In November 2013 and January 2014, the FDA and the EMA said they were reviewing whether increased weight and body mass index (BMI) reduce the efficacy of emergency contraceptives.An analysis of four WHO randomised clinical trials, published in January 2017, showed pregnancy rates of 1.25% (68/5428) in women with BMI under 25, 0.61% (7/1140) in women with BMI between 25 and 30, and 2.03% (6/295) in women with BMI over 30. These values yield an eight-fold reduction in efficacy for women with BMI over 30 compared to women with BMI under 25. However, emergency contraceptives remain effective regardless of BMI. Hormone therapy
Levonorgestrel is used in combination with an estrogen in menopausal hormone therapy. It is used under the brand name Klimonorm as a combined oral tablet with estradiol valerate and under the brand name Climara Pro as a combined transdermal patch with estradiol. Available forms
As a type of emergency contraception, levonorgestrel is used after unprotected intercourse to reduce the risk of pregnancy. However, it can serve different hormonal purposes in its different methods of delivery. It is available for use in a variety of forms:

By mouth
Levonorgestrel can be taken by mouth as a form of emergency birth control. The typical dosage is either 1.5 mg taken once or 0.75 mg taken 12–24 hours apart. The effectiveness in both methods is similar. The most widely used form of oral emergency contraception is the progestin-only pill, which contains a 1.5 mg dosage of levonorgestrel.
It is a weakly androgenic progestin and in women may cause androgenic biochemical changes and side effects such as decreased sex hormone-binding globulin (SHBG) levels, decreased HDL cholesterol levels, weight gain, and acne.In combination with a potent estrogen like ethinylestradiol however, all contraceptives containing androgenic progestins are negligibly androgenic in practice and in fact can be used to treat androgen-dependent conditions like acne and hirsutism in women. This is because ethinylestradiol causes a marked increase in SHBG levels and thereby decreases levels of free and hence bioactive testosterone, acting as a functional antiandrogen. Nonetheless, contraceptives containing progestins that are less androgenic increase SHBG levels to a greater extent and may be more effective for such indications. Levonorgestrel is currently the most androgenic progestin that is used in contraceptives, and contraceptives containing levonorgestrel may be less effective for androgen-dependent conditions relative to those containing other progestins that are less androgenic. Other activity
Levonorgestrel stimulates the proliferation of MCF-7 breast cancer cells in vitro, an action that is independent of the classical PRs and is instead mediated via the progesterone receptor membrane component-1 (PGRMC1). Certain other progestins act similarly in this assay, whereas progesterone acts neutrally. It is unclear if these findings may explain the different risks of breast cancer observed with progesterone and progestins in clinical studies. Pharmacokinetics
The bioavailability of levonorgestrel is approximately 95% (range 85 to 100%). The plasma protein binding of levonorgestrel is about 98%. It is bound 50% to albumin and 48% to SHBG.