Comparative Pharmacology
Head-to-head clinical analysis: PHENAPHEN 650 W CODEINE versus PHENAPHEN W CODEINE NO 4.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHENAPHEN 650 W CODEINE versus PHENAPHEN W CODEINE NO 4.
PHENAPHEN-650 W/ CODEINE vs PHENAPHEN W/ CODEINE NO. 4
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Acetaminophen: Weak COX-1 and COX-2 inhibitor in CNS, antipyretic via hypothalamic heat-regulating center. Codeine: Prodrug converted to morphine; mu-opioid receptor agonist.
Phenaphen w/ Codeine No. 4 contains acetaminophen and codeine. Acetaminophen inhibits prostaglandin synthesis in the CNS, reducing pain and fever. Codeine, an opioid prodrug, is converted to morphine via CYP2D6 and binds to mu-opioid receptors, inhibiting ascending pain pathways.
Acetaminophen 650 mg and codeine 60 mg orally every 4 hours as needed for pain; maximum acetaminophen 3 g/day.
1-2 tablets (300-600 mg acetaminophen / 30-60 mg codeine phosphate) orally every 4 hours as needed for pain; maximum 12 tablets per day.
None Documented
None Documented
Acetaminophen: 2-3 hours (normal liver function); prolonged in liver disease (up to 5-10 hours) or overdose. Codeine: 2.5-3.5 hours; active metabolite morphine ~2 hours. Clinical context: half-life affects dosing interval; accumulation in hepatic or renal impairment.
Codeine: 2.5-3.5 h; morphine: 2-4 h; clinically, analgesia correlates with morphine levels
Acetaminophen: renal excretion of conjugates (glucuronide ~55%, sulfate ~30%, cysteine/mercapturate ~4%), with <5% unchanged. Codeine: renal excretion as codeine (~10%), norcodeine (~10%), morphine (~10%), and their conjugates; total 70-90% in urine as glucuronide conjugates.
Renal: 90-100% as codeine and metabolites (codeine: 5-15%, morphine: 10%, norcodeine: 10%, morphine-3-glucuronide: 50%, morphine-6-glucuronide: <5%); biliary/fecal: minimal (<5%)
Category D/X
Category D/X
Opioid Agonist
Opioid Agonist