New data show Norplant effective for 7 years
Just-published research indicates that the current model of Norplant levonorgestrel contraceptive implant offers up to seven years of effective use, two years beyond the current labeling approved by the Food and Drug Administration.1
The studies submitted for the FDA’s 1990 approval included data on currently manufactured "soft-tubing" implants and "hard-tubing" implants, which are no longer manufactured, says Irving Sivin, a researcher in the New York City-based Population Council’s Center for Biomedical Research. The hard-tubing implants were used early in the introduction of the method and were later replaced by the soft-tubing implants, which are less dense and release hormone at a higher rate.2
Three-quarters of the subjects included in the data analysis on which the current U.S. product labeling is based used "hard-tubing" capsules. As a result, the pregnancy rates in the labeling are substantially greater than data reflecting "soft-tubing" implants alone, Sivin states.
The Population Council is compiling the information needed for updating the product labeling for submission to the U.S. manufacturer, Wyeth-Ayerst Laboratories in Philadelphia. The company subsequently will decide whether to seek revised labeling for the drug.
Look at the data
The research involves two independent studies of 1,210 women ages 18 to 40 in Chile, the Dominican Republic, Egypt, Finland, Singapore, Thailand, and the United States. All the women were using soft-tubing Norplant implants. Of the enrollees, 42% were U.S. residents. One-sixth of the women weighed 70 kg (154 lbs) or more at the time of implant placement.
No pregnancies occurred during the study in the 400 women who were both 30 years old or older and who weighed less than 100 kg (220 lbs) at the time Norplant was inserted. None of the women weighing less than 50 kg (110 lbs) when they entered the study became pregnant.
Women who weighed less than 70 kg when they entered the study had a pregnancy rate of less than one per 100 throughout the seven years. Women who weighed 80 kg (176 lbs) or more when they entered the study, however, experienced higher pregnancy rates at the five-year point and beyond.
"It seems to me that for the great majority of women, there is just no question that it is a seven-year method," Sivin observes. "However, for women who weigh 80 kg, we saw that the pregnancy rate over the seven years was above 10 per 100, so I think one simply has to advise these women what are the rates so they may make their own decision."
Among women ages 18 to 33, the seven-year Norplant pregnancy rates are comparable to the median pregnancy rates of tubal sterilization methods for women of the same age and duration of use. For women ages 34 and older, without regard to weight at admission, the seven-year effectiveness of soft-tubing Norplant equals or surpasses that of tubal sterilization, researchers found.
The news of Norplant’s extended effectiveness will be an even stronger motivation for women who are looking for safe, long-term, reversible contraception, predicts Haleh Sangi-Haghpeykar, PhD, assistant professor in the department of OB/GYN’s division of contraceptive research and development at Baylor College of Medicine in Houston. Sangi-Haghpeykar has conducted research of long-term Norplant users and says the majority of women she has interviewed would reuse the method at the current five-year reinsertion date.3
"If they think they can use it for seven years, I think it will be even a stronger motivation for them to keep it," she says.
Many of the women who were included in Sangi-Haghpeykar’s research had experienced side effects with Norplant, particularly during the first year. However, they chose to continue its use due to their strong desire for a long-term, effective, convenient contraceptive, coupled with their ability to control the method with no need of cooperation from their partners. Thorough counseling prior to implant insertion also prepared women for reduction of side effects following the first year or two of use.
Many of the women had negative experiences with other contraceptives, or other methods simply didn’t work for them, Sangi-Haghpeykar notes. All of the users had tried most other methods and were dissatisfied with the results.
"The study indicates that women do need long-term methods; there is really nothing else out there besides sterilization," she says. "Women need something, and they are willing to put up with side effects if they think it is going to work for a long period of time."
References
1. Sivin I, Mishell DR, Diaz S, et al. Prolonged effectiveness of Norplant capsule implants: A 7-year study. Contraception 2000; 61:187-194.
2. Anonymous. Norplant found highly effective up to seven years. Population Briefs 2000; 6:3.
3. Sangi-Haghpeykar H, Frank M, Leonard L, et al. A qualitative study of perceptions, attitudes, and experiences of long-term levonorgestrel implant users. Women and Health 2000; 30:91.
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