- Inhibition of fertilisation by its toxic effect on sperm and ova. Adversely affects the motility and viability of sperm and the viability and transport of ova
- If fertilisation does occur, the local endometrial inflammatory reaction prevents implantation
- Can be inserted up to:
- 5 days following first UPSI since LMP, or
- 5 days after the earliest likely ovulation date
- This is the most effective method of EC. Failure rate is below 0.1%
Mode of action/efficacy of available methods
Warning
- Selective progesterone receptor modulator
- Acts by delaying ovulation for at least 5 days, until sperm from the UPSI for which EC was taken are no longer viable
- It delays ovulation even after the start of the luteinising hormone (LH) surge, whereas LNG-EC is no longer effective after the start of the LH surge
- Not effective after ovulation
- After UPA-EC, the majority of women will go on to ovulate later in the cycle and are therefore at risk of pregnancy from subsequent UPSI
- It is essential that women are made aware of this risk and advised regarding ongoing contraception
- Efficacy is dependent on timing of UPSI in relation to ovulation
- The overall pregnancy rate after administration of UPA-EC is about 1% to 2%
- Efficacy may be reduced in women with BMI greater than 30kg/m2 or weight greater than 85kg. Double dose UPA–EC is not currently recommended
- Inhibits ovulation, delaying or preventing follicular rupture and causing luteal dysfunction
- Needs to be taken prior to the start of the luteal hormone (LH) surge, LNG inhibits ovulation for the next 5 days, until sperm from the UPSI for which it was taken are no longer viable
- UPA-EC can delay ovulation even after the start of LH surge
- After taking LNG-EC, women who ovulate later in the cycle are at risk of pregnancy from further UPSI
- It is essential that women are made aware of this risk and advised regarding ongoing contraception
- Efficacy is dependent on timing of UPSI in relation to ovulation
- Efficacy of LNG-EC within 72 hours of a single episode of UPSI is thought to be 85%
- Women weighing greater than 70kg or BMI greater than 26 kg/m2, offer double dose (3mg) LNG-EC, if copper coil and UPA-EC are not appropriate