Diphenhydramine Syrup

Diphenhydramine Syrup – Full Introduction

Diphenhydramine syrup is a first-generation antihistamine commonly used to relieve allergic symptoms and cold-related complaints, especially in children and adults who prefer a liquid formulation. It also has sedative, antiemetic, and antitussive properties.

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Drug Class

• First-generation H₁ antihistamine

• Anticholinergic agent

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Mechanism of Action

Diphenhydramine works by blocking H₁ histamine receptors, thereby preventing the effects of histamine released during allergic reactions. It also readily crosses the blood–brain barrier, leading to:

• Relief from sneezing, itching, runny nose, and watery eyes

• Sedation and drowsiness

• Anticholinergic effects such as drying of secretions

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Therapeutic Uses

• Allergic rhinitis (hay fever)

• Urticaria (hives) and other allergic skin conditions

• Common cold symptom relief (runny nose, sneezing, cough)

• Motion sickness and vertigo

• Night-time sleep aid (due to sedative effect)

• Cough suppression (off-label in combination syrups)

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Benefits

• Rapid relief of allergic symptoms

• Effective for night-time allergy and cold symptoms

• Available in syrup form for pediatric use

• Also useful for motion sickness and insomnia

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Common Side Effects

• Drowsiness and sedation (very common)

• Dry mouth and throat

• Dizziness

• Constipation

• Blurred vision

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Serious but Rare Side Effects

• Paradoxical excitation in children (restlessness, irritability)

• Severe anticholinergic effects (urinary retention, confusion)

• Respiratory depression in overdose

• Cardiac arrhythmias (very rare)

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Contraindications & Precautions

• Newborns and premature infants

• Acute asthma attacks

• Narrow-angle glaucoma

• Prostatic hypertrophy

• Avoid use with alcohol or other CNS depressants

• Use caution in elderly patients (risk of confusion and falls)

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Dosage & Administration

• Children: Dose depends on age and weight (as prescribed)

• Adults: As directed, usually 2–3 times daily

• Take with or without food

• Measuring cup/spoon should be used for accuracy

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Conclusion

Diphenhydramine syrup is an effective medication for allergic symptoms and cold relief, especially when sedation is acceptable or beneficial. However, due to its sedative and anticholinergic effects, it should be used cautiously, particularly in children and the elderly.