Therapeutic Drug Monitoring

Question 1

What is meant by first order kinetics?

Answer 1

Rate of elimination is proportional to the amount of drug

Question 2

What is meant by zero order kinetics?

Answer 2

Rate of elimination is independent of the amount of the drug (ethanol, phenytoin, salicyclates)

Question 3

Give examples of drugs with a wide therapeutic index

Answer 3

NSAIDs, benzodiazepines, antibiotics, beta blockers

Question 4

Give examples of drugs with a narrow therapeutic index

Answer 4

Anti-epileptics (phenytoin, sodium valproate), lithium, strong antibiotics (gentamycin, amikacin, vancomycin), digoxin, immunosuppressives (ciclosporin, tacrolimus)

Question 5

What drug levels are commonly monitored during their use?

Answer 5

Digoxin, aminophylline, phenytoin, carbazmazepine, lithium, gentamycin, amikacin, vancomycin, ciclosporin

Question 6

What are digoxin levels affected by?

Answer 6

Renal impairment, amiodarone and hypokalaemia

Question 7

When should you check genatmycin levels?

Answer 7

o If they are taking once daily – check level dose after 3 doses
o If they have renal impairment – check their trough level
o For multiple daily dosing (as in infective endocarditis) – do a peak level after the 3rd dose and a trough level before the next dose

Question 8

When should you check digoxin levels?

Answer 8

6 hours after previous dose