A subdermal implant is a small rod like contraceptive device, which is inserted underneath the skin of the upper arm by a healthcare professional under local anaesthesia. It is the most effective contraceptive method because its failure rate is zero. The implant releases etonogestrel (a progestogen) 25-70 μg every day into the blood stream. Etonogestrel is metabolised to a third-generation progestogen called desogestrel. The action of a subdermal implant lasts for three years, and the dose released from the device decreases gradually with time. It can be easily removed at any time or otherwise; it can be replaced with a new one after three years.
Mechanism of action
The action of subdermal implants is similar to all progestogen-only contraceptive methods.
Timing of inserting an implant
- A subdermal implant can be inserted at any time in the cycle.
- If a woman, who is using a hormone-releasing intrauterine system (IUS) or copper intrauterine device (IUD), needs to insert an implant, the subdermal implant can be inserted, but she has to continue IUS or IUD for at least seven days.
- If a woman has absent periods (the woman should not be pregnant.) or insertion of an implant happens after day five of the cycle, she needs to use extra precautions for seven days.
- A subdermal implant can be inserted immediately, if termination of pregnancy (TOP) occurs in the first or second trimester.
- After abortion or miscarriage, an implant can be used immediately. If the insertion occurs five days after abortion or miscarriage, extra precautions are needed for seven days.
- After pregnancy, the implant should be used 21-28 days after childbirth or termination of pregnancy (TOP). If the insertion of the implant occurs after 28 days, extra contraceptive methods should be used for seven days.
Benefits of the subdermal implant
- Its action lasts for up to three years.
- Its failure rate is zero. Therefore, the subdermal implant is a highly effective contraceptive method.
- After removing the implant, there is a rapid return of fertility.
- It is useful for women, who have difficulty remembering to take a tablet daily.
- It improves the symptoms of premenstrual syndrome (A collection of symptoms related to a menstrual cycle).
- It causes lighter periods.
- It improves painful periods.
- There is no evidence of osteoporosis, unlike the progestogen injections.
- It reduces the rates of ectopic pregnancy.
- Migraine, obesity, breastfeeding, and diabetes are not contra-indications for subdermal implants.
Disadvantages and adverse effects of the subdermal implant
- No protection against sexually transmitted diseases (STDs)
- If a woman wants to insert or remove a subdermal implant, she needs involvement of a trained healthcare professional.
- Difficulty finding the implant or broken rod is a complication.
- Absent menstrual cycles
- Irregular menstrual cycles.
- Heavy menstrual cycles
- Nausea and vomiting
- Breast pain
- Worsening of pimples (acne)
- Mood changes, and loss of libido are rare adverse effects.
- Hypersensitivity to subdermal implants
- Progestogen-dependent cancers
- Heavy or irregular vaginal bleeding, which is not evaluated.
- Severe liver failure
- History of liver adenoma (A non-cancerous lump in the liver)
- Hydatid mole (A growth, which forms inside the womb at the beginning of a pregnancy.)
- Choriocarcinoma (A rapid-growing cancer, which occurs in the womb.) with a detectable hCG level in the blood
- High risk for arterial disease
- History of severe arterial disease
- Breast cancer
(Photo courtesy: Alejandra Mavroski)