Effects of parenteral amino acid nutritional regimens on oxidative and conjugative drug metabolism.

Our goals were to determine the time-course of the increase in oxidative drug metabolism that occurs when parenteral nutrition is changed from dextrose to amino acids (23% branched-chain), whether the composition of the amino acid regimen influences this effect, and whether drug conjugation is similarly altered. We examined in healthy volunteers the effects of changing isocalorically from intravenous dextrose 440 kcal/day to amino acids, on one occasion 23% branched-chain and on another 85%. The change to the 23% regimen produced a significant increase in metabolic clearance of antipyrine, a model for oxidation (mean +/- SE 3.0 +/- 0.3 to 3.7 +/- 0.4 L/h, N = 6, P less than 0.003), but the change to the 85% regimen did not, indicating that the composition of an amino acid infusion can influence its effect on oxidative metabolism. Analysis of the concentration-time curve for antipyrine after simultaneous dosing and start of the 23% regimen suggests that the increase in metabolic capacity occurred within a few hours. Metabolic clearance of acetaminophen, a model for conjugation, was not altered by changing to either amino acid regimen.