Does smoking affect efficacy of the pill?
Contraceptive Technology Update reader Sharon Swain, RN, a public health nurse with the Peel Health Department in Brampton, Ontario, asks, "Is there any documentation supporting reduced efficacy of oral contraceptives [OCs] in women who smoke?"
These CTU editorial advisory board members addressed this question:
-Michael Rosenberg, MD, MPH, clinical professor of obstetrics and gynecology and epidemiology at the University of North Carolina at Chapel Hill and president of Health Decisions, a private research firm;
- Andrew Kaunitz, MD, professor and assistant chair of the department of obstetrics and gynecology at the University of Florida Health Sciences Center in Jacksonville, FL;
- Susan Wysocki, RNC, BSN, NP, president of the National Association of Nurse Practitioners in Women’s Health in Washington, DC.
Rosenberg: There are two lines that suggest that the anti-estrogenic effect of smoking diminishes the effectiveness of OCs. First, several studies of cycle control indicate that, after control for other factors affecting spotting and bleeding, smokers experience a higher frequency of such problems.1,2 A single study of the contraceptive efficacy of OCs in smokers indicates a slightly diminished effectiveness in smokers.2 Second, laboratory work indicates that estrogen increases the catabolism of estrogen, providing a rationale for these observed effects.
The interesting import of this is that the traditional treatment of smokers, which is to use a lower-estrogen preparation, may bear re-examination. The use of low-dose pills in smokers is driven more by safety than efficacy concerns, since smoking acts synergistically with age and other risk factors to increase the chances of thrombosis. This concern has been recognized by the fact that one preparation, Loestrin 1/20 (Parke-Davis, Morris Plains, NJ), has been marketed to smokers for more than a decade.
The bottom line is that although relevant information is sparse, it suggests that OCs may be less effective in smokers. Especially with the increasing use of lower-dose OCs (20 mcg preparations), there is a need to balance the safety and efficacy risks. Clinically, in a younger smoker without risk factors for thrombosis, I would be tempted to start with a 20 mcg preparation and move up to 30 if cycle control problems occurred. A similar approach for other smokers who lack risk factors probably also is reasonable. However, in the infrequent patients at risk for thrombosis, I believe that lower estrogen should be more important.
Kaunitz: As shown by Rosenberg, OC users who smoke experience more breakthrough bleeding.1 I am not aware of data, however, that demonstrates higher OC failure rates among smokers.
Wysocki: We know that smoking decreases estrogen levels; hence, smokers have a higher incidence of irregular bleeding on the pill. This is the reason that smokers are at higher risk for osteoporosis in later years. One important point to remember is that the efficacy of OCs largely depends on the progestin, so it may be possible to have pills that are even lower than 20 mcg of estrogen. The estrogen in combination OCs, for the most part, is for cycle regularity.
References
1. Rosenberg MJ, Waugh MS, Stevens CM. Smoking and cycle control among oral contraceptive users. Am J Obstet Gynecol 1996; 174:628-632.
2. Baron JA, Greenberg ER. "Cigarette smoking and estrogen related disease in women." In: Rosenberg MJ, ed. Smok ing and Reproductive Health. Boston: PSG, 1987:149-160.
You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
- Award-winning Medical Content
- Latest Advances & Development in Medicine
- Unbiased Content