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