What is “opioid tolerance”?
In general, tolerance to a drug occurs when, with continuous administration over time, greater amounts of that drug are required to achieve the original degree of its desired therapeutic effect. Patients will develop tolerance to both the analgesic effect as well as the side effects of opioids.
To avoid the adverse drug reaction of fatal respiratory depression, minimum opioid dosages that assure tolerance have been defined. The minimum dosage at which a patient is deemed “opioid tolerant” is oral morphine 60 mg/day, or oxycodone 30 mg/day, or an equi-analgesic (morphine mg equivalent) dose of another opioid for at least 1 week. Patients are considered “opioid naïve” if they have not taken opioids at these specific dosages for a week or longer.