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Diphenhydramine (Benadryl)
class
Antihistamine, anticholinergic.
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Diphenhydramine (Benadryl)
Mechanism of action
Blocks cellular histamine receptors; decreases vasodilation; decreases motion sickness. Reverses extrapyramidal reactions.
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Diphenhydramine (Benadryl)
Indications
Symptomatic relief of allergies, allergic reactions, anaphylaxis, acute dystonic reactions (Phenothiazines). Blood administration reactions; used for motion sickness, hay fever.
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Diphenhydramine (Benadryl)
Contraindications
Asthma, glaucoma, pregnancy, hypertension, narrow angle glaucoma, infants, Pts taking MAOIs.
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Diphenhydramine (Benadryl)
Adverse reactions
Sedation, hypotension, seizures, visual disturbances, vomiting, urinary retention, palpitations, arrhythmias, dry mouth and throat, and paradoxical CNS excitation in children.
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Diphenhydramine (Benadryl)
Drug interactions
Potentiates effects of alcohol and other anticholinergics, may inhibit corticosteroid activity; MAOIs prolong anticholinergic effects of diphenydramine.
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Diphenhydramine (Benadryl)
How supplied
Tablets:25, 50mg, capsules:25, 50mg, prefilled syringes:50 or 100mg, vials:(IVorIM), elixer, 12.5mg/5mL
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Diphenhydramine (Benadryl)
Dosage and administration
- Adult: 25-50mg IM or IV or PO.
- Pediatric: 1-2mg/kg IV, IO slowly or IM. If given PO 5mg/kg/24hrs.
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Diphenhydramine (Benadryl)
Duration of action
- Onset: 15-30 min.
- Peak effect: 1 hour
- Duration: 3-12 hours
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Diphenhydramine (Benadryl)
special considerations
not used in infants or in pregnancy: category B. If used in anaphylaxis, will be in conjunction with epinephrine, corticosteroids.
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