Comparative Pharmacology
Head-to-head clinical analysis: BENADRYL PRESERVATIVE FREE versus PROMETHACON.
Peer-Reviewed Evidence
Head-to-head clinical analysis: BENADRYL PRESERVATIVE FREE versus PROMETHACON.
BENADRYL PRESERVATIVE FREE vs PROMETHACON
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 with antihistaminic (H1 receptor antagonist), antiemetic, sedative, and anticholinergic properties. It inhibits central and peripheral H1 receptors, blocks dopamine D2 receptors in the chemoreceptor trigger zone, and has weak alpha-adrenergic blockade.
25-50 mg IV/IM every 4-6 hours as needed; maximum single dose 100 mg, maximum daily dose 400 mg.
25-50 mg intramuscularly or intravenously every 4-6 hours as needed. Maximum intravenous rate: 25 mg/minute. Maximum daily dose: 150 mg.
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).
Terminal elimination half-life: 4-6 hours in healthy adults; prolonged to 10-14 hours in hepatic impairment
Primarily renal (90% as metabolites and unchanged drug); ~1% excreted in feces via bile. Unchanged diphenhydramine accounts for <5% of urinary recovery.
Renal (80%) as inactive metabolites, 20% fecal via bile
Category C
Category C
Antihistamine
Antihistamine