Question

A 50-year-old male patient has high cholesterol

levels and is placed on lovastatin. He is
counseled
to stop drinking his usual glass of
grapefruit juice every morning.
Given that grapefruit juice interferes with
lovastatin action, which one of the following
best explains this interaction?
(A) Grapefruit juice inhibits the cytochrome
p450 enzyme which modifies lovastatin for
excretion.
(B) Grapefruit juice stimulates the cytochrome
p450 enzyme which modifies lovastatin for
excretion.
(C) Grapefruit juice is a competitive inhibitor
of lovastatin binding to cholesterol.
(D) Grapefruit juice is a competitive inhibitor
of HMG-CoA reductase.
(E) Grapefruit juice reduces the maximal
velocity
of HMG-CoA reductase.

Answer 1

Grapefruit juice inhibits the cytochrome P450 enzyme, particularly CYP3A4, which is responsible for metabolizing lovastatin, thus interfering with its excretion and potentially elevating its levels in the body.

Step-by-step explanation:

The interaction between grapefruit juice and lovastatin is a known issue in the management of patients with high cholesterol levels. The correct explanation for this interaction is: (A) Grapefruit juice inhibits the cytochrome P450 enzyme which modifies lovastatin for excretion. This enzyme, specifically CYP3A4, is responsible for metabolizing many drugs, and grapefruit juice contains compounds that inhibit this enzyme. As a result, the metabolism and excretion of lovastatin are decreased, leading to higher levels of the drug in the body, which can increase the risk of side effects such as muscle pain or rhabdomyolysis.