Women who wear an adhesive patch that delivers a combination hormonal contraceptive through the skin are no more likely to become pregnant than women who use a combination oral contraceptive, according to a study of more than 1,400 women at 45 clinics in the United States and Canada.1 In addition, women's compliance with using the patch is significantly higher than that with using the pill (88% vs. 78%). While the patch is comparable to the pill in cycle control, some adverse reactions, such as breast discomfort and painful menstruation, are significantly more common among women who use the patch.
Between October 1997 and June 1999, researchers recruited women aged 18-45 from 39 clinics in the United States and six in Canada. Women were eligible to participate in the study if they were in good health and sexually active. Women could not participate if they had contraindications to hormone use, were pregnant, or had been pregnant or lactating within the past 42 days. The researchers randomly assigned participants to use either the patch (812 women) or an oral contraceptive (605). For each cycle of use, women assigned to the patch group used one seven-day patch weekly for three consecutive weeks and discontinued use for one week (always changing the patch on the same day of the week); women in the oral contraceptive group used a daily oral contraceptive for 21 days and a placebo for seven days. Women participated in the study for either six or 13 cycles.
Researchers instructed the women to apply the patch to the buttocks, upper outer arm, lower abdomen or upper torso, excluding the breast. If a patch became partially or completely detached, women were to replace it with a new patch and wear it for the remainder of the week. The patch is designed to be wearable during bathing and swimming.
Women received physical and gynecologic exams before and after study participation; they were given a pregnancy test upon early withdrawal from the study or 10 days after the end of their last scheduled cycle. Those who became pregnant were classified into four groups: those who conceived prior to study participation; those who conceived after their last cycle in the study; those who experienced a method failure; and those who had not complied with instructions for using their method (user-failure).
The researchers measured contraceptive efficacy by calculating overall and method-related Pearl Indices (numbers of pregnancies occurring per 100 person-years of use) and cumulative probabilities of pregnancy. Blood tests, evaluations of vital signs, clinic personnel's observations and women's self-reports were used to assess the occurrence of adverse side effects. The investigators also assessed cycle control (breakthrough bleeding and spotting), method compliance and patch adhesion on the basis of information women recorded in daily diaries.
The women in both groups had similar demographic characteristics and histories of oral contraceptive use. Their mean age was 28, and about nine in 10 were white. In each group, nearly one-quarter of women had not used oral contraceptives in the two months before entering the study, and slightly more than half had used oral contraceptives in their last menstrual cycle.
Five women who used the patch became pregnant--four as a result of method failure and one as a result of noncompliance. Seven women who used the pill became pregnant--four as a result of method failure and three as a result of noncompliance. The overall and method-related Pearl Indices were numerically lower among women who used the patch than among women who used the pill, but the differences were not statistically significant. The overall Pearl Index was 1.2 pregnancies per 100 person-years among women who used the patch and 2.2 among women who used the pill. For method failure, the Pearl Indices were 1.0 and 1.3, respectively. The probabilities of pregnancy also were similar among women who used the patch and those who used the pill (1-2% over 13 cycles).
Overall, the researchers found no significant difference in women's experience with breakthrough bleeding with the two methods. Women who used the patch had significantly more breakthrough bleeding or spotting than women who used the pill in cycle one (18% vs. 11%) and cycle two (12% vs. 8%) because of a difference in spotting only, but for cycles 3-13, the two groups did not differ.
The types of adverse reactions women reported were generally similar between the two groups. Headaches and nausea were the most common side effects, reported by about one in five women in each group. Only about 2% of women in each group experienced a serious adverse event, such as abdominal pain, vomiting, migraine, dehydration or depression.
While a significantly greater proportion of women who used the patch than of women who used the pill reported breast discomfort (19% vs. 6%), the difference was limited to cycles one and two. A larger proportion of women who used the patch than of women who used the pill reported painful menstruation (13% vs. 10%); a significantly higher proportion of women using the patch than of those using the pill discontinued their method for this reason (2% vs. 0.2%). The same was true for women who experienced headache: While the occurrence of headache was not different between the two groups, 2% of women who used the patch discontinued it because of headaches, compared with 0.3% of women who used the pill. Twenty percent of women who used the patch experienced mild or moderate skin reactions at the application site, and 3% of women discontinued use for this reason.
The proportion of women who demonstrated perfect compliance with the dosing schedule of their contraceptive was significantly larger among women using the patch (88%) than among women who used the pill (78%). Five percent of all patches used had to be replaced because they became partially (3%) or completely (2%) detached.
The investigators note that "contraceptive compliance is clearly related to contraceptive efficacy" and that problems with women's compliance with instructions for using oral contraceptives have been well documented in other research. They speculate that because the patch's "weekly dosing was associated with significantly better compliance than is observed with daily dosing regimens," women's use of the patch could result in lower contraceptive failure rates. However, they recommend further research to determine whether that would occur.--B. Brown
REFERENCE
1. Audet M-C et al., Evaluation of contraceptive efficacy and cycle control of a transdermal contraceptive patch vs. an oral contraceptive: a randomized controlled trial, Journal of the American Medical Association, 2001, 285(18):2347-2354.