When an opioid drug is used on a regular basis, the brain adjusts so the effects of the same amount of the drug become less over time. A person developing tolerance to opioid drugs may:
- Need larger amounts of the drug to get the same effect or “high”
- Experience reduced effects when taking the same amount of a drug
Tolerance levels can vary greatly between different people.
How does the body develop tolerance? Tolerance can occur when parts of the body affected by the drug begin to respond less to repeated stimulation over time. The body may also get better and faster at breaking down a specific drug over time.
Can tolerance be lost? Patients may lose their tolerance to an opioid if the drug is not taken for a period of time, such as during rehab, incarceration, or a period of successful abstinence in the recovery process. Because of this loss of tolerance, patients are more vulnerable to opioid overdose and death if they later return to the same doses of opioids to which they had previously been tolerant. Caution must be taken during these vulnerable periods of time and patients should be maintained on a medication for opioid use disorder to minimize the risk of relapse, overdose, and death. Patients should also be explained this change so they know they should be careful if they return to drug use.
How do doctors test for tolerance? Sometimes a person’s opioid tolerance is difficult to assess based on listening to a patient’s story. Laboratory tests, like blood tests to determine the level of opioids in the body, can be helpful when used along with a physical exam and signs of intoxication.
