MSK (Opiates - Codeine)

Question 1

Examples of drug (Opiates - Codeine)

Answer 1

• Codeine

Question 2

Mechanism of action (Opiates - Codeine)

Answer 2

• Opioid receptor agonist; acts on mu, kappa and delta on presynaptic neurones. This gives numerous effects that increase nociceptive thresholds throughout the central and peripheral nervous system.

Question 3

Indications (Opiates - Codeine)

Answer 3

• Mild to moderate pain
• Persistent dry cough
• Diarrhoea

Question 4

Important pharmacokinetics/pharmacodynamics (Opiates - Codeine)

Answer 4

• Metabolised to morphine which is responsible for analgesic effects.
• Predominantly metabolised by the liver.
• Active metabolites are excreted in the urine so can accumulate in renal failure.
• 10% of population resistant to codeine’s analgesic properties as they lack the demethylating enzyme that converts it to morphine.

Question 5

Patient information (Opiates - Codeine)

Answer 5

• Can be taken with paracetamol for a better analgesic effect.
• Constipation is a likely side effect.

Question 6

Side effects (Opiates - Codeine)

Answer 6

• Nausea
• Vomiting
• Constipation
• Biliary spasm
• Headache on withdrawal