Naltrexone is classified as which type of opioid?

Naltrexone is classified as an antagonist because it works by blocking the effects of opioids at the receptor level, specifically at the mu-opioid receptors. This action helps to prevent the euphoric effects that opioids produce, making it useful in treating opioid dependence and overdose.

By attaching to the mu receptors, naltrexone prevents other opioids from binding to these sites and activating them, which would typically lead to pain relief and feelings of euphoria. This blocking mechanism is beneficial for individuals who are recovering from opioid addiction because it diminishes the rewarding effects of opioid use, thereby reducing the likelihood of relapse.

In contrast, an agonist stimulates the receptor to produce effects, an agonist/antagonist has properties of both activating and blocking receptors, and a selective mu-1 receptor antagonist would target a specific subtype of receptors rather than providing a broader blockade of opioid effects. Thus, the classification of naltrexone as an antagonist is based on its primary action of opposing the effects of opioids rather than mimicking or partially activating the receptors.