Loading and maintenance dose for the determination of amino acid kinetics in plasma

Intravenous bolus kinetics of amino acids and calculation of the kinetic parameters with an 1-compartment model revealed weak spots. Therefore, a new study design with a loading and maintenance dose and description of the plasma concentration time data with a 2-compartment model was created and studied in 9 healthy volunteers. After an over night fast the amino acid mixture Thomaeamin n 10% was infused with a loading dose of 20 mg AA/kg-1 X min-1 for 5 min and a maintenance dose of 5 mg AA/g-1 X min-1 for 55 min. The postinfusion period lasted 120 min. The PAA was determined with a Biotronic LC 6001 and the kinetic parameters were calculated by a Wang 2200 computer with the TOPFIT program package. The results showed mean values (means +/- SE) of the volume distribution between 4.7 +/- 0.6 till 9.4 +/- 1.8 liters, an elimination rate constant of 1.7 +/- 0.5 till 11.0 +/- 2.0 h-1, a total clearance of 186 +/- 37 till 846 +/- 66 ml X min-1 and transfer or endogenous production rate between 12 +/- 0.8 till 135 +/- 16 mumol kg-1 X h-1. The total transfer amounts to 17.6 mmol kg-1 X d-1 (= 2.2 g AA/kg-1 X d-1). It can be concluded that an optimal study design for the investigation of AA kinetics should increase the PAA levels 2-3 fold above basal during the infusion period.(ABSTRACT TRUNCATED AT 250 WORDS)