What is Codeine phosphate - Meaning and definition

Published by Roberto Wenk. Reviewed by Alison Ramsey. Last updated date: October 30, 2018.

The phosphate salt of codeine, a naturally occurring phenanthrene alkaloid and opioid agonist with analgesic, antidiarrheal, and antitussive activities.
Codeine mimics the actions of endogenous opioids by binding to the opioid receptors at many sites within the central nervous system (CNS).
- Stimulation of mu-subtype opioid receptors results in a decrease in the release of nociceptive neurotransmitters, such as substance P, GABA, dopamine, acetylcholine, and noradrenaline; in addition, the codeine metabolite morphine induces opening of G-protein-coupled inwardly rectifying potassium (GIRK) channels and blocks the opening of N-type voltage-gated calcium channels, resulting in hyperpolarization and reduced neuronal excitability.
- Stimulation of gut mu-subtype opioid receptors results in a reduction in intestinal motility and delayed intestinal transit times.
- Antitussive activity is mediated through codeine’s action on the cough center in the medulla.

National Cancer Institute. NCI Drug Dictionary. Internet. September 15, 2009.

Published by Roberto Wenk. Last updated date: February 8, 2016.

Adult
PO
Pain: 15-60 mg 4 hrly. Max: 360 mg/day.
Cough suppressant: 15-30 mg 3-4 times daily.
Acute diarrhoea: 15-60 mg 3-4 times daily. Syr 1-2 5 mL every 4-6 hr.

IV/IM/SC
Pain: 30-60 mg 4 hrly. Max: 240 mg/day.

Codeine is the commonest weak opioid; if pain relief is not achieved on the ceiling dose (max dose 240mg per day), move to strong opioids.
Codeine is often combined with step 1 analgesics (paracetamol, ibuprofen, diclofenac); give laxatives to avoid constipation unless patient has diarrhoea.

Adverse drug reactions: dependence, nausea, vomiting, constipation, drowsiness, confusion, difficulty in micturition, ureteric or biliary spasms, urinary retention, dry mouth, dizziness, sweating, facial flushing, headache, vertigo, palpitations, postural hypotension, vertigo, restlessness, mood changes, decreased libido or potency, hallucination, miosis, raised intracranial pressure, muscle rigidity, visual disturbances.

Adapted CIMS Drug Information System. Internet. Accessed on January 10, 2016.

Codeine phosphate

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