13. Pharmacokinetics II

Question 1

A pharmacist is working on R&D of a new drug which works primarily by Phase II reactions. What is true of this kind of drug.

A. Involved in conjugation reaction between drug and acetate
B. Involved in decoxylations
C.An example is Cyclophosphamide
D. Often involves hydrolysis of an ester or amide linkage
E. Usually converts the parent drug to a more polar metabolite

RFA

Answer 1

ANS. A Phase II is involved is conjugation of GAS (Glucuronate, acetate, sulfate) and primally in the cytosol

B. Phase I (primarily in the ER)

C. Prodrugs

D. Prodrugs

E .Phase I

Question 2

A 32 year old man is smoking a cigarette and drinking beer. What of the listed would have the same effect on the mans rate of metabolism of alcohol.

A. Ketoconazole
B. Grapefruit juice
C. Chloramphenicol 
D. St. John's Wort
E. Amiodarone

RFA

Answer 2

D. St. Johns Wort - induces the CYP3A4 increasing metabolism. Just like cigarettes increase alcohol metabolism.

All the other are drugs that inhibit P450 and metabolism

Question 3

You are treating a TB patient who recently traveled to Zambia. Which of the following drug increases transcription of cytochrome P450?

A. Amiodarone
B. Cimetidine
C. Erythromycin
D. Ketaconazole
E. Rifampin 

SZ

Answer 3

Ans. E Rifampin

The remaining drugs are enzyme inhibitors.

Question 4

A suicidal 21 y/o female takes an entire bottle of acetaminophen. You administer N-acetylcysteine as an antidote. What is the mechanism of the antidote?

A. It carboxylates acetaminophen
B. Increases production of NAPQ1
C. Supplies cysteine for glutathione replenishment
D. Inhibits CYP3A4 and P-glycoprotein in the intestine
E. Decreases excretion of mercaptopuric acid

SZ

Answer 4

Ans. C
Supplies cysteine for glutathione replenishment.

Glutathione converts the toxic metabolite NAPQ1 to be converts to Mercaptopuric acid which can be excrete in the urine.