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Flashcards in drug biotransformation Deck (10):
1


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

DRUG BIOTRANSFORMATION OR METABOLISM

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

PHASE I

3


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

PHASE II

4


 Maybe metabolized by gastric fluid
 Must be given 2 hours before meals if given through the oral route

PENICILLIN

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

1. ADDITIVE

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

2. SYNERGISTIC

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)

3. POTENTIATION

8

DRUG INTERACTION

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

4. ANTAGONISM

9

TYPES OF DRUG INTERACTION MECHANISM

 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

10

OTHER DRUGS METABOLIZED

 Gastric acid
• Penicillin

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

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