Drug Metabolism and Excretion Flashcards
Explain the importance of drug metabolism; dosing, safety.
- Dosing issue
–> metabolism /clearance determines amount of drug at site of action and so steady state levels
-Safety
–> Daughter compounds may have side effects
Define and describe the two phases of drug metabolism: PHASE 1
PHASE 1
–> Add oxygen molecules to C/N/S in drug and this is done by Cytochrome P450 enzymes
-Oxygen binds to drug and other oxygen atom (o2) is reduced to water
Define and describe the two phases of drug metabolism: PHASE 2
PHASE 2
–> Conjugation of Phase 1 product with glucose increasing water solubility
Explain the role of drug metabolism in paracetamol overdose.
- No phase 1 metabolism
- phase 2 includes glucuronidation preventing doormat n of toxic quinone-mine
Describe the factors influencing drug metabolism and elimination.
- Age
–> Cytochrome P450 activity reduced in elderly/neonates
–> GFR reduced
–>Increased fat content in elderly
-Genetics
–> slow metabolism
Drug metabolising enzymes (induced/inhibited by other drugs).
–> Disease = liver toxicity, renal disease
Outline the general appreciation needed of ADME when prescribing
- Compliance
- Toxicity
- Drug interactions
- Therapeutic effets
- Individualise therapy