A framework for quantifying the influence of adherence and dose individualization.

A failure to accommodate for a patient's imperfect adherence may result in therapeutic failure. Similarly, failure to accommodate a patient's individual needs via dose individualization may also result in poor patient outcomes. The property of a drug that signifies the likelihood of therapeutic success to imperfect adherence is termed "forgiveness." We introduce an extension to this concept as: (1) a priori forgiveness (forgiveness when dose individualization is not considered) and (2) a posteriori forgiveness (forgiveness when considering dose individualization). We illustrate cases when adherence is of primary importance and in which dose individualization is of primary importance. The concept of a priori forgiveness and a posteriori forgiveness provides a quantitative measure that allows the influence of adherence to be disentangled from dose individualization and could be used to provide clear guidelines about the relative importance of each in clinical practice.