Therapeutic Drug Monitoring Flashcards
Name 3 common drugs that are TDM’d
- Thyroxin - hypothyroidism
- Warfarin - blood thinner
- Paracetamol - acute poisoning
Why is it important to monitor drugs?(3)
To ensure that the correct dose is achieved at a steady-state level in the patient
May result in toxicity
Suspected drug overdose
Define pharmacodynamics
The effects of the drug at a cellular and whole body level.
▸concentration at the drug target (receptor)
▸Tissue responsiveness
▸Other drug interactions
Define pharmacokinetics
The kinetics of drug uptake, tissues distribution, metabolism and elimination.
Name the 4 key considerations when interpreting drug levels
Timing
Units
Clinical information
Drug metabolites
Define pharmacogenetics
How a drug response is influenced by genes
Define Cytochrome P450
Detoxification system that modifies substances to make them more readily secreted from the body by increasing soluability.
Acts on both endogenous and exogenous substances
Humans have 57x P450 cytochromes
What are the three possible outcomes of drugs metabolised by P450
1️⃣Inactivation
2️⃣Activation
3️⃣Formation of a toxic metabolite
Name three specialised tests employed in TDM
Ethylene glycol
Lithium
Methanol
What is the antidote for paracetamol poisoning?
N-Acetylcysteine
Explain paracetamol poisoning
Normally detoxified by glutathione conjugation in the liver
Hepatocyte necrosis
At therapeutic doses oxidation by P450 is a minor route
In overdose, the normal conjugation syste is overloaded and the P450 pathway becomes more important => more NAPQI
Glutathione also becomes depleted and cannot detoxify NAPQI
Signs and symptoms of paracetamol poisoning
<24hrs nausea and vomiting
24-48hrs abdominal pain; hepatic tenderness
>48hrs jaundice; liver failure
Administration of ________________ is effective within the first hour of paracetamol overdose.
Active charcoal
List three factors that affect effective drug concentration
Demographics
Physiology
Chemical interactions
