Therapeutic Drug

Therapeutic Drug Information

Clinical
Biochemistry

These ranges were replaced with National Pathology Harmonisation Ranges on April 16th 2012.
Click here to view the new ranges.

The ranges below applied between 1^st April 2007 and 16^th April 2012, and NO LONGER APPLY.

Previous "molar" therapeutic ranges used prior to this date can be viewed here.

Measurement of the concentration of a therapeutic drug in serum/plasma can serve as a useful aid in patient management. The aim of this analytical service is to help physicians tailor drug therapy to individual needs so that the beneficial effects of drugs are optimised and toxicity is minimised. Measurement of drug levels may be of value in assessment of compliance, therapeutic control, and confirmation of clinical toxity. Individual drug pharmacokinetics may be influenced by many factors. For advice concerning interpretation or for drug assays not included in the table below, please contact the Duty Biochemist or Medical Staff.

Drug Therapeutic Range Units Half life Sampling Time Time to
Steady
state

Carbamazepine 4.0 - 10.0 mg/L 12 hrs pre-dose 2 - 6 days

Cyclosporin A^* See CYA therapeutic ranges ug/L 2 - 6 hrs pre-dose 2 -3 days

Digoxin 1.00 - 2.00 ug/L 36 - 48 hrs pre-dose but at least 6hrs post-dose 5 - 7 days

Lamotrigine 3.0 - 15.0 mg/L 20 - 30 hrs pre-dose 4 - 15 days

Lithium 0.40 - 1.00 mmol/L 18 - 36 hrs pre-dose (12h) 3 - 7 days

Phenobarbitone 10.0 - 30.0 mg/L 96 hrs pre-dose 10 - 25 days

Phenytoin 8.0 - 15.0 mg/L 7 - 42 hrs pre-dose 7 - 35 days

Tacrolimus Renal transplant: 10 - 20
Auto-immune disease: 5 - 15
pre-dose (trough) samples
Values >20 may be associated
with nephrotoxicity, glucose
intolerance etc. ug/L 4 - 33 hrs pre-dose 2 days

Theophylline 10.0 - 20.0 mg/L 3 -13 hrs pre-dose (or see below) 2 -3 days

sampling time: oral dosing - pre and/or 2 - 4 hrs post dose
infusion - sampling at least 2 hrs into a 24hr infusion

Valproic acid 50 - 100 mg/L 8 - 20 hrs pre-dose 2 - 4 days

N.B. Toxic effects for some drugs may be observed at the upper limit of therapeutic levels.
N.B. To aid interpretation, time of sampling relative to the dose must be specified.

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Drug	Therapeutic Range	Units	Half life	Sampling Time	Time to Steady state
Carbamazepine	4.0 - 10.0	mg/L	12 hrs	pre-dose	2 - 6 days
Cyclosporin A^*	See CYA therapeutic ranges	ug/L	2 - 6 hrs	pre-dose	2 -3 days
Digoxin	1.00 - 2.00	ug/L	36 - 48 hrs	pre-dose but at least 6hrs post-dose	5 - 7 days
Lamotrigine	3.0 - 15.0	mg/L	20 - 30 hrs	pre-dose	4 - 15 days
Lithium	0.40 - 1.00	mmol/L	18 - 36 hrs	pre-dose (12h)	3 - 7 days
Phenobarbitone	10.0 - 30.0	mg/L	96 hrs	pre-dose	10 - 25 days
Phenytoin	8.0 - 15.0	mg/L	7 - 42 hrs	pre-dose	7 - 35 days
Tacrolimus	Renal transplant: 10 - 20 Auto-immune disease: 5 - 15 pre-dose (trough) samples Values >20 may be associated with nephrotoxicity, glucose intolerance etc.	ug/L	4 - 33 hrs	pre-dose	2 days
Theophylline	10.0 - 20.0	mg/L	3 -13 hrs	pre-dose (or see below)	2 -3 days
sampling time:	oral dosing - pre and/or 2 - 4 hrs post dose infusion - sampling at least 2 hrs into a 24hr infusion
Valproic acid	50 - 100	mg/L	8 - 20 hrs	pre-dose	2 - 4 days