Diphenhydramine (Benadryl)

Question 1

Diphenhydramine Class?

Answer 1

Antihistamine

Question 2

Diphenhydramine Action?

Answer 2

Blocks histamine H1 receptor sites thereby inhibiting actions of histamine release.

Question 3

Diphenhydramine Indications?

Answer 3

Allergic reactions, anaphylaxis, acute extrapyramidal reaction (dystonia)

Question 4

Diphenhydramine Contraindications?

Answer 4

Hypersensitivity, pt’s taking MAO inhibitors, caution with glaucoma.

Question 5

Diphenhydramine Onset/Duration?

Answer 5

Onset: 5-15 min with max effects in 1-3 hrs
Duration: 6-12 hrs

Question 6

Diphenhydramine Dose/Route?

Answer 6

Adult: 25-50mg IV/IM/PO with a max of 400 mg/day

Peds: 1 mg/kg IV/IM/PO with a max of 300 mg/day

Question 7

Diphenhydramine Side Effects?

Answer 7

Drowsiness, palpitations, hypotension, tachycardia or bradycardia, disturbed
coordination, dry mouth/throat, thickening of bronchial secretions.

Question 8

Diphenhydramine Note*

Answer 8

Use with caution in CNS depressed pts and pts with lower respiratory tract diseases such
as asthma.