Maximizing the use of the progestin minipill
The progestin-only minipill offers safe, effective birth control for lactating women and for those who cannot take estrogen, yet it represents a small fraction of the contraceptive market in the United States. It is estimated that only 1% of the 26% of U.S. reproductive-age women who use oral contraceptives (OCs) choose minipills.1
Progestin-only pills (POPs), often called minipills, are generally less effective than combined oral contraceptives. About 5% of women who use the minipill consistently and correctly will become pregnant in the first year.2 In lactating women, however, the added contraceptive effect of breast-feeding makes the method nearly 100% effective.
Unlike combined OCs, minipills do not interfere with the quality or quantity of milk production during breast-feeding, says Linda Potter, DrPH, visiting research collaborator at the Office of Population Research at Princeton (NJ) University. Except for increased menstrual irregularities, they cause fewer and milder side effects and have fewer serious adverse effects than do combined pills, she states.
Irregular bleeding is a potential downside, agrees Andrew Kaunitz, MD, professor and assistant chair of the department of OB/GYN at the University of Florida Health Sciences Center in Jacksonville, FL. Despite such downsides, minipills offer excellent contraception for lactating women and can play an important role for women with medical contraindications such as migraine headaches, hypertension, diabetes, or cardiovascular problems.
How minipills work
Minipills have very low doses of progestin, even lower than combined pills. Both Nor-QD, manufactured by G.D. Searle and Co. of Chicago, and Micronor, manufactured by Ortho-McNeil Pharmaceutical Corp. of Raritan, NJ, contain 0.35 mg of norethindrone. Ovrette, manufactured by Wyeth-Ayerst Laboratories of Philadelphia, relies on 0.075 mg of norgestrel. The progestin in minipills inhibits ovulation and causes a thickening of the cervical mucus. Minipills also produce changes in the endometrium so it becomes less receptive to implantation, and they help to slow the movement of the egg through the fallopian tube.3
The small amount of progestin in minipills is quickly metabolized by the body, with little or no progestin left 24 hours following ingestion of the dose. This mechanism of action demands that minipills be taken every day at the same time for contraceptive efficacy.
If pills are taken more than three hours late, a backup method of contraception, such as condoms, must be used until the woman is back on the pill schedule for 48 hours, unless she is fully breast-feeding, says Potter.
Women who cannot follow such a rigid pill-taking schedule should be counseled to select another less-demanding method. Although the pill-taking schedule is stricter for minipills, backup contraception is only needed for 48 hours after the late dose, rather than the seven days needed for combined OCs, she notes.
"It is actually easier to use minipills: one pill every single day, no time off, and pills can be started at any time during a woman’s cycle," says Robert Hatcher, professor of OB/GYN at Emory University in Atlanta. "While easier to explain to women, it is also true that the woman must adhere to her schedule very attentively. The method is less forgiving if women miss pills."
Change in label a plus
Family Health International, a nonprofit research and technical assistance agency in Research Triangle Park, NC, drafted new labeling for minipills, which was accepted in 1995 with some modifications by the federal Food and Drug Administration (FDA) and issued as guidance to manufacturers. The labeling is much shorter and simpler to read than that in combined OC packs, says Potter.
The revised labeling states that fully breast-feeding women can start using minipills six weeks after delivery. If women are partially breast-feeding, they should begin minipills three weeks after delivery. These revised instructions are now included in norethindrone pill labeling; Wyeth-Ayerst has similar labeling now under review with the FDA, says Robyn Boyle, RPh, product information manager.
Managing Contraception states that if a woman is breast-feeding her baby, is immediately postpartum, and desires to use minipills soon after leaving the hospital, it may be appropriate to provide them.4 Providers at Grady Memorial Hospital in Atlanta, San Francisco General Hospital, and Harbor General Hospital in Torrance, CA, follow that advice. The National Medical Committee of the Planned Parenthood Federation of America, in sharp contrast to the World Health Organization in Geneva, Switzerland, and the International Planned Parenthood Federation in London, states that DMPA, Norplant, and minipills may begin immediately postpartum in lactating and nonlactating women.
Women in the later years of their reproductive lives, including smokers over 35, may be good candidates for minipills, says Kaunitz. The pills provide efficacy during a time of diminishing fertility and do not have the thrombotic complications associated with combined OC use.
Ectopic pregnancies more likely
When a pregnancy occurs in a woman using minipills, it is more likely to be ectopic because of the contraceptive effect of the progestin on the endometrial lining.2 "Because of the low dose of progestin, minipills are not a good choice for women taking hepatic enzyme-inducing medications, such as carbamazepine, felbamate, phenobarbitol, phen ytoin, primidone, rifampin, and topiramate," says Kaunitz.
A recent study found that use of minipills during lactation by mothers with a history of gestational diabetes was associated with an elevated risk of developing type 2 diabetes.5 The same study found that use of combination OCs by women with a history of gestational diabetes was not associated with an increased risk of developing diabetes.
"Although future investigations will help clarify the impact that hormonal contraception has on risk of developing diabetes in low- and high-risk women, this study reminds clinicians that monitoring for evidence of diabetes is important when following high-risk women, regardless of their contraceptive method," Kaunitz says.
References
1. Kaunitz AM. Revisiting progestin-only OCs. Contem OB/GYN 1997; Dec:91-104.
2. Hatcher RA, Trussell J, Stewart F, et al. Contraceptive Technology. 17th ed. New York, NY: Ardent Media; 1998.
3. Blaney CL. POPs are very safe, have few side effects. Network 1995; 15:10-15.
4. Hatcher RA, Zieman M, Watt A, et al. Managing Contraception. Tiger, GA: Bridging the Gap Foundation; 1999.
5. Kjos SL, Peters RK, Xiang A, et al. Contraception and the risk of type 2 diabetes mellitus in Latina women with prior gestational diabetes mellitus. JAMA 1998; 280:533-538.
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