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Contraceptive Efficacy

The Pearl Index, a standard measure of contraceptive efficacy, is defined as the number of pregnancies per 100 women-years of use. The Pearl Index for LYBREL® is calculated as the number of pregnancies occurring on-treatment and during the first 14 days post-treatment divided by the number of woman-cycles (28-day intervals), multiplied by 1,300.9

LYBREL is indicated for the prevention of pregnancy in women who elect to use this product as a method of contraception.1 The incidence of pill failure resulting in pregnancy is approximately 1-2% per year (1 to 2 pregnancies per 100 women per year of use) if taken every day as directed. The average failure rate is approximately 5% per year (5 pregnancies per 100 women per year of use), including women who do not always take the pill exactly as directed without missing any pills.1

Results from two 1-year clinical trials (313-NA and 315-EU) demonstrated the contraceptive efficacy of LYBREL. The North American trial (313-NA) included a total of 2,134 women aged 18 to 49 years.1 The efficacy of LYBREL was assessed by the number of pregnancies that occurred after the onset of treatment and within 14 days of the last dose.1 Among subjects aged 18 to 35 years, there were 23 pregnancies (4 of these occurred during the 14-day interval after the last pill) during 12,572 twenty-eight–day pill packs of use.1 The resulting total Pearl Index was 2.38 (95% CI: 1.51, 3.57), and the 1-year life table pregnancy rate was 2.39 (95% CI: 1.57, 3.62) (Table 1).1 Pill packs during which subjects used back-up contraception or were not sexually active were not included in these calculations.

TABLE 1. Contraceptive Efficacy of LYBREL1

Among women 35 years or younger who took the pills completely as directed, there were 15 pregnancies (method failures) resulting in a Pearl Index of 1.55 (95% CI: 0.87, 2.56), and the 1-year life table pregnancy rate was 1.59 (95% CI: 0.95, 2.67).1

In a second supportive study conducted in Europe (315-EU), 641 subjects were randomized to LYBREL (n = 323) or the cyclic comparator of levonorgestrel (LNG) 100 mcg and ethinyl estradiol (EE) 20 mcg (n = 318).1 The efficacy analysis among women 35 years or younger included 2,756 LYBREL pill packs and 2,886 cyclic comparator pill packs.1 There was 1 pregnancy in the LYBREL group that occurred within 14 days following the last dose.1 There were 3 pregnancies in the cyclic comparator group.1

Next: Inhibition of Menses (Bleeding Profile) »

Important Safety Information

  • Oral contraceptives (OCs) do not protect against HIV infection or other sexually transmitted diseases.
  • When prescribing LYBREL, the convenience of having no scheduled menstrual bleeding should be weighed against the inconvenience of unscheduled breakthrough bleeding and spotting.
  • OCs are contraindicated in women who have blood clots; breast, uterine, or liver cancers; a history of heart attack, stroke, or breast cancer; as well as those who are or may be pregnant.
The risks of serious cardiovascular side effects are substantially increased in women who smoke and use OCs, especially in women over age 35. Women who use oral contraceptives should be strongly advised not to smoke.
  • Serious risks associated with OCs include blood clots, heart attack, and stroke.
  • LYBREL provides women with more hormonal exposure on a yearly basis (13 additional weeks of hormone intake per year) than conventional cyclic oral contraceptives containing the same strength of synthetic estrogens and similar strength of progestins.
  • Scheduled withdrawal bleeding does not occur with the use of LYBREL, therefore, the absence of withdrawal bleeding cannot be used as a sign of an unexpected pregnancy and as such, unexpected pregnancy may be difficult to recognize. Although pregnancy is unlikely if LYBREL is taken as directed, if for any reason, pregnancy is suspected in a woman using LYBREL, a pregnancy test should be performed.
  • The most commonly reported treatment emergent adverse events reported with LYBREL in a clinical trial were headache, dysmenorrhea, upper respiratory infection, vaginal bleeding (defined as metrorrhagia and vaginal hemorrhage), and nausea.

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