Chapter 8 Qs: Drug Monitoring Flashcards Preview

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Flashcards in Chapter 8 Qs: Drug Monitoring Deck (14):
1

Most suitable approach to monitoring statins

think most suitable option e.g. statins

→ myopathy if RFs (personal/FH of muscular disorders/toxicity, +++alcohol, renal impairment, hypothyroidism, elderly) = check baseline creatine kinase.

→ if no RFs, measure serum ALT

2

Q8.1: IV Vancomycin Monitoring

Q8.1: IV vancomycin.

  • Check serum creatinine at baseline, as clearance of vancomycin reduced in renal dysfunction + important for choosing dosing regimen.
  • 2 classic S/Es = nephrotoxicity + ototoxicity.

3

Q8.3: Phenytoin monitoring 

  • Phenytoin given at initial loading dose of IV 1200mg + maintenance dose 300mg orally daily.
  • Day 14 trough = 54micromoles/L (in N range).
  • So, 300mg is a reasonable dose.
  • Post-dose phenytoin levels not routinely required as half-life of phenytoin ~24h so significant diurnal variation unlikely after 14days.
  • N range should be considered in context of patient – if no seizures, don’t increase dose.
  • If S/Es despite N trough level, then decrease dose (if seizures controlled) or seek alternative.

4

Q8.4: Lithium Drug monitoring

  • Recommended sampling time for lithium = 12h after last dose. N RR = 0.4-0.8mmol/L.
  • FBCs not routinely required.
  • Routine serum lithium monitoring = weekly after initiation + after each dose change until stable concentrations, then every 3 months thereafter.
  • Sodium depletion >risk of lithium toxicity so avoid diet changes.

5

Q8.5: Methotrexate Drug Monitoring

  • Methotrexate can cause fatal blood dyscrasias.
  • FBC is monitored regularly, but once stabilised, reduce to 2-3months.
  • CXR not needed at baseline.
  • Due to risk of liver cirrhosis, don’t start if LFTs abnormal.
  • If significant WBC/platelets drop, must STOP it.
  • Predominantly renally excreted so toxicity more likely if renal dysfunction.

6

Q8.6: Olanzapine Drug Monitoring

  • For olanzapine, fasting blood glucose should be measured at baseline as hyperglycaemia + diabetes can occur.
  • Baseline ECG only indicated if CV disease or RFs.

7

Q8.7: COCP drug monitoring

  • For COCP (ethinylestradiol), measure BP as HTN >risk of arterial disease associated with contraceptive medication.
  • Don’t need monitoring of serum creatinine, resting HR, serum AST or haemoglobin.

8

Q8.8:Amiodarone Drug monitoring

  • For amiodarone, do baseline CXR.
  • T3, TSH + T4 all needed as T4 may be raised without hyperthyroidism.
  • Monitor LFTs regularly throughout not just if suspected hepatotoxicity.
  • Dose of amiodarone independent of renal function (renal failure not a S/E).
  • Commence with caution if hypokalaemia as increased risk of arrhythmias.

9

Q8.9:Carbimazole drug monitoring

  • Carbimazole + sore throat = infection from possible BM suppression – so need FBC with neutrophil count.
  • Throat swab won’t reveal BM suppression.
  • Blood cultures indicated later.
  • Carbimazole can cause hepatic disorders (option is to measure ALT), but not key here.
  • TFTs not relevant first-line.

10

Q8.10:Gentamicin Drug Monitoring

  • For multiple daily dose regimen, 1 hour peak serum concentration should be 3-5mg/L for treatment of endocarditis (just check BNF for this).
  • Gentamicin principally renally excreted from body, so renal dysfunction >toxicity risk, so monitor renal function at regular intervals.

11

Q8.11: ACEi Drug Monitoring

ACE-i known to cause hyperkalaemia + hyponatraemia – in some cases, AKI. Check U&Es at baseline + after every dose change.

ACE-i do not affect HR, urinary sodium not a suitable method, urine output measurement not practical in primary care setting, can measure serum levels of ACE but not relevant for monitoring – and also elevated in sarcoidosis.

12

Q8.12:Digoxin Drug Monitoring

  • Plasma digoxin concentration not measured unless toxicity/non-compliance/inadequate effect (even though listed first on BNF, it doesn’t say to monitor it per se).
  • Digoxin predominantly renally excreted so measure serum creatinine.
  • BP + CXR + serum sodium not required – not specific as doesn’t cause hypotension, no pulmonary S/Es + not specific enough and checked as part of U&Es.
  • Serum potassium more relevant as hypokalaemia increases risk of digoxin toxicity.

13

Q8.13: Sodium Valproate Drug Monitoring

  • Sodium valproate therapy → hepatotoxicity + liver function – measure at baseline + regular intervals throughout duration.
  • Pancreatitis = S/E but amylase only measured if symptoms.
  • Vitamin D supplements considered as S/E is osteoporosis but not checked at baseline.
  • Serum potassium not required.
  • Renal function not routinely required as neither significantly renally excreted nor nephrotoxic.

14

Q8.14: Clozapine Drug Monitoring

Clozapine = risk of neutropenia + fatal agranulocytosis, so monitor FBCs weekly for 18months – all must register with clozapine monitoring service.

Serum creatinine not routinely required.

If leucocytes or neutrophils drop, then STOP clozapine immediately – don’t just reduce the dose!