Comparative Pharmacology
Head-to-head clinical analysis: TYLENOL W CODEINE NO 4 versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: TYLENOL W CODEINE NO 4 versus WESTADONE.
TYLENOL W/ CODEINE NO. 4 vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Codeine is a prodrug that undergoes O-demethylation by CYP2D6 to morphine, which acts as a μ-opioid receptor agonist, inhibiting adenylate cyclase and modulating neurotransmitter release in the CNS. Acetaminophen inhibits cyclooxygenase (COX) enzymes, primarily in the CNS, reducing prostaglandin synthesis and modulating pain perception.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
One or 2 tablets (acetaminophen 300 mg-codeine 60 mg per tablet) 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 half-life of 2.5-3.5 hours; however, its active metabolite morphine has a half-life of 1.5-2 hours, and morphine-6-glucuronide (M6G) has a half-life of 2-4 hours. Acetaminophen: Terminal half-life of 2-3 hours in adults; prolonged in hepatic impairment (up to 4-5 hours) or overdose (4-12 hours). Clinically, duration of analgesic effect is approximately 4-6 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.
Codeine and its metabolites (including morphine, morphine-6-glucuronide, and norcodeine) are primarily excreted renally. Approximately 90% of a codeine dose is excreted in urine within 24 hours, with 5-15% as free codeine, 5-13% as free morphine, 40-60% as codeine conjugates, and 5-10% as morphine conjugates. Fecal excretion accounts for less than 5%. Acetaminophen is primarily metabolized in the liver to glucuronide and sulfate conjugates; about 85% of a dose is excreted renally as conjugates within 24 hours, with 2-4% excreted unchanged. Minor biliary/fecal elimination occurs for both drugs.
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