Diphenhydramine Pediatric Dose — Acute Allergy
Diphenhydramine is a first-generation H1-receptor antagonist that competitively blocks histamine at peripheral and central receptor sites, reducing the hallmark symptoms of allergic reactions. It is widely used in pediatric acute care for the management of mild-to-moderate allergic reactions, urticaria, and as an adjunct in anaphylaxis management alongside epinephrine.
Pediatric Dosing
- Route: Intravenous (IV)
- Dose: 1 mg/kg per dose IV
- Maximum single dose: 50 mg
For a 20 kg child: 20 × 1 mg/kg = 20 mg IV. For a 60 kg adolescent: 60 × 1 mg/kg = 60 mg, capped at the maximum of 50 mg IV. Frequency and repeat dosing should be guided by clinical response and institutional protocol.
Indications and Clinical Context
Diphenhydramine is indicated for the symptomatic management of acute allergic reactions in pediatric patients, including urticaria, pruritus, and angioedema. In the setting of anaphylaxis, it serves as an adjunctive agent and should never replace epinephrine as the primary intervention, consistent with PALS and AAP guidance.
It may also be used to attenuate histamine-mediated adverse effects associated with certain medication infusions (e.g., vancomycin-related flushing). Clinical context should guide route selection and timing, with IV administration preferred when rapid onset is required in an acute care setting.
Administration and Monitoring
Diphenhydramine IV should be administered as a slow intravenous push over a minimum of 5 minutes to reduce the risk of hypotension. Rapid IV administration may cause cardiovascular effects including hypotension and reflex tachycardia. IO access is an alternative route in emergencies where IV access is unavailable; consult institutional protocol for IO administration guidance.
- Maximum single dose: 50 mg IV
- Key adverse effects: Sedation, anticholinergic effects (dry mouth, urinary retention, blurred vision), paradoxical CNS excitation (particularly in young children), hypotension with rapid infusion
- Contraindications/cautions: Use with caution in neonates and premature infants; avoid in patients with angle-closure glaucoma or significant anticholinergic burden
- Monitoring: Heart rate, blood pressure, level of consciousness, and respiratory status during and after administration
Disclaimer: This article is an educational reference summarizing standard pediatric dosing values. It is not a substitute for clinical judgment. Always verify doses against institutional protocols, the current edition of authoritative references (e.g., Lexicomp, Harriet Lane Handbook, PALS guidelines), the patient’s accurate weight, and any patient-specific factors (renal/hepatic function, allergies, comedications) before administration.