Formulation: A crystalline solid
Formal Name: 17-(cyclopropylmethyl)-4,5α-epoxy-3,14-dihydroxy-17-methyl-6-oxo-morphinanium, monobromide
Purity: ≥95%
Formula Markup: C21H26NO4 • Br
Formula Weight: 436,3
Shelf life (days): 1460
CAS Number: 73232-52-7
Notes: Methylnaltrexone is a quaternary positively-charged form of naltrexone (Item No. 15520) that does not cross the blood brain barrier. It is a peripherally restricted µ-opioid receptor antagonist with a Ki value of 10 nM for human recombinant receptors expressed in CHO-K1 cells and IC50 values of 130.7 and 0.43 nM in rat brain membranes prepared with sodium chloride or water, respectively.{41513} Methylnaltrexone is selective for µ-opioid receptors over δ- and κ-opioid receptors (Kis = 630.95 and 31.62 nM, respectively). It inhibits contractions evoked by electrical field stimulation (EFS) in ileum isolated from morphine-naïve guinea pigs and dose-dependently decreases spontaneous mechanical activity in ileum isolated from morphine-treated guinea pigs when administered at doses of 1 and 10 µM.{41514} It does not inhibit heroin self-administration in rats and does not induce withdrawal syndrome in morphine-dependent rhesus monkeys when administered at doses up to 32 mg/kg.{41513,41515} Formulations containing methylnaltrexone have been used in the treatment of opioid-induced constipation.
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