17.1.4
The approval of etonogestrel implants adds to the choice of progestogen-only methods of contraception. Etonogestrel is a metabolite of desogestrel which is used in some combined contraceptive pills.
The implant is 40 mm long and has a diameter of 2 mm. It is loaded inside a stainless steel applicator. After anaesthetising the area, the implant is inserted under the skin of the inner side of the upper arm. The inserting is done in the first five days of the menstrual cycle if the woman is not using the contraceptive pill. Women changing from a progestogen-only pill can have the implant at any stage of the cycle.
While etonogestrel does affect the cervical mucus, its main contraceptive effect is the inhibition of ovulation. Inhibitory concentrations of etonogestrel are reached within one day of insertion. One implant will release these concentrations of etonogestrel for at least two years. It should be removed after three years. The effect of etonogestrel quickly wears off after the implant is removed. This may be useful when managing adverse effects.
In clinical trials no pregnancies have occurred. The main problems have been the adverse effects associated with progestogens. The menstrual pattern is likely to change, some women will have irregular bleeding, others will have amenorrhoea. These changes often prompt women to ask for the implant to be removed. Other adverse effects include breast pain, acne and weight gain.
Prescribers who intend to offer etonogestrel as a contraceptive option should ensure they are instructed in how to insert and remove the implant.
