Polyethylene glycol 400

The metabolism of PEG involves the oxidation of the alcohol groups located on the PEG to a carboxylic acid. For example, the diacid and hydroxyl acid metabolites of PEG have been measured in the plasma and urine of burn patients and rabbits and in the bile of cats. In the isolated guinea pig liver and in rat/guinea pig in vitro, PEG has demonstrated to be sulfated. Evidence from experiments with PEG400 suggests that ethylene glycol is not formed as a metabolite of PEG in humans. Negligible amounts of oxalic acid are liberated after the metabolism of PEG ^L1790. The first phase of metabolism of PEG in mammals is regulated by the enzyme alcohol dehydrogenase. Liver cytochorome P450 enzymes may also play a role in the oxidation of PEG, although the evidence for this is not clear ^L1790. Also, PEG has been shown to be metabolized by sulfotransferase enzymes. Although there is evidence that PEG can be metabolized to various phase 1 and phase 2 metabolites, the toxicology data presented above indicate that these metabolites are of very little toxicological concern. However, metabolism of PEG to the acid metabolite(s) has been implicated in the acidosis and hypercalcemia observed in patients after overdose ^L1790. It is clear that these metabolites can be formed in multiple toxicology species and that the phase 1 metabolites are seen in animals and humans. These data indicate that humans and animals will be exposed to similar metabolites after administration of PEG ^L1790. metabolic clearance of PEG decreases markedly as molecular weight increases. For PEG400, up to 25% of the dose may be metabolized in humans (Schaffer et al., 1950); similar results are also seen in the rabbit ^L1790. The absorption of PEG by the oral route is molecular weight- dependent. Urinary recovery data for PEG400 indicate that 50 to 60% of PEG with this molecular weight is absorbed from the intestine ^L1790. In the case of PEG-400, up to 25% of the dose may be metabolized in humans. Similar results have also been obtained in studies on the rabbit ^L1790.

Human excretion studies have demonstrated that 86% and 96% of PEG1000 and 6000 were excreted in the urine 12 h after intravenous administration. Specific data on PEG-400 are not available ^L1790. In rats, urine PEG undergoes biliary excretion, and this process is depending on molecular weight, with hepatic clearance reaching a minimum at about 50 kDa molecular mass (in mouse)^L1790.