Non-Sedating Antihistamine Dosing
For non-sedating (second-generation) antihistamines, use loratadine 10 mg once daily for adults and children ≥6 years, or 5 mg once daily for children 2 to <6 years, as the standard dosing regimen. 1
Standard Dosing by Age
Adults and Children ≥6 Years
- Loratadine: 10 mg (2 teaspoonfuls) once daily
- Maximum dose: 10 mg in 24 hours 1
Children 2 to <6 Years
- Loratadine: 5 mg (1 teaspoonful) once daily
- Maximum dose: 5 mg in 24 hours 1
Children <2 Years
- Consult a physician before dosing 1
Special Populations
Patients with liver or kidney disease require physician consultation before initiating therapy, as dose adjustments may be necessary 1
Clinical Context for Non-Sedating Antihistamines
While the guidelines acknowledge that non-sedating second-generation antihistamines can be used as alternatives to diphenhydramine, they do not provide specific dosing recommendations in the acute allergic reaction setting 2. The FDA labeling for loratadine provides the standard dosing framework 1.
Advantages Over First-Generation Agents
- Second-generation antihistamines (loratadine, fexofenadine, cetirizine, desloratadine) are preferred over first-generation agents because they avoid sedation, impairment, and disruption of sleep architecture that occurs with diphenhydramine and chlorpheniramine 3
- The safety differences among second-generation antihistamines are smaller than the differences between first and second generations 3
Critical Clinical Pitfalls
Never use antihistamines as monotherapy for anaphylaxis—they take significantly longer to work than epinephrine and cannot reverse life-threatening symptoms 4. Epinephrine 0.01 mg/kg IM (maximum 0.5 mg) must be administered immediately for anaphylaxis, with antihistamines serving only as adjunctive therapy 4, 5.
For acute allergic reactions requiring rapid onset, the perceived advantage of intramuscular diphenhydramine over oral fexofenadine is marginal and not statistically significant, making the risk-to-benefit ratio favor oral second-generation agents given diphenhydramine's adverse effect profile 6.