Comparative Pharmacology
Head-to-head clinical analysis: DIPHENHYDRAMINE HYDROCHLORIDE PRESERVATIVE FREE versus PHENERGAN VC.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DIPHENHYDRAMINE HYDROCHLORIDE PRESERVATIVE FREE versus PHENERGAN VC.
DIPHENHYDRAMINE HYDROCHLORIDE PRESERVATIVE FREE vs PHENERGAN VC
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Competitive antagonist of histamine H1 receptors; centrally acting anticholinergic agent that inhibits acetylcholine muscarinic receptors.
Phenergan VC is a combination of promethazine (a phenothiazine derivative with antihistaminic, sedative, antiemetic, and anticholinergic effects) and phenylephrine (a sympathomimetic amine that acts as a decongestant via alpha-1 adrenergic receptor agonism). Promethazine antagonizes H1 receptors, thereby suppressing allergic reactions and motion sickness. Phenylephrine causes vasoconstriction in the nasal mucosa, reducing congestion.
25 to 50 mg intravenously or intramuscularly every 4 to 6 hours as needed; maximum 400 mg per day.
10-20 mL orally every 4-6 hours as needed; each 5 mL contains 6.25 mg promethazine HCl and 5 mg phenylephrine HCl.
None Documented
None Documented
Terminal elimination half-life: 4-10 hours (mean ~8 hours); prolonged in hepatic impairment or elderly (up to 20 hours).
9-16 hours; prolonged in hepatic impairment.
Primarily renal as inactive metabolites; ~60% of a dose appears in urine as metabolites, with <5% unchanged. Minor biliary/fecal elimination (<10%).
Renal: 70-80% as metabolites; biliary/fecal: 20-30%.
Category A/B
Category C
Antihistamine
Antihistamine/Decongestant Combination