Tolerance, dependence and addiction: Definitions and Misconceptions

Tolerance, physical dependence and addiction: Definitions, clinical relevance and misconceptions


Definition: Tolerance is a physiological state characterized by a decrease in the effects of a drug (e.g., analgesia, nausea or sedation) with chronic administration.


  • To some, the need to increase the dose in response to the patient’s report of pain is misinterpreted as a sign that tolerance may be developing. Unfortunately, this sometimes leads the physician to reduce the dose in a mistaken attempt to avoid or delay the development of tolerance. The appropriate response is to reassess the pain and increase the dose as indicated to relieve pain.
  • Sometimes, to prevent the development of analgesic tolerance, opioids are administered at intervals which are too far apart to maintain continuous pain relief. This practice is inappropriate because it subjects patients to needless cycles of pain and pain relief.
  • Often, health care professionals and patients are concerned about using opioids from the 3rd step of the WHO ladder, such as morphine, because of the mistaken belief that the medication will lose its analgesic effect; they want to save it until the pain is really severe. This concern about analgesic tolerance is unfounded and can lead to inadequate pain management.
  • Some health care workers and patients believe that using morphine for pain relief will suppress respiration and possibly cause death. In fact, clinically significant respiratory depression and sedation are very rare in cancer patients. This is because tolerance to the sedative effects of morphine develop rapidly, and because pain reverses morphine’s depressant effects


Physical dependence is the physiological adaptation of the body to the presence of an opioid. It is defined by the development of withdrawal symptoms when opioids are discontinued, when the dose is reduced abruptly or when an antagonist (e.g., naloxone) or an agonist-antagonist (e.g., pentazocine) is administered.


  • Physical dependence is frequently equated mistakenly with addiction. It is incorrect to use the term ‘physical dependence’ (a physiological state) to describe addiction (a dysfunctional psychological and behavioral syndrome).
  • Patients who express concern about physical dependence should be given correct information and reassured. Example: “Do not to stop taking your medication abruptly or you will have symptoms of withdrawal. If you no longer need opioids for pain relief (for example after a course of radiotherapy), your physician can gradually decrease your dose over several days.”


While tolerance and physical dependence are physical changes in the body, addiction is defined by aberrant changes in behavior. Addiction is compulsive use of drugs for nonmedical reasons; it is characterized by a craving for mood altering drug effects, not pain relief.

Addiction means dysfunctional behavior, in sharp contrast to the improved function and quality of life that result from pain relief. Aberrant behaviors which indicate addiction may include: denial of drug use; lying; forgery of prescriptions; theft of drugs from other patients or family members; selling and buying drugs on the street; using prescribed drugs to get “high”.


  • People who fear addiction, yet desire pain relief sometimes think “So what if I get addicted, I am going to die anyway.” Such thinking creates an unnecessary trade-off between addiction and pain relief; in fact, addiction is rare and should not be a worry when opioids are used appropriately to relieve pain.
  • Patients and family members who express concern about addiction should be given correct information and reassured. Example: “Sometimes patients taking opioids for pain relief are concerned about addiction. However, you are taking opioids for pain relief whereas addicts take drugs to get high. You are not an addict if you take pain medications to relieve your pain.”


Definition Pseudo-addiction describes what happens when healthcare workers perceive as addictive behavior a pain patient’s requests for more or stronger pain medications. In fact, the patient’s behavior may be a response to inadequate pain management. Pseudo-addictive behavior is pain-relief seeking behavior. Pseudo-addiction is an iatrogenic phenomenon, e.g. it is when problems result from the treatment efforts of health professionals.



1 thought on “Tolerance, dependence and addiction: Definitions and Misconceptions

  1. painkills2

    “To some, the need to increase the dose in response to the patient’s report of pain is misinterpreted as a sign that tolerance may be developing.”

    I was just reading how some doctors believe that anything more than one increase in dosage is a red flag. But I remember a frequent change in dosages during the first year and a half I was on opioid treatment, when my doctor and I were attempting to figure out the best combination of medications. All these fears and restrictions are just creating less options for pain patients, and more under-treatment of pain. Obviously.



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