Naloxone

Uses

The reversal of respiratory depression due to opiods and the diagnosis of suspected opiod overdose.

Chemical

Substitued oxymorphne derivative

Presentation

Solution containing 0.4mg/ml naloxone HCl

Main Actions

Reversal of mu-opiod receptor effects

Mode of action

Competive antagonist at mu, delta, kappa and sigma opiod receptors.

Route of administration / Dose

For reversla of respiratory depression 100-200µg i.v. In treatment of known or suspected opiod overdose 0.4 - 2.0mg may be required and this may be given iv, im or sc.

Effects

Toxicity / Side effects

Acute withdrawal in opiate addicts

Kinetics

91% absorbed orally but has only 2% bioavailabiliy because of an extensive first-pass metabolism.

Distribution

46% protein-bound with a VD of 2l/kg

Metabolism

Hepatic conjugation to form a glucuronide.

Excretion

Clearance of 25ml/min/kg and a plasma T½ of 1.2hrs

Special points

Duration of action is only about 20 minutes and as a result, care must be exercised that the patient does not become obtunded as the effects of the naloxone wear off.