Estradiol-containing birth control pill
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Combined birth control pills that contain natural estradiol or an estradiol ester (e.g., estradiol valerate) include:[1][2][3]
- Estradiol valerate and cyproterone acetate (brand name Femilar) – introduced in Finland (only) in 1993[3]
- Estradiol valerate and dienogest (brand names Qlaira, Natazia) – introduced in Europe in 2009 and the U.S. in 2010[4]
- Estradiol and nomegestrol acetate (brand name Zoely) – introduced in Europe in 2011[5]
Estradiol, mainly as esters including estradiol valerate, estradiol cypionate, and estradiol enanthate, is also the exclusive estrogen used in combined injectable contraceptives.[6]
As of 2021, more than 95% of prescriptions are for combined hormonal birth control forms containing the synthetic estrogen ethinylestradiol (EE).[7] Hence, estradiol-based birth control pills are still not widely used.[7]
Side effects
Birth control pills containing estradiol have less impact on liver protein synthesis than ethinylestradiol-containing birth control pills, and it is thought that for this reason, they may pose less of a risk of venous thromboembolism (VTE).[8][9] In accordance, although birth control pills containing estradiol valerate/dienogest are associated with a significantly increased risk of VTE, they are associated with a significantly lower risk of venous thromboembolism than birth control pills containing ethinylestradiol and a progestin.[10] The risk of VTE with estradiol/nomegestrol acetate birth control pills is under study.[11]
Incidence of irregular vaginal bleeding may be higher with estradiol-containing birth control pills in relation to the fact that estradiol is a weaker estrogen than ethinylestradiol in the endometrium.[3]
Pharmacology
The pharmacodynamics and pharmacokinetics of estradiol in the context of use in birth control pills have been studied and reviewed.[12][2][9]
Research
Experimental estradiol-containing birth control pills that were studied but never marketed include:[3]
- Estradiol/norethisterone (Netagen, Netagen 403)
- Estradiol/estriol/norethisterone (Netagen 423)
- Estradiol/estriol/norethisterone acetate
- Estradiol/desogestrel
- Estradiol cyclooctyl acetate/desogestrel
- Estradiol/ethinylestradiol/dienogest
A large randomized controlled trial of a birth control pill containing ethinylestradiol/norethisterone acetate versus a birth control pill containing estradiol/estriol/norethisterone acetate has been conducted.[13]
See also
References
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