What is the recommended dosage and administration of fexofenadine (Allegra) for adults and children with normal renal function and potential drug interactions?

Fexofenadine Dosing and Administration

Standard Adult Dosing

For adults and children ≥12 years with seasonal allergic rhinitis or chronic idiopathic urticaria, the recommended dose is 60 mg twice daily or 180 mg once daily with water. 1

• Both dosing regimens (60 mg BID and 180 mg once daily) demonstrate equivalent efficacy for symptom control 2, 3
• The 180 mg once-daily formulation improves compliance while maintaining 24-hour symptom relief 2, 3
• Fexofenadine should be taken with water only—avoid fruit juices as they may reduce absorption 1

Pediatric Dosing (Ages 6-11 Years)

Children ages 6-11 years should receive 30 mg twice daily with water for both seasonal allergic rhinitis and chronic idiopathic urticaria. 1

• This dose has been validated in large safety studies involving 875 pediatric patients 4
• The 30 mg BID regimen significantly reduces total symptom scores including nasal blockage, sneezing, rhinorrhea, and ocular symptoms 5
• Adverse event rates in children (35-37%) are comparable to placebo (36%), with headache being most common 4

Renal Impairment Adjustments

Patients with decreased renal function require dose reduction to prevent drug accumulation:

• