Opioid drugs are either derived from the Asian poppy plant or made into synthetic chemicals that are designed to chemically resemble opium or derivatives of opium. They all share a similar mechanism of action.

These drugs bind to the neural receptor sites in the brain that are specialized for neurotransmitters involved in reducing the subjective experience of pain, stress, and exertion. Opioid drugs are chemically similar to these neurotransmitters (enkephalins and endorphins), so they are primarily used to reduce the experience of pain.

Opioids also have the side effect of producing euphoria, relaxation, and feelings of overall well-being. This mechanism of action results in these substances being used for recreational purposes. Ultimately, they carry a very significant potential for abuse.

What Is The Difference Between An Opioid, An Opiate, And A Narcotic?

Originally, the labels opioid, opiate, and narcotic were designed to differentiate between three effects of drugs that had similar mechanisms of action.

The term opioid was initially used for any drug that was believed to attach to the opiate receptors in the brain. The term opiate was first used to refer to medications that were directly developed from opium. The term narcotic was initially used to describe any medication that produced drowsiness or sleepiness, though law enforcement agencies often refer to any illicit or controlled substance as a narcotic.

These specific definitions are no longer utilized. The three terms essentially refer to the same class of drugs.

Why Are There So Many Different Opioid Drugs?

Numerous drugs are classified as opioids, and the classification is based on the mechanism of action discussed above. Different opioids are developed to address different situations. Because of individual differences in body chemistry, some individuals may have a better response to one opioid compared to another.

Having a large array of opioids allows physicians to treat many levels of pain, to use opiates to treat other issues such as chronic coughing, and to offer variability in the treatment of pain for people who have very intense pain and people who have milder levels of chronic pain.

All opioid drugs are listed as controlled substances by the U.S. Drug Enforcement Administration (DEA). They all require a physician’s prescription to legally obtain and use them.

How Does Medical Use Differ From Abuse?

The clinical term substance use disorder is used to define either drug abuse or addiction to drugs. Any abuse of a substance refers to a chronic pattern of using it in a manner that is not consistent with its purpose or using illicit drugs for recreational purposes.

Medical use refers to the application of medications for their recognized purpose. The use of controlled substances medicinally is defined as using the medication under the supervision of a physician.

Even though people who use opioid medications under the supervision of a physician for lengthy periods will experience some of the effects listed here, chronic abuse is more likely to produce more severe and longer-lasting effects.

The Effects Of Opioid Use On The Reward Pathways In The Brain

Chronic use of opioids will have many effects on the brain and spinal cord (CNS: the central nervous system). Some of the most prevalent effects include alterations in the reward pathways of the brain, which occur with repeated use of nearly any drug, including opioids.

The reward pathways of the brain primarily use the neurotransmitter dopamine. Over time, structural changes to these areas of the brain occur with repeated use.

  • The stimulation of the release of neurotransmitters associated with opioid use leads to the system reducing the numbers of neurons specialized for these specific neurotransmitters (dopamine, endorphins, enkephalins, and others). This is a natural reaction (downregulation) for the system to attempt to maintain balance.
  • The effects of downregulation result in the person eventually having greater difficulty experiencing pleasure from events that usually would give them pleasure. They then use more and more of the drug to experience pleasure.
  • The system also increases the output of neurotransmitters, hormones, and other substances that offset the effects the drug produces (upregulation).
  • The effects of upregulation lead to the person feeling irritable and nauseous as well as other adverse emotional and physical states when they are not using the drug.
  • Upregulation and downregulation are associated with the development of physical dependence (tolerance and withdrawal).

Other Central Nervous System Effects

Long-term use of opioids is associated with several other changes to the CNS.

  • Compensatory alterations in other neural pathways of the brain and spinal cord
  • Changes in the structure and function of many of the neurons in the brain due to the direct and indirect effects of the drug
  • Alterations in the vascular structure of the brain and spinal cord due to the stimulation of the drug increasing the activity in some areas and decreasing activity in others
  • An increased risk of other pathological brain conditions, including increased risk for brain damage (encephalopathy), disease, and head trauma

Other Physical Effects Of Long-Term Opioid Abuse

Long-term opioid use and abuse have many other potential physical effects.

  • These substances are central nervous system (CNS) depressants, meaning they slow down the functioning of the CNS. This reduced functioning also affects breathing rate. Over time, one will be more susceptible to diseases and conditions that affect their lungs, such as pneumonia, bronchitis, and other serious respiratory issues.
  • Increased susceptibility to numerous diseases as a result of injecting opiates can occur over time, including increased risk to contract hepatitis, HIV, and others.
  • Chronic use of opiate drugs can lead to a significant burden on the liver and kidneys, leading to the potential for many diseases, including cancer, cirrhosis, renal failure, and other conditions.
  • Chronic abusers of opiates often begin to neglect various aspects of their self-care, which can lead to physical and mental issues, including nutritional deficiencies, increased risk for infection or disease, poor dentition, and other potential problems.

Cognitive, Emotional & Social Issues

Chronic opioid abuse leads to damage that will affect other areas of life.

  • Potential cognitive issues can occur associated with the effects of the drug and the alterations occurring in the CNS. These can include problems with attention, memory, judgment, and even physical movement due to brain damage.
  • Individuals with opioid use disorders are often diagnosed with some other co-occurring mental health disorder, such as major depressive disorder, trauma- and stressor-related disorders, and anxiety disorders.
  • Issues with relationships, employment, school, finances, and freedom (due to potential incarceration) can result from chronic opioid use.

Research has suggested that individuals who have chronic opioid use disorders:

  • Demonstrate lower levels of achievement in life
  • Report lower levels of overall life satisfaction
  • Have far lower life expectancies
  • Have higher rates of criminal convictions and incarceration
  • Demonstrate significantly higher rates of serious medical problems
  • Have higher rates of divorce, unemployment, and suicide attempts

Complications Associated With Physical Dependence On Opioids

Opioids are notorious for producing physical dependence in people who use them for more than a few weeks. Physical dependence on an opioid is not considered to be a serious issue when the person is using the medication under the supervision of a physician.

Patients take the drug regularly in prescribed doses, and any physical dependence is typically not serious or problematic.

Abusers of drugs take them in far higher amounts than individuals who use them medicinally, and they often use them in a fashion that leads to even greater tolerance, such as injecting. For abusers of opioids, physical dependence becomes a motivating factor to use the drug more often because the withdrawal symptoms are typically highly distressing.

They use to avoid withdrawal symptoms, and this behavior fuels the cycle of addiction. Opioid abuse becomes a type of lifestyle, such that the person needs the opioid just to get through the day.

Are These Effects Reversible?

The brain’s ability to repair itself (neuroplasticity) is remarkable but limited. Most individuals will experience some reversal of the effects of opioid use, but the actual reversal of any physical and neurological effects of drug use is dependent on many factors.


Older individuals will experience less of a reversal than younger ones in most cases.

Affected Systems

Some systems repair more easily than others. For instance, liver damage may not be reversible after a certain point.

Extent Of Abuse

People who used the drug for longer or in higher doses will experience less reversal.

The bottom line is that anyone at any level of abuse will experience some resolution of the effects, but numerous factors will determine how much of the damage is reversible. To experience any potential reversal, one must stop all opioid abuse.

Treatment Can Facilitate Positive Change

Treatment in a formal substance use disorder recovery program can go a long way in reversing the effects of opioid drug abuse. Individuals who adhere to their treatment plans have the best chance to get the full potential of recovery.

Anyone who believes they have a problem with opioid abuse should discuss their situation with a licensed addiction treatment professional.

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