Comparative Pharmacology
Head-to-head clinical analysis: BENADRYL PRESERVATIVE FREE versus PROMETHAZINE DM.
Peer-Reviewed Evidence
Head-to-head clinical analysis: BENADRYL PRESERVATIVE FREE versus PROMETHAZINE DM.
BENADRYL PRESERVATIVE FREE vs PROMETHAZINE DM
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Diphenhydramine competitively antagonizes histamine at H1-receptors on effector cells, leading to relief of allergic symptoms. It also possesses anticholinergic, antiemetic, sedative, and local anesthetic effects.
Promethazine is a phenothiazine derivative that acts as a histamine H1 receptor antagonist, antiemetic via blockade of dopamine D2 receptors in the chemoreceptor trigger zone, and sedative via central anticholinergic effects. Dextromethorphan is an NMDA receptor antagonist and sigma-1 receptor agonist, suppressing cough by central action on the cough center.
25-50 mg IV/IM every 4-6 hours as needed; maximum single dose 100 mg, maximum daily dose 400 mg.
2 teaspoonfuls (10 mL) orally every 4-6 hours, not to exceed 8 teaspoonfuls (40 mL) per 24 hours.
None Documented
None Documented
Terminal elimination half-life: 4-8 hours (mean ~5 hours). Prolonged in hepatic impairment (up to 2-fold) and elderly (7-12 hours).
16-19 hours (terminal); note: effect may last longer due to active metabolites and tissue binding
Primarily renal (90% as metabolites and unchanged drug); ~1% excreted in feces via bile. Unchanged diphenhydramine accounts for <5% of urinary recovery.
Renal (70-80% as metabolites, <1% unchanged); biliary/fecal (20-30%)
Category C
Category A/B
Antihistamine
Antihistamine / Antiemetic