The pharmacodynamics and efficacy of Implanon. An overview of the data.

Implanon is a long-acting reversible contraceptive method, consisting of a single rod that is applied subdermally. Ovulation inhibition was determined by serum progesterone (P) levels and ultrasound scanning (USS) of the ovaries. Ovarian function was further assessed by serum estradiol (E2) levels. The effects of Implanon on serum gonadotropin levels (follicle-stimulating hormone [FSH] and luteinizing hormone [LH]) and on cervical mucus were also investigated, by means of Insler scores and sperm penetration tests. The effect of the endometrium was assessed by endometrial biopsies and USS. The Pearl index was calculated over 13 studies performed according to Good Clinical Practice (GCP), including 1716 women using Implanon. Return of ovulation after implant removal was determined by P levels and USS of the ovaries. The contraceptive efficacy of Implanon was high, with zero pregnancies during 53,530 cycles (4103 woman-years), resulting in a Pearl index of 0.0 (95% confidence interval, 0.00-0.09). This was achieved by inhibition of ovulation, which was reflected by suppressed P levels, as the primary mode of action. Ovulation was inhibited, but otherwise ovarian activity was still present (follicle growth, E2 synthesis). The FSH serum concentrations were only slightly lower than preinsertion levels and LH surges were prevented. The viscosity of the cervical mucus was increased. The endometrium was thin but not atrophic; it showed primarily inactive or weak proliferation. Return of ovulation after removal of Implanon was rapid.

Clinical performance of a new two-rod levonorgestrel contraceptive implant: a three-year randomized study with Norplant implants as controls.

In a randomized three-year clinical trial at seven clinics, the performance of levonorgestrel rod (LNG ROD) implants used by 600 women was compared with that of soft tubing NORPLANT implants used by 598 women. No pregnancies occurred in either group of women and, accordingly, body weight did not affect the efficacy of either type of implant. There were neither statistically significant nor important differences in termination rates for any reason over the three years. Complaint and illness rates during use of either of the two implant types were statistically indistinguishable and were attributable to the same set of conditions. Seventy-one per 100 of the women using each implant regimen continued to the three-year point, for an average annual continuation rate of 89 per 100. Removals of LNG ROD implants were accomplished in about half the time required for removal of Norplant capsule implants (p < 0.001).

Comparative study on intermittent versus continuous use of a contraceptive pill administered by vaginal route.

A multicenter, international, randomized, comparative trial was conducted to assess the acceptability, efficacy and safety of two different schedules of a contraceptive pill, containing 250 micrograms levonorgestrel and 50 micrograms ethinyl estradiol, administered by the vaginal route. One schedule of daily administration for 21 days with a seven-day interruption to allow withdrawal bleeding was compared to daily administration without interruption for bleeding. A total of 900 women were recruited in three countries, Brazil, Egypt and China; 7,090 women-months of vaginal pill use were recorded (3,364 using the pills intermittently and 3,726 continuously). Four undesired pregnancies occurred, one in Egypt and three in China, all four in women using the pills intermittently. There was a statistically significant difference (p = 0.486) in pregnancy rate between the two groups. There were no other significant differences in discontinuation rates despite marked differences in bleeding patterns, amenorrhea predominating in the continuous use group. Hemoglobin levels increased significantly in the two groups but hematocrit was significantly higher in the continuous use group.

PIP: 900 healthy women 16-42 years old were recruited in Brazil, China, and Egypt for a multicenter, randomized, comparative clinical trial to determine the acceptability, efficacy, and safety of two different schedules of a contraceptive pill with 250 mcg levonorgestrel and 50 mcg ethinyl estradiol administered vaginally. The two schedules were: 1) daily vaginal use of the pill for 21 days, followed by withdrawal for regular bleeding, and restarted 7 days later, and 2) use of the pill by the vaginal route nonstop for one year. There were no significant difference in cumulative discontinuation rates between the two groups (total, 15.5 for intermittent group and 14.64 for continuous group), except for unwanted pregnancy. The only unwanted pregnancies occurred to 4 women in the intermittent group (1.04%) (p = 0.0486). Women in the continuous use group were more likely than those in the intermittent group to have spotting at least once (20.6% vs. 4.4%; p 0.001). Women in the continuous group were more likely than those in the intermittent group to have amenorrhea. For example, the mean number of bleeding/spotting days during all time intervals was lower for the continuous group than for the intermittent group (p 0.001; last interval, 0.97 vs. 12.83). Hemoglobin levels increased considerably in both groups between baseline and one year of use (11.61 vs. 11.9 g/dl for intermittent group and 11.54 vs. 11.81 g/dl for continuous use; p 0.001). The mean value of hematocrit at 12 months for the continuous group was higher than that at baseline (38.8% vs. 38.2%; p = 0.011). It did not increase in the intermittent group, however. Women in both groups gained weight during the 12 months of pill use. The weight gain was significant for the continuous group only. These findings suggest that continuous use of vaginal contraceptive pills may be more advantageous than intermittent use oral contraceptives and may benefit anemic women and those who bleed heavily during menstruation.

Evaluation of the clinical performance of a levonorgestrel-releasing IUD, up to seven years of use, in Campinas, Brazil.

The clinical performance of a levonorgestrel IUD, releasing 20 mcg/day, used by 293 women at the Family Planning Clinic of the State University of Campinas, was evaluated up to the end of the seventh year of use. No pregnancies occurred in 899 women-years of observation. The cumulative removal rate for amenorrhea or severe hypomenorrhea was 15.7 per 100 women at seven years. The expulsion rate was within ranges observed with copper IUDs in the same clinic. The continuation rate was 49.5% at three years and 23.7 at seven years. The cumulative loss to follow-up rate was 13.7% at seven years. The effectiveness, good continuation rate, and reduction of the amount of blood loss make this device appropriate to be offered to Brazilian women, as an additional contraceptive option.