[W3] Therapeutic drug monitoring Flashcards
(39 cards)
What is therapeutic drug monitoring (TDM)?
The use of drug measurements in body fluids to aid the management of drug therapy.
What is the main goal of TDM?
To optimize treatment outcomes and avoid adverse drug effects.
Why are only a small number of drugs measured routinely via TDM?
Only drugs that meet specific criteria benefit from routine TDM.
What are the four main criteria for a drug to be suitable for TDM?
- Poor correlation between dose and effect
- Good correlation between concentration and effect
- Lack of other clinical/laboratory markers
- Narrow therapeutic index
What is meant by a ‘narrow therapeutic index’?
A small range between therapeutic and toxic concentrations of a drug.
What does ADME stand for?
Absorption, Distribution, Metabolism, Excretion.
What is pharmacokinetics?
The study of how the body affects a drug (ADME processes).
What is pharmacodynamics?
The study of how a drug affects the body at the site of action.
What variation makes a drug ideal for TDM?
High pharmacokinetic variation and low pharmacodynamic variation.
Give an example of when clinical markers make TDM unnecessary.
Measuring blood pressure for antihypertensives or glucose for hypoglycaemics.
Why is TDM helpful when no other markers of effect exist?
It helps assess drug efficacy or toxicity when clinical signs are unclear.
Why might symptoms of toxicity be confused with disease symptoms?
Because some toxic effects mimic the underlying illness being treated.
What must be considered before requesting TDM?
- Clinical question
- Patient details
- Proper sample
- Accurate analysis
- Interpretation and action
What information should accompany a TDM request?
- Age
- Sex
- Renal/hepatic function
- Drug name
- Dose
- Route
- Timing
- Other medications
What type of sample is commonly used for TDM?
Serum or plasma; whole blood for some drugs like tacrolimus.
When are trough samples usually taken?
Just before the next dose, to assess the lowest drug concentration.
What methods are used to measure drug levels in TDM?
- Immunoassay
- HPLC
- Liquid chromatography-mass spectrometry (LCMS)
Why must TDM assays be specific?
To avoid interference from other compounds or drug metabolites.
What is the guiding principle in interpreting TDM results?
Treat the patient, not the number—clinical context is critical.
Name antibiotics commonly monitored using TDM.
- Gentamicin
- Tobramycin
- Vancomycin
Name anticonvulsants that require TDM.
- Phenytoin
- Carbamazepine
Name immunosuppressants monitored via TDM.
- Ciclosporin
- Tacrolimus
- Sirolimus
What cardiac drug is commonly monitored?
Digoxin.
What antidepressant is commonly monitored?
Lithium.
