Comparative Pharmacology
Head-to-head clinical analysis: DIPHEN versus PROMETHAZINE DM.
Peer-Reviewed Evidence
Head-to-head clinical analysis: DIPHEN versus PROMETHAZINE DM.
DIPHEN vs PROMETHAZINE DM
Comparing the clinical profiles, pharmacokinetic behaviors, and safety indices of these two therapeutic agents.
Diphenhydramine is a first-generation antihistamine that competitively antagonizes histamine at H1 receptors. It also exhibits anticholinergic, sedative, antiemetic, 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.
50 mg IV/IM every 4 hours as needed for nausea/vomiting; 25-50 mg PO every 4-6 hours as needed for nausea/vomiting or motion sickness; 25 mg PO 3-4 times daily for vertigo; 15.6-25 mg IM/IV for antiemetic in surgery; maximum 300 mg/day.
2 teaspoonfuls (10 mL) orally every 4-6 hours, not to exceed 8 teaspoonfuls (40 mL) per 24 hours.
None Documented
None Documented
Clinical Note
moderateDiphenoxylate + Torasemide
"The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Torasemide."
Clinical Note
moderateDiphenoxylate + Etacrynic acid
"The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Etacrynic acid."
Clinical Note
moderateDiphenoxylate + Furosemide
"The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Furosemide."
Clinical Note
moderateTerminal elimination half-life is 22–72 hours (mean 30–40 hours); increases with hepatic disease or enzyme inhibitors.
16-19 hours (terminal); note: effect may last longer due to active metabolites and tissue binding
Primarily hepatic metabolism; renal excretion of inactive metabolites accounts for ~70% of eliminated drug; biliary/fecal excretion accounts for ~30%.
Renal (70-80% as metabolites, <1% unchanged); biliary/fecal (20-30%)
Category C
Category A/B
Antihistamine
Antihistamine / Antiemetic
Diphenoxylate + Bumetanide
"The risk or severity of adverse effects can be increased when Diphenoxylate is combined with Bumetanide."