Pharmacology Update: NuvaRing®: A New Method of Contraception?
August 15, 2002
NuvaRing®: A New Method of Contraception?
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD
Organon has introduced the first monthly vaginal ring for birth control. This flexible, transparent, colorless, polymer ring provides a continuous release of etonogestrel and ethinyl estradiol. The ring was approved by the FDA in October 2001 and is marketed by Organon as NuvaRing®.
Indications
The etonogestrel/ethinyl estradiol vaginal ring is indicated for the prevention of pregnancy in women.
Dosage
The vaginal ring is inserted in the vagina by the woman and is to remain in place continuously for 3 weeks. It is removed for 1 week at which time withdrawal bleeding should occur. A new ring is inserted 1 week after the last was removed.1 The exact position of the ring in the vagina is not critical for appropriate function. For women not on any hormonal contraception, the ring should be inserted on or prior to Day 5 of the cycle. An additional contraceptive is recommended until after the first 7 days of continuous ring use. For those switching from a combination oral contraceptive, the ring may be inserted anytime within 7 days after the last pill and no later than the day that a new cycle would have been started.
No additional contraception is needed. For those switching from progestin-only contraceptives, the ring may be inserted any day of the month with no break between the last tablet and the ring insertion, or the same day the implant or IUD is removed, or the day when the next contraceptive injection is due. If the ring is expelled or voluntarily removed it may be reinserted (after rinsing with cool-to-lukewarm water) if it has been out less than 3 hours. If left out longer than 3 hours, an alternative method of contraception must be used for 7 continuous days.1
Potential Advantages
The vaginal ring provides a convenient method of contraception. It is effective for 1 month and can be easily inserted and removed by the woman. The ring releases 120 mg of etonogestrel and 15 mg daily of ethinyl estradiol and the amount of estrogen is less than any combination oral contraceptive.
Potential Disadvantages
Etonogestrel is the active metabolite of desogestrel. Third generation progestin such as desogestrel and gestodene have been associated with increased risk of venous thromboembolism, specifically deep vein thrombosis.2-4 Device-related side effects (~5%) included expulsion, coital problems, foreign body sensation, and male partner discomfort.2 Decreased libido has been reported in 8% of patients compared to 0% with levonorgestrel/ethinyl estradiol combination OC.5 Twenty percent (20%) of women reported difficulty in inserting the ring and 15% had difficulty removing it.2
Comments
NuvaRing is the first vaginal device that delivers a combination of progestin and estrogen. The delivery system provides a constant drug delivery avoiding fluctuation associated with first-pass metabolism with oral contraceptives. It is a nonbiodegradable, flexible, transparent ring with an outer diameter of 54 mm and a cross-section diameter of 4 mm. The ring has been studied in 2 large, open-label, noncomparative trials, one in Europe and Israel (n = 1145) and the other in the United States and Canada (n = 1177). The combined intent-to-treat Pearl Index (pregnancies rate per 100-women years) was 1.23 (1.86 for the US study and 0.65 in the European study).1 The reason for the difference in efficacy is not known although US patients were heavier at baseline.2 The Pearl Index for the ring is similar to those reported for other combination hormonal contraceptives.8 In general, the ring was well tolerated with good cycle control and a low incidence (< 5%) of irregular bleeding.5-7 In a comparative trial with a combination oral contraceptive (levonorgestrel/ethinyl estradiol; n = 247) for 6 cycles, NuvaRing provided at least comparable cycle control.5 The vaginal ring costs about $40 per month which is more expensive than a typical cycle of an oral contraceptive (about $30).
Clinical Implications
NuvaRing provides a convenient, reversible, once-monthly contraceptive alternative to other contraceptive methods. It may not be an ideal method for patients at risk for venous thromboembolic events. Women who smoke and are considering this method of contraception are strongly encouraged to stop smoking.
References
1. NuvaRing Product Information 2001. Organon.
2. Medical review FDA (www.fda.gov/cder/foi/nda/2001/21-187_NuvaRing.htm).
3. Hering RMC, et al. Lancet. 1999;353:127-128.
4. Walker AM. Contraception. 1998;57:169-181.
5. Bjarnadottir RI, et al. Am J Obstet Gynecol. 2002; 186(3):389-395.
6. Roumen FJ, et al. Hum Reprod. 2001;16(3):469-475.
7. Jaffe RB. Obstet Gynecol Surv. 2001;56(8):481-482.
8. Audet MC, et al. JAMA. 2001;285(18):2347-2354.
Dr. Elliott is Chair, Formulary Committee, Northern California Kaiser Permanente; Assistant Clinical Professor of Medicine, University of California-San Francisco. Dr. Chan is Pharmacy Quality and Outcomes Manager, Kaiser Permanente, Oakland, CA. Both are Associate Editors of Internal Medicine Alert.
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