RT Journal Article SR Electronic T1 PHYSIOLOGICALLY BASED PHARMACOKINETIC MODEL FOR PRALMORELIN HYDROCHLORIDE IN RATS JF Drug Metabolism and Disposition JO Drug Metab Dispos FD American Society for Pharmacology and Experimental Therapeutics SP 1488 OP 1494 DO 10.1124/dmd.104.001040 VO 33 IS 10 A1 Risa Nasu A1 Yoichi Kumagai A1 Hirokuni Kogetsu A1 Masayuki Tsujimoto A1 Hisakazu Ohtani A1 Yasufumi Sawada YR 2005 UL http://dmd.aspetjournals.org/content/33/10/1488.abstract AB Pralmorelin hydrochloride (pralmorelin), consisting of six amino acid residues, is a growth hormone-releasing peptide. The aim of this study is to analyze the pharmacokinetics of pralmorelin after intravenous bolus administration to rats, and to develop a physiologically based pharmacokinetic (PB-PK) model to describe and predict the concentrations of pralmorelin in blood and tissues. Pralmorelin (3 mg/kg) was administered intravenously to 24 Sprague-Dawley rats. Groups of three rats were sacrificed by decapitation at each designated time point (up to 4 h), and plasma and tissues (brain, lung, heart, liver, kidney, small intestine, muscle, adipose, and skin) were collected. Bile was also pooled until decapitation. The concentration of pralmorelin in samples was determined by liquid chromatography-tandem mass spectrometry. Plasma concentrations of pralmorelin declined rapidly in a biexponential manner. Biliary excretion of pralmorelin was so rapid that 80% of the dose was recovered unchanged in the bile within 1 h after administration. The distribution parameters in each tissue were obtained by using a hybrid model and an integration plot. They revealed that the distribution of pralmorelin into liver was blood flow-limited, and its distribution was permeability-limited in all other tissues. The PB-PK model developed in this study well described the time courses of pralmorelin concentration in the blood and tissues of rats. The American Society for Pharmacology and Experimental Therapeutics