Levonorgestrel (LNG)

The levonorgestrel (or I-norgestrel or D-norgestrel) is a synthetic biological active progestin. It is the active beginning of the contraceptive of emergency called " pill of the day later " or "morning after pill". It is one of the available methods for women used to anticipate the pregnancy during the first days after having had sexual relations without protection. As any contraceptive method of emergency, one does not use the levonorgestrel regularly for avoiding the not wished pregnancies.

Mechanism of action
Due to the fact that it possesses a mechanism of multiple action, the effect of the levonorgestrel is dependent on the dose and the calendar of consumption in relation with the menstrual feminine cycle. In the context of the contraception, the levonorgestrel disables the liberation of the hormones gonadotróficas of the pituitary gland. The hormone gonadotrofina coriónica human (HCG) controls the activity of the ovaries and the remodelled one in the endometrium.

1. He prepares the ovulation, the ripeness and the exit of the ovum of the ovary (effect anovulatorio), avoiding the union of the ovum with the sperm.

2. It impedes the transport of the sperms, preventing that these join the ovum (contraceptive effect).
3. It alters the internal walls of the uterus (it reduces the endometrium) preventing the implantation of the blastocito in the uterus. This impedes that the blastocito could reach the uterus.

Efficiency
The use of levonorgestrel in 72 hours later to a sexual relation without protection tends to reduce the probabilities of pregnancy between 60 and one 90 per cent. The efficiency increases while there is in use the formulation of high dose as promptly as possible after the sexual relation.