Metabolism Flashcards
(26 cards)
When does metabolism occur?
Prior to and during absorption
What is first pass metabolism?
Drugs go via liver and liver breaks down drug
What 4 major metabolic barriers much drug pass before reaching general circulation?
- Intestinal lumen
- Intestinal wall
- Liver
- Lung
What does intestinal lumen do?
- Digestive enzyme secreted by mucosal cells and pancreas
- Certain enzymes break down proteins and stop them being absorbed
What does intestinal wall do?
Rich in enzymes that further metabolise drugs
What do lungs to?
Cells of lungs have high affinity for many drugs and are site of metabolism for many local hormones
What does liver do?
Major site of drug metabolism
What are the 2 phases of metabolism?
Phase 1 –> Oxidation, reduction and hydrolysis
Phase 2 –> Conjunction
What is result of phase 1?
Forms more reactive products, sometimes toxic
What is result of phase 2?
Usually forms inactive and readily excretable products (hydrophilic drug)
What are the family of enzymes in the liver called?
Cytochrome P450 (CYP450) system
Individual one called isoenzyme
What are enzyme inducers in regards to CYP450 system?
When are they given?
Enhance production of liver enzymes which breakdown drugs
Given alongside drugs
What is result of enzyme inducers?
Faster rate of drug breakdown
Can lead to drug not being in system long enough
What are enzyme inhibitors in regards to CYP450 system?
Inhibit production of enzymes that breakdown drugs
What is result of enzyme inhibitors?
Reduced rate of drug breakdown
End up with too much drug in system
What is result of too much warfarin?
Bleeding
What happens during paracetamol overdose?
- All receptors become saturated
- Paracetamol cannot go down normal conjunction route
- Goes back to oxidation route via phase 1
- Production of toxic metabolite (NAPQI)
What is given during paracetamol overdose?
Acetyl cysteine - push it back down conjugation route
What is bioavailability?
Proportion of dose that reaches systemic circulation (only really applies to oral medication)
What is bioequivalence?
What is benefit?
2 or more products are chemically/pharmaceutically equivalent
May replace one with another without causing clinical problems
What is metabolism?
- Process to alter drugs to facilitate their removal from the body
- The activation of inactive drug
- Production of active drug with increased activity from active drug
- Inactivation of active drug change in nature of activity
What is warfarin?
Anticoagulant, or blood thinner. It makes your blood flow through your veins more easily. This means your blood will be less likely to make a dangerous blood clot.
If a patient on warfarin is given an inducer, what is effect on warfarin levels?
Decrease
What is normal metabolism of paracetamol?
Paracetamol –> paracetamol glucuronide / paracetamol sulphate
Goes down conjugation route
