Birth control At low doses,<unk>  is used in monophasic and triphasic formulations of combined oral contraceptive pills, with available monophasic doses ranging from 100 to 250 µg, and triphasic doses of 50 µg/75 µg/125 µg. It is combined with the estrogen ethinylestradiol in these formulations. At very low daily dose of 30 µg,<unk>  is used in some progestogen-only pill formulations.<unk>  is the active ingredient in a number of intrauterine devices including Mirena and Skyla. It is also the active ingredient in the birth control implants Norplant and Jadelle. One of the more common forms of contraception that contains only<unk>  is an IUD. One IUD, the Mirena is a small hollow cylinder containing<unk>  and polydimethylsiloxane and covered with a release rate controlling membrane. Emergency birth control<unk>  is used in emergency contraceptive pills (ECPs), both in a combined Yuzpe regimen which includes estrogen, and as a<unk> -only method. The<unk> -only method uses<unk>  1.5 mg (as a single dose or as two 0.75 mg doses 12 hours apart) taken within 3 days of unprotected sex, with one study indicating that beginning as late as 120 hours (5 days) after intercourse could be effective. The primary mechanism of action of<unk>  as a progestogen-only emergency contraceptive pill is, according to International Federation of Gynecology and Obstetrics (FIGO), to prevent fertilization by inhibition of ovulation and thickening of cervical mucus.Copper-releasing IUCsWhen used as a regular or emergency method of contraception, copper-releasing IUCs act primarily to prevent fertilization. Emergency insertion of a copper IUC is significantly more effective than the use of ECPs, reducing the risk of pregnancy following unprotected intercourse by more than 99%.2,3 This very high level of effectiveness implies that emergency insertion of a copper IUC must prevent some pregnancies after fertilization.Emergency contraceptive pillsTo make an informed choice, women must know that ECPs—like the birth control pill, patch, ring, shot, and implant,76 and even like breastfeeding77—prevent pregnancy primarily by delaying or inhibiting ovulation and inhibiting fertilization, but may at times inhibit implantation of a fertilized egg in the endometrium. However, women should also be informed that the best available evidence indicates that ECPs prevent pregnancy by mechanisms that do not involve interference with post-fertilization events.ECPs do not cause abortion78 or harm an established pregnancy. Pregnancy begins with implantation according to medical authorities such as the US FDA, the National Institutes of Health79 and the American College of Obstetricians and Gynecologists (ACOG).80Ulipristal acetate (UPA). One study has demonstrated that UP can delay ovulation.81... Another study found that UPA altered the endometrium, but whether this change would inhibit implantation is unknown.82p. 122:Progestin-only emergency contraceptive pills. Early treatment with ECPs containing only the progestin<unk>  has been show to impair the ovulatory process and luteal function.83–87p. 123:Combined emergency contraceptive pills. Several clinical studies have shown that combined ECPs containing ethinyl estradiol and<unk>  can inhibit or delay ovulation.107–110In 2002, a judicial review ruled that pregnancy begins at implantation, not fertilisation.8 The possible mechanisms of action should be explained to the patient as some methods may not be acceptable, depending on individual beliefs about the onset of pregnancy and abortion.Copper-bearing intrauterine device (Cu-IUD). Copper is toxic to the ovum and sperm and thus the copper-bearing intrauterine device (Cu-IUD) is effective immediately after insertion and works primarily by inhibiting fertilisation.9–11 A systematic review on mechanisms of action of IUDs showed that both pre- and postfertilisation effects contribute to efficacy.11 If fertilisation has already occurred, it is accepted that there is an anti-implantation effect,12,13Levonorgestrel <unk> . The precise mode of action of<unk>  <unk>  is incompletely understood but it is thought to work primarily by inhibition of ovulation.16,17Ulipristal acetate (UPA). UPA’s primary mechanism of action is thought to be inhibition or delay of ovulation.2LNG ECPs do not interrupt an established pregnancy or harm a developing embryo.15 The evidence available to date shows that<unk>  ECP use does not prevent a fertilized egg from attaching to the uterine lining. The primary mechanism of action is to stop or disrupt ovulation;<unk>  ECP use may also prevent the sperm and egg from meeting.16LevonorgestrelMechanism and efficacy FIGO has stated that: "review of the evidence suggests that<unk> <unk> l ECPs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in<unk>  ECP product labeling."