II. Indications
- See Sedating Antihistamine
- Local Anesthesia for Lidocaine Allergy
III. Mechanism
- Sedating Antihistamine
- H1 Receptor Antagonist
- Ethanolamine with strong Anticholinergic activity
IV. Dosing: Standard
- Adult (age >=12 years): 25-50 mg PO/IV/IM every 6 hours (maximum: 300 to 400 mg/day)
- Child (age <12 years): 5 mg/kg/day divided four times daily (12.5 mg/5 ml)
- Age 2 to 5 years: 6.25 mg every 4 hours as needed
- Age 6 to 12 years: 12.5 mg every 4 years as needed
V. Dosing: Local Injection
- Diphenhydramine may be used for local injection when patients are allergic to other Local Anesthesia
- Diphenhydramine 1% (for Local Anesthesia)
- Dilute Diphenhydramine 5% in Normal Saline (1:4)
- Longer delay to onset of action than Lidocaine
- Shorter duration of action than Lidocaine
VI. Adverse Effects
- See Sedating Antihistamine
-
Poisoning
- See Anticholinergic Toxicity
- Mild Overdose
- Causes sedation and muscarinic Anticholinergic Toxicity (Dry Mouth, Tachycardia, Mydriasis, Urinary Retention)
- Severe Overdose
- Causes Agitation, Delirium, Hallucinations, Seizures and coma
- Diphenhydramine blocks myocardial Sodium and Potassium channels (Wide QRS, QTc Prolongation)
- Diphenhydramine Overdose is responsible for >3% of U.S. Overdose deaths (within top 15 drugs)
- References
- Lacey and Dietrich (2023) Crit Dec Emerg Med 37(3): 18-9
VII. Safety
- Pregnancy Category B
- Avoid in Lactation
VIII. Pharmacokinetics
- Duration 4 to 6 hours
- Hepatic metabolism
- Renal Clearance
IX. Resources
- Diphenhydramine film coated tablet (DailyMed)
X. References
- Olson (2020) Clinical Pharmacology, Medmaster Miami, p. 90
- Hamilton (2020) Tarascon Pocket Pharmacopoeia
Images: Related links to external sites (from Bing)
Related Studies
diphenhydramine (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
DIPHENHYDRAMINE 12.5 MG/5 ML | Generic OTC | $0.01 per ml |
DIPHENHYDRAMINE 25 MG CAPSULE | Generic OTC | $0.03 each |
DIPHENHYDRAMINE 25 MG TABLET | Generic OTC | $0.04 each |
DIPHENHYDRAMINE 50 MG CAPSULE | Generic OTC | $0.02 each |
DIPHENHYDRAMINE 50 MG/ML VIAL | Generic | $0.85 per ml |
banophen (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
BANOPHEN 25 MG CAPSULE | Generic OTC | $0.03 each |
BANOPHEN 25 MG TABLET | Generic OTC | $0.04 each |
BANOPHEN 50 MG CAPSULE | Generic OTC | $0.02 each |
BANOPHEN ANTI-ITCH 2% CREAM | Generic OTC | $0.05 per gram |
diphen (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
DIPHENHIST 25 MG CAPSULE | Generic OTC | $0.03 each |
DIPHENOXYLATE-ATROPINE 2.5-0.025 MG TABLET | Generic | $0.18 each |
siladryl (on 12/21/2022 at Medicaid.Gov Survey of pharmacy drug pricing) | ||
SILADRYL 12.5 MG/5 ML LIQUID | Generic OTC | $0.02 per ml |
Ontology: Diphenhydramine (C0012522)
Definition (CHV) | a drug used to treat allergy symptoms |
Definition (CHV) | a drug used to treat allergy symptoms |
Definition (NCI) | A first generation antihistamine and ethanolamine with sedative and anti-allergic properties. Diphenhydramine competitively inhibits the histamine-1 (H1) receptor, thereby alleviating the symptoms caused by endogenous histamine on bronchial, capillary and gastrointestinal smooth muscles. This prevents histamine-induced bronchoconstriction, vasodilation, increased capillary permeability, and GI smooth muscle spasms. |
Definition (NCI_NCI-GLOSS) | A drug used to treat allergies and relieve cough and itching caused by insect bites, sunburn, and poison oak or ivy. It is also used to treat mild Parkinson disease, to prevent and treat motion sickness, to relieve cough and cold symptoms, and as a sleep aid. It is a type of antihistamine. |
Definition (MSH) | A histamine H1 antagonist used as an antiemetic, antitussive, for dermatoses and pruritus, for hypersensitivity reactions, as a hypnotic, an antiparkinson, and as an ingredient in common cold preparations. It has some undesired antimuscarinic and sedative effects. |
Definition (CSP) | histamine H1 antagonist used as an antiemetic, antitussive, for dermatoses and pruritus, for hypersensitivity reactions, as a hypnotic, an antiparkinson, and as an ingredient in common cold preparations; it has some undesired antimuscarinic and sedative effects. |
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | D004155 |
SnomedCT | 256043008, 26458009, 372682005 |
LNC | LP16116-3, MTHU019051, MTHU013946 |
English | Benhydramin, Benzhydramine, Diphenhydramine, Diphenylhydramin, Diphenylhydramine, 2-Diphenylmethoxy-N,N-dimethylethylamine, diphenylhydramine, Ethanamine, 2-(diphenylmethoxy)-N,N-dimethyl-, diphenhydramines (medication), diphenhydramines, diphenhydramine (medication), Diphenhydramine [Chemical/Ingredient], DIPHENHYDRAMINE, diphenhydrAMINE, O-Benzhydryldimethylaminoethanol, 2-(Diphenylmethoxy)-N,N-dimethylethylamine, Rigidyl, Probedryl, diphenhydramine, Diphenhydramine product, Diphenhydramine (product), Diphenhydramine (substance), Diphenhydramine [dup] (substance) |
Swedish | Difenhydramin |
Czech | difenhydramin |
Finnish | Difenhydramiini |
Russian | DIFENGIDRAMIN, DIMEDROL, BENGIDRAMIN, DIFENILGIDRAMIN, БЕНГИДРАМИН, ДИМЕДРОЛ, ДИФЕНГИДРАМИН, ДИФЕНИЛГИДРАМИН |
Japanese | ベンヒドラミン, ジフェンヒドラミン, ジフェニルヒドラミン |
Italian | 2-difenilmetossi-N,N-dimetiletanamina, Difenilidramina |
Polish | Difenhydramina, Benzhydramina |
Spanish | difenhidramina (producto), difenhidramina (sustancia), difenhidramina, Benhidramina, Difenhidramina, Difenilhidramina |
French | Diphénhydramine |
German | Benhydramin, Diphenhydramin, Diphenylhydramin |
Portuguese | Benidramina, Difenidramina, Difenilidramina |
Ontology: Benadryl (C0700899)
Concepts | Pharmacologic Substance (T121) , Organic Chemical (T109) |
MSH | D004155 |
English | Benadryl |