Naloxone is a potent, competitive opioid antagonist with high affinity for mu-opioid receptors. It is a pure antagonist with no agonist properties. The 40 mcg strength is primarily used in the context of opioid-induced side effect management, particularly in post-operative settings or for opioid-induced pruritus, rather than for acute overdose reversal which requires higher doses. It rapidly reverses the effects of natural and synthetic opioids.
Adult: For Opioid Reversal (Standard): 0.4 mg to 2 mg (400 mcg to 2000 mcg) IV/IM/SC/IN. For Opioid-Induced Side Effect Management (Low Dose): 40 mcg (0.04 mg) IV boluses, titrated to effect. May be diluted in saline and given as an infusion (e.g., 40 mcg/hr) in post-operative settings.
Note: For the 40 mcg dose: Often administered intravenously as a slow bolus (over 30-60 seconds) to manage side effects. Can be administered IM, SC, or intranasally for overdose, but 40 mcg is insufficient for that purpose. For IV use, may be diluted with Normal Saline or 5% Dextrose. Must have resuscitation equipment available. Monitor patient closely for re-sedation.
Naloxone is a competitive antagonist at mu, kappa, and delta opioid receptors, with the highest affinity for the mu-opioid receptor. It displaces opioid agonists from these receptors without activating them, thereby rapidly reversing central and peripheral effects of opioids, including respiratory depression, sedation, and hypotension.
Pregnancy: Category B (US FDA). Crosses the placenta. Use only if clearly needed. May precipitate withdrawal in the opioid-dependent fetus. Should be used for life-threatening opioid overdose in the mother.
Driving: Naloxone administration reverses sedation. However, patients recovering from opioid overdose or sedation should be advised not to drive or operate machinery until fully recovered and medically cleared, as re-sedation can occur.
| Opioid Agonists (Morphine, Fentanyl, Tramadol, etc.) | Naloxone will reverse the analgesic and adverse effects of these drugs. May precipitate withdrawal in dependent patients. | Major |
| Opioid Partial Agonists (Buprenorphine) | Reversal may be incomplete and require higher, repeated doses of naloxone due to buprenorphine's high receptor affinity. | Major |
| Clonidine | Naloxone may theoretically reverse the hypotensive effects of clonidine. In overdose, naloxone may be used as an adjunct. | Moderate |
| Cardiotoxic Drugs (e.g., Halogenated Hydrocarbons) | Increased risk of ventricular arrhythmias when naloxone is administered. | Moderate |