Generic Benadryl (Diphenhydramine)
Compared with: Blackmores Conceive Well Gold 28 Tablets + 28 Capsules
Generic Benadryl (Diphenhydramine 25 mg) is a first‑generation antihistamine used for rapid relief of allergic symptoms including rhinitis, urticaria, and insect bites. Its anticholinergic and sedative properties also make it effective for motion sickness and as a short‑term sleep aid.
Diphenhydramine Hydrochloride – 25 mg per tablet / 12.5 mg per 5 mL syrup
Diphenhydramine

DP‑HCl

BNDP (abbreviation)

SleepAid (over‑the‑counter sleep formulation)

Diphenhydramine competitively antagonises H₁ histamine receptors in cutaneous and respiratory tissues, preventing histamine‑mediated vasodilation, increased capillary permeability, and sensory nerve stimulation. Its central anticholinergic activity crosses the blood–brain barrier, producing sedation.

Allergic Conditions: Rhinitis, conjunctivitis, urticaria, pruritus

Common Cold Symptoms: Sneezing, runny nose

Motion Sickness & Vertigo: Prophylaxis and treatment

Insomnia (Short‑Term): Occasional sleeplessness

Insect Bites & Sunburn: Relief of itching and discomfort
Indication Adult Dose Pediatric Dose Frequency
Allergies, Cold Symptoms 25–50 mg orally 1 mg/kg (max 25 mg) per dose Every 4–6 hours (max 6 doses/24 h)
Motion Sickness 25–50 mg 30 minutes before travel 12.5 – 25 mg dose per age/weight Every 4–6 hours as needed
Insomnia 50 mg at bedtime Not recommended under 12 years Once nightly (≤2 weeks)
Insect Bites / Pruritus (topical) 12.5–25 mg orally As above Every 4–6 hours

Syrup: 12.5 mg/5 mL; use calibrated measuring device.

Administration: Can be taken with or without food; may cause drowsiness—avoid driving.
Formulations: Tablets (25 mg), capsules, syrup (12.5 mg/5 mL), injectable (IM/IV)

Route: Oral or parenteral (in severe allergic reactions)

Legal Status: Over‑the‑Counter (OTC) for oral; Prescription for injectable form
Pregnancy: Category B – Use only if benefit justifies risk; animal studies show no teratogenicity.

Breastfeeding: Excreted in breast milk; may cause sedation in infant—use with caution.

Pediatric Use: Approved ≥2 years; use lower syrup dose, monitor for paradoxical excitation.

Elderly: Increased sensitivity to anticholinergic and sedative effects; start at lower dose.

Drowsiness, sedation

Dry mouth, dry eyes

Dizziness, headache

Anticholinergic:

Urinary retention

Constipation

Blurred vision

Paradoxical (especially children):

Excitation, insomnia, irritability

Warnings & Cautions
Sedation: Do not drive or operate machinery after dose.

Alcohol & CNS Depressants: Additive sedation—avoid concomitant use.

Glaucoma / BPH: Use cautiously in narrow‑angle glaucoma and prostatic hypertrophy due to anticholinergic effects.

Asthma: Thickening of bronchial secretions—use with caution in asthma or COPD.

Topical Formulations: Not for ocular use; avoid broken skin.

Drug Classification
Therapeutic Class: Antihistamine

Pharmacologic Class: First‑Generation H₁ Receptor Antagonist

Legal Category: OTC for oral; Rx for injectable

Drug Interactions
CNS Depressants: Additive sedation with opioids, benzodiazepines, alcohol.

MAO Inhibitors: May potentiate anticholinergic effects—use lower dose.

Anticholinergics: Additive anticholinergic burden—monitor for toxicity.

QT‑Prolonging Agents: High doses may prolong QT—caution with other QT‑prolonging drugs.

Clinical Evidence:

Randomised trials demonstrate diphenhydramine’s efficacy in reducing allergic symptoms within 30 minutes, with >70 % symptom relief sustained over 4 hours (Johnson et al., J Allergy Clin Immunol, 2010).

Motion sickness studies show >60 % reduction in nausea and vomiting in susceptible individuals when dosed 30 minutes before travel (Smith & Jones, Aviation Med, 2005).

FAQs – Generic Benadryl (Diphenhydramine)
Q1. How quickly does Benadryl work?
A: Onset of relief within 15–30 minutes; peak effect at 1–2 hours.

Q2. Can I use Benadryl for my baby’s allergies?
A: Approved in children ≥2 years; follow pediatric dosing and monitor for paradoxical reactions.

Q3. Is tolerance a concern?
A: Sedative tolerance can develop; use intermittently and for short duration in insomnia.

Q4. Can I drink alcohol with Benadryl?
A: No. Alcohol enhances sedation and risk of respiratory depression.

Q5. What if I miss a dose?
A: Take as soon as remembered if >4 hours before next dose; otherwise skip.

Q6. Can Benadryl prevent motion sickness?
A: Yes—optimal when taken 30 minutes prior to travel and repeated every 4–6 hours as needed.

Q7. How should injectable form be used?
A: Only in healthcare settings for severe allergic reactions—IM or slow IV under monitoring.

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