Comparative Pharmacology
Head-to-head clinical analysis: PHENERGAN W CODEINE versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHENERGAN W CODEINE versus WESTADONE.
PHENERGAN W/ CODEINE vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Promethazine is a phenothiazine derivative with H1 receptor antagonist activity, antiemetic, and sedative properties. Codeine is an opioid agonist that binds to mu-opioid receptors in the CNS, inhibiting pain transmission and causing cough suppression.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
10 mL (containing promethazine 6.25 mg and codeine 10 mg) orally every 4 to 6 hours, not to exceed 60 mL (codeine 60 mg) per day.
Oral: 2.5-10 mg every 4-6 hours as needed for pain; maximum 40 mg per day.
None Documented
None Documented
Promethazine: 9-16 h; codeine: 3.5 h (terminal), prolonged in renal impairment (up to 18 h).
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: 70% (codeine as unchanged and metabolites, ~10% as morphine-3-glucuronide, <10% as morphine); biliary/fecal: 30% (promethazine as sulfoxides and glucuronides).
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