rHuEPO plays a central role as chemicals for the treatment of many diseases. Due to its short half-life, the main aim for\nthis pharmacokinetic study is to investigate a newly developed PEG-rHuEPO with large molecular weight in SD rats. After a\nsingle intramuscular administration of different doses of 125I-PEG-rHuEPO, pharmacokinetic parameters, tissue distribution,\nand excretion were analyzed. In in vivo half-life time measured after 125I-PEG-rHuEPO administration at the doses of 1, 2, and\n3�µg/kg, t1/2a was 1.90, 1.19, and 2.50 hours, respectively, whereas t1/2�Ÿ was 22.37, 26.21, and 20.92 hours, respectively; at 8, 24,\nand 48 hours after intramuscular administration, PEG-rHuEPO was distributed to all of the examined tissues, however, with high\nconcentrations of radioactivity, only in plasma, blood, muscle at the administration site, and bone marrow. Following a 2 �µg/kg\nsingle intramuscular administration, approximately 21% of the radiolabeled dose was recovered after almost seven days of study.\nUrine was the major route of excretion; 20% of the administered dose was recovered in the urine, while excretion in the feces was\nless than 1.4%. Therefore, this PEG-rHuEPO has potential to be clinically used and could reduce frequency of injection.
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