The molecular weight, bioavailability, protein binding, elimination half-life, the time to achieve maximum plasma concentration and binding affinity are present in the table below. +Table 1: Pharmacokinetic parameters of<unk> s Chemical name Chemical structure Molecular weight (g/mol) Bioavailability (%) Plasma protein binding (%) t1/2 (h) tmax Ki<unk>  (nM) Ki κ (nM) Ki δ (nM) Methylnaltrexone bromide frameless 436,3 Low 11-15 8 30 min 5.50 32.1 3453.8 Alvimopan frameless 424,53 6 80-90 10-17 2 h 0.77 40 4.4 Naloxegol frameless 651,798 NA 4,2 6-11 2 h 7.42 8.65 203.0 Naldemedine frameless 570,6 29 93-94 11 45 min 0.34 0.94 0.43 * t1/2: Biological half-life * tmax: Time to achieve maximum plasma concentration * pKi: the measurement of ligand binding affinity Methylnaltrexone bromide has poor oral bioavailability, and for that reason, every other day it is administered subcutaneously. About half of the dose is excreted in the urine and somewhat less in feces with 85% eliminated unchanged. Alvimopan has considerable low bioavailability (6%) due to its high binding affinity and low dissociation rate. Essentially, alvimopan is mediated by biliary secretion with an average plasma clearance of 400 ml/min. Metabolism of alvimopan is via intestinal flora resulting in hydrolysis of alvimopan to the active amide metabolite (ADL 08-0011). However, the metabolite is considered clinically irrelevant due to its low binding affinity. When naloxegol is given with a fatty meal, absorption increases. Clearance is mostly via hepatic metabolism (P450-CYP3A) with unknown actions of the metabolites. Naloxegol has small fragments eliminated by renal excretion. Naldemedine metabolites mainly via CYP3A to nor-naldemedine, it also metabolites via UDP-glucuronosyltransferase 1A3 to naldemedine 3-G, but in a lesser extent. Those metabolites are both<unk>  receptor<unk> s but are less potent than the parent compound.
Peripherally acting μ-opioid receptor antagonist
Serotonin–dopamine releasing agent
Serotonin receptor agonist
Norepinephrine–dopamine releasing agent
Serotonin–norepinephrine–dopamine releasing agent
Long-acting beta-adrenoceptor agonist
Noradrenergic and specific serotonergic antidepressant
Serotonin–norepinephrine releasing agent