[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Hormonal contraceptives](https://durgical.com/en/pharmacology/classes/hormonal-contraceptives/) › Levonorgestrel

[Pharmacology](https://durgical.com/en/pharmacology/) · [Hormonal contraceptives](https://durgical.com/en/pharmacology/classes/hormonal-contraceptives/)

# Levonorgestrel

Progestin used alone as emergency contraception (within 3 days), in progestin-only pills, implants and intrauterine systems. No estrogen.

Updated 2026-11-01

- Class: [Hormonal contraceptives](https://durgical.com/en/pharmacology/classes/hormonal-contraceptives/)
- Receptor: Progesterone receptor (PGR)
- ATC code: G03AC03
- WHO Model List of Essential Medicines

◎**Progesterone receptor (PGR)**Levonorgestrel

ⓘ Crystal structure of the ligand-binding domain of the human progesterone receptor with levonorgestrel bound.

**Target in 3D:** Progesterone receptor (PGR). PDB structure 3D90 (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/3D90) · Drag to rotate · pinch to zoom

## Mechanism of action

Levonorgestrel is a synthetic progestin that activates the progesterone receptor. As emergency contraception it mainly prevents or delays ovulation; in daily or long-acting forms it also thickens cervical mucus and thins the endometrium. It does not work once a pregnancy is established and does not harm it.

- Levonorgestrel activates the progesterone receptor
- Ovulation is prevented or delayed
- Cervical mucus thickens; an established pregnancy is not affected

## Pharmacokinetics

**Absorption**
Almost complete by mouth, without first-pass metabolism

**Metabolism**
Reduction, hydroxylation and conjugation; enzyme inducers lower its levels

**Half-life**
About 34 hours (measured with the combined pill)

## Indications

- Emergency contraception after unprotected sex or contraceptive failure, as soon as possible and within 3 days
- Progestin-only contraception (pill, implant, intrauterine system)

## Adverse effects

### Common

- Changes in the next period (earlier, later, heavier or lighter)
- Nausea, vomiting and lower abdominal pain
- Tiredness, headache and dizziness
- Breast tenderness

### Serious (rare, important)

- Ectopic pregnancy if the method fails (severe abdominal pain)
- Allergic reactions

## Contraindications

- Known allergy to levonorgestrel
- Not used in a known pregnancy: it does not work then

## Key interactions

**Efavirenz, rifampicin and some antiepileptics**
Lower levels and less effect

**St John's wort and other enzyme inducers**
Less contraceptive effect

## What is monitored

- Timing of the next period; pregnancy test if it is more than a week late
- Severe abdominal pain (ectopic pregnancy)

## Administration and safety

- Emergency use: one oral dose as soon as possible after unprotected sex, within 3 days; the earlier, the better it works.
- If vomiting occurs within 2 hours, the patient contacts the health service about another dose.
- It is a backup method, not for regular contraception.

## Nursing care

- Ask the timing of unprotected sex and the last period, and current medicines (enzyme inducers).
- Teaching: it does not protect against HIV or other sexually transmitted infections.
- Advise a pregnancy test if the period is more than a week late.
- Severe abdominal pain needs urgent review for ectopic pregnancy.
- Offer information on regular contraceptive methods.

## Pregnancy and breastfeeding

It does not end or harm an established pregnancy; it is not used when pregnancy is known.

## Memory aid

«Levo = 3 days, Uli = 5 days»: the sooner, the better.

## Test yourself

Think of the answer, then tap the question to see it.

## What is the main mechanism of levonorgestrel as emergency contraception?

It prevents or delays ovulation; it does not end an established pregnancy.

## Within how many days after unprotected sex is levonorgestrel used, compared with ulipristal?

Levonorgestrel within 3 days; ulipristal up to 5 days. Both work better the sooner they are taken.

## Which HIV medicine lowers the effect of levonorgestrel?

Efavirenz, an enzyme inducer.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/levonorgestrel/)

## Related drugs

- [Ethinylestradiol + levonorgestrel](https://durgical.com/en/pharmacology/ethinylestradiol-levonorgestrel/)
- [Ulipristal](https://durgical.com/en/pharmacology/ulipristal/)

[← Back to the class: Hormonal contraceptives](https://durgical.com/en/pharmacology/classes/hormonal-contraceptives/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - LEVONORGESTREL TABLET, 1.5 MG tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=98f6367e-14d2-4c7a-9418-d996f0040d22) (DailyMed (U.S. National Library of Medicine), 2026); [DailyMed - LEVONORGESTREL AND ETHINYL ESTRADIOL kit](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=167b12a0-cdff-4081-a0a4-164482c239fa) (DailyMed (U.S. National Library of Medicine), 2026); [eEML - Electronic Essential Medicines List](https://list.essentialmeds.org/medicines/186) (World Health Organization, 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=G03AC) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake

Representative model, for educational purposes only.

---
Source: https://durgical.com/en/pharmacology/levonorgestrel/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/levonorgestrel/