Diphenhydramine Hydrochloride (Benadryl®)

Section 1.1

Midwives may independently prescribe, order and administer this drug.

Competes with histamine for H1-receptor sites on effector cells in the gastrointestinal tract, blood vessels, and respiratory tract; sedative effects are also seen.

Indications and Clinical Use:

Adjunctive therapy in the treatment of anaphylactic reactions related to the administration of drugs, vaccines or sera.


Hypersensitivity to diphenhydramine or any component of the formulation; acute asthma.

Warnings and Precautions:

This drug is for emergency purposes, and its use should be immediately followed by a physician consultation and if out-of-hospital, emergency transport to hospital. Further definitive treatment would be managed by a physician.

Patients should be cautioned about the possibility of CNS depression, which may impair physical or mental abilities.
Use with caution in patients with a history of asthma.
Use with caution in patients with cardiovascular disease (including hypertension and ischemic heart disease).
Use with caution in patients with thyroid dysfunction.




Category L2 – Limited Human Data – Probably Compatible

Adverse Reactions:

Chest tightness, hypotension, palpitation, tachycardia, chills, confusion, convulsion, dizziness, fatigue, headache, insomnia, irritability, nervousness, restlessness, sedation, sleepiness, constipation, diarrhea, dry mucous membranes, nausea, throat tightness and vomiting.

Dosage and Administration:

Adult – 50 mg IM

Onset of Action:

Sedative effect – 1-3 hours


2-10 hours


Urine (as unchanged drug)