Naloxone

Chemical

Thebaine derivative

Use

  1. Reverse opioid depression
  2. Diagnosis of opioid overdose
  3. Prevent opioid abuse

Presentation

400mcg/ml

Dose

100-200mcg at 2min intervals up to 2mg

5mcg/kg/hr infusion

Route

IV/IM/SC

Onset

Immediate

DoA

90min

MoA

Pure pioid antagonist (competitive)

μ>>>k>y opioid receptors in CNS

PD

Reversal of µ-opioid receptor effects

  • Sedation, ↓BP, Resp depression, dysphoria

CVS – ↑SNS activity → ↑HR, ↑MAP, dysrhythmias

CNS – reverses opioid depression, ↓pain threshold

Gut – N&V

Pregnancy – crosses placenta (v lipid soluble) → acute withdrawal of neonate

Other – acute withdrawal symptoms

Alleviates pruritus, nausea + resp D assoc with CNB opioids

PK

A

90% oral absorption

High 1st PM → OBA 2%

D

Highly lipophilic, distributes rapidly to brain

VD 2L/kg PPB 30-45%

pKa 8

25% UNIONISED at pH 7.4

M

Liver by conjugation to glucuronic acid forming naloxone-3-glucuronide and excreted in urine

E

t1/2b 1-1.5hrs

Adverse Effects

Opioid withdrawal/Pain crisis

Seizures

Pulmonary oedema