What Do Opioid Agonists Do?

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As one of the world’s oldest known drug types, opioids include any drug or substance that produces morphine-like effects. Mainly used as pain-relieving agents, most all opioids carry a risk of addiction.

Prescription pain pills represent the largest group of opioid agonist substances, some of which include –

  • Percodan
  • Dilaudid
  • OxyContin
  • Atarax
  • Lortab
  • Demerol

Opioid agonists work in much the same way as heroin in terms of the how these drugs interact with the brain. While opioid agonists provide an invaluable source of pain relief for most any type of pain symptoms, these drugs can cause real damage to brain chemical functions as well as to brain cell structures.

Like all types of addictive drugs, opioid agonists target certain types of brain cell receptors, which in turn secrete various types of neurotransmitter chemicals. Understanding what opioid agonists do can go a long way towards helping a person avoid the many pitfalls that come with excess drug use.


The human body houses specialized cell receptor sites known as opioid receptors. Opioid receptors exist throughout the brain, central nervous system and gastrointestinal tract. Each receptor site secretes the body’s own pain-relieving chemicals, also known as endorphins.

According to Macalester College, opioid agonists work by activating the body’s receptor sites and triggering the release of endorphin chemicals. When opioids activate cell receptor sites, the release of endorphins blocks or muffles any incoming pain signals to the brain, which accounts for their pain relieving effects.

Opioid drugs also have a chemical make-up that’s quite similar to the body’s own endorphin substances. This similarity makes it possible for opioids to infiltrate and even overpower the body’s own natural chemical systems.

As a group, opioids come in synthetic and semi-synthetic forms. As synthetically-made drugs, opioids can deliver a range of analgesic effects that relieve different degrees of pain.

Some opioid agonist drugs act as full agonists while others produce a partial agonist effect. Whereas full agonists “fully” stimulate cell receptor sites, partial agonists don’t, which allows for varying effects depending on how any one drug is formulated.

Opioid Agonist Effects

Opioid agonist effects

Opioid agonists effect the brain and central nervous system.

Overall, opioid agonists act as depressants, which have a slowing effect on the brain and central nervous system. The endorphin chemicals involved in this exchange include –

  • Norepinephrine
  • Serotonin
  • Dopamine

These chemicals not only regulate pain and pleasure sensations, but also any and all bodily functions that rely on the brain and central nervous system. Bodily functions most affected include –

  • Heart function
  • Digestion
  • Respiratory function
  • Coordination and movement
  • Emotional responses
  • Cognitive functions
  • Body temperature regulation

Prescription agonists drugs, while effective, come with specific instructions regarding dosage levels, frequency of use and treatment duration times. As long as a person follows prescription guidelines, opioids carry little risk of abuse or addiction.

Unfortunately, opioids do produce certain unintended effects, such as feelings of euphoria and well-being. These aftereffects greatly increase the likelihood of abuse. Considering the wide range of effects opioids have on the body’s major systems, the abuse of opioids comes with widespread repercussions that can affect a person’s overall health and mental well-being.

Addictive Opioid Agonists

Technically speaking, most all types of opioid agonist drugs carry a potential for addiction. What most characterizes addictive opioid agonists has to do with how these drugs breed both a physical and psychological dependency when used for prolonged periods of time.

Heroin and prescription pain pills all carry a high addiction potential due to the way these drugs stimulate endorphin production in the brain, while at the same time causing actual structural damage to endorphin-secreting cell sites. This damage leaves cells less responsive to opioid agonist effects and impairs their ability to release endorphin chemicals.

People who’ve come to expect the “high” that comes with drug abuse will likely increase the dosage amount in order to experience the drug’s full effects. These interactions set the cycle of addiction in motion as cell sites will continue to deteriorate for as long as a person keeps using. Likewise, users will have to keep increasing their dosage amounts along the way.

Opioid Agonist Treatment Medications

As synthetically-made drugs, opioid agonists can be formulated to interact with brain cell receptor sites in different ways. In this manner, agonist-type drugs can be put to use as opiate addiction treatment medications.

Rather than “drain” receptor sites of endorphin chemicals, agonist treatment medications trigger chemical secretions at a slower rate. For people recovering from chronic opioid addictions, this slow-release effect can help relieve withdrawal effects and drug cravings.

According to the Mayo Clinic, medications commonly used in this capacity include –

  • Suboxone
  • Methadone
  • Slow-release morphine
  • Subutex
  • LAMM

The therapeutic effects of agonist medications also make for effective long-term maintenance therapies in cases where withdrawal aftereffects and drug cravings persist for months into the recovery process.

Possible Adverse Effects

Ideally, opioid agonists should only be taken on a short-term basis or else their “slowing” effects will start to take a toll on a person’s functional capacity. The chemical interactions that work to block pain signals to the brain have a cumulative effect in terms of the chemical imbalances that take shape with prolonged opioid use.

Adverse physical effects may take the form of –

  • Sedation
  • Confused thinking
  • Depressed breathing and heart rates
  • Brief lapses in consciousness
  • Excess sweating
  • Constipation

In cases where, cell receptor site damage increases at a rapid rate, users will likely experience withdrawal effects in response to the brain’s demand for increasingly larger amounts of the drug. Withdrawal effects typically take the form of –

  • Restlessness
  • Mood swings
  • Anxiety
  • Feelings of fatigue
  • Depression
  • Irritability

Addiction Risks

Addiction only becomes an issue when drug users start to believe they need the drug in order to cope with daily life. In effect, the drug’s ongoing effects on brain chemical balance have reached a point where the brain’s reward pathway has become warped in the process.

This reward pathway regulates the same cognitive functions that form a person’s belief systems, motivational influences as well as his or her emotional responses. With long-term use, the effects of opioid agonists on the brain’s reward pathway will start to play out in a person’s daily behaviors and routines, at which point addiction has taken hold.

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