Drug monitoring Flashcards
Digoxin toxicity
- Confusion
- Nausea
- Visual halos
- Arrhythmias
Lithium toxicity
- Early: tremor
- Intermediate: tiredness
- Late: arrhythmias, seizures, coma, renal failure, diabetes insipidus
Phenytoin toxicity
- Gum hypertrophy
- Ataxia
- Nystagmus
- Peripheral neuropathy
- Teratogenicity
Gentamicin and Vancomycin toxicity
- Ototoxicity
- Nephrotoxicity
general toxicity treatment (3)
- Stop drug
- IV fluids
- Antidote if exists
Gentamicin dosing
- most patients on high dose regimen of 5-7 mg/kg/day
- Severe renal failure (CrCl < 20) or endocarditis: divided daily doses (1mg/kg, 12hrly in renal failure, 8hrly in endocarditis
Once-daily regimen monitoring
- Measure 6-14 hrs after last gent infusion
- target is < 1
- OR use nomograms (Hartford > 7, Urban and Craig if >5)
- If falls within 24hr, continue at same dose, if higher up then increase intervals to this time
- If beyond 48 hrs then don’t give next dose until conc < 1mg/L
Warfarin anticoagulation treatment
If INR:
- <6: reduce warfarin dose
- 6-8: omit warfarin for 2 days, then reduce dose
- > 8: omit and give 1-5 mg PO Vit K
If >5 INR and minor bleed:
- Give 1-3 mg IV Vit K
If major bleed:
- Stop warfarin
- Give 5-10 mg IV Vit K
- Give prothrombin complex (Beriplex)
Vancomycin
Monitoring requirements
- Measure trough concentration before 3rd and 6th doses
- Measure levels after 36-72 hrs
- Concentration: 10-15 mg/litre
- Is nephrotoxic and excreted by kidneys so check renal function prior
Vancomycin toxicity
- Blood dyscrasias (do not need platelets or WCC prior to starting)
- Fever and chills
- N+V
- Red man syndrome
- Renal dysfunction
- Skin disorders → toxic epidermal necrolysis, Stevens-Johnson Syndrome
Statins
Monitoring
- AST
- Baseline, 3 months and 12 months after starting
- If AST/ALT > 3x times normal range, statins are CI or need to be stopped if already taking
Statins
CK
Statins are associated with a risk of myopathy in those with risk factors for it:
- a personal or family history of muscular disorders
- previous history of muscular toxicity
- a high alcohol intake
- renal impairment
- hypothyroidism
- elderly
When prescribing simvastatin, a creatine kinase level should be checked at baseline in these patients.
Phenytoin
Monitoring requirements
- Pre-dose trough dose (40 - 80 micromol/L)
Lithium
Monitoring requirements
- Measure 12 hrs post-dose
- FBC prior to initiation but no need after
- Routine serum lithium weekly after initiation, then every 3 months once stable
- Sodium depletion increases risk of toxicity, so patients should avoid making diet changes that might change sodium intake
Methotrexate
Monitoring requirements
- Monitor FBCs every 2-3months once stable
- Renal function
- Do not start methotrexate if liver problems
- Stop immediately if drop in WCC/platelets
- Only need to do CXR if pulmonary toxicity suspected
Lithium
Reference range
Toxicity beyond what?
Reference range 0.4-0.8 mmol/L
Toxicity < 1.5 mmol/L
Olanzapine
- Baseline fasting blood glucose then at regular intervals (hyperglycaemia)
- Baseline ECG only if CVS disease or RFs
COCP
- BP every 6 months
Amiodarone
Monitoring requirements
- Baseline CXR (risk of pulmonary toxicity)
- TFTs (T3, TSH and T4) baseline and every 6 months
- LFTs at regular intervals
- Commence in caution in hypokalaemia
Gentamicin
Monitoring requirements
Multiple daily dose routine:
- Peak (1-hour): 3-5 mg/L
- Trough (predose): < 1 g/L
- Monitor renal function at regular intervals
Ramipril
Monitoring requirements
- Serum urea and electrolytes (risk of hyperkalaemia, hyponatreaemia, AKI). Measure at baseline and after every dose change.
Digoxin
Monitoring requirements
- Renal function
- Serum potassium is particularly relevant as hypokalaemia can increase risk of digoxin toxicity
- Only measure serum concentration if suspect toxicity
- HR in hospital before administration
Sodium Valproate
Monitoring requirements
- ALT - risk of hepatotoxicity, at baseline and regularly throughout
Clozapine
Monitoring requirements
- FBCs every week for first 18 weeks
- STOP if low WCC
