Research eyes new oral contraceptives
Review the list of oral contraceptives (OCs) in your current formulary. While it might seem there are several options, research scientists are focusing on development of new pills to expand women's choices.
Three pill formulations under investigation in the United States include a four-phasic pill composed of estradiol valerate (E2) and a new progestin, dienogest; a monophasic oral contraceptive containing E2 and the progestin nomegestrol acetate; and an estrogen/progestin/androgen pill. The first pill is being developed by Bayer Schering Pharma AG in Berlin, Germany; the E2/nomegestrol acetate OC is under investigation by Schering-Plough Corp. of Kenilworth, NJ; and the third formulation is under research by BioSante Pharmaceuticals in Lincolnshire, IL.
The E2/dienogest pill is poised for release in Europe. Bayer Schering Pharma AG reported completion of the European drug approval procedure in October 2008. The pill will be marketed as Qlaira. Phase III studies are being conducted for U.S. regulatory authorities.
Two pivotal Phase IIIa trials for the E2/nomegestrol acetate formulation are scheduled to be completed in 2009. More than 180 centers in 24 countries, including the United States, are taking part in the trials.
Dienogest and nomegestrol acetate are considered new progestins, along with drospirenone, trimegestone, and Nestorone.1 These new progestins have been designed to bind very specifically to the progesterone receptor and not to other steroid receptors in an effort to avoid androgenic, estrogenic, or glucocorticoid side effects.1
Developers of the estrogen/progestin/androgen pill, dubbed "Pill-Plus," see the addition of androgen as a way to prevent androgen deficiency that might occur with combined pill use. The Pill-Plus for oral use is licensed to Pantarhei Bioscience, a Netherlands-based pharmaceutical company for development and marketing in the United States, while BioSante retains rights to the Pill-Plus for transdermal development and marketing.
Little is known about the effects of OCs on sexual functioning; a 2004 review of research found that overall, women experience positive effects, negative effects, as well as no effect on libido during OC use. Better-designed studies are needed to establish the independent, causal effects of OCs on libido, researchers concluded.2
Results from a small 2006 retrospective study indicate that use of birth control pills is associated with elevated sex hormone-binding globulin (SHBG) levels and reduced bioavailable testosterone. This effect may persist even after discontinuation of pill use, researchers note.3
The study examined SHBG levels in 124 premenopausal women who had reported sexual dysfunction for at least six months; 62 of the women were current Pill users who had been taking OCs for longer than six months (called continued users), 39 who had used OCs for longer than six months and then discontinued use, and 23 women who had never used the method. All patients were offered use of transdermal testosterone therapy to improve sexual function.
Sex hormone-binding globulin levels were measured at four points during the study: at baseline, while using oral contraceptives, at a mean of 80 days after discontinuing pills, and then again at more than 120 days after discontinuation.3 According to the research, SHBG levels in the women who continued to use pills were four times higher than those in the never-users group. Despite a decrease of more than 50% in SHBG values after discontinuation of Pill use, SHBG levels in women discontinuing pills remained elevated for more than 120 days (mean of 234 days) in comparison with those who had never used the method.3
BioSante reports that results of a completed Phase II double-blind randomized clinical trial of the Pill-Plus indicated that the addition of an oral androgen resulted in restoration of testosterone levels to the normal and physiological range for healthy women. The Pill-Plus is in various Phase II/III trials measuring women's response to testosterone while taking OCs, says Alan Zachary, PhD, a spokesman for BioSante Pharmaceuticals. The company is doing preclinical research on a transdermal version of the Pill-Plus, he states.
Zachary declined to identify the hormonal components found in the Pill-Plus. Results of the Phase II trial have not yet been published, he reports.
Are more options needed when it comes to contraception? Evidently so, according to a 2008 survey conducted on behalf of Schering-Plough by Harris Interactive. Women's feelings and behaviors concerning contraception are conflicted, yet many don't seek out methods that could better satisfy their needs, research findings indicate.4
Almost 80% of current hormonal contraceptive users have concerns about their current birth control method, the survey reports; however, 39% have stayed with their chosen method for five or more years. About 25% of 18- to 34-year-old women said daily birth control would be most convenient for them, yet 46% of women in the same age group who currently use a hormonal contraceptive said they have more difficulty remembering to use their current method correctly when their daily routine is interrupted.4
Researchers are eyeing changes in pill regimens. Trials of the E2/dienogest pill are using a regimen with two days of placebo pills, while the E2/nomegestrol acetate formulation is being studied with a four-day placebo phase.
References
- Sitruk-Ware R. New progestagens for contraceptive use. Hum Reprod Update 2006; 12:169-178.
- Davis AR, Castaño PM. Oral contraceptives and libido in women. Ann Rev Sex Res 2004; 15:297-320.
- Panzer C, Wise S, Fantini G, et al. Impact of oral contraceptives on sex hormone-binding globulin and androgen levels: A retrospective study in women with sexual dysfunction. J Sex Med 2006; 3:104-113.
- Harris Interactive on behalf of Schering-Plough. Contraceptive Habits. Accessed at www.contraceptivehabits.com.
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