Contraceptive Implants

Subdermal contraceptive implants are progestin-only, long-acting reversible methods made of one or two flexible rods placed under the skin of the inner upper arm, where they release a progestin at a slow, steady rate for 3 to 5 years depending on the system. They contain no oestrogen, need no daily or periodic action from the patient, and are the most effective reversible method available, with about 0.05 pregnancies per 100 women in the first year.

Classification. Long-acting reversible contraception, progestin-only, hormonal. Two active agents are used: etonogestrel (single rod) and levonorgestrel (two rods).

Mechanism. The progestin thickens cervical mucus and impairs sperm penetration, suppresses the mid-cycle luteinising hormone surge and so inhibits ovulation in many or most cycles, and thins the endometrium. Etonogestrel suppresses ovulation more consistently than levonorgestrel rods, which rely more on the cervical mucus effect as release falls in later years.

Systems in use.

Release profile. Release is highest in the first weeks after insertion and falls gradually over the life of the device, which is why lifespan is fixed by system rather than by class.

Effectiveness. About 0.05 pregnancies per 100 women in the first year with typical use and with perfect use; the two figures are the same because no user action is needed after insertion.

Onset of protection. Inserted within the first 7 days after menstrual bleeding starts, the implant protects at once and no backup is needed. Inserted at any other time, once pregnancy is reasonably excluded, condoms or abstinence are needed for 7 days.

Return to fertility. Serum progestin falls to undetectable levels within days of removal and ovulation usually returns within the first month. Most patients regain fertility promptly, although a delay of up to 1 year is occasionally reported.

Ideal candidates. Any patient of reproductive age, any parity, including adolescents and nulliparous patients, who wants highly effective long-term contraception, has difficulty with daily or repeated methods, cannot use oestrogen, is postpartum (breastfeeding or not) or postabortion, or is waiting to complete a family before permanent contraception.

History and examination. Take a menstrual history, last menstrual period, sexual activity since then, current contraception, postpartum and breastfeeding status, medicines (especially enzyme inducers and antiretrovirals), liver disease, breast cancer, unexplained vaginal bleeding, and current venous thromboembolism. Examine the arm for skin infection, scarring or tattoos at the insertion site.

Investigations not needed. Pelvic examination, breast examination, cervical screening, blood tests and blood pressure measurement are not required before insertion. A pregnancy test is needed only when pregnancy cannot be reasonably excluded on history.

Reasonable certainty of non-pregnancy. The patient has no symptoms or signs of pregnancy and meets one of these: no intercourse since the last normal menses; correct and consistent use of a reliable method; within 7 days of the start of normal menses; within 4 weeks postpartum; within 7 days after abortion or miscarriage; or fully or nearly fully breastfeeding, amenorrhoeic and under 6 months postpartum.

Key eligibility categories.

• Category 1 (no restriction): adolescents, nulliparity, smoking at any age, obesity with BMI 30 kg/m2 or more, hypertension with blood pressure under 160/100 mm Hg, history of venous thromboembolism in a family member, sickle cell disease, HIV infection, epilepsy, endometriosis, fibroids, current pelvic infection.

• Category 2 (benefits usually outweigh risks): breastfeeding under 6 weeks postpartum, past venous thromboembolism, uncomplicated diabetes, migraine without aura, irregular or heavy bleeding patterns, rifampicin or rifabutin, efavirenz or nevirapine, ritonavir-boosted protease inhibitors, enzyme-inducing antiseizure medicines.

• Category 3 (risks usually outweigh benefits): current deep vein thrombosis or pulmonary embolism, severe decompensated cirrhosis, hepatocellular adenoma or malignant hepatoma, unexplained vaginal bleeding before evaluation, ischaemic heart disease, stroke or migraine with aura that develops or worsens during use.

• Category 4 (do not use): current or past breast cancer.

Noncontraceptive benefits. Reduced menstrual blood loss in many users, reduced dysmenorrhoea and endometriosis pain with etonogestrel, reduced iron deficiency anaemia, reduced symptomatic pelvic inflammatory disease, and lower absolute risk of ectopic pregnancy.

Counselling points for the clinician. Explain the expected change in bleeding pattern before insertion, because unpredictable bleeding is the main reason for early removal. Confirm the patient knows the implant can be removed at any time on request and that removal must never be delayed or refused. Advise condoms for STI and HIV protection where there is risk. Obtain informed consent; patients under 18 years give assent with consent in line with the law, and no method is withheld on age alone.

