Comparative Pharmacology
Head-to-head clinical analysis: CODEINE ASPIRIN APAP FORMULA NO 2 versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: CODEINE ASPIRIN APAP FORMULA NO 2 versus WESTADONE.
CODEINE, ASPIRIN, APAP FORMULA NO. 2 vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Codeine is a prodrug that is metabolized to morphine, which acts as an agonist at mu-opioid receptors in the central nervous system, producing analgesia. Aspirin irreversibly inhibits cyclooxygenase-1 and -2, reducing prostaglandin synthesis and providing analgesic, anti-inflammatory, and antipyretic effects. Acetaminophen (APAP) inhibits cyclooxygenase centrally, with weak peripheral activity, producing analgesia and antipyresis.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
1 to 2 tablets orally every 4 to 6 hours as needed for pain; maximum 12 tablets per day. Each tablet contains codeine 30 mg, aspirin 325 mg, and acetaminophen 325 mg.
Oral: 2.5-10 mg every 4-6 hours as needed for pain; maximum 40 mg per day.
None Documented
None Documented
Codeine: 2.5-4 hours. Aspirin (as salicylate): 2-3 hours (low dose), up to 15-30 hours (high dose due to saturable metabolism). Acetaminophen: 2-3 hours (therapeutic doses), prolonged in overdose or hepatic impairment.
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: Renal 90% (10% unchanged, 80% as conjugates). Aspirin: Renal 80-100% (dose-dependent, as salicylate and metabolites). Acetaminophen (APAP): Predominantly renal (90-100% as conjugates, <5% unchanged).
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