The common contraceptive drugs in clinical use for women contain estrogens or progestogens, either singly or in a variety of combinations and contrations. The estrogens are usually synthetic derivatives of ethinyl estradiol. The progestogen are usually 19-nor testosterone or 17-hydroxy-progesterone derivatives such as norethindrone. The combination contraceptive preparations contain an estrogen and a progestogen and are often administered daily for 21 days and stopped for 7 days, during which time withdrawal uterine bleeding occurs.
Through a combined negative feedback to the hypothalamus, LH and FSH secretion are suppressed. There is an absence of the LH/FSH surge, and the failure of a follicular phase rise in FSH secretion results in lack of ovarian follicular development.
Progesterone administered alone have complex effects that relate to the dosage. Besides suppression of gonadotropin secretion and inhibition of follicular development, cervical mucus composition is modified, which may prevent sperm entry into the uterus cavity. In addition, endometrial histology may be altered and thus interfere with implantations of the ovum should fertilization occur.
Some contraceptives steroids regimes consist of estrogens administered alone for a number of days (usually 15) followed by a progesterone for several days (5). These sequential contraceptive preparations stimulate to some degree the normal sequence of ovarian steroid secretion. A dose of a progestin, e.g., "Plan-B" (Duramed Pharmaceuticals), has been used with success as "morning pill", often used as an emergency postcoital contraceptive.
Increased plasma progesterone concentrations are responsible for the lack of ovulation during pregnancy, this inhibitory effect of progesterone is the basis of current oral contraceptives, which contain a synthetic progesterone analog (a progestin).
Super-active agonistic analogs of GnRH have been developed whose stimulatory effect have been discovered to exert paradoxical inhibitory effects on pituitary-gonadal functions in both sexes, probably because they down regulate pituitary responsiveness to GnRH stimulation. The effect of these GnRH analogs may be mediated at the level of the pituitary, to cause a down regulation of GnRH receptors. Antibodies to choriogonadotropin may provide a novel method of contraception.
Through a combined negative feedback to the hypothalamus, LH and FSH secretion are suppressed. There is an absence of the LH/FSH surge, and the failure of a follicular phase rise in FSH secretion results in lack of ovarian follicular development.
Progesterone administered alone have complex effects that relate to the dosage. Besides suppression of gonadotropin secretion and inhibition of follicular development, cervical mucus composition is modified, which may prevent sperm entry into the uterus cavity. In addition, endometrial histology may be altered and thus interfere with implantations of the ovum should fertilization occur.
Some contraceptives steroids regimes consist of estrogens administered alone for a number of days (usually 15) followed by a progesterone for several days (5). These sequential contraceptive preparations stimulate to some degree the normal sequence of ovarian steroid secretion. A dose of a progestin, e.g., "Plan-B" (Duramed Pharmaceuticals), has been used with success as "morning pill", often used as an emergency postcoital contraceptive.
Increased plasma progesterone concentrations are responsible for the lack of ovulation during pregnancy, this inhibitory effect of progesterone is the basis of current oral contraceptives, which contain a synthetic progesterone analog (a progestin).
Super-active agonistic analogs of GnRH have been developed whose stimulatory effect have been discovered to exert paradoxical inhibitory effects on pituitary-gonadal functions in both sexes, probably because they down regulate pituitary responsiveness to GnRH stimulation. The effect of these GnRH analogs may be mediated at the level of the pituitary, to cause a down regulation of GnRH receptors. Antibodies to choriogonadotropin may provide a novel method of contraception.
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