Diphenhydramine HCL Flashcards
Generic Name:
Diphenhydramine HCL
Trade Name:
Benadryl
Supplied:
50mg/mL vial
Class:
Antihistamine; anticholinergic
Mechanism of Action:
- Blocks cellular histamine receptors, but does not prevent histamine release; results in decreased capillary permeability and decreased vasodilation, as well as prevention of bronchospasm.
- Has some anticholinergic effects.
Indications and Field Use:
- Anaphylaxis (2nd line)
- Phenothiazine reactions (extrapyramidal symptoms)
- Antimetic
Contraindications:
- Known hypersensitivity to diphenhydramine or drugs of similar chemical structure.
- Newborn or premature infants; nursing mothers
- Considerable caution in patients with glaucoma, acute narrow angle; stenosing or obstructive diseases of the GI tract: bronchial asthma: hyperthyroidism: cardiovascular disease or hypertension; age greater than 60 years (all relative benefit vs risk).
Adverse Reactions:
CV: Hypotension; palpitations; arrhythmias; hemolytic anemia.
Resp: Anaphylaxis; thickening of bronchial secretions, tightness in chest; wheezing; nasal stuffiness.
CNS: Sedation; visual disturbances; seizures.
GU/GI: Urinary frequency or retention; vomiting.
Children: In children, may cause paradoxical CNS excitation, seizures, palpitations, thickening of bronchial secretions.
Incompatibilities/Drug Interactions:
- Additive effects with alcohol and other CNS depressants (hypnotics, sedatives, tranquilizers, etc.)
- MAO inhibitors prolong and intensify anticholinergic (drying) effects.
Adult Dosage: Anaphylaxis:
25-50mg slow IV push or deep IM
Adult Dosage: Extrapyramidal symptoms and antiemetic:
10-50mg IV or deep IM, dose should be individualized according to the needs and patient response.
Pediatric Dosage:
1.0 - 1.25 mg/kg slow IV push
May also be given deep IM
Routes of Administration:
IV/IO, Deep IM
Onset of Action:
IV 5-10 minutes
Peak Effects:
1 hour
