Head-to-head clinical analysis & difference comparison: details on mechanism of action, dosing, half-life, interactions, and maternal-fetal safety.
NALOXONE vs EVZIO
Clinician-reviewed, head-to-head comparison of mechanism, dosing, pharmacokinetics, and safety profiles.
Last clinically reviewed: July 2026 · OpiCalc Medical Review Team
Competitive antagonist at mu, kappa, and delta opioid receptors, reversing opioid effects.
Naloxone is an opioid antagonist that competitively binds to mu-opioid receptors, reversing opioid-induced respiratory depression and analgesia.
Reversal of opioid overdose,Reversal of opioid-induced respiratory depression,Treatment of opioid-induced pruritus,Diagnosis of opioid dependence
Emergency treatment of known or suspected opioid overdose, as manifested by respiratory and/or central nervous system depression.
0.4-2 mg IV/IM/SC, may repeat every 2-3 minutes; if no response after 10 mg, reconsider diagnosis.
2 mg intramuscular (IM) or subcutaneous (SC) autoinjector into anterolateral thigh; repeat every 2-3 minutes as needed for opioid overdose.
60-90 minutes in adults; shorter in neonates (3 hours); prolonged in hepatic impairment (up to 2-3 hours).
The terminal elimination half-life of naloxone in adults is approximately 1-2 hours. In neonates, half-life may be prolonged to 3-4 hours. Clinical context: Short half-life necessitates repeated dosing or continuous infusion for sustained opioid reversal, especially with long-acting opioids.
Primarily hepatic via glucuronidation (UGT2B7) to naloxone-3-glucuronide; minor CYP450 involvement.
Primarily hepatic glucuronidation, with N-allylnoroxymorphone as the major metabolite; CYP450 system not significantly involved.
Renal: ~70% as metabolites (naloxone-3-glucuronide, naloxone-3-sulfate) and <2% unchanged; biliary/fecal: ~25% primarily as conjugated metabolites.
Naloxone undergoes extensive hepatic metabolism primarily via glucuronidation, with approximately 70% excreted in urine as naloxone-3-glucuronide. About 25% is excreted in feces via biliary elimination. Less than 1% is excreted unchanged in urine.
~50-60% primarily to albumin; less bound than opioids.
Approximately 30-40% bound to plasma proteins, mainly albumin.
2.0-3.0 L/kg; high due to lipophilicity, distributing rapidly into tissues including brain.
Volume of distribution is approximately 2-3 L/kg, indicating extensive distribution into tissues beyond plasma volume. Clinical meaning: High Vd suggests rapid distribution and short half-life.
Oral: <2% (extensive first-pass metabolism); Intranasal: ~50%; IM/SC: near 100% with rapid absorption.
Intramuscular bioavailability is approximately 100% (assumed complete absorption). Oral bioavailability is <2% due to extensive first-pass metabolism; therefore, not used orally.
No dose adjustment required; naloxone is not significantly renally eliminated.
No dose adjustment required for renal impairment.
No dose adjustment required; naloxone undergoes extensive hepatic metabolism, but no guidelines exist for Child-Pugh adjustments.
No dose adjustment required for hepatic impairment.
0.01-0.1 mg/kg IV/IM/SC, maximum 2 mg per dose; may repeat every 2-3 minutes as needed.
Weight-based: <20 kg: 0.1 mg/kg IM/SC; ≥20 kg: 2 mg IM/SC; repeat every 2-3 minutes if needed.
Use lower initial doses (0.4 mg) and titrate cautiously due to increased sensitivity and risk of withdrawal.
No specific dose adjustment; use standard adult dosing with monitoring for adverse effects due to potential comorbidities.
Risk of precipitating severe opioid withdrawal in physically dependent patients; caution in neonates.
Risk of recurrent respiratory depression: The duration of action of naloxone is shorter than that of most opioids, so repeat doses may be necessary. Patients should be monitored until respiratory function is fully recovered.
