Estradiol (medication)
Estradiol is also widely available in combination with progestogens. It is available in combination with norethisterone acetate under the major brand names Activelle, Cliane, Estalis, Eviana, Evorel Conti, Evorel Sequi, Kliogest, Novofem, Sequidot, and Trisequens; with drospirenone as Angeliq; with dydrogesterone as Femoston, Femoston Conti; and with nomegestrol acetate as Zoely. Estradiol valerate is available with cyproterone acetate as Climen; with dienogest as Climodien and Qlaira; with norgestrel as Cyclo-Progynova and Progyluton; with levonorgestrel as Klimonorm; with medroxyprogesterone acetate as Divina and Indivina; and with norethisterone enantate as Mesigyna and Mesygest. Estradiol cypionate is available with medroxyprogesterone acetate as Cyclo-Provera, Cyclofem, Feminena, Lunelle, and Novafem; estradiol enantate with algestone acetophenide as Deladroxate and Topasel; and estradiol benzoate is marketed with progesterone as Mestrolar and Nomestrol.
Levonorgestrel
Levonorgestrel is a hormonal medication which is used in a number of birth control methods. In pill form, sold under the brand name Plan B among others, it is useful within 120 hours as emergency birth control. It becomes less effective the longer after sex and only works before pregnancy has occurred. It is also combined with an estrogen to make combined oral birth control pills. Within an intrauterine device (IUD), sold as Mirena among others, it is effective for long-term prevention of pregnancy. An implantable form of levonorgestrel is also available in some countries.
Common side effects include nausea, breast tenderness, headaches, and increased, decreased, or irregular menstrual bleeding. When used as a form of emergency contraception, if pregnancy occurs, there is no evidence its use harms the baby. It is safe to use during breastfeeding. Birth control that contains levonorgestrel will not change the risk of sexually transmitted infections. It is a progestin and has effects similar to those of the hormone progesterone. It works mostly by preventing ovulation and closing off the cervix to prevent the passage of sperm.
Levonorgestrel was discovered in 1963 and was introduced for medical use together with ethinylestradiol in 1970. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication. The wholesale cost in the developing world costs between 0.23 and US$1.65 for the dose required for emergency birth control. In the United States it is over the counter for all ages.