Methylnaltrexone

Methylnaltrexone
Clinical data
Trade names	Relistor
Other names	MNTX, naltrexone-methyl-bromide
AHFS/Drugs.com	Monograph
MedlinePlus	a608052
License data	EU EMA: by INN; US DailyMed: Methylnaltrexone; US FDA: Methylnaltrexone;
Pregnancy; category	AU: B1;
Routes of; administration	Oral, intravenous, subcutaneous
ATC code	A06AH01 (WHO) ;
Legal status
Legal status	AU: S4 (Prescription only); BR: Class C1 (Other controlled substances); CA: ℞-only; UK: POM (Prescription only); US: ℞-only; EU: Rx-only;
Pharmacokinetic data
Protein binding	11–15.3%
Metabolism	Liver
Elimination half-life	8 hours
Excretion	Urine (50%), faeces (50%)
Identifiers
	IUPAC name (5α)-17-(cyclopropylmethyl)-3,14-dihydroxy-17-methyl-4,5-epoxymorphinanium-17-ium-6-one;
CAS Number	916055-93-1 ;
PubChem CID	5361918;
IUPHAR/BPS	7563;
DrugBank	DB06800 ;
ChemSpider	4514884 ;
UNII	0RK7M7IABE;
ChEMBL	ChEMBL1186579 ;
CompTox Dashboard (EPA)	DTXSID30868236 ;
ECHA InfoCard	100.122.861
Chemical and physical data
Formula	C21H26NO4
Molar mass	356.442 g·mol−1
3D model (JSmol)	Interactive image;
	SMILES O=C6[C@@H]3Oc1c2c(ccc1O)C[C@@H]4[C@@](O)([C@@]23CC[N+]4(C)CC5CC5)CC6;
	InChI InChI=1S/C21H25NO4/c1-22(11-12-2-3-12)9-8-20-17-13-4-5-14(23)18(17)26-19(20)15(24)6-7-21(20,25)16(22)10-13/h4-5,12,16,19,25H,2-3,6-11H2,1H3/p+1/t16-,19+,20+,21-,22?/m1/s1 ; Key:JVLBPIPGETUEET-GAAHOAFPSA-O ;
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Methylnaltrexone (MNTX, brand name Relistor), used in form of methylnaltrexone bromide (INN, USAN, BAN), is a medication that acts as a peripherally acting μ-opioid receptor antagonist that acts to reverse some of the side effects of opioid drugs such as constipation without significantly affecting pain relief or precipitating withdrawals. Because MNTX is a quaternary ammonium cation, it cannot cross the blood–brain barrier, and so has antagonist effects throughout the body, counteracting effects such as itching and constipation, but without affecting opioid effects in the brain such as pain relief. However, since a significant fraction (up to 60%) of opioid analgesia can be mediated by opioid receptors on peripheral sensory neurons, particularly in inflammatory conditions such as arthritis, traumatic or surgical pain, MNTX may increase pain under such circumstances.