drug biotransformation

Question 1

• Mechanism by which the body terminates the action of some drugs
• In some cases, it serves to activate prodrugs

Answer 1

DRUG BIOTRANSFORMATION OR METABOLISM

Question 2

TYPES OF METABOLIC REACTIONS

 Non-synthetic reactions
 Converts the parent drug to a more polar conjugate (water soluble) or inactive product
 Introducing/inserting/unmasking a polar functional group
 -OH, -SH, -NH2
 In some instances, it may modify or enhance the activity of the drug

Answer 2

PHASE I

Question 3

 Synthetic reactions

 Endogenous substrate is conjugated to the parent drug to make it more polar

Answer 3

PHASE II

Question 4

 Maybe metabolized by gastric fluid

 Must be given 2 hours before meals if given through the oral route

Answer 4

PENICILLIN

Question 5

DRUG INTERACTION

 1 + 1 = 2
 Response elicited by combined drugs is equal to the combined response of the individual drugs
 Sedative (chlorpheniramine maleate found in decongestants like Neozep + ethanol

Answer 5

1. ADDITIVE

Question 6

DRUG INTERACTION
 1 + 1 = 3
 Response elicited by combined drugs is greater than the combined responses of each individual
 Penicillin G (antibiotic) removes the cell wall of the organism
Gentamicin (aminoglycoside antibiotic) inhibits protein synthesis in the organism

Answer 6

2. SYNERGISTIC

Question 7

DRUG INTERACTION

 0 + 1 = 2
 Drug which has no effect enhances the effect of the second drug
 Cimetidine + heparin (anticoagulant
(Cimetidine enhances the anticoagulation)

Answer 7

3. POTENTIATION

Question 8

DRUG INTERACTION

 1 + 1 = 0
 Drug inhibits the effect of another drug
 Heparin + protamine

Answer 8

4. ANTAGONISM

Question 9

TYPES OF DRUG INTERACTION MECHANISM

Answer 9

 Altered absorption
Cholestyramine (binds bile in the GI tract and prevents its reabsorption) inhibits the effect of digoxin (drug for congestive heart failure) when combined with it
 Altered metabolism
Affects drug action
 Altered plasma binding protein
 Altered excretion
 Probenecid (drug that increases excretion of uric acid in the urine, for treatment of gout) inhibits the secretion of acids
 Penicillin inhibits the excretion of probenecid

Question 10

OTHER DRUGS METABOLIZED

Answer 10

 Gastric acid
• Penicillin

 Gastric and digestive enzymes
• Insulin
 Intestinal wall enzymes
• Epinephrine