Oral Contraceptives
Oral Contraceptives: An Update on Health Benefits and Risks: Components of COCs
COCs contain synthetic estrogen and progestin. A selected list of available COCs is shown in Table 1 . The two estrogen components available in the United States are ethinyl estradiol (EE), the most commonly used estrogen, and mestranol. Mestranol is a prodrug that must be converted to EE by the liver.[5] No product has less than 50 mcg mestranol because lower dosages have diminished contraceptive efficacy. Most low-dose oral contraceptives contain 30 to 35 mcg EE, while ultralow-dose contraceptives contain 20 mcg EE. Some newer formulations (e.g., Cyclessa -- Organon) contain 25 mcg EE.
Currently, nine progestins with various biologic activities are available in the United States. They include the first-generation estrane progestins: norethindrone, norethindrone acetate, and ethynodiol diacetate. The second-generation gonane progestins are levonorgestrel and norgestrel (a racemic mixture of dextronorgestrel and levonorgestrel in which dextronorgestrel is inert). Third-generation gonane progestins consist of desogestrel and norgestimate. An older progestin, norethynodrel, is not commonly prescribed because of its high estrogenic activity. The newest progestin available in the United States is drospirenone. A spironolactone analogue, drospirenone has a molecular structure and activity profile that is markedly different from those of other progestins.
Mechanism of Action and Biologic Activity
Oral contraceptives prevent pregnancy primarily by inhibiting ovulation through the combined actions of progestin and estrogen.[5] The dominant component is progestin, which inhibits ovulation by suppressing the cyclical release of luteinizing hormone (LH) from the anterior pituitary gland. Progestins also create a thick cervical mucus that slows sperm transport and inhibits capacitation (the activation of enzymes that permit the sperm to penetrate the ovum). Estrogen in COCs contributes to
COCs contain synthetic estrogen and progestin. A selected list of available COCs is shown in Table 1 . The two estrogen components available in the United States are ethinyl estradiol (EE), the most commonly used estrogen, and mestranol. Mestranol is a prodrug that must be converted to EE by the liver.[5] No product has less than 50 mcg mestranol because lower dosages have diminished contraceptive efficacy. Most low-dose oral contraceptives contain 30 to 35 mcg EE, while ultralow-dose contraceptives contain 20 mcg EE. Some newer formulations (e.g., Cyclessa -- Organon) contain 25 mcg EE.
Currently, nine progestins with various biologic activities are available in the United States. They include the first-generation estrane progestins: norethindrone, norethindrone acetate, and ethynodiol diacetate. The second-generation gonane progestins are levonorgestrel and norgestrel (a racemic mixture of dextronorgestrel and levonorgestrel in which dextronorgestrel is inert). Third-generation gonane progestins consist of desogestrel and norgestimate. An older progestin, norethynodrel, is not commonly prescribed because of its high estrogenic activity. The newest progestin available in the United States is drospirenone. A spironolactone analogue, drospirenone has a molecular structure and activity profile that is markedly different from those of other progestins.
Mechanism of Action and Biologic Activity
Oral contraceptives prevent pregnancy primarily by inhibiting ovulation through the combined actions of progestin and estrogen.[5] The dominant component is progestin, which inhibits ovulation by suppressing the cyclical release of luteinizing hormone (LH) from the anterior pituitary gland. Progestins also create a thick cervical mucus that slows sperm transport and inhibits capacitation (the activation of enzymes that permit the sperm to penetrate the ovum). Estrogen in COCs contributes to