DGRefHelp - NHS Dumfries & Galloway- 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; no longer effective after the start of the 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.