Recommendations for Therapeutic Drug Monitoring

Also see 'Biochemistry' on Trust Intranet for sample type, test frequency and target range.

Drug (Therapeutic range)	Sample size (ml)	Tube	Recommended minimum time from start of therapy to sampling	Optimum sample time
Phenobarbitone (70-140 micromols/L)	5	Plain (Serum)	14 days	Unimportant (but must be standardised)
Phenytoin (30-70micromol/L)	5	Plain (Serum)	7 days	Pre-dose
Carbamazepine (20-50micromol/L)	5	Plain (Serum)	14 days for new therapy, 3-5 days for dose change	Pre-dose
N.B. One 5ml sample suffices for any combination of anticonvulsant requests
Teicoplanin (Severe infection 20-60mg/l, other infections 10-60mg/l)	5	Plain (Serum)	4 to 7 days	Pre-dose
Theophylline (10-20mg/L)	5	Plain (Serum)	Variable depends on formulation. Contact lab.	Oral peak, slow release sample after 4 hrs. Oral peak, rapid release sample after 2 hrs. Trough pre-dose.
Digoxin (1-2.5nmol/L)	5	Plain (Serum)	7 days	At least 6 hours post dose.
Lithium (0.5-0.8mmol/L)	5	Plain (Serum)	4-5 days	12 hours post dose
Gentamicin	1	Plain	Refer to pharmacy or microbiology or to 'Protocol for extended interval gentamicin dosing'
Tobramycin (Peak 6-10mg/L) (Trough 0.5-2mg/L)	1	Plain	Around 3rd dose	Pre-dose and 1 hour post completion of infusion.
Vancomycin (Peak < 30mg/L) (Trough < 5-10mg/L)	1	Plain	Around 3rd dose	Pre-dose and 2 hours post completion of infusion.