Nalmefene

[SH4:p121]

Structure

• Nalmefene is a pure opioid antagonist
• 6-methylene analogue of naltrexone

Pharmacodynamics

Potency

• Nalmefene is equipotent to naloxone

Side effects

• Acute pulmonary oedema has been reported
  * Like naloxone

Pharmacokinetics

• Primary advantage of nalmefene over naloxone is longer duration of action

Metabolism

• Metabolised by hepatic conjugation

Elimination

• Elimination half-time of nalmefene = 10.8 hours
• <5% of nalmefene is excrete unchanged in urine

Clinical

Administration

• Recommended dose = 15-25 micrograms IV every 2-5 min, titrate to effect
  * Total dose not exceeding 1 microgram/kg