RU-486

Mifepristone

Clinical data
Trade names	Mifeprex
AHFS/Drugs.com	Monograph
MedlinePlus	a600042
Pregnancy category	US: X (Contraindicated) Used for terminating pregnancy
Routes of administration	By mouth
ATC code	G03XB01 (WHO)
Legal status
Legal status	US: ℞-only In general: ℞ (Prescription only)
Pharmacokinetic data
Bioavailability	69%
Protein binding	98%
Metabolism	Liver
Excretion	Fecal: 83%; Kidney: 9%
Identifiers
IUPAC name 11β-[p-(Dimethylamino)phenyl]-17β-hydroxy-17-(1-propynyl)estra-4,9-dien-3-one
CAS Number	84371-65-3 Y
PubChem CID	55245
IUPHAR/BPS	2805
DrugBank	DB00834 Y
ChemSpider	49889 Y
UNII	320T6RNW1F
KEGG	D00585 Y
ChEBI	CHEBI:50692 Y
ChEMBL	CHEMBL157 Y
ECHA InfoCard	100.127.911
Chemical and physical data
Formula	C29H35NO2
Molar mass	429.60 g/mol
3D model (Jmol)	Interactive image
Density	1.189 g/cm3
Melting point	194 °C (381 °F)
Boiling point	629 °C (1,164 °F)
SMILES O=C5\C=C4/C(=C3/[C@@H](c1ccc(N(C)C)cc1)C[C@]2([C@@H](CC[C@]2(C#CC)O)[C@@H]3CC4)C)CC5
InChI InChI=1S/C29H35NO2/c1-5-15-29(32)16-14-26-24-12-8-20-17-22(31)11-13-23(20)27(24)25(18-28(26,29)2)19-6-9-21(10-7-19)30(3)4/h6-7,9-10,17,24-26,32H,8,11-14,16,18H2,1-4H3/t24-,25+,26-,28-,29-/m0/s1 Y Key:VKHAHZOOUSRJNA-GCNJZUOMSA-N Y

Mifepristone, also known as RU-486, is a medication typically used with misoprostol to bring about an abortion. This combination is more than 95% effective during the first 50 days of pregnancy. It is also effective in the second trimester of pregnancy. Two weeks after use effectiveness should be verified. It is taken by mouth.

Common side effects include abdominal pain, feeling tired, and vaginal bleeding. Serious side effects may include heavy vaginal bleeding, bacterial infection, and a malformed baby if the pregnancy does not end. If used, appropriate follow up care needs to be available. Mifepristone works by blocking the effects of progesterone and causing contractions of the uterus.

Mifepristone was developed in 1980 and came into use in France in 1987. It became available in the United States in 2000. It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system. Mifepristone was approved by Health Canada in 2015 and became available in Canada in January 2017. Cost and availability limits access in many parts of the developing world. In the United States it costs more than US$200 (equivalent to $202.08 in 2016) a dose.

Mifepristone followed by a prostaglandin analog (misoprostol or gemeprost) is used for medical abortion.

A 2011 evidence-based clinical guideline by the Royal College of Obstetricians and Gynaecologists (RCOG) says medical abortion using mifepristone followed by the prostaglandin analog misoprostol is effective and appropriate at any gestational age.

A 2012 technical and policy guidance book and a 2014 clinical practice handbook by the World Health Organization (WHO) recommend mifepristone followed by the prostaglandin analog misoprostol for first and second trimester medical abortions.