Therapeutic window (or pharmaceutical window) is an index for estimation of drug dosage which can treat disease effectively while staying within the safety range. In other words, it is the dosage of a medication between the amount that gives an effect (effective dose) and the amount that gives more adverse effects than desired effects. For instance, medication with a small pharmaceutical window must be administered with care and control, e.g. by frequently measuring blood concentration of the drug, since it easily loses effects or gives adverse effects.
This index is believed to be more reliable than that of therapeutic index since this index considers the biological variation among individuals to a larger extent.