ABSTRACT
The most common subdermal implants (SDIs) worldwide contain a progestogen in a slow-release carrier, made either of polydimethylsiloxane, as in Jadelle® or Sino-implant with two implants, or ethylene vinyl acetate (EVA), as in Nexplanon® otherwise known in some locations as Implanon NXT®, a single rod. Nexplanon®, formerly known as Implanon, works primarily by ovulation inhibition, supplementing it is thought the usual sperm-blocking mucus effect caused by progestogens. Sustained low blood levels of the progestogen block LH surges while allowing some ovarian follicular activity. It is a single 40-mm rod, just 2 mm in diameter, containing 68 µg of etonogestrel – the chief active metabolite of desogestrel – and so has much in common with a well-taken DSG POP. The SPC states that hepatic enzyme inducers may lower the blood levels of etonogestrel and there have certainly been associated failures, though without confirmatory interaction studies.
