Opioid tolerance: the clinical perspective.

Uncertainty about the clinical significance of tolerance to opioid analgesia has important and diverse implications. Although understanding of the characteristics and mechanisms of experimental tolerance has grown, the clinical correlates and ramifications of these findings remain ambiguous to practitioners prescribing long-term opioid therapy to patients for the treatment of malignant and non-malignant pain. In this review I shall discuss clinical aspects of tolerance and the associated phenomena of dependence, withdrawal and addiction to opioids as they apply to the practice of clinicians who manage patients with chronic malignant and non-malignant pain.