Pharmacokinetics/Pharmacodynamics

changes, this ratio changes. The unbound steady-state

concentration does not change, but the total concentra-

tion decreases, which causes the change in the ratio.

Using the equations for low extraction ratio drugs (like

phenytoin) to explain what has occurred, the unbound

fraction is inversely proportional to the total concen-

tration but has no effect on the unbound steady-state

concentration (Answer D is correct; Answers A, B, and

C are incorrect).

Answer: A

The kidney plays a role in the excretion and metabo-

lism of insulin. Acute kidney injury will decrease the

ability of the kidney to metabolize insulin, which will

increase circulating insulin and contribute to hypogly-

cemia (Answer A is correct). The Vd of insulin in AKI

is not well studied and has not been linked with epi-

sodes of hypoglycemia (Answer B is incorrect). Hepatic

impairment may increase the risk of hypoglycemia

with insulin, but an increase in hepatic metabolism

is unlikely to affect the risk of hypoglycemia in AKI

(Answer C is incorrect). Insulin resistance has been

reported in patients with AKI, but this would not con-

tribute to hypoglycemia (Answer D is incorrect).