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codeine

codeine

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Due to its variable analgesic effect, the utility of codeine phosphate as an analgesic in the ED is limited. Consider using oxycodone, non-steroidal anti-inflammatory drugs (NSAIDs) or parenteral opiates instead.
Avoid opiates including codeine in those at risk of type II respiratory depression such as obstructive sleep apnoea, severe COPD, lactating mothers, young children
avoid codeine in the elderly as risk of sedation, confusion and increased falls as well as constipation risk

introduction

  • codeine phosphate is an opioid analgesic which is also sometimes used as an antitussive agent.
  • its analgesic effect is thought to be due to its partial metabolic conversion to morphine
  • structurally similar to morphine and oxycodone so should be avoided in patients with hypersensitivities to these
  • codeine is metabolised in the liver via:
    • glucuronidation to codeine-6-glucuronide which is the main metabolic pathway
    • O-demethylation to morphine catalysed by CYP2D6 (~10% of the codeine dose in most patients) is the main therapeutic pathway
      • unfortunately, 5-10% of the Caucasian population are deficient in this pathway “slow metabolisers” which means in these patients they will not get the same analgesic benefit.
        • <1% of those from eastern Asia are deficient, while up to 20% of Africans are.
      • furthermore, some are ultrafast metabolisers increasing risk of respiratory depression:
        • 5-30% of Africans
        • up to 20% of Arabians
        • 7-10% of southern Europeans
        • 1-4% of western Europeans
      • patients on CYP2D6 inhibitors such as many antidepressants, may also be slow metabolisers
      • patients on enzyme inducers such as phenytoin may have increased effects as they metabolise codeine faster to the active form
    • N-demethylation to normorphine catalysed by CYP3A4
    • N-demethylation to norcodeine then glucuronidation to norcodeine glucuronide, or O-demethylation to normorphine
  • plasma half-life of codeine is 2-4 hours

dosage

  • adults 30mg every 4-6hrs when used as codeine phosphate tablets
  • more commonly it is used in tablets containing 8-15mg codeine with another analgesic such as paracetamol (eg. Panadeine or Panadeine forte) or aspirin (eg. Aspalgin)

adverse effects and C/I

  • common dose related adverse effects include nausea, vomting, constipation and dizziness
  • elderly are particularly susceptible to sedation, confusion and increased falls
  • slow metabolisers are at risk of inadequate analgesia
  • patients with obstructive sleep apnoea, or COPD with risk of type 2 respiratory failure, and those given high dose or who are ultrafast metabolisers, have risk of life-threatening respiratory depression, particularly when used with other respiratory depressant drugs such as benzodiazepines
  • avoid in lactating mothers as there have been cases of neonatal death which may be related to mother being an ultrafast metaboliser
  • do NOT use cough suppressant doses in those under the age of 18 years as risks outweigh the benefits
  • avoid in young children
codeine.txt · Last modified: 2012/04/23 17:22 (external edit)