Therapeutic Drug Level Monitoring 

Carbamazepine - Sample immediately before next dose (trough) 

Clozapine - Sample immediately before next dose (trough) or at anytime if toxicity suspected 

Cyclosporin - Sample immediately before next dose (C0) or exactly 2 hours post dose (C2) 

Digoxin - Sample 8-24 hours post dose 

Gentamicin - Sample trough level 2-4 hours before next dose is due 

Lithium - Sample 12 hours post dose 

Phenobarbitone - Sample immediately before next dose (trough) 

Phenytoin - Sample at least 12 hours post dose (trough) 

Theophylline - For i/v infusion, sample at any time 

Tobramycin 

  - Trough: immediately before next dose 

  - Peak: 30 mins post dose 

Vancomycin 

  - Intermittent dosing: sample immediately before 4th dose 

  - Continuous infusion: sample after 18 hours duration 



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