Diphenhydramine (Benadryl)
Dose/Admin
*Adult: 25-50mg IV, IO, IM, or PO *Ped: 1-2mg/kg IV, IO, IM or PO
Class
Antihistamine, anticholinergic
Contraindications
Asthma, glaucoma, pregnancy, HTN, infants, patients taking MAOIs.
Mechanism of action
Blocks cellular histamine receptors, decrease vasodilation, decrease motion sickness. Reverse extrapyramidal reactions.
Special considerations
If used in analphylaxis, will be in conjunction with epinephren, corticosteroids.
Drug interactions
Potentiates the effects of alcohol and other anticholinergics, may inhibit corticosteroid activity; MAOIs prolong anticholinergic effects of diphenhydramine.
Adverse reactions
Sedation, hypotension, seizures, visual disturbances, urinary retention, palpitations, arrhythmias, dry mouth and throat, paradoxical CNS excitation in children.
Indications
Symptomatic relief of allergies, allergic reactions, anaphylaxis, acute dystonic reactions.
Duration
onset: 15-30min peak: 1 hour duration: 3-12 hours