Therapeutic Index
TIDefinición
The ratio between the toxic dose and the therapeutic dose of a drug (TD50/ED50). A narrow therapeutic index means there is a small margin between the dose that produces the desired effect and the dose that causes toxicity, requiring careful dosing and monitoring.
Ejemplo
Lithium has a narrow therapeutic index (blood levels of 0.6-1.2 mEq/L are therapeutic, while levels above 1.5 mEq/L can be toxic), requiring regular blood monitoring.