A. False. In zero-order kinetics, plasma drug concentration rises out of proportion to dose increment and is highly unpredictable. In first-order kinetics the plasma concentration at all time points increases in direct proportion to dose.
B. False. The rapid increase in plasma concentration with dose, after the point of saturation has been reached, will usually be associated with adverse (toxic) effects. In the case of some drugs, serial measurements of plasma concentration may provide a warning of the rapid increase in concentration prior to the development of adverse effects.
C. True. Alcohol intoxication results because metabolism is delayed by saturation of alcohol dehydrogenase, so that insufficient acetaldehyde is formed.
D. False. The dose above which zero order kinetics apply differs significantly between individuals because of the different concentrations produced by the same dose and inter-individual variation in CYP2C9 enzyme capacity.
E. False. The volume of distribution for a specific drug is constant and the peak concentration post-dose is directly proportional to dose and unrelated to the process of elimination. The achievement of concentrations that are associated with zero-order kinetics will, however, mean slower elimination, larger area under the curve (AUC) and greater overall exposure to the drug.
Which of the following statements concerning zero-order kinetics are true?
Select true or false for each of the following statements