TDM Flashcards
What does TDM assess
Therapeutic compliance - see if the patient is taking the meds
If the drug is actually working
The cause of drug induced toxicity
Pharmacokinetics
How the body deals with the drug
Absorption, dosage intervals, excretion and metabolism
Pharmacodynamics
How the drug works on the body
Conc of drug at active site
How the drug works
What is a sub therapeutic response
Ineffective dosage
What is an adverse response
The dosage of the drug is above the therapeutic window causing side effects
What needs to be considered for dosage
Other medications, age, health, ethnicity
Absorption/metabolism/excretion of the drug 
Timing between dosages
Drug half life
When do you use TDM for a drug
If used chronically
Narrow therapeutic index
Variable pharmacokinetics
Problem with compliance
Severe side effects if failed
When is digoxin given
For heart failure like afib
How does digoxin work
It inhibits Na/K transporters leading to an increased internal Na and Ca conc to make a greater force of concentration
How is digoxin measured
Immunoassays
Like have digoxin like proteins in the body causing interference
Digoxin - blood vs tissues
Peaks in 2-3 hours in the blood
Peaks in 6-10 hours in the tissue
Conc in tissue is 15-30 times greater
When is digoxin measured
At the trough
Who can tolerate higher doses of digoxin
Children
Most excreted unchanged in urine some metabolised
Digoxin toxicity symptoms
Nausea
Vomiting
Anorexia
Heart problems - tachycardia, arrhythmia, PVCs, ventricular bigeminy
What to consider for digoxin toxicity
Dosage
Last dose time
Test for digoxin like immunoreactive substance assay
Test K and Mg as low levels increase sensitivity
What does lord of paracetamol lead too
Hepatic toxicity
Converted to NAPQ1, if this builds up it leads to necrosis
NAPQ1 converted to cysteine conjugates by GSH, this gets quenched with too much paracetamol
Do you always treat a paracetamol overdose
You want to reduce hepatic toxicity but treatments have effects too so not always needed
Depends on when dose was last taken and how much is left in the blood so if it’s above the red line you must treat if below blue low risk, if green depends if they already have liver dysfunction
What conc in blood means paracetamol danger
After 4 hours if it is greater than 200mg/L
Or if the half life of the drug is over 2-4 hrs you need treatment and LFTs
What is aspirin converted too
Salicylic acid
How quickly is aspirin distributed to all the tissues
Within 30 mins
Excreted unchanged within 36 hours
What can aspirin cause
Hyperventilation
Respiratory alkalosis
Levels of aspirin lethal
Above 500 Mg/kg
Less than 150 Mg/kg not toxic
Treatment for aspirin overdose
Activated charcoal will stop further absorption
Sodium bicarbonate via IV correct the acid-base
Increase excretion (sodium bicarbonate IV and potassium)
When do you do osmolarity gaps
When you don’t know what the patient has taken
