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Acetaminophen and Codeine Phosphate

Brand and Other Names: Acetaminophen and Codeine Phosphate
Mechanism of Action:

Codeine

  • Opioid agonist acting on mu-opioid receptors
  • Converted to morphine by CYP2D6 enzyme, variability in response due to genetic polymorphisms
  • Produces analgesia, respiratory depression, and euphoria

Acetaminophen

  • Non-opioid analgesic, mechanism not fully understood
  • Metabolized mainly in the liver, risk of toxicity at doses >4,000 mg/day
Indications:

Acetaminophen and Codeine Phosphate Tablets, USP are indicated for the management of mild to moderate pain, where treatment with an opioid is appropriate and for which alternative treatments are inadequate.

Route: oral
Dose:

1–2 tablets of 300/30 mg every 4 hours as needed

Adverse Reactions:

The most frequently observed adverse reactions with codeine administration include drowsiness, lightheadedness, dizziness, sedation, shortness of breath, nausea, vomiting, sweating, and constipation.

Contraindication:

Children <12 years

Post-tonsillectomy/adenoidectomy in <18 years

Severe asthma without resuscitative support

Concurrent use with MAO inhibitors (within 14 days)

Known hypersensitivity to codeine or acetaminophen

GI obstruction

Warnings and Precautions:

Respiratory Risks:

  • Especially in elderly, cachectic, or those with COPD
  • Opioid-naïve patients or dose escalations

Drug Interactions:

  • CYP2D6/CYP3A4 inhibitors or inducers significantly affect metabolism
  • Benzodiazepines, alcohol, antidepressants → increased sedation and respiratory depression

Other Concerns:

  • Adrenal insufficiency
  • Seizures in predisposed individuals
  • Anaphylaxis and skin reactions (e.g., SJS, TEN)
  • Avoid abrupt discontinuation due to withdrawal risk
See package insert for full prescribing information.