AdultPediatricDosage Forms & Strengths injectable solution 2mg/2mL (single-dose vial; generic) Opioid Overdose and Reversal Indicated in the management of known or suspected opioid overdose Also, indicated for complete or partial reversal of opioid drug effects, including respiratory depression, induced by either natural or synthetic opioids Initial dose Non-opioid dependent patients: 0.5 mg/70 kg; may administer a second dose of 1 mg/70 kg 2-5 minutes later if necessary Suspected opioid dependency: Administer a challenge dose of 0.1 mg/70 kg initially; if no evidence of withdrawal within 2 minutes, the recommended dosing should be followed If no clinical response after administering a total dose of 1.5 mg/70 kg, additional nalmefene is unlikely to have an effect Do not give more nalmefene than is required to restore respiratory rate to normal, thus minimizing the likelihood of cardiovascular stress and precipitated withdrawal syndrome If respiratory depression recurs, titrate dose again to clinical effect using incremental doses to avoid over-reversal Dosage Modifications Loss of IV access Single intramuscular (IM) or subcutaneous (SC) 1-mg doses have been shown to effective within 5-15 min of administration Renal impairment Renal failure substantially reduces clearance of nalmefene; for single episodes of opioid antagonism, deliver incremental doses slowly (over 60 seconds) to minimize hypertension and dizziness following abrupt administration Hepatic impairment All severities: Hepatic disease substantially reduces clearance of nalmefene; for single episodes of opioid antagonism, no dosage adjustment necessary Dosing Considerations Nalmefene had no effect in cases where opioids were not responsible for sedation and hypoventilation Only treat when likelihood of an opioid overdose is high, based on a history of opioid overdose or clinical presentation of respiratory depression with concurrent pupillary constriction Patients tolerant to or physically dependent opioids May cause acute withdrawal symptoms in individuals who have some degree of tolerance to and dependence on opioids Closely observe for symptoms of withdrawal following administration Administer subsequent doses with intervals of at least 2-5 minutes between doses to allow the full effect of each incremental dose of nalmefene to be reached Safety and efficacy not establishedInteraction CheckerEnter a drug name and nalmefeneNo Results No Interactions Found Interactions FoundContraindicatedSerious - Use AlternativeSignificant - Monitor CloselyMinorAll Interactions Sort By: SeverityName Contraindicated (0)Serious - Use Alternative (0)Monitor Closely (0)Minor (0) >10% Nausea (18%) 1-10% Vomiting (9%) Tachycardia (5%) Hypertension (5%) Postoperative pain (4%) Fever (3%) Dizziness (3%) Headache (1%) Chills (1%) Hypotension (1%) Vasodilation (1%) <1% Transient increases in creatinine phosphatase kinase (0.5%) Cardiovascular: Bradycardia, arrhythmia Digestive: Diarrhea, dry mouth Nervous system: Somnolence, depression, agitation, nervousness, tremor, confusion, withdrawal syndrome, myoclonus Respiratory: Pharyngitis Skin: Pruritus Urogenital: Urinary retention Contraindications Hypersensitivity to nalmefene and any excipients in the product Cautions Nalmefene, like all drugs in this class, is not primary treatment for ventilatory failure Treatment with this drug should follow, not precede, establishment of a patent airway, ventilatory assistance, administration of oxygen, and establishment of circulatory access Pulmonary edema, cardiovascular instability, hypotension, hypertension, ventricular tachycardia, and ventricular fibrillation reported in connection with opioid reversal; in many cases, these effects appear to be the result of abrupt reversal of opioid effects Use with caution in patients at high cardiovascular risk or who have received potentially cardiotoxic drugs Use extreme caution in patients with known physical dependence on opioids or following surgery involving high doses of opioids; imprudent use or excessive doses of opioid antagonists in the postoperative setting has been associated with hypertension, tachycardia, and excessive mortality in patients at high risk for cardiovascular complications Preclinical studies have shown that nalmefene at doses up to 10 mg/kg (437x maximum recommended human dose) produced incomplete reversal of buprenorphine-induced analgesia in animal models; nalmefene may not completely reverse buprenorphine-induced respiratory depression Risk of recurrent respiratory depression Accidental overdose with long-acting opioids (eg, methadone, levo-alpha-acetylmethadol [LAAM]) may result in prolonged respiratory depression Be aware that a recurrence of respiratory depression is possible, even after an apparently adequate initial response to nalmefene treatment Observe treated patients until, in the opinion of the physician, there is no reasonable risk of recurrent respiratory depression Drug interaction overview Flumazenil Coadministration of both flumazenil and nalmefene produced fewer seizures than expected in a study in rodents, based on the expected effects of each drug alone An adverse interaction from the coadministration of the two drugs is not expected, but physicians should remain aware of the potential risk of seizures from agents in these classes Pregnancy There was no evidence of impaired fertility or harm to the fetus There are no adequate and well-controlled studies in pregnant females Use during pregnancy only if clearly needed Lactation Nalmefene and its metabolites were secreted into rat milk, reaching concentrations ~3x those in plasma at 1 hr and decreasing to about half the corresponding plasma concentrations by 24 hr following bolus administration As no clinical information is available, exercise caution when administered to nursing femalesPregnancy Categories A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk. B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk. C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done. D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk. X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist. NA: Information not available. Mechanism of Action An opioid antagonist, is a 6-methylene analogue of naltrexone, prevents or reverses effects of opioids, including respiratory depression, sedation, and hypotension Studies have shown that nalmefene hydrochloride injection has a longer duration of action than naloxone at fully reversing doses Absorption Peak plasma time IM: 2.3 hr SC: 1.5 hr Peak plasma concentration (IV) 19-32 years: 3.7 ng/mL 62-80 years: 5.8 ng/mL AUC 19-32 years: 16.6 ng·hr/mL 62-80 years: 17.3 ng·hr/mL Bioavailability IM: 101.5% SC: 99.7% Distribution Vd (steady-state): 8.6 L/kg Vdc 19-32 years: 3.9 L/kg 62-80 years: 2.8 L/kg Metabolism Metabolized by liver, primarily by glucuronide conjugation Metabolized to trace amounts of an N-dealkylated metabolite Metabolites: Nalmefene glucuronide (inactive); N-dealkylated metabolite (minimal pharmacological activity) Elimination Systemic clearance: 0.8 L⋅hr/kg Renal clearance: 0.08 L⋅hr/kg Half-life 19-32 years: 10.8 hr 62-80 years: 9.4 hr Excretion Feces: 17% Urine: <5% Administration Take proper steps to prevent use of the incorrect concentration May administer IV bolus (preferred), SC, or IM Discard unused portion Storage Store at 20-25ºC (68-77ºF) in original carton Protect from light No images available for this drug. No images available for this drug.A Patient Handout is not currently available for this monograph.Print FormularyPatient DiscountsAdding plans allows you to compare formulary status to other drugs in the same class.To view formulary information first create a list of plans. Your list will be saved and can be edited at any time.Create Your List of PlansAdding plans allows you to:View the formulary and any restrictions for each plan.Manage and view all your plans together – even plans in different states.Compare formulary status to other drugs in the same class.Access your plan list on any device – mobile or desktop. The above information is provided for general informational and educational purposes only. Individual plans may vary and formulary information changes. Contact the applicable plan provider for the most current information. View explanations for tiers and restrictions Tier Description 1 This drug is available at the lowest co-pay. Most commonly, these are generic drugs. 2 This drug is available at a middle level co-pay. Most commonly, these are "preferred" (on formulary) brand drugs. 3 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs. 4 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products. 5 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products. 6 This drug is available at a higher level co-pay. Most commonly, these are "non-preferred" brand drugs or specialty prescription products. NC NOT COVERED – Drugs that are not covered by the plan. Code Definition PA Prior Authorization Drugs that require prior authorization. This restriction requires that specific clinical criteria be met prior to the approval of the prescription. 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