Elementary Drug Metabolism

Question 1

Drug metabolism

Answer 1

Process of converting drug into active or innactive form.

Question 2

Prodrug:

Answer 2

drug given in innactive form

Question 3

Liver:

Answer 3

where Phase I and Phase II mostly take place

Question 4

Portal vein:

Answer 4

transports drug to liver

Question 5

Hepatic enzymes:

Answer 5

(embedded in SER of liver hepatocytes) break down drug

Question 6

Orally administered drug:

Answer 6

reduced bioavailability when metabolised in liver

Question 7

Bioavailabillity

Answer 7

Amount of drug that reaches systemic circulation for that route of administration

Question 8

Phase I metabolism:

Answer 8

• change in the drug by oxidation, reduction or hydrolysis
  
  • Form metabolites that are active and/or toxic
  • Converts non-polar, lipid-soluble medications into more polar water-soluble.

Question 9

Oxidation

Answer 9

Accomplished by cytochrome P450 (CYP 450) enzymes

Question 10

Toxicity of paracetamol

Answer 10

• Paracetamol converted to toxic metabolite by P450
• Not enough enzymes to detoxify this metabolite at large dose of paracetamol

Question 11

Phase II metabolism:

Answer 11

involves combination of the drug w polar molecules to form a water-soluble metabolite - conjugate

Question 12

Conjugation:

Answer 12

involves the reactive group produced by phase I

Question 13

Glucuronidation

Answer 13

• Addition of naturally present molecules in body to drug
• Drug is conjugated to glucose through the enzyme: uridine diphosphate-glucoronosyltransferase

Question 14

Poor metabolisers:

Answer 14

higher drug plasma levels (dangerous side effects)

Question 15

Rapid metabolisers:

Answer 15

reduced drug action (more likely to experience side effects)

Question 16

Difficulty in metabolising certain medications, at birth:

Answer 16

metabolic enzymes not fully developed

Question 17

Difficulty in metabolising certain medications, elderly individuals:

Answer 17

enzymatic activity reduced