Chapter 8 Qs: Drug Monitoring Flashcards
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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!*
