Introduction
Nexplanon (etonogestrel implant) is a single-rod, radiopaque contraceptive implant that provides long-acting, reversible contraception for up to three years. It represents a significant advancement in hormonal contraception, offering highly effective pregnancy prevention with minimal user intervention.
Mechanism of Action
Nexplanon works primarily by suppressing ovulation through the continuous release of etonogestrel, a progestin. The drug inhibits the midcycle surge of luteinizing hormone (LH), prevents follicular development, and thickens cervical mucus to create a barrier to sperm penetration. Additionally, it causes endometrial changes that make implantation less likely.
Indications
- Prevention of pregnancy for up to 3 years
- Long-acting reversible contraception in women of reproductive age
Dosage and Administration
Standard dosing: One implant (68 mg etonogestrel) inserted subdermally in the inner aspect of the upper arm Insertion timing:- Day 1-5 of menstrual cycle
- Immediately after first-trimester abortion
- 21-28 days postpartum in non-breastfeeding women
- 4 weeks postpartum in breastfeeding women
- Hepatic impairment: Contraindicated in severe hepatic disease
- Renal impairment: No dosage adjustment necessary
- Elderly: Not indicated in postmenopausal women
- Adolescents: Approved for use in women of reproductive age
Pharmacokinetics
Absorption: Etonogestrel is released at an initial rate of 60-70 mcg/day, decreasing to approximately 35-45 mcg/day by the end of the first year, and to 30-40 mcg/day by the end of the second year Distribution: Protein binding: 32% to sex hormone-binding globulin (SHBG) and 66% to albumin Metabolism: Hepatic metabolism via CYP3A4-mediated hydroxylation and conjugation Elimination: Half-life: approximately 25 hours; excreted in urine (43%) and feces (37%)Contraindications
- Known or suspected pregnancy
- Current or past history of thrombosis or thromboembolic disorders
- Hepatic tumors, benign or malignant, or active liver disease
- Undiagnosed abnormal genital bleeding
- Known or suspected breast carcinoma or other progestin-sensitive cancers
- Hypersensitivity to any components of Nexplanon
- Arterial cardiovascular disease
Warnings and Precautions
Thrombotic disorders: Increased risk of thrombotic and thromboembolic events Hepatic effects: May cause benign hepatic adenomas and rare hepatocellular carcinomas Carbohydrate metabolism: May decrease glucose tolerance Lipid metabolism: May alter lipid profiles Ectopic pregnancy: Consider ectopic pregnancy in women who become pregnant or complain of lower abdominal pain while using Nexplanon Ovarian cysts: May occur and usually resolve spontaneously Depression: May worsen depression; monitor patients with history of depression Insertion/removal complications: Rare cases of neurovascular injury, implant migration, and broken implantsDrug Interactions
Enzyme inducers: Drugs that induce CYP3A4 may decrease etonogestrel concentrations:- Carbamazepine, phenytoin, barbiturates
- Rifampin, rifabutin
- St. John's Wort
- Topiramate
- Efavirenz may reduce contraceptive effectiveness
- Broad-spectrum antibiotics may potentially reduce efficacy (controversial)
Adverse Effects
Very common (>10%):- Headache
- Vaginitis
- Weight increase
- Acne
- Breast pain
- Abdominal pain
- Influenza-like symptoms
- Emotional lability
- Depression
- Nervousness
- Dizziness
- Nausea
- Back pain
- Application site reactions
- Thrombophlebitis/thromboembolism
- Ectopic pregnancy
- Ovarian cysts
- Gallbladder disease
- Allergic reactions
- Migration of implant
Monitoring Parameters
- Blood pressure at baseline and periodically
- Clinical breast examination at baseline and annually
- Pelvic examination as clinically indicated
- Signs and symptoms of thromboembolic disorders
- Mood changes and depression screening
- Weight changes
- Headache pattern changes
- Insertion site for signs of infection or migration
- Pregnancy testing if symptoms suggest pregnancy
Patient Education
Key points to discuss:- Nexplanon does not protect against HIV or other sexually transmitted diseases
- Expected changes in menstrual patterns (irregular bleeding, amenorrhea)
- Implant must be removed after 3 years
- Report severe abdominal pain, chest pain, headaches, visual changes, or jaundice
- Insertion site care: keep clean and dry for 3-5 days
- Palpate implant periodically to ensure presence
- Notify all healthcare providers about implant presence before procedures
- Potential decreased efficacy with concomitant use of enzyme-inducing drugs
- Return for removal if desired or at 3-year expiration
- >99% effective in preventing pregnancy
- Begins working immediately if inserted during first 5 days of menstrual cycle
- Requires backup contraception for 7 days if inserted at other times
References
1. FDA Prescribing Information: Nexplanon (etonogestrel implant) 2. Curtis KM, Jatlaoui TC, Tepper NK, et al. U.S. Selected Practice Recommendations for Contraceptive Use, 2016. MMWR Recomm Rep. 2016;65(4):1-66 3. Mansour D, Gemzell-Danielsson K, Inki P, Jensen JT. Fertility after discontinuation of contraception: a comprehensive review of the literature. Contraception. 2011;84(5):465-477 4. Darney P, Patel A, Rosen K, Shapiro LS, Kaunitz AM. Safety and efficacy of a single-rod etonogestrel implant (Implanon): results from 11 international clinical trials. Fertil Steril. 2009;91(5):1646-1653 5. American College of Obstetricians and Gynecologists. Long-Acting Reversible Contraception: Implants and Intrauterine Devices. Practice Bulletin No. 186. Obstet Gynecol. 2017;130:e251-e269 6. Trussell J. Contraceptive failure in the United States. Contraception. 2011;83(5):397-404