Among the different contraceptive methods which are long-lasting and reversible is the contraceptive implant. Here, a thin plastic rod impregnated with progestin is placed under the skin over the medial side of the upper arm.
Progestin acts in different ways to prevent fertilization. The slow sustained release of progestin causes a negative feedback loop on the hypothalamopituitary axis which regulates gonadotropin secretion, and thereby controls the ovarian cycle. As a result, it suppresses ovulation. Another action is on the cervical mucus which becomes thick and unfavorable to spermarozoa entry, preventing fertilization. Finally, as a result of inhibition of the ovarian cycle, the menstrual cycle is arrested, and endometrial preparation for implantation does not occur, preventing successful implantation.
The contraceptive implant consists of a flexible plastic rod about 40 mm long, which contains progestin. This is released at a constant low rate into the body. It should be inserted only by a trained healthcare provider. Its action usually lasts for three years.
In all cases, the woman should have the implications of use of the contraceptive implant explained to her, and informed consent should be recorded. A complete medical history and examination are mandatory, including a gynecologic examination. Allergies to anesthetic should be excluded by testing.
Older implants release levonorgestrel, while currently used implants release etonogestrel. While all have the same mechanism of action, current implants are claimed to be easier to insert, and to trace by X-ray or CT scan if misplaced.
Most current implants comprise a single rod composed of a semi-rigid polymer. The insertion technique is easy, as follows:
Choose a site on the inner side of the upper arm, away from major vessels and nerves, about 3 inches above the medial epicondyle. The site is marked, cleaned, and anesthetized. The applicator needle penetrates the skin at an angle below 30 degrees to avoid injury to any deeper structure. Then the needle is placed horizontally and slid under the skin to its entire length. Once this is in place, the slider which keeps the rod in place is released and withdrawn to its full length, keeping the implant in position under the skin. A small bandage (covered by a pressure dressing for 24 hours) is sufficient to prevent bruising. The woman should palpate the rod for confirmation of insertion.
The earlier six-capsule Norplant implant had a slightly more complicated insertion procedure. However, with all implants, insertion is usually uneventful and quick.
The ideal time of implantation is on the first day after the active tablets in the combined oral contraceptive pack are finished, or at least on the first day after the last placebo tablet in the oral contraceptive pack. If vaginal rings or transdermal patches were in use, the implant is recommended for immediately after their removal. In such cases, the implant is effective at once, but otherwise, seven days of backup contraception with another technique is recommended. In all cases, pregnancy should be ruled out first if sexual intercourse has occurred already.
The Implanon implant is removed by the 'pop out' technique. The skin over the tip of the rod is anesthetized and a 2-mm longitudinal incision is made over the distal end of the implant, which is visualized and stabilized by pressing on the proximal end. Through this, the rod is pushed out a little, grasped firmly with small mosquito forceps, if necessary, and plucked out cleanly from the surrounding subcutaneous tissue. Implanon or Nexplanon are easier to remove than Norplant, with only 2-3 minutes required on average, compared to 10 minutes with Norplant. This makes training easier with the former.