MIAMI BEACH — Nearly a year after the approval of a contraceptive implant, its advantages and disadvantages are becoming better known, but there are still no data on its efficacy in overweight or obese women, according to a presentation at an ob.gyn. conference sponsored by the University of Miami.
The Food and Drug Administration cleared Implanon (Organon International) for marketing in July 2006. It is the first single-rod, 68-mg etonogestrel, subdermal implant. The core is 40% ethylene vinyl acetate, which provides a slow, steady release of progestin for up to 3 years, according to clinical trials.
However, women who weighed more than 130% of their ideal body weight were excluded from the preapproval studies, said Dr. Paul M. Norris, adding that for physicians, such an exclusion would be “very impractical” in the United States.
Implanon replaces the six-rod Norplant device, which was removed from the market following reports of product migration and side effects, he said. “The data on Norplant suggested it was still efficacious, although less so, in overweight patients. But I am not sure you can apply this finding to Implanon.”
Implanon is inserted in the subepidermal groove of a woman's arm between her biceps and triceps, about 6–8 inches up from the crux of elbow. Physicians can order Implanon only if they have completed a training program on insertion and removal sponsored by the manufacturer.
“The device to insert the implant looks like the Depo Provera syringe,” said Dr. Norris, who is on the obstetrics and gynecology faculty at the University of Miami. He is also on the speakers' bureau for Organon. “The blue placebo injector for practice has a pregnancy rate of about 85% so make sure you are using the white injector with the active ingredient!”
Insertion time is faster than the Norplant, about a mean of 1 minute, compared with 4 minutes for the Norplant, The 4 cm-long, 2 mm-diameter Implanon rod is not radio-opaque. “If you lose an implant, you cannot palpate it 3 years later. It is easy to pick up on ultrasound, but you need at least a 10-MHz wand, which is not common in most [primary care physician] offices,” he said.
Implanon's contraceptive effects are reversible—a woman's fertility quickly returns after removal, according to the manufacturer.
The mean removal time for Implanon is 3 minutes, compared with 11 minutes for Norplant, Dr. Norris said. “This is the mean, and some cases can take almost an hour.” In clinical trials, 1% of 923 participants experienced complications at implant insertion and 1.7% had complications at implant removal.
Contraindications include a known or suspected pregnancy. “It likely won't hurt the pregnancy, but it will not prevent a pregnancy if it is already there,” Dr. Norris said. History of or current thrombotic disease, history of breast cancer, hepatic tumors, active liver disease, and undiagnosed abnormal genital bleeding are other contraindications. “Make sure there is nothing serious going on before you place the Implanon.”
Bleeding changes were the most common reason women chose to stop Implanon treatment in clinical trials (cited by 11% of participants). Irregular bleeding and spotting is a common side effect, Dr. Norris said. In the studies, patients using Implanon reported an average of 18 days of bleeding or spotting every 90 days
Prolonged bleeding occurs in almost 20% of patients, so you will have some patients who are unhappy, Dr. Norris said. “The bottom line is you counsel patients about the unpredictable pattern and frequency of bleeding.”
In terms of contraceptive efficacy, six pregnancies were reported in 20,648 cycles in the clinical trials. These patients were likely to have been already pregnant when they had the implant inserted, Dr. Norris said.