Classifications: narcotic (opiate) antagonist;
Therapeutic: narcotic antagonist

Prototype: Naloxone
Pregnancy Category: B


100 mcg/mL, 1 mg/mL injection


Analog of oxymorphone. A "pure" narcotic antagonist, essentially free of agonistic (morphine-like) properties. Thus, it produces no significant analgesia, respiratory depression, psychotomimetic effects, or miosis when administered in the absence of narcotics while processing more potent narcotic antagonist action.

Therapeutic Effect

Reverses the effects of opiates, including respiratory depression, sedation, and hypotension. These effects are dose related.


Complete or partial reversal of opioid drug effects, management of opioid overdose.


Hypersensitivity to nalmefene, naloxone, naltrexone, nalnefene; respiratory depression due to non-opioid drugs; substance abuse.

Cautious Use

Patients at high cardiovascular risk or who have received potential cardiotoxic drugs; patients with known physical dependence on opioids; renal or hepatic impairment; pregnancy (category B), lactation. Safety and efficacy in children are not established.

Route & Dosage

Reversal of Postoperative Opioid Depression (use 100 mcg/mL)
Adult: IV/IM/SC 0.25 mcg/kg followed by 0.25 mcg/kg incremental doses q2–5min until desired degree of reversal or 1 mcg/kg cumulative dose is reached

Known/Suspected Opioid Overdose (use 1 mg/mL)
Adult: IV/IM/SC For nonopioid-dependent patients: 0.5 mg/70 kg, may repeat with 1 mg/70 kg 2–5 min later; for opioid-dependent patients: 0.1 mg/70 kg, if no evidence of withdrawal in 2 min, continue with 0.5 mg/70 kg, may repeat with 1 mg/70 kg 2–5 min later (doses >1.5 mg/70 kg not likely to be more effective)


  • Note: When using the 100 mcg/mL concentration, calculate the volume of a dose equal to 0.25 mcg/kg by multiplying the weight in kilograms by 0.0025. When using the 1 mg/mL concentration, calculate the volume of a dose equal to 0.1, 0.5, or 1 mg/70 kg by dividing the weight in kilograms by 70, then multiplying that result by the number of milligrams ordered per 70 kg.
  • Note: If IV access is lost, a single 1-mg dose may be given IM or SC. Allow 5–15 min for effect to occur.

PREPARE: Direct: Give undiluted.  

ADMINISTER: Direct: Give over 15–30 sec. In patients with kidney failure give over 60 sec.  

Adverse Effects (≥1%)

Body as a Whole: Fever, chills. CV: Tachycardia, hypotension, hypertension, pulmonary edema, ventricular arrhythmias (especially in patients with preexisting cardiovascular disease). GI: Nausea, vomiting, diarrhea, dry mouth, dyspepsia, elevation of liver function tests. CNS: Dizziness, headache, irritability, tremor, paresthesias, confusion, paranoia, drowsiness, fatigue, vertigo, agitation, nervousness. Special Senses: Blurred vision.


Drug: Potential risk of seizures when combined with flumazenil.


Absorption: Well absorbed from IM and SC sites. Onset: 2–5 min IV; 15 min IM/SC. Peak: 5 min IV; 2 h IM/SC. Duration: 4–8 h. Distribution: Blocks >80% of brain opioid receptors within 5 min; distributed into breast milk of rats. Metabolism: In liver by glucuronidation. Elimination: Metabolites primarily in urine, 17% in feces. Half-Life: 8.5–10.8 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor carefully for reversal of opioid depression within 2–5 min of an IV dose or 5–15 min of an IM/SC dose.
  • Note: If recurrent respiratory depression following the reversal, titrate the dose again to avoid over-reversal.
  • Monitor cardiovascular status closely, assessing for changes in blood pressure and heart rate and development of arrhythmias.

Patient & Family Education

  • Tell your physician all of the other drugs that you are taking including over-the-counter drugs, herbals, and nutritional products.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

© 2006-2022 Last Updated On: 11/24/2022 (0)
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