Most of the emergency contraceptives have which one of the following active ingredients?

Contraception or birth control is a procedure used to prevent pregnancy. The most common form of contraception is used to prevent pregnancy is contraceptive pills. Contraceptive pills mostly contain hormones. They prevent pregnancy by interfering in the ovulation or the release of the egg from the ovaries.

Levonorgestrel (LNG) is commonly used as the active ingredient in emergency contraceptive pills. It is a synthetic steroid and derived from testosterone. LNG (17α-ethynyl-18-methyl-19-nortestosterone) is a progestin and works similar to the progesterone hormone. The chemical formula of LNG is C ₂₁ H ₂₈ O ₂ . LNG prevents the ovulation or release of eggs and prevents the passage of sperms by closing the cervix.

In the target cells, LNG binds to the progesterone receptors and acts as a transcription activator. The hormone-receptor complex translocates to the nucleus to increase the synthesis of target proteins. This causes suppression of luteinizing hormone activity and prevents the release of eggs from ovaries. LNG stimulates the cervical mucus and endometrium.

Norgestrel (levonorgestrel and dextronorgestrel) was discovered by G.A. Hughes, H. Smith, and colleagues at Wyeth pharmaceutical company in 1963.