Therapeutic index

Therapeutic index


The therapeutic index is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes death. A drug with a narrow therapeutic range usually needs to have its dosage adjusted according to measurements of the actual blood levels achieved in the person taking it.

Important drugs used in psychiatry with a narrow therapeutic index (and therefore require monitoring) are:-

  • Carbamazepine
  • Lithium
  • Phenytoin