Mirena – contraceptive of choice for 3m women
Delvivo technology has been used for some 20 years in the fertility control intrauterine hormonal system (IUS) Mirena, which is approved in 95 countries and used by around 3m women worldwide.
Because Mirena releases levonorgestrel (LNG) directly into the uterine cavity, the daily dose required is low and the plasma concentrations achieved are lower than those seen with the combined contraceptive pill and the mini-pill. Furthermore, unlike oral contraceptives, plasma levels do not display peaks and troughs. Using Mirena is said to be as effective as sterilisation,1 but can be easily reversed with an immediate return to full fertility.2 The failure rate is said to be lower than that for the combined oral contraceptive pill.
Mirena consists of a small, plain, plastic T-shaped frame bearing an LNG-containing cylinder. After insertion into the uterus, LNG is released from the cylinder directly into the uterus continuously for five years. The hormone is released at a small dosage of 20µg/day, which is comparable to taking four mini-pills a week.
The LNG acts in several ways, including preventing endometrial proliferation and by thickening the cervical mucus.
One of Mirena's most significant benefits is its ease and convenience of use: its efficacy is not influenced by patient compliance or by gastrointestinal impairment. However, it may also have medical benefits, in the form of reduced menstrual bleeding and period pains and lower risk of uterine and pelvic infections. In some women, the reduction in bleeding could even offer an alternative to hysterectomy.
Many of these benefits arise because the hormone is delivered directly to the uterus without travelling through the GI tract and the entire circulation before reaching its target; this also results in fewer concerns over side effects.