Levonorgestrel
A synthetic progestogen used in combined pills, hormonal intrauterine systems and the emergency contraceptive pill.
Also called LNG (abbreviation).
Drug card
- Class
- Progestogen
- How it works
- Activating progesterone receptors, so cervical mucus thickens against sperm
- Used for
- Contraception (pills and intrauterine systems)
- Emergency contraception (within 72 hours)
- Heavy menstrual bleeding (intrauterine system)
- Known for
- Irregular bleeding or spotting
- Its name
- -gest- means a progestogen
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does levonorgestrel work?
Levonorgestrel, the active form of norgestrel, binds progesterone receptors and also has some androgenic activity. By mouth it suppresses LH and blocks or delays ovulation, which is how the emergency pill works; it cannot end an established pregnancy. Released inside the uterus from an intrauterine system, it thickens cervical mucus, impairs sperm and thins the endometrium.
Like other progestogens: Progestogens bind progesterone receptors, nuclear receptors that switch on progesterone-responsive genes. They turn estrogen-primed endometrium from proliferative to secretory and thin it over time, thicken cervical mucus so sperm cannot pass, and at higher or depot doses suppress LH so ovulation stops. Given with estrogen in HRT they protect the endometrium.
Uses
What is levonorgestrel used for?
- Contraception (pills and intrauterine systems)
- Emergency contraception (within 72 hours)
- Heavy menstrual bleeding (intrauterine system)
Side effects
Side effects of levonorgestrel
- Irregular bleeding or spottingKnown for
- Nausea and vomiting (emergency pill)
- Lower abdominal pain and cramping
- Headache
- Breast pain or tenderness
- Tiredness
- Dizziness
- Acne
- Low mood or depression
- Ovarian cysts (intrauterine system)
- Ectopic pregnancy if pregnancy occursSerious
- Pelvic infection after intrauterine insertionSerious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- As an emergency pill, take it as soon as possible and within 72 hours; it does not work once pregnancy is established.
- Rifampicin, efavirenz and some antiepileptic drugs can make it less effective.
- Intrauterine system: exclude pregnancy and pelvic infection first; perforation and expulsion can occur.
- If pregnancy occurs with an intrauterine system in place, rule out ectopic pregnancy and remove the device.
Good to know: The same molecule serves daily pills, a single-dose emergency pill and intrauterine systems that last for years.
Remember it
A way to remember it
Progestogens plug and thin.
They plug the cervix with thick mucus and thin the lining of the uterus, which is why irregular or absent bleeding is the commonest complaint.
Written for biofideX
Its name
-gest- means progestogen
Covers progesterone and synthetic progestogens such as levonorgestrel, medroxyprogesterone and desogestrel. Norethisterone is a progestogen without it.
- Every drug name stem
Its class
Progestogens
Other progestogens with a card:
Easily mixed up with estrogens.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
- Levonorgestrel intrauterine system (5-year): label (DailyMed)
- Levonorgestrel intrauterine system (8-year): label (DailyMed)
- Levonorgestrel 1.5 mg emergency contraceptive: label (DailyMed)
- Levonorgestrel (NCI Thesaurus)
- Emergency contraception (WHO)
- Emergency contraception (NHS)
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Reproductive and urinary health
Levonorgestrel is one of 9 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
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