Nalmefene

opioid antag.

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Pronunciation: NAL-me-feen

Nalmefene ballicule: receptor binding, kinetics and half-life diagram — Mechanism of action: Nalmefene ballicule

Nalmefene Opvee mascot mnemonic cartoon — Visual mnemonic: Nalmefene mascot
**“Nail my fingers (to Open V)”**

What it isLong-acting opioid receptor antagonist used intranasally for emergency reversal of known or suspected opioid overdose.

Why this oneIts duration is longer than naloxone’s and may better match long-acting or high-potency synthetic opioids.

What limits itIt can precipitate severe, prolonged withdrawal and does not replace ventilation, repeat dosing, surveillance, or emergency care.

Nalmefene molecular structure (skeletal formula) — Molecular structure: Nalmefene

FDA-approved for

opioid overdose (1995)
alcohol use disorder (EU)

FDA label

Read the full label on DailyMed ↗

FDA dosing	Population	Start	Target	Max
Opioid overdose (emergency reversal)	Adults & peds ≥12 yr	1.5 mg IM/SC	1.5 mg IM/SC	repeat q2–5 min PRN (new auto-injector each dose)

Renal No adjustment needed for single episodes of opioid antagonism (clearance reduced in impairment)

Hepatic No adjustment needed for single episodes of opioid antagonism (clearance reduced in impairment)

Repeat every 2–5 min with a new auto-injector until emergency help arrives

Instructions

IM/SC into anterolateral (outer) thigh only, through clothing if needed
Single-use auto-injector; do not prime or reuse
Seek emergency medical care immediately after first dose
Re-administer with a new auto-injector every 2–5 min if no response or relapse into respiratory depression

Available strengths

inj 0.1, 1 mg/mL
sol 1.5 mg/0.5 mL
sol 2 mg/2 mL
sol 0.1 mg/mL
nasal spray 2.7 mg/spray

Cautions

Recurrent respiratory/CNS depression — keep under surveillance
Limited efficacy vs partial/mixed opioid agonists (e.g., buprenorphine); repeat doses may be needed
May precipitate severe opioid withdrawal (life-threatening in neonates)
Abrupt reversal may cause adverse cardiovascular effects (esp. preexisting CV disease)
Attempts to overcome the blockade with opioids can cause intoxication and death

Adverse reactions

Feeling hot
Nausea
Headache
Dizziness
Chills
Vomiting
Allodynia
Palpitations
Tinnitus

Pregnancy No human data; do not withhold for opioid overdose; no embryo-fetal harm in animals

Lactation No human data; present in rat milk

Cost

Nalmefene (OPIOID ANTAG.)

Strength		#/mo	generic $/unit	CostPlus
0.1 mg/mL	inj	per unit		not offered
1 mg/mL	inj	per unit		not offered

NADAC is a voluntary CMS survey of what retail community pharmacies pay for the drugs they stock. Nalmefene is administered under clinical supervision and dispensed outside retail pharmacies, so it rarely appears on surveyed invoices.

Generic entryBy 2023

NO BOXED WARNINGS

Principal risksevere, prolonged precipitated opioid withdrawal

Classes and tags

Clinical profile

Therapeutic safety burden1 / 4

Overdose danger1 / 4

Weight-gain liability0 / 4

Sedation liability0 / 4

QT / Torsades0 / 4

Direct muscarinic antagonism0 / 4

Embryofetal risk2 / 4

Legacy pregnancy categoryC

Defining liabilityUsually well tolerated; abrupt opioid withdrawal can be severe and prolonged.

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Memory aids: interaction avatars

no kinetic interactions

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