Therapeutic Drug Monitoring

Question 1

Indications for TDM

Answer 1

Optimise dose/ therapeutic response
Avoid Toxicity 
Monitor Compliance
Detect Resistance
Detect changes in PK (pregnancy, young and elderly)

Question 2

Appropriate drugs for TDM

Answer 2

Drugs with narrow therapeutic range (lithium, digoxin, aminoglycosides, warfarin)

High interpatient variability in plasma concentrations (i.e. Phenytoin)

Correlation between concentrations and clinical effect

Pharmacological effect dependent on plasma concentration

Question 3

Special considerations: Warfarin

Answer 3

Eat vit K

Question 4

Food interactions: Grapefruit juice

Answer 4

Inhibits PGP, an efflux transporter in gut

Question 5

Saturable metabolism

Answer 5

Phenytoin (small dose increase –> big concentration increase)

Question 6

Non saturable metabolisms

Answer 6

?

Question 7

narrow range drugs

Answer 7

List

Question 8

TCA overdose issue

Answer 8

Prolonged qt

Question 9

Factors affecting drug concentrations

Answer 9

Absorption rate (route, drug nature and acidity, coating of drug)
Drug interactions (inducers and inhibitors)
Metabolism (substrates of enzymes)
Excretion/elimination (renal vs hepatic impairment)