Effective contraception can also be achieved by injecting 150 mg of depot medroxyprogesterone acetate (DMPA) every 3 months. After a 150-mg dose, ovulation is inhibited for at least 14 weeks. Almost all users experience episodes of unpredictable spotting and bleeding, particularly during the first year of use. Spotting and bleeding decrease with time, and amenorrhea is common. This preparation is not desirable for women planning a pregnancy soon after cessation of therapy because ovulation suppression can sometimes persist for as long as 18 months after the last injection. Long-term DMPA use reduces menstrual blood loss and is associated with a decreased risk of endometrial cancer. Suppression of endogenous estrogen secretion may be associated with a reversible reduction in bone density, and changes in plasma lipids are associated with an increased risk of atherosclerosis.
The progestin implant method utilizes the subcutaneous implantation of capsules containing etonogestrel. These capsules release one-fifth to one-third as much steroid as oral agents, are extremely effective, and last for 2–4 years. The low levels of hormone have little effect on lipoprotein and carbohydrate metabolism or blood pressure. The disadvantages include the need for surgical insertion and removal of capsules and some irregular bleeding rather than predictable menses. An association of intracranial hypertension with an earlier type of implant utilizing norgestrel was observed in a small number of women. Patients experiencing headache or visual disturbances should be checked for papilledema.
Contraception with progestins is useful in patients with hepatic disease, hypertension, psychosis or mental retardation, or prior thromboembolism. The side effects include headache, dizziness, bloating and weight gain of 1–2 kg, and a reversible reduction of glucose tolerance.
A. Postcoital Contraceptives
Pregnancy can be prevented following coitus by the administration of estrogens alone, progestin alone, or in combination (“morning after” contraception). When treatment is begun within 72 hours, it is effective 99% of the time. Some effective schedules are shown in Table 40–4. The hormones are often administered with antiemetics, since 40% of patients have nausea or vomiting. Other adverse effects include headache, dizziness, breast tenderness, and abdominal and leg cramps. Considerable controversy has accompanied the proposal to make these agents available without a prescription in the United States.
Mifepristone, an antagonist at progesterone and glucocorticoid receptors, has a luteolytic effect and is effective as a postcoital
TABLE 40–4 Schedules for use of postcoital contraceptives.
Conjugated estrogens: 10 mg three times daily for 5 days
Ethinyl estradiol: 2.5 mg twice daily for 5 days
Diethylstilbestrol: 50 mg daily for 5 days
Mifepristone: 600 mg once with misoprostol, 400 mcg once1
L-Norgestrel: 1.5 mg once (Plan B One-Step2)
L-Norgestrel: 0.75 mg twice daily for 1 day (eg, Plan B2)
Norgestrel, 0.5 mg, with ethinyl estradiol, 0.05 mg (eg, Ovral, Preven2): Two tablets and then two in 12 hours 1Mifepristone given on day 1, misoprostol on day 3. 2Sold as emergency contraceptive kits.
contraceptive. When combined with a prostaglandin it is also an effective abortifacient.
Beneficial Effects of Oral Contraceptives