Comparative Pharmacology
Head-to-head clinical analysis: PHENAPHEN W CODEINE NO 3 versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHENAPHEN W CODEINE NO 3 versus WESTADONE.
PHENAPHEN W/ CODEINE NO. 3 vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Codeine is an opioid agonist that binds to mu-opioid receptors, inhibiting adenylate cyclase and reducing cAMP production, leading to decreased neurotransmitter release and modulation of pain perception. Acetaminophen produces analgesia through central cyclooxygenase (COX) inhibition and activation of descending serotonergic pathways.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
One to two tablets (30-60 mg codeine phosphate/300-600 mg acetaminophen) orally every 4 hours as needed for pain, maximum 12 tablets per day.
Oral: 2.5-10 mg every 4-6 hours as needed for pain; maximum 40 mg per day.
None Documented
None Documented
Codeine: terminal elimination half-life is 2.5–3.5 hours in healthy adults; morphine: 1.5–4.5 hours; morphine-6-glucuronide: 2.5–4.5 hours. Half-life is prolonged in hepatic or renal impairment; in end-stage renal disease, half-life of codeine and metabolites may exceed 24 hours.
Terminal elimination half-life: 15-60 hours (mean ~24 hours). Clinical context: Prolonged half-life supports once-daily dosing in opioid maintenance; accumulation occurs with repeated dosing due to long half-life.
Renal excretion of codeine and its metabolites (morphine, norcodeine, codeine-6-glucuronide, morphine-3-glucuronide, morphine-6-glucuronide). Approximately 80-90% of the dose is eliminated in urine within 24 hours, with about 10% as unchanged codeine, 10% as norcodeine, 10% as free and conjugated morphine, and the remainder as conjugated codeine and other metabolites. Fecal excretion accounts for less than 10%.
Primarily renal (40-50% as unchanged methadone and its metabolites, 15-20% as metadone-N-oxide), biliary/fecal (5-10%).
Category D/X
Category C
Opioid Agonist
Opioid Agonist