etonogestrel
Brand: Nexplanon (subdermal implant), NuvaRing (vaginal ring — combined with ethinyl estradiol)
Prototype: medroxyprogesterone
Drug Class: progestogen
Drug Family: hormone
Subclass: third-generation progestogen — long-acting implant
Organ Systems: endocrinereproductive
Mechanism of Action
Active metabolite of desogestrel; highly selective progesterone receptor agonist with low androgenic activity. In the subdermal implant (Nexplanon), etonogestrel suppresses ovulation primarily and secondarily thickens cervical mucus. Provides 3 years of highly effective contraception.
progesterone receptor
Indications
- long-term contraception (Nexplanon implant up to 3 years)
- short-term hormonal contraception (NuvaRing monthly)
Contraindications
- known pregnancy
- undiagnosed vaginal bleeding
- liver disease
- breast cancer
- history of thromboembolic disease (NuvaRing — has estrogen component)
Adverse Effects
Common
- irregular menstrual bleeding (implant — most common reason for early removal)
- amenorrhea
- headache
- breast tenderness
Serious
- ectopic pregnancy (if failure)
- ovarian cysts (temporary)
- implant migration (rare)
Pharmacokinetics (ADME)
| Absorption | subdermal: continuous sustained release; peak levels in 4 days |
| Distribution | widely distributed |
| Metabolism | hepatic; CYP3A4 |
| Excretion | renal and fecal |
| Half-life | 25 hours |
| Onset | days (implant) |
| Peak | 4 days (implant) |
| Duration | 3 years (Nexplanon) |
| Protein Binding | ~32% albumin, ~66% SHBG |
| Vd | 201 L |
Drug Interactions
| Drug / Agent | Mechanism | Severity |
|---|---|---|
| CYP3A4 inducers (rifampin, anticonvulsants) | increased etonogestrel metabolism; reduced contraceptive efficacy; alternative contraception needed | major |
Nursing Considerations
- Nexplanon is inserted subdermally in the inner upper arm by a trained healthcare provider; it is radiopaque for detection with standard X-ray if location is uncertain.
- Insert during days 1–5 of menstrual cycle or immediately after abortion/delivery to ensure non-pregnancy.
- Irregular bleeding is the most common cause of early removal; counsel extensively before insertion to set expectations.
- Patients on enzyme-inducing medications (anticonvulsants, rifampin) should not rely solely on the implant for contraception; additional methods are required.
Clinical Pearls
- The etonogestrel implant (Nexplanon) is the most effective reversible contraceptive available, with a failure rate of 0.01%/year — lower even than bilateral tubal ligation.
- Etonogestrel's low androgenic activity (compared to older levonorgestrel-based progestogens) makes it less likely to cause androgenic side effects (acne, hirsutism) in sensitive patients.
Safety Profile
Pregnancy contraindicated
Lactation safe
Renal Adjustment Not required
Hepatic Adjustment Required
TDM Not required
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.