Regimen lines.

• Etonogestrel implant: 68 mg single rod, subdermal, inner aspect of the non-dominant upper arm; one insertion; effective for 3 years; replace at 3 years. Backup 7 days if inserted outside the first 7 days of the cycle.

• Levonorgestrel 5-year implant: two 75 mg rods, subdermal, inner upper arm in a narrow V; effective for 5 years; replace at 5 years. Backup 7 days if inserted outside the first 7 days of the cycle.

• Levonorgestrel 3-year implant: two 75 mg rods, subdermal, inner upper arm in a narrow V; effective for 3 years; replace at 3 years. Backup 7 days if inserted outside the first 7 days of the cycle.

• No missed-dose or grace-window rule applies; protection ends at the end of the device lifespan, and an overdue implant needs replacement and pregnancy exclusion.

Start timing.

Switching. From a hormonal method used correctly: insert immediately, no backup. From an injectable: insert on or before the date the next injection is due, no backup. From a copper or hormonal IUD: insert within 7 days of bleeding and remove the IUD the same day; after day 7, insert the implant and keep the IUD until the next period.

Follow up. No routine visit is required. Record on the follow up card the implant type, insertion date and removal date. Advise the patient to keep the site dry for 5 days, remove the gauze after 1 day, leave the adhesive plaster for a further 5 days, and return for pain, heat, pus or redness at the site, a rod coming out, suspected pregnancy, or any concern.

Discontinuation. Removal by a trained provider at the end of lifespan or at any time on request. A new implant can be inserted through the same incision at removal if the patient wishes to continue, with no gap in protection.

Special groups. Adolescents: category 1, first-line option. Postpartum and breastfeeding: no adverse effect on milk volume or infant growth. Perimenopause: may be used until menopause is confirmed. HIV: category 1 for the infection itself; efavirenz lowers implant effectiveness. Obesity: no weight-based restriction. Liver disease: avoid in severe cirrhosis and hepatic tumours other than focal nodular hyperplasia.

Expected effects. Change in bleeding pattern is the rule: amenorrhoea, infrequent bleeding, frequent bleeding, or prolonged bleeding, which may change over time. Headache, dizziness, nausea, breast tenderness, mood change, acne, weight change and mild abdominal pain can occur. Functional ovarian follicles may enlarge and usually resolve without treatment.

Bleeding management. Exclude pregnancy, STI, cervical pathology and other gynaecological causes when bleeding is persistent, heavy or new after a settled pattern. With no cause found:

• Ibuprofen 800 mg orally three times daily for 5 days, with food; avoid in peptic ulcer disease, significant kidney impairment and NSAID hypersensitivity; compatible with breastfeeding.

• Mefenamic acid 500 mg orally twice daily for 5 days; same cautions.

• Combined oral contraceptive containing ethinylestradiol 30 micrograms and levonorgestrel 150 micrograms, one tablet daily for 21 days, only where oestrogen is eligible (not in breastfeeding under 6 months, venous thromboembolism, migraine with aura, uncontrolled hypertension or smoking at 35 years or more).

• Tranexamic acid 500 mg orally three times daily for 5 days for heavy bleeding; avoid in active or past thromboembolism; reduce dose in kidney impairment.

• Remove the implant and offer another method if bleeding remains unacceptable to the patient or becomes heavy enough to threaten health.

Serious complications. Infection at the site, expulsion, deep or migrated rod, neurovascular injury from deep insertion, and rarely pregnancy, including ectopic pregnancy.

Red flags. Unilateral leg swelling or chest pain, severe abdominal pain with amenorrhoea, a new breast lump, new migraine with aura, jaundice, a site abscess or spreading cellulitis, numbness or weakness in the hand after insertion, and a rod that cannot be felt.

Management. Site infection without abscess: clean and treat with an oral antibiotic covering skin flora, keep the implant and review in 1 week; remove if infection persists or an abscess forms. Expulsion: insert a new implant in the other arm or in the reverse direction in the same arm, or provide another method. Pregnancy: exclude ectopic pregnancy, remove the implant if the pregnancy continues; there is no known risk to the foetus.

Referral and escalation. Refer a non-palpable implant, a deep implant, suspected nerve injury, suspected ectopic pregnancy, breast mass and suspected venous thromboembolism. Exploration for a non-palpable rod is never done blind.