L7 Drug Metabolism

Question 1

Pharmacokinetics

Answer 1

Absorption
Excretion
Distribution
Metabolism

Question 2

The conversion of the drug into a
more Water soluble compound.

Answer 2

Metabolism

Question 3

Family number
Subfamily
Isoenzyme numberThe main site of drug metabolism is
the …….

Answer 3

liver

Question 4

Family number
Subfamily
Isoenzyme number

Answer 4

CYP 3A4

Question 5

drugs or environmental pollutants can enhance the activity of hepatic metabolizing enzymes.

Answer 5

Enzyme inducers

Question 6

Increasing biotransformation of drugs

Answer 6

Enzyme inducers

Question 7

decreasing their plasma concentrations & pharmacologic effect.

Answer 7

Enzyme inducers

Question 8

N.B. if the metabolite is active, the drug activity is increased = prodrugs

Answer 8

Enzyme inducers

Question 9

Factors that inhibit hepatic metabolizing enzyme, Decreasing drug biotransformation

Answer 9

Enzyme Inhibitors

Question 10

leads to higher levels and greater potential for toxic effects with drugs
Example erythromycin, ketoconazole, Natural substances (grapefruit)

Answer 10

Enzyme Inhibitors

Question 11

Neonates
Starvation
Cancer
Liver disease
Enzyme inhibitors

Answer 11

Enzymatic inhibition

Question 12

 Environmental Contaminants as insecticides/pesticides
, Smoking

Answer 12

Enzymatic induction

Question 13

Drugs affecting activity of metabolizing enzymes
Enzyme inducers:

Answer 13

• Phenobarbitone
  *Phenytoin
  *Rifampicin
  *Carbamazepine

Question 14

Drugs affecting activity of metabolizing enzymes
Enzyme inhibitors

Answer 14

*Erythromycin
*Ketoconazole
*Grapefruit
*Cimetidine
*Clarithromycin

Question 15

The rate of drug metabolism and elimination is directly proportional to
the concentration of free drug, (Most drugs)

Answer 15

first-order kinetics (Linear kinetics):

Question 16

The mechanisms of metabolism and excretion are SATURABLE (At high drug concentration)

Answer 16

zero-order (non-linear kinetics):

Question 17

The mechanisms of metabolism and excretion are SATURABLE (At high drug concentration)

Answer 17

zero-order (non-linear kinetics):

Question 18

the rate of metabolism and excretion is constant. (does not depend on the drug concentration) e.g. aspirin in high doses

Answer 18

zero-order (non-linear kinetics):

Question 19

Mechanisms of hepatic drug metabolism
1. Phase I:

Answer 19

• reduction, oxidation, hydrolysis.
• may increase, decrease, or have no effect on pharmacologic activity.
• If the metabolite is sufficiently polar, it is excreted by the kidneys.
• many phase I metabolites are still too lipophilic to be excreted, they need phase-II.

Question 20

Mechanisms of hepatic drug metabolism
2. Phase-2

Answer 20

• conjugation reactions with an endogenous substrate, (glucuronic acid, sulfuric acid, acetic acid, or an amino acid)
• Some Drugs may enter phase II directly without prior phase I metabolism.
• It results in more water-soluble compounds that are often therapeutically inactive, then excreted by the kidney or in bile.