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Flashcards in Drug Metabolism Deck (18)
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1
Q

Drug metabolism

A

Biochemical modification of pharmaceutical substances by living organisms usually through specialised enzymatic activity

2
Q

How does drug metabolism limit life of substance in the body?

A

Rendering lipid soluble compounds water soluble to be excreted

3
Q

Lipid soluble drug reabsorption

A

Passively from renal or extra renal back into blood

4
Q

Where are most drugs metabolised before excretion?

A

Liver, lining of gut, kidneys, lungs

5
Q

Pro drugs

A

Some drugs are pro drugs and only become active after metabolism eg codeine

6
Q

What are some effects of toxic metabolites

A

Direct toxicity
Carcinogenesis
Teratogenesis

7
Q

Metabolising enzymes

A
  • wide substrate specificity and many metabolise a drug

- Expressed constantly or when needed

8
Q

Phase 1 metabolism steps

A
  • Oxidation
  • reduction
  • hydrolysis
9
Q

What does phase 1 metabolism do?

A

Increases polarity and provides an active site

Introduce or expose polar groups

10
Q

Cytochrome p450

A

Enzymes in liver which are important in oxidative drug metabolism
Isoform determines drug specifity

11
Q

CYP 1

A

CYP1A2 induced by smoking so a higher dose of theophylline needed

12
Q

CYP2

A

CYP2D6 metabolise antidepressants and codeine and are reduced in 5-10% of population and are induced by smoking q

13
Q

CYP3A4

A

Major liver enzyme works on a wide range of drugs eg cyclosporine and also found in gut for pre systemic metabolism

14
Q

Phase 2 reactions

A

Conjugation - Eg acetate, sulphate attached to metabolite from phase 1

15
Q

What does phase 2 reactions do?

A

Increase water solubility and enhance secretion of metabolised compound
Mostly inactivation although sometimes activation

16
Q

What do endogenous substances do in phase 2?

A

Donates portion of itself to the foreign molecule

17
Q

What factors affect metabolism?

A

Age, sex, ethnicity, pregnancy, liver disease, genetics, other drugs

18
Q

Drugs which can inhibit drug metabolising enzymes

A

Erythromycin

Grapefruit