Drug Metabolism

Question 1

What are xenobiotics?

Answer 1

-foreign substances that are absorbed or ingested

Question 2

What is a pro-drug?

Answer 2

• a compound with little or no activity that is metabolized to an active species in order to:
  1) promote absorption
  2) prevent acid destruction
  3) minimize exposure toxicity

*e.g. L-dopa

Question 3

What is the first-pass effect?

Answer 3

-occurs when more than half of the amount of a drug is metabolized on its 1st pass through an organ (usually the liver)

Question 4

What are the three general properties of metabolites?

Answer 4

1. more polar than the parent compound
2. not as well reabsorbed and therefore more efficiently excreted
3. many will become inactive or less active than their parent compound

Question 5

The _______ is the most important organ for elimination of drugs and their metabolites.

Answer 5

Kidney

Question 6

Excretion of drugs and metabolites in the urine involves three processes:

Answer 6

• glomerular filtration
• active tubular secretion
• passive tubular reabsorption

Question 7

Which of the following processes in the kidney is affected most by drug metabolism?

1. glomerular filtration
2. active tubular secretion
3. passive tubular reabsorption

Answer 7

3. passive tubular reabsorption

* metabolite is more polar than administered drug. Harder to reabsorb.

Question 8

Why are drugs able to be metabolized by enzymes?

Answer 8

Drugs are structural analogs of naturally occurring substrates

Question 9

The kinetics of drug metabolism reactions at ‘therapeutic doses’ is typically ______ order.

Answer 9

First

Question 10

The kinetics of drug metabolism reactions at saturation is _______ order.

Answer 10

Zero

Question 11

What types of reactions occur in phase I metabolism vs Phase II metabolism?

Answer 11

Phase I:

• oxidation
• reduction
• hydrolysis

Phase II:
-Conjugation

Question 12

What are the requirements of the Cytochrome P450 system?

Answer 12

• Reduced NADPH

- O2

Question 13

Is cytochrome P450 mainly involved in Phase I or Phase II metabolism reactions?

Answer 13

Phase I

oxidation

Question 14

Is P450 developed in neonates?

Answer 14

-Yes, but it functions slower

Question 15

Which of the following drugs will cause an increased metabolism of combination pill oral contraceptives?

A. ampicillin
B. ciprofloxacin
C. erythromycin
D. tetracycline

Answer 15

A. ampicillin

&

D. tetracycline

Question 16

What does cytochrome P450 actually do?

Answer 16

-Oxidize drugs

OXIDATION