Codeine

Chemical

Orally active, naturally occurring opioid found in opium

Use

  1. Analgesia → mild – moderate
  2. Antitussive
  3. Antidiarrheal

Presentation

PHENANTHRENE ALKALOID

Structurally identical to morphine except for methylation of C3, giving ‘methylmorphine’ aka codeine!

Dose

(PO) 30 – 60mg QID

Route

PO/IM/PR

Not given IV → histamine release +++

Onset

15 – 30 mins

DoA

4 – 6hrs

MoA

  • Codeine has low affinity for µOP
  • Metabolised to morphine → µOP, kOP, δOP agonist
  • High affinity codeine receptor activation → ANTITUSSIVE

PD

CNS – analgesia

GI – marked ↓GI motility → constipation

Resp – antitussive

PK

A

Well absorbed

70% OBA

D

7% PPB

VD 5.4L/kg

M

Liver

  • 70% conjugated to glucuronic acid

↓

Codeine-6-glucuronide

  • 10% Demethylated by CYP2D6

↓

Morphine

↓

M3G & M6G

  • 10% Demethylated to norcodeine
  • Codeine 6 glucuronide has some analgesic activity
  • All analgesia from morphine & morphine metabolism

E

Renally excreted metabolites

10% unchanged as codeine

Adverse Effects

  • N&V
  • Dizziness
  • Bowel perf!
  • Low abuse risk