Levonorgestrel-only emergency contraception was introduced under the brand name Postinor by 1978. Ho and Kwan published the first study comparing levonorgestrel only and the Yuzpe regimen as methods of emergency contraception in 1993 and found that they had similar effectiveness but that levonorgestrel alone was better-tolerated. In relation to this, the Yuzpe regimen has largely been replaced as a method of emergency contraception by levonorgrestrel-only preparations. Levonorgestrel-only emergency contraception was approved in the United States under the brand name Plan B in 1999, and has also been marketed widely elsewhere throughout the world under other brand names such as Levonelle and NorLevo in addition to Postinor. In 2013, the Food and Drug Administration approved Plan B One-Step for sale over-the-counter in the United States without a prescription or age restriction.Levonorgestrel has also been introduced for use as a progestogen-only intrauterine device under the brand names Mirena and Skyla among others, as a progestogen-only birth control implant under the brand names Norplant and Jadelle, as a combined oral tablet with estradiol valerate for menopausal hormone therapy under the brand name Klimonorm, and as a combined transdermal patch with estradiol for menopausal hormone therapy under the brand name Climara Pro. Ester prodrugs of levonorgestrel such as levonorgestrel acetate and levonorgestrel butanoate have been developed and studied as other forms of birth control such as long-acting progestogen-only injectable contraceptives and contraceptive vaginal rings, but have not been marketed for medical use.
Levonorgestrel-only emergency contraceptive pills are reported to have an 89% effectiveness rate if taken within the recommended 72 hours after sex. The efficacy of the drug decreases by 50% for each 12 hour delay in taking the dose after the emergency contraceptive regimen has been started. Skin patch
Estradiol with levonorgestrel in the form of a skin patch is used under the brand name Climara Pro for hormone replacement therapy in postmenstrual women, treating symptoms such as hot flashes or osteoporosis. The simultaneous delivery of a progestogen such as levonorgestrel is necessary for the protection of the endometrium. Intrauterine device
The levonorgestrel intrauterine system (LNG-IUS) is a type of long-term birth control that releases the progestin into the uterine cavity. Levonorgestrel is released at a constant, gradual rate of 0.02 mg per day by the polydimethylsiloxane membrane of the device, which renders it effective for up to five years. Because it is inserted directly into the uterus, levonorgestrel is present in the endometrium in much higher concentrations that would result from a LNG-containing oral pill; the LNG-IUS delivers 391 ng of levonorgestrel to the inner uterine region while a comparable oral contraceptive delivers only 1.35 ng. This high level of levonorgestrel impedes the function of the endometrium, making it hostile for sperm transport, fertilization, and implantation of an ovum. Implant
Subcutaneous implants of levonorgestrel have been marketed as birth control implants under the brand names Norplant and Jadelle and are available for use in some countries. Contraindications
Known or suspected pregnancy is a contraindication of levonorgestrel as an emergency contraceptive.