Comparative Pharmacology
Head-to-head clinical analysis: PHERAZINE VC W CODEINE versus WESTADONE.
Peer-Reviewed Evidence
Head-to-head clinical analysis: PHERAZINE VC W CODEINE versus WESTADONE.
PHERAZINE VC W/ CODEINE vs WESTADONE
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Codeine: Opioid receptor agonist (mu-receptor), suppresses cough reflex. Phenylephrine: Alpha-1 adrenergic receptor agonist, vasoconstrictor. Promethazine: Histamine H1 receptor antagonist, anticholinergic, antiemetic.
Mu-opioid receptor agonist; also acts as an NMDA receptor antagonist and inhibits serotonin and norepinephrine reuptake.
Adults: 5 mL (one teaspoonful) orally every 4 to 6 hours as needed; each 5 mL contains promethazine hydrochloride 5 mg, phenylephrine hydrochloride 5 mg, and codeine phosphate 10 mg. Maximum daily dose: codeine 120 mg (6 doses).
Oral: 2.5-10 mg every 4-6 hours as needed for pain; maximum 40 mg per day.
None Documented
None Documented
Codeine: 2.5-3.5 hours (terminal); phenylephrine: 2-3 hours; promethazine: 10-19 hours (clinical context: prolonged in renal impairment, accumulation with chronic use).
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: codeine (40-70% as free and conjugated metabolites, including morphine, norcodeine, and hydromorphone); phenylephrine (80-90% as conjugated metabolites, 10% unchanged); promethazine (primarily as sulfoxides and glucuronides, renal elimination about 70%). Fecal/biliary: minor.
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