May precipitate acute withdrawal; monitor for recurrent respiratory depression due to short half-life; use caution in opioid-dependent patients and neonates.
May precipitate acute opioid withdrawal in opioid-dependent patients; risk of incomplete response or need for repeat doses due to short half-life; not effective for non-opioid overdoses; avoid in known hypersensitivity; use caution in patients with cardiovascular disease or those taking cardiotoxic drugs.
Hypersensitivity to naloxone; acute opioid withdrawal syndrome.
Hypersensitivity to naloxone or any component of the formulation.
None. Naloxone is not known to interact with food or beverages.
None known; naloxone is not absorbed orally due to first-pass metabolism. No dietary restrictions.
FDA Pregnancy Category B. Animal reproduction studies have not shown fetal risk; no adequate human studies in pregnant women. Naloxone crosses the placenta but has low bioavailability. Risk in first trimester is unknown; theoretical benefit in opioid reversal outweighs potential risk. Second and third trimesters: no known teratogenicity; may cause withdrawal in opioid-dependent fetus if maternal use reversed.
EVZIO (naloxone) is not associated with major congenital malformations; limited data in pregnancy. Immediate reversal of opioid effects may precipitate withdrawal in the fetus, potentially causing adverse outcomes such as preterm labor or fetal distress. Third trimester use may cause neonatal opioid withdrawal syndrome (NOWS) in opioid-dependent mothers if naloxone is administered.
Naloxone is excreted into breast milk in small amounts. M/P ratio is unknown. Milk levels are low and unlikely to affect nursing infant. Oral bioavailability of naloxone is poor (<2%), so infant exposure via breast milk is minimal. Considered compatible with breastfeeding; use when clinically indicated.
Naloxone is unlikely to be excreted in breast milk in significant amounts due to low bioavailability. M/P ratio not established. Preterm infusion studies show minimal transfer. Consider benefits of breastfeeding against risk of maternal opioid overdose reversal.
No dose adjustment required during pregnancy. Pharmacokinetics of naloxone are not significantly altered by gestational changes. Use standard adult dosing for opioid reversal. Titrate to effect based on clinical response.
No pharmacokinetic studies in pregnancy demonstrate need for dose adjustment. Standard dosing (0.4 mg or 2 mg intranasal/IM) is used. Pregnant patients may require higher doses due to increased volume of distribution and metabolic changes, but evidence insufficient to recommend routine dose adjustment.
Naloxone has a short half-life (30-90 minutes) relative to many opioids, necessitating repeat doses or continuous infusion for long-acting opioid overdoses. In opioid-dependent patients, naloxone can precipitate acute withdrawal, which is distressing but not life-threatening. Use the smallest effective dose to reverse respiratory depression while minimizing withdrawal. Consider intranasal administration for ease of use in community settings; onset is slightly slower than IV but comparable efficacy. Monitor for recurrence of respiratory depression after initial reversal, especially with methadone, buprenorphine, or sustained-release formulations. In neonates, naloxone should be used cautiously due to risk of seizures; it is not recommended for routine resuscitation.
EVZIO is a naloxone auto-injector for emergency treatment of opioid overdose. Administer intramuscularly or subcutaneously into outer thigh; can be given through clothing. Repeat every 2-3 minutes if no response. Onset of action within 2-5 minutes. Duration shorter than most opioids; monitor for recurrence of respiratory depression. Not for non-opioid overdoses.
Naloxone is a life-saving emergency medication used to reverse opioid overdose; it has no effect if no opioids are present.,Call 911 immediately after administering naloxone; it is a temporary measure and medical help is essential.,After giving naloxone, stay with the person and monitor their breathing; rescue breaths may be needed.,Naloxone may cause withdrawal symptoms like agitation, nausea, sweating, and rapid heart rate; these are signs it is working.,Store naloxone at room temperature, protect from light, and check expiration dates regularly.,If the person does not respond within 2-3 minutes, a second dose may be given if available.,Even if the person wakes up, do not leave them alone; the effects of some opioids can last longer than naloxone, causing breathing to stop again.