• Interfere with the process of ovulation;• May possibly prevent the sperm and the egg from meeting.Implications of the research:• Inhibition or delay of ovulation is<unk>  ECPs principal and possibly only mechanism of action.• Review of the evidence suggests that<unk> -ECs cannot prevent implantation of a fertilized egg. Language on implantation should not be included in<unk>  ECP product labeling.• The fact that<unk> -ECs have no demonstrated effect on implantation explains why they are not 100% effective in preventing pregnancy, and are less effective the later they are taken. Women should be given a clear message that<unk> -ECs are more effective the sooner they are taken.•<unk>  ECPs do not interrupt a pregnancy (by any definition of the beginning of pregnancy). However,<unk>  ECPs can prevent abortions by reducing unwanted pregnancies. In November 2013, the European Medicines Agency (EMA) approved a change to the label saying it cannot prevent implantation of a fertilized egg. Other studies still find the evidence to be unclear. While it is unlikely that emergency contraception affects implantation it is impossible to completely exclude the possibility of post-fertilization effect. In November 2013, the EMA also approved a change to the label for HRA Pharma's NorLevo saying: "In clinical trials, contraceptive efficacy was reduced in women weighing 75 kg 165 pounds or more, and<unk>  was not effective in women who weighed more than 80 kg 176 pounds." In November 2013 and January 2014, the FDA and the EMA said they were reviewing whether increased weight and body mass index (BMI) reduce the efficacy of emergency contraceptives. An analysis of four WHO randomised clinical trials, published in January 2017, showed pregnancy rates of 1.25% (68/5428) in women with BMI under 25, 0.61% (7/1140) in women with BMI between 25 and 30, and 2.03% (6/295) in women with BMI over 30. These values yield an eight-fold reduction in efficacy for women with BMI over 30 compared to women with BMI under 25. However, emergency contraceptives remain effective regardless of BMI. Hormone therapy<unk>  is used in combination with an estrogen in menopausal hormone therapy. It is used under the brand name Klimonorm as a combined oral tablet with estradiol valerate and under the brand name Climara Pro as a combined transdermal patch with estradiol. Available forms As a type of emergency contraception,<unk>  is used after unprotected intercourse to reduce the risk of pregnancy. However, it can serve different hormonal purposes in its different methods of delivery. It is available for use in a variety of forms: By mouth<unk>  can be taken by mouth as a form of emergency birth control. The typical dosage is either 1.5 mg taken once or 0.75 mg taken 12–24 hours apart. The effectiveness in both methods is similar. The most widely used form of oral emergency contraception is the progestin-only pill, which contains a 1.5 mg dosage of<unk> .<unk> -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<unk>  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<unk>  is necessary for the protection of the endometrium. Intrauterine device The<unk>  intrauterine system <unk> -IUS) is a type of long-term birth control that releases the progestin into the uterine cavity.<unk>  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 5 years. Because it is inserted directly into the uterus,<unk>  is present in the endometrium in much higher concentrations that would result from a<unk> -containing oral pill; the<unk> -IUS delivers 391<unk>  of<unk>  to the inner uterine region while a comparable oral contraceptive delivers only 1.35<unk> . This high level of<unk>  impedes the function of the endometrium, making it hostile for sperm transport, fertilization, and implantation of an ovum. Implant Subcutaneous implants of<unk>  have been marketed as birth control implants under the brand names Norplant and Jadelle and are available for use in some countries.
Levonorgestrel
Etonogestrel
Norgestrel
Desogestrel
Chloroethynylnorgestrel
Gestodene
5α-Dihydrolevonorgestrel
Norelgestromin