Therapeutic drug monitoring

Question 1

what are the signs of acute phenytoin toxicity?

Answer 1

nystagmus, ataxia, slurred speech, confusion, seizures

Question 2

what is phenytoin used for

Answer 2

seizures

Question 3

what are some chronic side effects of phenytoin

Answer 3

gingival hyperplasia, hirsutism, asplastic anaemia, hepatitis, myelosuppresion/agranulocytosis

Question 4

when is pheytoin monitored?

Answer 4

not routinely
trough levels immediatedly after dose if adjusting dose, signs of toxicity or non-adherence

Question 5

how do you manage phenytoin toxicity

Answer 5

largely supportive

Question 6

what is digoxin used for

Answer 6

rate control in AF, sometimes heart failure

Question 7

when is digoxin monitored? how should it be measured?

Answer 7

not routinely, only in suspected toxicity - should be measured between 8-12 hours from last dose

Question 8

features of digoxin toxicity?

Answer 8

arrhythmias (reverse tick sign ECG), heart block, confusion, yellow-green vision (xanthopsia), gynaecomastia

Question 9

what electrolyte abnormality classically precipitates digoxin toxicity

Answer 9

hypokalaemia

Question 10

what can precipitate digoxin toxicity

Answer 10

hypokalaemia (and thus thiazides)
renal failure
elderly

Question 11

how is digoxin toxicity treated

Answer 11

Digibind (digoxin immune fab)

Question 12

what is lithium used for

Answer 12

replapse of mania in bipolar disorder

Question 13

what are the signs of lithium toxicity

Question 14

when should lithium be monitored

Answer 14

-12 hours post dose
-after starting lithium levels should be monitored weekly and after each dose change until concentrations are stable.
-after that check every 3 months
-thyroid & liver function should be checked every 6 months

Question 15

features of lithium toxicity

Answer 15

CHAPS

-coarse tremor/coma
-hyperreflexia
-acute confusion
-polyuria
-seizures

Question 16

what can precipitate lithium toxicity

Answer 16

-dehydration
-renal failure
-hyponatraemia
-diuretics

Question 17

treatment of lithium toxicity

Answer 17

-IV saline
-haemodialysis in severe toxicity

Question 18

features of aminoglycoside abx toxicity (eg. gentamicin, vancomycin)

Answer 18

-ototoxicity (tinnitus & deafness)
-nephrotoxicity (renal failure)
-nystagmus

Question 19

how to monitor gentamicin

Answer 19

both peak (1 hr after administation) and trough (just before next dose) are measured - plasma concentration

Question 20

how to manage gentamicin toxicity

Answer 20

omit/reduce next dose

Question 21

when is gentamicin contraindicated

Answer 21

myasthenia gravis

Question 22

what is theophylline used for

Answer 22

bronchial smooth muscle relaxation - asthma

Question 23

features of theophylline toxicity?

Answer 23

arrythmias, convulsion, anxiety, tremor, dilated pupils, vomiting, hypokalaemia

Question 24

how is theophylline toxicity managed?

Answer 24

-measure acute levels
-give activated charcoal regardless of time
-supportive management
-definitive treatment: haemodialysis

Question 25

what can precipitate theophylline toxicity

Answer 25

acute illness and meds (erythromycin, ciprofloxacin)

Question 26

why are loading doses used?

Answer 26

to increase the initial blood concentraiton & reduce time needed to reach steady state

Question 27

which drug cannot be found in hair

Answer 27

cannabis (level too low)

Question 28

what recreational drug can increase CK and cause rhabdo

Answer 28

ecstasy