therapeutic index
The ratio between toxic and therapeutic doses of a medication, indicating its safety margin.
Full Definition
A pharmacological concept representing the ratio between the dose that produces toxicity and the dose that produces therapeutic effect, indicating how safe a medication is to use. A wide therapeutic index means there is a large safety margin between effective and toxic doses, while a narrow therapeutic index requires careful monitoring and dose adjustment. In psychopharmacology, lithium is the classic example of a medication with a narrow therapeutic index, requiring regular blood level monitoring. Understanding therapeutic index is essential for editors reviewing dosing guidelines and safety protocols.
Usage
Usage note: Often confused with 'therapeutic range' which refers to blood levels, not dose ratios.
In Context
- "Lithium's narrow therapeutic index necessitates frequent serum level monitoring." — Pharmacology review
- "Medications with wide therapeutic indices are generally safer for outpatient management." — Clinical practice guideline