07 - Drug elimination Flashcards
Drugs are eliminated by being metabolised. Drug metabolism is…
The enzymatic modification of the drug
3 Phases of drug metabolism
- Drug
- Derivative
- Conjugate
During metabolism, drugs may be modified by (5)…
- Oxidation
- Hydroxylation
- Dealkylation
- Deamination
- Hydrolysis
Cytochrome P450 is what kind of enzyme?
Isoenzyme
Cytochrome P450 (or CYPs) introduce a functional group. This is called…
Functionalisation
Cytochrome P450 contains a heme cofactor (True / False)
True
Cytochrome P450s are highly expressed within (2)…
Intestines and liver
Cytochrome P450s are found in the…
Endoplasmic Reticulum
Ethanol is metabolised by P450 (True / False)
False
Ethanol is an exception
Phase II reactions are conjugation reactions, such as…
Glucuronidation
Conjugation reactions further decrease…
Lipid solubility (usually resulting in an inactive metabolite)
Genetic factors may influence drug metabolism. For example some people may be either…
Fast or slow metabolisers
Age influences drug metabolism beyond just the differences in size and weight. Explain this effect for two age groups…
- Neonates (<6wks) have low CYP, conjugating activity
2. The elderly, as CYP activity declines with age
What is the effect of induction of drug metabolising enzymes on:
a) rate of metabolism
b) pharmocological effect
a) increases
b) increases
What is the effect of inhibition of drug metabolising enzymes on:
a) rate of metabolism
b) pharmocological effect
a) decreases
b) decreases
Decreased metabolism, decreased…
Pharmocological effect
Renal excretion can eliminate proteins with a molecular weight (MW) of:
a) > 20,000
b) 10-20,000
c) <20,000
d) <500
c) <20,000
pKa of a drug is equivalent to the pH at which…
50% of the drug is ionised in solution
Ionised drugs can’t…
Move through membranes
To estimate % ionisation, subtract…
pKa of the drug from the pH of the solution
Drug metabolism involves how many phases?
2 (Phases I & II)
Phase I metabolism is highly dependent on…
Cytochrome P450 isoenzymes
Phase II metabolism improves excretion by…
Increasing water solubility
Drug metabolism can be altered by a variety of Endogenous or Exogenous factors that alter the function of…
Enzymes involved in phases I and II
