Pharmacokinetics/Pharmacodynamics

that the Vd has changed, which would likely result in

lower or unchanged concentrations (Answer B is incor-

rect). Vancomycin tissue penetration may be better if

inflammation is present, but no documented studies

correlate decreased inflammation with increased serum

concentrations (Answer C is incorrect). The liver does

not appreciably metabolize vancomycin, and liver blood

flow would not be a factor in the vancomycin concentra-

tion (Answer D is incorrect).

Answer: C

Prospective controlled studies of prolonged piperacil-

lin/tazobactam infusions have shown no improvement

in mortality (Answer A is incorrect). No studies have

reported neurotoxicity as an outcome (Answers B and

D are incorrect). Only retrospective studies have shown

improvements in mortality with the use of prolonged

or continuous infusions of piperacillin/tazobactam

(Answer C is correct).

Answer: C

Morphine is a high extraction ratio drug. As such, its

hepatic metabolism or hepatic clearance depends only

on hepatic blood flow. Hepatic clearance equals hepatic

blood flow (Answer C is correct). Morphine does not

bind to AAG (Answer A is incorrect). Because hepatic

blood flow is the main determinant of hepatic metab-

olism of morphine, changes in protein binding do not

affect metabolism (Answer B is incorrect). Changes

in intrinsic clearance do not affect the metabolism of

morphine as significantly as does hepatic blood flow

(Answer D is incorrect).