Tri-Levlen

Levonorgestrel

Clinical data
Trade names	Plan B, others
AHFS/Drugs.com	Monograph
MedlinePlus	a610021
Pregnancy category	X
Routes of administration	Implant, insert (extended-release), by mouth
ATC code	G03AC03 (WHO) G03AD01 (WHO)
Legal status
Legal status	Rx only, or OTC
Pharmacokinetic data
Bioavailability	~100%
Protein binding	55%
Metabolism	Liver via CYP3A4
Biological half-life	36 ± 13 hours
Excretion	Kidney: 45%; Feces:32%
Identifiers
IUPAC name (17α)-(−)-13-Ethyl-17-hydroxy-18,19-dinorpregn-4-en-20-yn-3-one
CAS Number	797-63-7 Y
PubChem CID	13109
IUPHAR/BPS	2881
DrugBank	DB00367 Y
ChemSpider	12560 Y
UNII	5W7SIA7YZW
KEGG	D00950 Y
ChEBI	CHEBI:6443 Y
ChEMBL	CHEMBL1389 Y
ECHA InfoCard	100.011.227
Chemical and physical data
Formula	C21H28O2
Molar mass	312.446 g/mol
3D model (Jmol)	Interactive image
SMILES [H][C@]12CCC(=O)C=C1CC[C@]1([H])[C@]2([H])CC[C@@]2(CC)[C@@]1([H])CC[C@@]2(O)C#C
InChI InChI=1S/C21H28O2/c1-3-20-11-9-17-16-8-6-15(22)13-14(16)5-7-18(17)19(20)10-12-21(20,23)4-2/h2,13,16-19,23H,3,5-12H2,1H3/t16-,17+,18+,19-,20-,21-/m0/s1 Y Key:WWYNJERNGUHSAO-XUDSTZEESA-N Y

Levonorgestrel is a manufactured hormone used in a number of birth control methods. In pill form, sold under the brand name Plan B among others, it is useful within 120 hours as emergency birth control. It becomes less effective the longer after sex and only works before pregnancy has occurred. It is also combined with an estrogen to make combined oral birth control pill. Within an IUD, sold as Mirena among others, it is effective for long term prevention of pregnancy. An implantable form of levonorgestrel is also available in some countries.

Common side effects include nausea, breast tenderness, headaches, and increased, decreased, or irregular menstrual bleeding. When used as a form of emergency contraception, if pregnancy occurs, there is no evidence its use harms the baby. It is safe to use during breastfeeding. Birth control that contains levonorgestrel will not change the risk of sexually transmitted infections. It works mostly by decreasing ovulation and closing off the cervix to prevent the passage of sperm.

Levonorgestrel was first made in the 1960s and its use as a method of birth control began in the 1980s. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. It is available as a generic medication. The wholesale cost in the developing world costs between 0.23 and 1.65 USD for the dose required for emergency birth control. In the United States it is over the counter for all ages.