etonogestrel
Nexplanon (etonogestrel) is a matchstick-sized implant from Organon placed under the skin of the upper arm. It releases a steady low level of progestin for up to five years, preventing ovulation and thickening cervical mucus to provide long-acting contraception.
This page is based on FDA prescribing information and the DailyMed label for the etonogestrel implant; the mechanism is explained in plain language, and analogies are used only where they stay accurate.
How it works
Explains what the medicine does in the body, not dosing, side effects, or safety.
An analogy
The implant is a tiny time-release reservoir buried under the skin, like a slow drip feed. It trickles out just enough progestin every day to keep the ovary's monthly release on hold and the cervix's gateway tightly closed, so no sperm can reach an egg — for years, without any daily action needed.
In simple terms
Etonogestrel is a synthetic progestin, a relative of the natural hormone progesterone. The implant releases a small, steady amount into the blood. This mainly stops the ovary from releasing an egg each month, and it also thickens the mucus at the cervix so sperm cannot pass. Because the dose is low and continuous, protection lasts up to five years from one insertion.
In depth
Etonogestrel is the biologically active metabolite of desogestrel, delivered from a single-rod ethylene vinyl acetate copolymer implant at a rate that declines slowly over time. It suppresses ovulation by inhibiting the luteinising hormone surge through hypothalamic-pituitary progestogenic activity, thickens cervical mucus and induces endometrial changes unfavourable to implantation. Serum levels remain contraceptive for up to five years, after which the rod is removed or replaced.
See it in motion
A schematic animation of the mechanism — simplified for clarity, not drawn to scale.
How a slow drip keeps the ovary's monthly release on hold
- Etonogestrel is a synthetic progestin, a relative of the natural hormone progesterone.
- The implant is a tiny time-release reservoir buried under the skin, like a slow drip feed.
- This mainly stops the ovary from releasing an egg each month, and it also thickens the mucus at the cervix so sperm cannot pass.
- Because the dose is low and continuous, protection lasts up to five years from one insertion.
Target: Progesterone receptor
The hormone receptor that progestins activate to suppress the ovulation signal from the pituitary and to thicken cervical mucus, both of which prevent conception.
Approved uses
Approved uses differ by country and change over time. Always follow your local prescribing information.
Approved uses in United States
FDA- Prevention of pregnancy in women of reproductive potential for up to 5 years
Official sources
The statements on this page trace back to these records.
- DailyMed: Nexplanon (etonogestrel) label
DailyMed, U.S. National Library of Medicine
- U.S. Food and Drug Administration: etonogestrel prescribing information
U.S. Food and Drug Administration
- Nexplanon 68 mg implant for subdermal use - Summary of Product Characteristics (SmPC) | (emc) 5720
electronic Medicines Compendium (emc)
This page explains how the medicine works — it isn’t the patient leaflet. For anything that applies to you, read the leaflet that came with your medicine or ask your pharmacist.
MedUnfold provides educational content and is not medical advice. Always follow your local prescribing information and healthcare professional.