Editor—Mansour and Guillebaud have drawn attention to the effective duration of use of the levonorgestrel intrauterine device.1 The Medicines Control Agency has reviewed clinical data on the product authorised in the United Kingdom (Mirena). After advice from the Committee on Safety of Medicines the licensing authority has now said that the period for which the device can be inserted can be extended from three years to five years.
The two studies that Mansour and Guillebaud cite as supporting the device’s efficacy over five years relate to a previous formulation of the device not marketed in the United Kingdom.2,3 Pharmacokinetic data suggest that the rates of release of levonorgestrel by both the old and the new formulations are similar over five years, so these data are supportive.
The updated product information for the levonorgestrel intrauterine device will allow a duration of use of five years and state that the device has a pregnancy rate of less than 1 per 100 woman years. Clinicians and users may be reassured that this method of contraception is effective when left in utero for five years.
References
- 1.Mansour D, Guillebaud J. Data support extended use of levonorgestrel intrauterine systems. BMJ. 1998;316:1671. doi: 10.1136/bmj.316.7145.1671. . (30 May.) [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2.Sivin I, El Mahgoub S, McCarthy T, Mishell DR, Jr, Shoupe D, Alvarez F, et al. Long term contraception with the levonorgestrel 20 mcg/day (LNg20) and the Copper T 380 Ag intrauterine devices: a five year randomised study. Contraception. 1990;42:361–378. doi: 10.1016/0010-7824(90)90046-x. [DOI] [PubMed] [Google Scholar]
- 3.Sivin I, Stern J, Coutinho E, Mattos C, El Mahgoub S, Diaz S, et al. Prolonged intrauterine contraception: a seven year randomised study of the levonorgestrel 20 mcg/day (LNg20) and the Copper T 380 Ag IUDs. Contraception. 1991;44:473–480. doi: 10.1016/0010-7824(91)90149-a. [DOI] [PubMed] [Google Scholar]