These methods are ideal for most women, but contraindications and cautions are associated with a few conditions listed in Table 38-2. Current breast cancer and pregnancy are the only two absolute contraindications. In a few instances, manufacturer restrictions difer from the US MEC. First, manufacturer prescribing information lists thrombosis or thromboembolic disorders as contraindications (Merck, 2016a; Pizer, 2015a,b). However, for individuals with these disorders, US MEC considers progestin-containing methods category 2. Moreover, evidence does not link progestin-only methods with thromboembolism, stroke, or cardiovascular disease (Mantha, 2012; Tepper, 2016b; World Health Organization, 1998). Second, for many progestin products, manufacturers note prior ectopic pregnancy as a contraindication. his is secondary to progesterone's efect of slowing fallopian tube motility and thereby delaying fertilized egg transport to the endometrial cavity. hat said, efective contraception lowers pregnancy rates overall. Thus, for those with prior ectopic pregnancy, US MEC considers progestin injectables and implants category 1, and progestin-only pills are category 2.
These currently are available in forms that contain both estrogen and progestin or contain only progestin. Progestin-only injectables and pills are considered very efective, yet secondtier agents, due to the need for increased patient compliance. Similarly, products containing both estrogen and progestin, often termed combination hormonal contraception (CHC), are considered in this tier. These may be supplied as pills, transvaginal rings, or transdermal patches.
• Combination Hormonal Contraceptives Mechanism of Action
Actions of combination hormonal contraceptives are multiple, but the most important efect is suppression of hypothalamic gonadotropin-releasing factors. his in turn blocks pituitary secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) and thereby inhibits ovulation. The progestin component of CHCs provides ovulation prevention by suppressing LH; it thickens cervical mucus and thereby retards sperm passage; and it renders the endometrium unfavorable for implantation. Estrogen blocks ovulation by suppressing FSH release. To promote cycle control, estrogen stabilizes the endometrium, which prevents intermenstrual bleeding-also known as breakthrough bleeding. The net efect is an extremely efective yet highly reversible method (Mansour, 2011).
hese pills are the most frequently used reversible birth control method in the United States. In a 2006 to 2010 survey, 16 percent of contracepting women in the United States were using these (Daniels, 2015). COCs are marketed in a wide variety of estrogen and progestin combinations. lvlost are available as generics, and the FDA (2016) confirms the bioequivalence of COC generics. The merican College of Obstetricians and Gynecologists (2015a) supports the use of either branded or generic preparations.
Pharmacologically, ethinyl estradiol is the most common estrogen present in COC formulations in the United States. Less frequently, mestranol or estradiol valerate is used. Unwanted efects most often attributed to the estrogen component include breast tenderness, weight gain, nausea, and headache.
COCs also contain one of several progestins that are structurally related to progesterone, testosterone, or spironolactone. hus, these progestins bind variably to progesterone, androgen, glucocorticoid, and mineralocorticoid receptors. hese ainities explain many pill-related side efects and are often used to compare one progestin with another.