Drugs used to control fertility and treat disorders of the female reproductive organs collectively are among the most frequently prescribed agents in clinical practice. This chapter discusses a number of common clinical issues and their drug therapies that are central to women's health. The focus is on reproductive disorders and aspects of therapy rather than comprehensive coverage of the drugs themselves, which are described in more detail elsewhere (e.g., Chapter 33 for prostaglandins; Chapter 38 for the gonadotropins, gonadotropin-releasing hormone [GnRH] agonists and antagonists, and oxytocin; Chapter 40 for estrogens and progestins; Section VII for antibiotics).
Contraception can either be administered as planned prophylaxis (e.g., oral contraceptive pills, patches, implants, vaginal or intrauterine devices, barrier foams, spermicides, tubal ligation, vasectomy) or postcoitally for emergency contraception (i.e., high-dose estrogen-containing oral contraceptive pills, high-dose progestin pills, a progesterone antagonist, intrauterine devices). The progesterone antagonist also can be used to terminate an established pregnancy.
Combination Oral Contraceptives. Of the various contraceptive methods, pills containing an estrogen and progestin in combination are the most widely used and are among the most effective of the nonsurgical modalities (Table 66–1); they act primarily by suppressing the luteinizing hormone (LH) surge and thereby preventing ovulation. A wide variety of preparations are available for oral, transdermal, and vaginal administration (Erkkola, 2007). (See Table 66–2 for a list of branded formulations. Many of the same formulations also are available as generics.) Almost all contain ethinyl estradiol as the estrogen and a 17α-alkyl-19-nortestosterone derivative as the progestin and are administered for the first 21-24 days of a 28-day cycle. The major functions of the estrogen are to sensitize the hypothalamus and pituitary gonadotropes to the feedback inhibitory effects of the progestin and to minimize breakthrough bleeding. The progestin exerts negative feedback, which suppresses the LH surge and thereby prevents ovulation, and protects against uterine cancer by opposing the proliferative effects of the estrogen on the uterine endometrium. Newer formulations offer effective contraception with improved activity profiles. They contain lower amounts of hormones to minimize adverse effects; some incorporate progestins with less androgenic activity (e.g., gestodene, desogestrel) or that antagonize the mineralocorticoid receptor and thereby reduce the tendency toward edema (e.g., drospirenone). Due to diminished endometrial proliferation, patients taking these newer formulations may not experience a menstrual bleed at the end of each cycle; if this occurs, a pregnancy test generally is performed after the first missed cycle to rule out contraceptive failure.
Table 66-1One-Year Failure Rate with Various Forms of Contraception ||Download (.pdf) Table 66-1 One-Year Failure Rate with Various Forms of Contraception
|BIRTH CONTROL METHOD ||FAILURE RATE (Perfect Use) ||FAILURE RATE (Typical Use) |
|Combination oral contraceptive pills ||0.3% ||8% |
|Progestin-only minipill ||0.5% ||8% |
|depo-provera ||0.3% ||3% |
|Copper intrauterine device ||0.6% ||0.8% |