Metabolism or Biotransformation

Question 1

Purposes of Metabolism or Biotransformation:

Answer 1

1. transform drugs from inactive to active or vice versa
2. transform drugs from bound form (inactive) to unbound or free form (free) or vice versa
3. transform drugs from non-polar (moderately lipid soluble) to polar (less lipid soluble or water soluble) to enhance renal excretion
4. formation of metabolites (inactive) by the active hepatic microsomal enzyme (cytochrome P-450) leading to termination of drug action (renal excretion)

Question 2

2 main Aims of Metabolism or Biotransformation:

Answer 2

1. meds reached the site of action (purpose 1-2)
2. enhance renal excretion of medication that failed to reach the site of action (purpose 3-4)

Question 3

convert parent drug to a more polar (water soluble) drug by unmasking or inserting polar functional group:

Answer 3

Phase 1 - Biotransformation

Question 4

– synthetic reaction that involves addition of polar moiety subgroup by conjugation to Polar functional group group during phase I reaction.

Answer 4

Phase 2 - Biotransformation

Question 5

This makes the drug more polar thus enhancing drug excretion.

Answer 5

Phase 2

Question 6

the Polar Functional Groups:

Answer 6

Hydroxyl - OH

Sulfhydryl - SH

Amine - NH2

Question 7

Polar moiety subgroup:

Answer 7

• Gluconate
• Acetate
• Glycine
• Glutathione
• Sulfate or Methyl Group

Question 8

Biochemical reactions involved in Phase 1 biotransformation:

Answer 8

• Oxidation
• Reduction
• Hydrolysis

Question 9

most common Biochemical reactions ,

involves addition of O2 or removal of H from drug

Answer 9

Oxidation

Question 10

Biochemical reactions that involves addition of H2 or removal of O2

Answer 10

Reduction

Question 11

Biochemical reactions when original drug is broken into separate parts

→ using enzyme Esterase

Answer 11

Hydrolysis

Question 12

Phase 2 Biochemical reactions– involves coupling of drug or metabolite to polar moiety

Answer 12

Conjugation

Question 13

– movement of drug molecules out of the body leading to termination of drug action

Answer 13

EXCRETION

Question 14

Drugs excreted are in ________ or metabolites thru the action of liver metabolism.

Answer 14

Polar (Water soluble) form

Question 15

Renal excretion types:

Answer 15

a. glomerular filtration
b. tubular secretions

Question 16

disappearance of active molecule of free form drug from blood circulation as it pass the liver metabolism (bile) thus related to termination of drug action

→ liver metabolism (free form + bile ) → intestine → feces

Answer 16

ELIMINATION

Question 17

*Drugs may be eliminated by ______ long before they are excreted by the kidneys

Answer 17

Liver metabolism

Question 18

Atropine is excreted ______ in urine thus used as test for atropine toxicity.

Ex. Cat’s eye test

Answer 18

Unchanged

Question 19

– rate of elimination is proportionate to the concentration of drugs in plasma

Answer 19

First Order Elimination

Question 20

-implies elimination at a constant rate regardless of the concentration of drugs in the plasma

Answer 20

Zero Order Elimination