More than 10 million women in the United States use oral contraceptive pills (OCPs) to prevent pregnancy.1 However, OCPs have a 6 percent failure rate within the first year.1 Data1–4 have shown that unintended pregnancy with this method of contraception often is related to incorrect or inconsistent use, side effects, or patient dissatisfaction. Adolescents are less likely than adult women to adhere to OCP regimens, and only 12 percent of adolescents continue OCP use beyond one year.5 It is clear that patient adherence and satisfaction are critically important for effective contraception. Recently introduced contraceptive options should improve both of these factors.
In this issue of American Family Physician, Herndon and Zieman6 review newer contraceptive methods, including the combined hormonal vaginal ring (NuvaRing), combined hormonal injection, combination contraceptive patch (Ortho Evra), and levonorgestrel intrauterine system (Mirena). These contraceptive methods have approximately the same efficacy and safety as OCPs, but they use delivery systems that have been designed to encourage adherence and improve patient acceptability.
The vaginal ring provides once-a-month contraception, with one cycle consisting of three weeks of ring use and one ring-free week. This contraceptive method avoids first-pass metabolism and gastrointestinal interference, thereby allowing use of lower hormone doses. The vaginal ring also provides more uniform hormone concentrations than OCPs. In a study7 evaluating user acceptability in North America and Europe, 96 percent of women stated that they were satisfied with the vaginal ring, and 97 percent indicated that they would recommend this method of contraception to a friend. Reasons for preferring the vaginal ring included not having to remember daily dosing, ease of use, and effectiveness of contraception. More than 90 percent of the women in the study thought that the instructions for vaginal ring use and storage were simple, and 93 percent were pleased with cycle control. In the small number of women who disliked or discontinued using the vaginal ring, primary reasons were interference with intercourse and ring expulsion. Previous worldwide studies8,9 support these findings, with most women considering the vaginal ring easy to use, effective, and convenient. The vaginal ring has not been directly compared with OCPs for adherence, but it seems logical that adherence would improve with a once-monthly contraceptive method that has straightforward instructions for use.
The combined hormonal injection provides monthly contraception without the need to take a pill or insert and remove a device. The injection is administered every 28 to 30 days and supplies a steady concentration of hormones.10 Compared with women who use triphasic combined OCPs, women who use the hormonal injection report more discomfort but less interference with daily and social activities.11 Interestingly, only 60 percent of injection users and approximately 80 percent of OCP users planned to continue their method, but more than 90 percent of the women indicated that they would recommend their respective contraceptive method to a friend.11 The combined hormonal injection appears to have a niche, in that it eliminates daily adherence and the use of a device or medication; however, treatment burden may be increased because of the need for monthly office visits. Furthermore, the hormonal injection, marketed as Lunelle, currently is not available. Prefilled syringes were voluntarily recalled in October, 2002, by the manufacturer because of concerns about full potency resulting in an increased risk of contraceptive failure. Vials of the injection were not affected by this recall but became unavailable in October, 2003. The status of future availability is unknown.
Randomized controlled trials12,13 comparing the contraceptive patch with a combination OCP have demonstrated similar efficacy rates, higher early discontinuation rates, and increased side effects (breast tenderness, application site reactions, dysmenorrhea) with use of the patch. Contraceptive patch users report more cycles of adherence than OCP users (odds ratio, 2.1; 95 percent confidence interval, 1.8 to 2.3); furthermore, age does not affect compliance among women 18 to 45 years of age.14 Complete or partial patch detachment is rare (5 percent incidence), and replacement patches are readily accessible. It should be noted that the efficacy rate for the patch may be lower in patients who weigh more than 90 kg (198 lb), but OCP failure has been reported in women weighing 70.5 kg (155 lb) or more.15 The contraceptive patch provides once-weekly dosing (to improve compliance), avoids first-pass metabolism, and provides consistent hormone concentrations. However, patch use requires reliable skin adhesion, even in active lifestyle conditions.
The acceptability of the levonorgestrel intrauterine system has been studied in numerous countries (e.g., Austria, Finland, Brazil, France).16–19 Women who choose this method of contraception tend to be older, to desire long-term contraception, or to have been dissatisfied with a different form of contraception. This contraceptive method is effective and safe, and is associated with decreased blood loss in women with menorrhagia. Compared with other intrauterine devices, the levonorgestrel intrauterine system is better tolerated, although use may be discontinued because of hormone-related side effects (e.g., mood changes, acne, headaches, weight gain). Adherence is high because there is no user involvement once the device is inserted; patient satisfaction increases when detailed information is provided at the insertion visit.17 The longest acceptability study to date found that 69 percent of women were very satisfied with this contraceptive method after six months of use and 77 percent were very satisfied after 36 months of use.16 The levonorgestrel intrauterine system is well accepted and is appropriate for use in women who desire long-term, reversible contraception.
The effectiveness of any contraceptive depends on the ability and willingness of the user to comply with the chosen method. The newer contraceptive methods have not yet been evaluated in adolescents. It is rational to assume that these contraceptive methods can improve unintended pregnancy rates in adolescents, although access and affordability may be problems.
|Contraceptive method||Failure rate||Side effects||Office visits||Easily reversible||Dosing||User controlled||Discreet|
|Combined hormonal vaginal ring (NuvaRing)||One to two pregnancies per 100 women-years21||Estrogen and proges in related||Yes (prescription)||Yes||Every 4 weeks||Yes||Yes|
|Combination hormonal injection*||<1% per year22||Estrogen and progestin related||Yes (monthly)||Yes||Monthly||No||Yes|
|Combination contraceptive patch (Ortho Evra)||One pregnancy per 100 women-years23||Estrogen and progestin related||Yes (prescription)||Yes||Weekly||Yes||Maybe|
|Levonorgestrel intrauterine system (Mirena)||0.2% per year, or 0.7% per 5 years24||Progestin related||Yes (insertion)||Yes||Every 5 years||No||Yes|