The latest contraceptive option: The single-rod implant

September 1, 2005

A new option for long-term contraception is coming soon. Here are the pros and cons on Implanon—an implant that doesn't get into breast milk nor diminish bone mineral density—but can cause irregular and unpredictable bleeding patterns.

A reversible, highly effective, and long-acting contraceptive is expected to become available soon to women in the United States. Once approved by the Food and Drug Administration, Implanon will be the only contraceptive implant available in this country. It will give women seeking long-acting reversible contraception a new option in addition to the levonorgestrel intrauterine system, the Copper-T IUD, and the depot medroxyprogesterone acetate quarterly injection. Already being used in Australia, Indonesia, the Netherlands, and at least 30 other countries, this single-rod implant has proven to be safe and highly effective. It provides continuous efficacy for up to 3 years, can be quickly inserted and removed, provides constant hormone levels, and does not affect bone mineral density.1 Furthermore, the new implant can be used during lactation and may even improve dysmenorrhea and acne.2-4 Yet, like most progestin contraceptives, it can cause side effects, particularly irregular vaginal bleeding.5

Basic information, pros and cons

About the size of a matchstick (40 mm long and 2 mm wide), Implanon is a flexible rod that contains ethylene vinyl acetate (EVA) impregnated with 68 mg of etonogestrel (the same drug used in the contraceptive vaginal ring). On average, the rod releases 40 μg of etonogestrel every day, inhibiting ovulation and thickening cervical mucus. The rod is typically inserted in the inside portion of the upper arm during a brief office procedure.

Real-life use. A 3-year post-marketing study in Australia that looked at "real-life" use of the implant, however, did report more than 200 pregnancies. In this case series, 218 pregnancies were reported out of 204,486 devices inserted, for a failure rate of 1.07 in 1,000 insertions.7 Of those, 45 (21%) had insufficient data to determine the reason for contraceptive failure, and 46 (21%) women were already pregnant when they received the implant. In 84 (39%) of the remaining 127 cases, pregnancies were due to failure to insert the implant. Some documented reasons for noninsertion were clinicians having left the implant in the introducers and, in one case, inserting a placebo implant from a training pack. Clinicians should always verify the presence of the implant by palpation directly after insertion.

In some cases, the reason for noninsertion was not documented. Interaction of etonogestrel with hepatic enzyme-inducing drugs was implicated in eight pregnancies, of which seven of these women were using carbemazepine. Incorrect timing of insertion accounted for 19 cases and expulsion of the implant for three others. After other reasons were excluded, 13 women were classified as product/method failures.

Rapid return to fertility. After removal of the implant, 94% of the 1,716 women ovulated within 3 months, most of them within 3 weeks.6

Noncontraceptive advantages. Key advantages of the single-rod implant include no decrease in bone mineral density and no effect on breast milk.1-2 But, research on dysmenorrhea and acne demonstrate variable effects. For example, a study of 635 women who used Implanon found that 85% of them with dysmenorrhea noted an improvement, while 4% noted new or worsened symptoms.3 In a study of 231 women with acne at baseline, 16% had less acne, 70% had no change, and 14% had increased acne with the implant. In those without acne at baseline, 16% reported having developed it.4

Acceptability and side effects. The main reason women discontinue the single-rod implant is due to irregular and unpredictable bleeding patterns. During the first 3 months following insertion, up to 40% of women are amenorrheic, 50% have infrequent bleeding (dropping to 30% by 6 months), and 30% have prolonged bleeding (eventually falling to between 10% and 20%).5