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The purpose of the Postmarketing Surveillance was to study, over a 5-year period, major short- to medium-term side effects of Norplant not identified in clinical trials. The Surveillance followed a sample of 7,977 women for 5 years (a total of 33,627 woman-years) and found a pregnancy rate of 0.23 per 100 woman-years. For purposes of comparison, the Surveillance also followed two control groups: women who had chosen the copper-bearing intrauterine device (IUD) and women who had chosen tubal ligation. The pregnancy rates for these two groups were 0.80 and 0.15 per 100 woman-years, respectively.
The Population Council studies, undertaken to gather data for Food and Drug Administration (FDA) approval of the two-rod implant and to obtain additional information for revision of Norplant's labeling, found similarly high efficacy. In studies between 1990 and 1996 of 2,798 women in seven countries, the Council found that Norplant and the LNG ROD had similar hormonal release rates and virtually indistinguishable pregnancy rates. The cumulative 5-year pregnancy rate for the samples analyzed collectively was 1.1 per 100 woman-years.
Table 2-1, provided to the subcommittee after the workshop as additional detail for purposes of comparison, presents data on first-year and 5-year pregnancy rates for Norplant and the LNG ROD from studies in 14 countries. The evidence from those studies and from the new data presented at the workshop was that both Norplant and two-rod levonorgestrel implant system are highly efficacious, with failure rates under 1 percent per year, thus providing reversible contraceptive protection essentially equal to that of permanent methods—tubal ligation and vasectomy.
Like all hormonal contraceptives, Norplant, even though it is well tolerated by many women, is associated with adverse reactions or events.4 These are described in the prescribing information for providers and in patient labeling, both of which continue to be updated as new data become available. Of greatest concern are potential medical complications that pose serious risks to the health of the user. The Postmarketing Surveillance analysis refers to these as ''major health-related events," defined as including the following: all pregnancies, all deaths, and all complications that are potentially life-threatening, require hospitalization or at least 1 month of convalescence, leave long-term sequelae, and/or require long-term medication. A second category comprises "significant health-related problems" that may affect quality of life; these were defined as virtually anything except common colds and minor injuries. Although not life-threatening, the problems in this category may range from tolerable to annoying for some women, from distressing to intolerable for others.