Hormonal
contraceptives
Hormonal contraceptives inhibit ovulation.
Contraceptives typi-cally contain a combination of hormones. For example,
ethinyl estradiol may be combined with desogestrel, drospirenone,
lev-onorgestrel, norethindrone, norgestimate, or norgestrel. Also, mestranol
may be combined with norethindrone. Ethinyl estradiol or ethynodiol diacetate
may also be used alone as a contraceptive.
Hormonal contraceptives are absorbed from the GI
tract and are widely distributed. They’re metabolized in the kidneys and
excret-ed in urine and feces.
Some forms of hormonal contraceptives are available
in a trans-dermal patch form. These contraceptives are absorbed through the
skin but have the same distribution, metabolism, and excre-tion as orally
administered contraceptives.
The primary mechanism of action of combination
hormonal con-traceptives (estrogen and progestin) is the suppression of
go-nadotropins, which inhibits ovulation. Estrogen suppress-
es secretion of follicle-stimulating hormone,
which blocks follicular development and ovulation. Progestin suppress-es the
secretion of luteinizing hormone, which prevents ovulation, even if the
follicle develops. Progestin also thickens the cervical mucus; this interferes
with sperm migration and causes endometrial changes that prevent implantation
of a fertilized ovum.
The primary purpose for taking hormonal
contraceptives is the prevention of pregnancy in women. The combination of
ethinyl estradiol and norgestimate is also used to treat moderate acne in
females younger than age 15.
Hormonal contraceptives can interact with other
medications in various ways:
§ Antibiotics, oxcarbazepine, phenobarbital,
phenytoin, topira-mate, and modafinil may decrease the effectiveness of oral
contra-ceptives. A patient taking these drugs with a hormonal contracep-tive
needs to use a barrier contraceptive.
§ Atorvastatin may increase serum estrogen
levels.
§ Cyclosporin and theophylline have an
increased risk of toxicity when taken with hormonal contraceptives.
§ Prednisone increases the therapeutic and
possibly toxic effects of hormonal contraceptives. (See Adverse reactions to hormonalcontraceptives.)
§ Several herbal medications can affect serum
levels of hormonal contraceptives.
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