mechanism of action
Last reviewed 01/2018
A contraceptive implant such as Norplant works by releasing levonorgestrel into the bloodstream. Levonorgestrel has several modes of action:
- an increases cervical viscosity, thus making sperm penetration more difficult
- there is a suppression of ovulation in approximately half of all menstrual cycles
- if ovulation occurs, the luteal phase is often deficient, so inhibiting fertilisation
- endometrial proliferation is supressed, so hindering implantation