Appropriate Dosage for Alaspan (Diphenhydramine) Syrup
For children over 12 years and adults, the appropriate dosage of diphenhydramine syrup is 25-50 mg (10-20 mL) every 4-6 hours, not exceeding 6 doses (300 mg) in 24 hours. 1
Age-Based Dosing Guidelines
- Adults and children over 12 years: 10-20 mL (25-50 mg) every 4-6 hours
- Children 6 to under 12 years: 10 mL (25 mg) every 4-6 hours
- Children under 6 years: Not recommended
Clinical Considerations
Efficacy and Indications
Diphenhydramine is commonly used for:
- Acute hypersensitivity reactions: 1-2 mg/kg (maximum initial dosage: 50 mg) 2
- Dystonic reactions: 1-2 mg/kg (maximum initial dosage: 50 mg) 2, 3
- Short-term insomnia: Though commonly used, evidence suggests limited efficacy 2
Safety Concerns
Sedation: May cause significant drowsiness, affecting ability to drive or operate machinery 4
Anticholinergic effects: Can cause dry mouth, blurred vision, urinary retention, and confusion, particularly in elderly patients
Cardiovascular effects: Rapid IV administration may precipitate seizures or cause hypotension 2
Paradoxical reactions: May cause paradoxical excitement or agitation, especially in children 2
Drug-induced liver injury: Rare but serious potential complication, especially with excessive doses 5
Important Cautions
Limited efficacy for insomnia: The American Academy of Sleep Medicine suggests against using diphenhydramine for sleep onset and maintenance insomnia due to minimal benefits compared to placebo 2
Safety in special populations: Use with caution in elderly patients who are more susceptible to anticholinergic side effects
Duration of use: Should be limited to short-term use due to tolerance development and potential for adverse effects 6
Alternatives: Second-generation antihistamines may offer similar efficacy with fewer adverse effects for allergic conditions 7, 6
Administration Considerations
For parenteral administration in emergency settings (e.g., allergic reactions), the standard dose is 25-50 mg IV 4
When used for migraine treatment as part of combination therapy, diphenhydramine can help address associated symptoms and potential side effects of other medications 4
Monitor for signs of toxicity, especially when maximum daily doses are approached
Despite its widespread use, recent evidence suggests reconsidering diphenhydramine use when newer alternatives with better safety profiles are available 7, 6. However, for short-term symptomatic relief, when used at appropriate doses, it remains an effective option for many patients.