Written By: Ehsan Jahandarpour

Tolerability refers to the degree to which overt adverse effects of a drug can be tolerated by a patient. Tolerability of a particular drug can be discussed in a general sense, or it can be a quantifiable measurement as part of a clinical study. Usually, it is measured by the rate of “dropouts”, or patients that forfeit participation in a study due to extreme adverse effects. Tolerability, however, is often relative to the severity of the medical condition a drug is designed to treat. For instance, cancer patients may tolerate significant pain or discomfort during a chemotherapeutic study with the hope of prolonging survival or finding a cure, whereas patients experiencing a benign condition, such as a headache, are less likely to.