Implanon

Implanon, made by Organon International, is a single-rod long acting reversible hormonal 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 Food and Drug Administration (FDA) on July 17, 2006.

In a comparison of birth control methods in terms of effectiveness in preventing pregnancy, Implanon is the most effective form of birth control currently available.^[2]

Mechanism of action

The mechanism of action of progestin only contraceptives depends on the progestin activity and dose.^[3] 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.^[4] 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.^[5]

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,^[6] 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.

Effectiveness in preventing pregnancy

Implanon, along with a similar product Jadelle, are the most effective methods of birth control currently available.

The failure rate for Implanon is 0.05%. This means that only 1 in 2,000 women using Implanon will become pregnant over the course of one year of use. Unlike other birth control methods, there is no differential for perfect use versus typical use, as no user action is required after insertion. Most cases of failure are due to incorrect insertion or insertion during pregnancy.

In comparison, surgical sterilization has a failure rate of 0.2%.^[7] While these statistics suggest that Implanon is four times more effective in preventing pregnancy than surgical sterilization; it is important to remember that sterilization is permanent, whereas Implanon must be replaced every three years to continue to be effective. On the other hand, Implanon is completely reversible, while sterilization is usually permanent and cannot be reversed.

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 (corrected for aging etc.).

Side effects and risks

There are notable side effects caused by Implanon that occur in some women. However, these side effects are similar to other hormonal birth control methods such as combined oral contraceptive pills, the Ring (Nuvaring), Depo-Provera, etc.

Irregular periods or prolonged bleeding, headaches, acne, weight gain and abdominal pain were among the most commonly reported side effects in clinical trials. Some women report that the side effect go away after a few months of use.^{[citation needed]} Eleven percent of women had Implanon removed because of irregular menstrual bleeding, which can include excessive menstrual bleeding. 20% of women may have no menstrual period at all while using Implanon.^[8] It is not known whether Implanon changes a woman's risk for breast cancer.^[1][9]

Other possible side-effects of Implanon include mood swings, anxiety, and clinical depression. ^[10]

Implanon has also been shown to induce mild insulin resistance though the effects are not clinically relevant for healthy women.^[11]

Complications

Complications which can occur include:

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

An implant that cannot be found through palpation may be caused by damage, migration or fibrosis, requiring an ultrasound assessment or removal.

See also

• Progestogen only contraception

References

1. ^ ^{a b} "Implanon label" (PDF). FDA. 2006-07-17. http://www.fda.gov/cder/foi/label/2006/021529lbl.pdf. Retrieved 2006-08-23. 
2. ^ Trussell, James (2007). "Contraceptive Efficacy". in Hatcher, Robert A., et al.. Contraceptive Technology (19th rev. ed.). New York: Ardent Media. ISBN 0-9664902-0-7.
3. ^ 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. 
4. ^ Organon (April 2006). "Implanon SPC (Summary of Product Characteristics)". http://emc.medicines.org.uk/emc/assets/c/html/displaydoc.asp?documentid=5382. Retrieved 2007-04-15. 
5. ^ 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. doi:10.1016/S0002-9378(99)70120-1. PMID 10561657. 
6. ^ 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. doi:10.1016/j.ajog.2005.09.016. PMID 16813761. 
7. ^ "Implanon effectiveness". http://www.fpahealth.org.au/news/20030211_implanon2.html. 
8. ^ Susan Heavey & Lisa Richwine (July 18, 2006). "New implantable contraceptive for women gets go-ahead". Reuters. http://today.reuters.com/News/newsArticle.aspx?type=healthNews&storyID=2006-07-18T205203Z_01_L18815482_RTRUKOC_0_US-CONTRACEPTIVE.xml&pageNumber=0&imageid=&cap=&sz=13&WTModLoc=NewsArt-C1-ArticlePage3. 
9. ^ "Implanon patient information" (PDF). Organon USA Inc.. July 2006. http://www.implanon-usa.com/authfiles/images/543_174732.pdf. Retrieved 2006-08-23. 
10. ^ Template:Url =http://www.implanon-usa.com/consumer/isimplanonrightforme/index.asp
11. ^ Biswas A, Viegas OA, Coeling Bennink HJ, Korver T, Ratnam SS (March 2001). "Implanon contraceptive implants: effects on carbohydrate metabolism". Contraception 63 (3): 137–41. doi:10.1016/S0010-7824(01)00182-2. PMID 11368985. http://linkinghub.elsevier.com/retrieve/pii/S0010782401001822. 

External links

• Official website