Biodistribution and excretion of radiolabeled 40 kDa polyethylene glycol following intravenous administration in mice.

The pharmacokinetics, excretion, and tissue distribution of [(14)C]-labeled polyethylene glycol-alanine (PEG-Ala) were determined after slow bolus administration into the femoral vein of male CD-1 mice. The pharmacokinetics of PEG-Ala in blood and plasma revealed a biphasic elimination with a terminal half-life of 20 h. Eighty-five percent of the excreted material was voided in the urine and the remaining amount was detected in the feces. PEG-Ala-derived radioactivity was widely distributed with detectable levels of radioactivity observed in all tissues examined. The highest concentration was observed in the kidneys followed by lungs, heart, and liver. Six hours after administration, PEG-Ala levels were significantly reduced in all tissues. Despite a slow prolonged decrease, radioactivity was still detectable after 28 days.