Diphendydramine

Question 1

Diphenhydramine (Benadryl)

Class

Answer 1

Antihistamine, anticholinergic

Question 2

Diphenhydramine (Benadryl)

Mechanism of Action

Answer 2

Blocks cellular histamine receptors, decreases vasodilation, decreases motion sickness.

Question 3

Diphenhydramine (Benadryl)

Indications

Answer 3

Symptomatic relief of allergies, allergic reactions, anaphylaxis, acute dystonic/extrapyramidal reactions (phenothiazines). Blood administration reactions.

Question 4

Diphenhydramine (Benadryl)

Contraindications

Answer 4

Asthma, glaucoma (increase intraocular pressure), pregnancy, hypertension, infants, patients taking monoamine oxidase inhibitors (MAOIs).

Question 5

Diphenhydramine (Benadryl)

Adverse Reactions

Answer 5

Sedation, hypotension, seizures, visual disturbances, urinary retention, palpitations, arrhythmias, dry mouth and throat, and paradoxical CNS excitation in children.

Question 6

Diphenhydramine (Benadryl)

Drug Interactions

Answer 6

Potentiates the effects of alcohol and other anticholinergics, may inhibit corticosteroid activity; MAOIs prolong anticholinergic effects of diphenhydramine.

Question 7

Diphenhydramine (Benadryl)

Adult Dose

Answer 7

Adult: 25 – 50 mg IV, IM, or PO.

Question 8

Diphenhydramine (Benadryl)

Pediatric Dose

Answer 8

Pediatric: 1 – 2 mg/kg IV, IO slow, or PO

Question 9

Diphenhydramine (Benadryl)

Onset

Answer 9

Onset: 15 – 30 minutes

Question 10

Diphenhydramine (Benadryl)

Peak Effect

Answer 10

Peak effect: 1 hour

Question 11

Diphenhydramine (Benadryl)

Duration

Answer 11

Duration: 3 – 12 hours

Question 12

Diphenhydramine (Benadryl)

Special Considerations

Answer 12

If used in anaphylaxis, will be in conjunction with epinephrine, corticosteroids.