Comparative Pharmacology
Head-to-head clinical analysis: PHENERGAN VC W CODEINE versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHENERGAN VC W CODEINE versus WESTADONE.
PHENERGAN VC W/ CODEINE vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Phenergan VC w/ Codeine combines codeine (opioid agonist, mu-receptor), promethazine (histamine H1 antagonist, anticholinergic, sedative), and phenylephrine (alpha-1 adrenergic agonist). Codeine is metabolized to morphine for analgesia and antitussive effects; promethazine suppresses cough via central nervous system depression; phenylephrine causes vasoconstriction to relieve congestion.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
1 to 2 teaspoonfuls (5-10 mL) orally every 4 to 6 hours as needed. Maximum 4 doses in 24 hours.
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 ~3 hours (range 2.5-4.5 h) in adults; extended in renal impairment. Promethazine: terminal half-life ~10-14 hours (range 7-20 h) in adults; prolonged in elderly and 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 elimination of metabolites (codeine-6-glucuronide, norcodeine, morphine, morphine-3-glucuronide, morphine-6-glucuronide); ~90% excreted in urine, <10% in feces. Promethazine: renal and biliary elimination as metabolites and unchanged drug; ~70-80% in urine, <20% in feces.
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