The therapeutic range is the range of drug concentrations in the plasma/blood which produce the desired therapeutic effects with minimum adverse effects.
Examples of the therapeutic range of some drugs
| Digoxin |
0.6 - 2 ng/ml |
Nortriptyline |
50 - 150 ng/ml |
| Lidocaine |
1 - 6 ug/ml |
Phenobarbital |
10 - 30 ug/ml |
| Phenytoin |
10 - 20 ug/ml |
Carbamazepine |
4 - 12 ug/ml |
| Theophylline |
10 - 20 ug/ml |
Quinidine |
2 - 6 ug/ml |
| Procainamide |
4 - 8 ug/ml |
Ethosuximide |
40 - 100 ug/ml |
The correlation between the drug plasma/blood concentration and the effect of the drug is much better than the correlation between the administered dose and the drug effect. This is because of the inter-patient variability in drug pharmacokinetics which affects the rate of drug disposition.