Always call 911 immediately after giving EVZIO.,Place the device against the outer thigh and press firmly; it will automatically inject.,A short, clicking sound indicates the injection has started.,Stay with the person after injection; they may become agitated due to opioid withdrawal.,Store at room temperature; check expiration date regularly.,Tell family and friends where you keep EVZIO.
"Cobicistat is a potent CYP3A4 inhibitor used to boost the pharmacokinetics of antiretroviral agents like atazanavir and darunavir. Naloxone primarily undergoes glucuronidation via UGT1A6 and UGT2B7, with minor CYP3A4 metabolism. Concomitant use with Cobicistat may modestly increase naloxone exposure due to CYP3A4 inhibition, but this is unlikely to be clinically significant given naloxone's wide therapeutic index and short half-life."
"Fluvoxamine, a selective serotonin reuptake inhibitor (SSRI), is primarily metabolized by cytochrome P450 (CYP) 1A2 and 2D6. Naloxone, an opioid antagonist, is reported to inhibit CYP1A2, potentially decreasing the clearance of fluvoxamine. This interaction may lead to increased fluvoxamine plasma concentrations, elevating the risk of serotonin syndrome, QT prolongation, and other dose-dependent adverse effects, especially in patients receiving high doses or those with hepatic impairment."
"Naloxone, an opioid receptor antagonist, may inhibit the cytochrome P450 isoenzyme CYP3A4, which is responsible for the metabolism of ivacaftor. Concomitant administration can lead to reduced clearance of ivacaftor, resulting in elevated serum concentrations. This increase may potentiate the therapeutic effects and adverse reactions of ivacaftor, such as hepatotoxicity and QT prolongation."
No interactions on record
Explore head-to-head clinical comparisons of other medications in the same therapeutic classes.
Common clinical questions about NALOXONE vs EVZIO, answered by our medical review team.
NALOXONE is a Opioid Antagonist that works by Competitive antagonist at mu, kappa, and delta opioid receptors, reversing opioid effects.. EVZIO is a Opioid Antagonist that works by Naloxone is an opioid antagonist that competitively binds to mu-opioid receptors, reversing opioid-induced respiratory depression and analgesia.. They differ in pharmacokinetic profiles, FDA-approved indications, and side effect profiles.
Potency comparisons between NALOXONE and EVZIO depend on the specific clinical indication. These are both Opioid Antagonist agents and are not directly interchangeable by dose. A physician or clinical pharmacist should guide any therapeutic switching decisions.
The standard adult dose of NALOXONE is: 0.4-2 mg IV/IM/SC, may repeat every 2-3 minutes; if no response after 10 mg, reconsider diagnosis.. The standard adult dose of EVZIO is: 2 mg intramuscular (IM) or subcutaneous (SC) autoinjector into anterolateral thigh; repeat every 2-3 minutes as needed for opioid overdose.. Dosing should always be individualized based on indication, renal and hepatic function, age, and other patient factors.
No direct drug-drug interaction has been formally documented between NALOXONE and EVZIO in current clinical databases. However, individual patient risk factors including other medications, organ function, and comorbidities should always be evaluated by a qualified healthcare provider.
The maternal-fetal safety profiles differ. NALOXONE is classified as Category A/B. FDA Pregnancy Category B. Animal reproduction studies have not shown fetal risk; no adequate human studies in pregnant women. Naloxone crosses the placenta but has low bioavailabil. EVZIO is classified as Category C. EVZIO (naloxone) is not associated with major congenital malformations; limited data in pregnancy. Immediate reversal of opioid effects may precipitate withdrawal in the fetus, pot. Always consult a maternal-fetal medicine specialist before taking either drug during pregnancy or lactation.