Oral contraceptives (OCs) are widely used and have been shown to be effective in clinical trials. However, OCs have a failure rate as high as 8.5 percent, primarily as a result of noncompliance. Audet and colleagues conducted a randomized trial to compare contraceptive efficacy, cycle control, compliance, and safety of OCs with those of a transdermal contraceptive patch.
Women between the ages of 18 and 45 were included. The trial was conducted at 45 clinics in the United States and Canada. Patients were randomized to receive either an oral contraceptive (levonorgestrel, in a dosage of 50 mg, plus ethinyl estradiol, in a dosage of 30 mg on days 1 through 6; 75 mg and 40 mg (respectively) on days 7 through 11; and 125 mg and 30 mg on days 12 through 21 (with placebo given on days 22 through 28); or a contraceptive patch that delivered 150 mg of norelgestromin and 20 mg of ethinyl estradiol daily, with a new patch used each week for three weeks and no patch used in the fourth week. Excluded from the study were the following: women who were lactating or had recently been pregnant; those with contraindications to hormonal therapy or uncontrolled thyroid disorders; those who had Papanicolaou test evidence of squamous intraepithelial lesions, adenocarcinoma, or other malignancy; those who had a history or presence of dermal hypersensitivity in response to topical applications; those who were older than 35 years and smoked; those who had alcohol or substance abuse within 12 months of screening; those who had been given injectable progestin within six months of screening; and those who had been given any experimental drug, device, or hepatic enzyme-inducing drug within 30 days of screening. Women in the patch group were told to avoid application of oils, creams, or cosmetics on or around the patch area. The primary end point was breakthrough bleeding or spotting during cycle 3 for cycle control evaluation.
The patch group included 812 women and the OC group included 605 women. The two groups were similar in demographics. There were four method-failure pregnancies and one user-failure pregnancy in the patch group per 5,240 cycles, compared with four method-failure and three user-failure pregnancies in the OC group per 4,167 cycles. This difference was not statistically significant.
There were no significant differences between the groups in terms of breakthrough bleeding, although there were significantly higher rates of breakthrough bleeding and spotting during cycles 1 and 2 in the patch group. Compliance was better in the patch group than in the OC group (88.1 percent versus 77.7 percent). The patch detached completely 1.8 percent of the time and partially 2.8 percent of the time.
Adverse events were as expected. The incidence of breast discomfort was significantly higher in the patch group during cycles 1 and 2. Similarly, the incidence of headache and dysmenorrhea was significantly higher in the patch group and more likely to cause discontinuation of the patch.
The authors conclude that compliance in women using a contraceptive patch is higher than compliance in women using oral contraceptives, and that effectiveness is similar. However, there were more (but similar) adverse effects in the patch group.