If you’ve been addicted to any form of opiods for very long then at some point you may have researched your addiction and heard the terms “opiate agonists” and “opiate antagonists”. If you were like me your next thought was What the fuck is that? Allow me to demystify them.
Agonists vs. Antagonists
An agonist is a drug that activates certain receptors in the brain. Full agonist opioids activate the opioid receptors in the brain fully resulting in the full opioid effect. Examples of full agonists are heroin, oxycodone, methadone, hydrocodone, morphine and others.
An antagonist is a drug that blocks opioids by attaching to the opioid receptors without activating them. Antagonists cause no opioid effect and block full agonist opioids. Examples are naltrexone and naloxone. Naloxone is sometimes used to reverse a heroin overdose.
Buprenorphine is a partial agonist, meaning it activates the opioid receptors in the brain, but to a much lesser degree than a full agonist.
Buprenorphine also acts as an antagonist, meaning it blocks other opioids, while allowing for some opioid effect of its own to suppress withdrawal symptoms and cravings.
How Opioids Work
Opioids attach to receptors in the brain. Normally these opioids are created naturally in the body. Once attached, they send signals to the brain which blocks pain, slows breathing, and has what I call “the warm fuzzy blanket feeling”.
Opioids can activate receptors in the brain because their chemical structure mimics that of a natural neurotransmitter. This similarity in structure” fools” the brains receptors and allows the drug to lock onto and activate the nerve cells. Although these drugs mimic brain chemicals, the don’t activate nerve cells in the same way as a neurotransmitter, and they lead to abnormal messages being transmitted through the network.
Opioids target the brain’s reward system by flooding the circuit with dopamine. Dopamine is a neurotransmitter present in regions of the brain that regulate movement, emotion, cognition, motivation and feelings of pleasure. The overstimulation of this system, which rewards our natural behaviors, produces the euphoric effects sought by people who abuse drugs and causes them to repeat the behavior.
The Very Special People
Patients with chronic pain who require high doses of opioids to achieve pain relief show exceptionally high rates of defects of the cytochrome P450 (CYP450) enzyme system compared with the general population.
The CYP450 enzyme system is known to play an important role in the metabolism of opioids, and recent advances in genetic testing allow for the easy detection of defects to the enzymes.
A small percentage of the population literally don’t feel the effects of opioids due to this defect.
When I was laying in jail once withdrawaling from heroin I remember thinking, “Now why couldn’t I have been one of those people?
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Memoirs of a Former Junkie 