Implanon

Implanon, made by Organon International, is a single-rod contraceptive subdermal implant that is inserted just under the skin of a woman's upper arm. The 4 cm by 2 mm Implanon rod contains 68 milligrams of the gonane progestin etonogestrel which is released over a three year period.

Peak serum etonogestrel concentrations have been found to reach 781–894 pg/mL in the first few weeks, gradually decreasing to 192–261 pg/mL after 1 year, 154–194 pg/mL after 2 years, and 156–177 pg/mL after 3 years, maintaining ovulation suppression and contraceptive efficacy.^[1] Implanon may be removed at any time, but must be removed after three years.

Implanon was first approved for use in Indonesia in 1998, was subsequently approved for use in over 30 other countries, and has been used by over 2.5 million women worldwide. Implanon was approved for use in the United States by the FDA on July 17, 2006.

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Mechanism of action

The mechanism of action of progestin-only contraceptives depends on the progestin activity and dose.^[2] Intermediate dose progestin-only contraceptives, like Implanon (and the progestin-only pill Cerazette) allow some follicular development but inhibit ovulation in almost all cycles as the primary mechanism of action. Ovulation was not observed in studies of Implanon in the first two years of use and only rarely in the third year with no pregnancies. A secondary mechanism of action is the progestogenic increase in cervical mucus viscosity which inhibits sperm penetration.^[3] Hormonal contraceptives also have effects on the endometrium that theoretically could affect implantation, however no scientific evidence indicates that prevention of implantation actually results from their use.^[4]

Insertion

Local anaesthetic is applied to the upper arm, and then a needle-like applicator is used to insert the implanon rod under the skin. The procedure can take less than a minute. An experienced clinician is required for proper insertion, to minimize the risk of nerve damage,^[5] or misplacement which could result in unintended pregnancy. Implant site complications are experienced by 3.6% of patients, and include swelling, redness, hematoma and pain.

Side effects and risks

There are notable side effects caused by Implanon that occur in some women. Irregular periods, headaches, acne, weight gain and abdominal pain were among the most commonly reported side effects in clinical trials.^{[citation needed]} Eleven percent of women had Implanon removed because of irregular menstrual bleeding, which can include excessive menstrual bleeding. Some women may have no menstrual period at all while using Implanon.^[6] It is not known whether Implanon changes a woman's risk for breast cancer.^[1][7] Failure rate for Implanon was reported at 0.1%. Most cases of failure were due to incorrect insertion or insertion during pregnancy. In comparison, surgical sterilization has a failure rate of 0.2%.^[8]

Fertility after Implanon

Within a few days of having Implanon removed the hormones released by Implanon will have left the body. The chances of becoming pregnant should be the same as they were before using Implanon.

Complications

Complications which can occur include:

• impalpability of implant
• broken or damaged implant
• slight migration
• fibrosis.

If Implanon is "impalpable"—cannot be felt—an ultrasound must be performed. Surgery under local or general anesthesia may be required to remove an impalpable Implanon implant, especially if it is broken, damaged, has migrated, or is deeply embedded in scar tissue or fibrosis.

References

1. ^ ^{a b} Implanon label (PDF). FDA (2006-07-17). Retrieved on 2006-08-23.
2. ^ Glasier, Anna (2006). "Contraception", in DeGroot, Leslie J.; Jameson, J. Larry (eds.): Endocrinology, 5th ed., Philadelphia: Elsevier Saunders, pp. 3000-1. ISBN 0-7216-0376-9. 
3. ^ Organon (April 2006). Implanon SPC (Summary of Product Characteristics). Retrieved on 2007-04-15.
4. ^ Rivera R, Yacobson I, Grimes D (1999). "The mechanism of action of hormonal contraceptives and intrauterine contraceptive devices". Am J Obstet Gynecol 181 (5 Pt 1): 1263-9. PMID 10561657.
5. ^ Wechselberger G, Wolfram D, Pulzl P, Soelder E, Schoeller T (July 2006). "Nerve injury caused by removal of an implantable hormonal contraceptive". Am J Obstet Gynecol 195 (1): 323-6. PMID 16813761.
6. ^ Susan Heavey & Lisa Richwine. "New implantable contraceptive for women gets go-ahead", Reuters, Jul 18, 2006. 
7. ^ Implanon patient information (PDF). Organon USA Inc. (July 2006). Retrieved on 2006-08-23.
8. ^ Implanon effectiveness.