Extended use of the intrauterine device: A literature review and recommendations for clinical practice

摘要

To the Editors: I read with interest the literature review performed by Wu and Pickle [1] to assess extended use of long-acting reversible contraceptives. I applaud their enthusiasm, but I believe that their conclusion regarding extended use of the 52 mg levonorgestrel (LNG) intrauterine system (IUS), currently marketed worldwide as Mirena?, is premature. The four studies included by Wu and Pickle to examine use of LNG IUS beyond 5 years included two using a 60-mg LNG product and two with a 52-mg product. The LNG IUS is formulated with a rate-controlling membrane that regulates LNG release; the properties of the membrane are different for each IUS. Although the studies with 60 mcg products stated that the release rate was 20 mcg/day (which is also the initial release rate for the 52-mg product) [2,3], the diminution over time cannot be considered equal to the marketed 52-mg product. Accordingly, data from a 60-mg LNG IUS cannot be extrapolated in any way to define extended efficacy for the 52-mg product.