Tolerance is the need for an increased dosage of a drug to produce the same level of analgesia that previously existed. Tolerance also occurs when a reduced effect is observed with constant dose. Analgesic tolerance is not always evident during opio id treatment and is not addiction. When a once-fixed opioid dose is no longer effective, the above conditions should be reviewed to exclude pseudotolerance. Physical dependence can be described as the occurence of withdrawal syndromes after opioid use is stopped or quickly decreased without titration.
Physical dependence can also occur if an antagonist is admisnistered.
It is not addiction. Pseudoaddiction is drug-seeking behavior that seems similar to addiction, but is due to unrelieved pain. This behavior stops once that pain is relieved, often through an increase in the opioid dose. Misunderstanding of this phenomenon may lead the clinician to inappropriately stigmatize the patient with the label 'addict'. In the setting of unrelieved pain, the request for increases in drug dose requires careful assessment, renewed efforts to manage pain and avoidance of stigmatizing labels.