Diphenhydramine Hydrochloride

Diphenhydramine Hydrochloride has anti-histaminic (H1-receptor), anti-emetic, anti-vertigo and sedative and hypnotic properties. The anti-histamine action occurs by blocking the spasmogenic and congestive effects of histamine by competing with histamine for H1 receptor sites on effector cells.

• Allergic rhinitis, hay fever, urticaria, angioedema, atopic dermatitis
• Pruritus, contact dermatitis, gastrointestinal allergy
• Motion sickness, postoperative nausea and vomiting
• Parkinsonism, insomnia, cough

Diphenhydramine Hydrochloride has anti-histaminic (H1-receptor), anti-emetic, anti-vertigo and sedative and hypnotic properties. The anti-histamine action occurs by blocking the spasmogenic and congestive effects of histamine by competing with histamine for H1 receptor sites on effector cells.

Diphenhydramine blocks histamine receptors to relieve allergy symptoms and acts on the CNS to produce sedation and prevent vomiting.

Adult: 25-50 mg 3-4 times daily; Motion sickness prevention: 30 min before motion; Insomnia: 50 mg 30 min before bedtime.
Child (2-6 years): 6.25 mg q4-6hr (max 37.5 mg/day).
Child (6-12 years): 12.5-25 mg q4-6hr (max 150 mg/day).
Child (>12 years): 25-50 mg q4-6hr (max 300 mg/day).

May be taken with or without food, but it is better to take it at a fixed time. Shake syrup well before use.

If you miss a dose of Diphenhydramine, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose. Do not double the dose.

Common: Drowsiness, dizziness, dry mouth, nausea, vomiting.
Other: Vertigo, palpitations, blurred vision, headache, restlessness, insomnia, thickening of bronchial secretions, allergic reactions, diarrhea, excitation.

Caution when driving or operating machinery (drowsiness, dizziness). Avoid alcohol. Caution in neonates, narrow-angle glaucoma, prostatic hypertrophy, stenosing peptic ulcer, pyloroduodenal obstructions.

Hypersensitivity; neonates; lactation; asthma attack; narrow-angle glaucoma; prostatic hypertrophy; stenosing peptic ulcer; pyloroduodenal obstructions; bladder neck obstruction; antidepressant therapy.

Tricyclic antidepressants, MAOIs: Potentiate and intensify anticholinergic effects.
Alcohol and other CNS depressants: Increased CNS effects.
Aminoglycosides: Masks ototoxicity.
Levodopa: Increases gastric degradation and decreases absorption.
Valerian, St. John's wort, Kava Kava, gotu kola: May increase CNS depression.

Alcohol may cause excessive drowsiness with Diphenhydramine.

Generally considered safe during pregnancy (animal studies show low or no adverse effects; limited human studies).

Probably safe during breastfeeding. Larger doses or prolonged use may cause sleepiness and other effects in the baby.

Dosage is established for children under 2 years (2.5 mL every 4-6 hours).

Use with caution in elderly patients.

Renal impairment: Safe; no dose adjustment needed.
Hepatic impairment: Limited information available.

Overdose may cause CNS depression to stimulation (especially in children), atropine-like signs (dry mouth, fixed dilated pupils, flushing, GI symptoms).

Do not store above 30°C. Keep away from light and moisture.

Diphenhydramine Hydrochloride