Opioids are a class of drugs that broadly includes heroin, hydrocodone, oxycodone, and other morphine-derived drugs. Brain abnormalities can result from chronic use of such drugs, causing tolerance, dependence, and addiction.

Dependence can resolve after detoxification. Addiction, however, has complex and long-lasting effects, involving craving that can lead to relapse long after the patient’s dependence resolves.

Psychological and Analgesic Tolerance

Psychological tolerance develops quickly, meaning a user must take more and more of the medication to achieve the same effect, often in doses significantly higher than a therapeutic dose for pain. In contrast, analgesic tolerance develops slowly. Patients with stable pain may be able to stay on the same dose for months or years.

Tolerance often accompanies dependence. When tolerance occurs, it can be difficult to evaluate whether a patient is developing a drug problem or has a medical need for higher doses to control symptoms (NIDA, 2020, June).

Dependence

Dependence is caused by physiologic adaptations due to chronic exposure to a drug. It is often part of addiction, but they are not equivalent. Addiction involves changes to brain circuitry and is distinguished by compulsive drug seeking and use despite negative consequences (NIDA, 2020, June).

Those who are dependent on a medication will experience unpleasant physical withdrawal symptoms when they abruptly reduce or stop use of the drug. These symptoms can be mild to severe, depending on the drug, and can usually be managed medically or avoided by slowly tapering down the drug dosage (NIDA, 2020, June).

Addiction

Addiction is characterized by inability for abstention, craving, impairment in behavioral control, diminished recognition of significant problems with one ’s behaviors and interpersonal relationships, and a dysfunctional emotional response. Like other chronic diseases, addiction often involves cycles of relapse and remission. Without treatment or engagement in recovery activities, addiction is progressive and can result in disability or premature death (ASAM, 2015).

Clarifying the difference between dependence and addiction is important to understanding of the issues in opioid use and abuse. Dependence, the physical tolerance of the drug, requires increased amounts of the drug to achieve the desired response. Withdrawal of the drug will result in physical symptoms such as shaking, tremors, nausea, and vomiting. Addiction/substance use disorder is a behavioral disorder that refers to the emotional desire for the drug and the desired effects it brings, which often creates strong drug-seeking behaviors.

Opioid Use Disorder

The DSM-5 defines opioid use disorder (OUD) as characterized by loss of control of opioid use, risky opioid use, impaired social functioning, tolerance, and withdrawal. Tolerance and withdrawal do not count toward the diagnosis of OUD in people experiencing these symptoms when using opioids under appropriate medical supervision. Diagnosis of OUD covers a range of severity and replaces what DSM-IV termed “opioid abuse” and “opioid dependence.”

Generally, those who are dependent on opioids vary between feeling sick without the drug and desiring the high that follows after taking the drug. Being addicted to the drug (having OUD) will motivate a person to do whatever it takes to procure and take the drug to avoid the dreaded withdrawal symptoms. Prescription Drug Monitoring Programs (PDPMs) are designed to identify patients who are drug-seeking or at risk for opioid use disorder.