Subdermal Contraceptive Implants
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Direct answer
A subdermal contraceptive implant is a small flexible rod placed under the skin of the upper arm that releases a progestin over several years. The etonogestrel implant contains 68 mg of etonogestrel and is among the most effective reversible contraceptives, and bleeding change is the commonest reason for discontinuation.
What you must remember
- Etonogestrel implant: A single rod containing 68 mg of etonogestrel, releasing hormone steadily over its life.
- Duration: Most labels state three years, and some products are approved for up to five years.
- Mechanism: Inhibits ovulation in most users, thickens cervical mucus and alters the endometrium.
- Insertion site: The medial aspect of the non-dominant upper arm, under local anaesthesia.
- Bleeding pattern: Irregular bleeding and spotting are common, and amenorrhoea occurs in a sizeable share of users.
- Enzyme inducers: Rifampicin, efavirenz, carbamazepine, phenytoin and St John's wort reduce efficacy.
- Fertility return: Fertility returns quickly after removal.
A stepwise approach to insertion and removal
The vignette often describes a woman choosing an implant, and the steps below cover the clinical sequence from eligibility to removal.
- Confirm eligibility: Exclude pregnancy and review current medicines, since enzyme inducers can reduce the implant's effect.
- Time the insertion: Insert within the first five days of a menstrual cycle, or at any other time once pregnancy is excluded, with backup contraception for seven days if inserted later.
- Insert under local anaesthesia: Place the implant subdermally in the medial upper arm of the non-dominant arm, using the trocar technique.
- Check placement: Palpate the rod after insertion and record its position in the patient's notes.
- Remove at the end of its life: Remove through a small incision under local anaesthesia. If the rod cannot be palpated, locate it by ultrasound before removal.
Counselling before insertion should cover the expected bleeding pattern, enzyme-inducer interactions and how removal works. Most later problems follow from these three points.
Where the exam tries to catch you
Implant questions often test enzyme-inducer interactions, the approach to irregular bleeding and the need to localise a non-palpable rod.
- Trap: Assuming the implant remains reliable with rifampicin. Correct: Rifampicin induces enzymes and lowers the implant's efficacy, so an alternative method or additional contraception is needed while on the drug.
- Trap: Removing the implant early for irregular bleeding. Correct: Irregular bleeding is the commonest effect and often improves, so pregnancy and pathology are excluded before removal.
- Trap: Removing a non-palpable implant without imaging. Correct: A non-palpable rod is located by ultrasound before surgery, which avoids an unnecessarily extensive operation.
Frequently asked questions
How long does the etonogestrel subdermal implant last?
The etonogestrel implant is licensed for three years in most labelling, and some products are approved for up to five years. Effectiveness depends on removal or replacement at the end of the licensed period.
Why are enzyme inducers a concern with contraceptive implants?
Enzyme inducers such as rifampicin, efavirenz, carbamazepine and phenytoin increase the metabolism of etonogestrel, lowering the implant's contraceptive effect. Women on these drugs need an alternative method or additional contraception for the duration of therapy.
What bleeding pattern is typical after etonogestrel implant insertion?
Irregular bleeding and spotting are the most typical pattern after etonogestrel implant insertion, and amenorrhoea occurs in a sizeable share of users. Bleeding often improves over time, so women should be counselled before insertion and reviewed if bleeding persists.
How is a non-palpable etonogestrel implant located for removal?
A non-palpable etonogestrel implant is located by ultrasound before removal, which helps avoid an unnecessarily extensive operation. Removal is then done through a small incision under local anaesthesia, and the rod is withdrawn intact.