/reference/drugs/narcotic-reversals
Naloxone, naltrexone, methylnaltrexone
Pure mu-opioid receptor antagonist
Competitive antagonist at mu (μ), kappa, and delta opioid receptors with highest affinity for μ. Reverses respiratory depression, sedation, analgesia, miosis, pruritus, GI hypomotility from exogenous opioids.
Long-acting pure opioid receptor antagonist
Competitive antagonist at μ, κ, δ opioid receptors. Long half-life makes it useful for opioid use disorder maintenance — but poses major perioperative challenges if patients with chronic naltrexone need opioid analgesia.
Peripherally-acting μ-opioid receptor antagonist (PAMORA)
Quaternary derivative of naltrexone — does NOT cross the blood-brain barrier. Reverses peripheral opioid effects (constipation, urinary retention, pruritus) without antagonizing central analgesia.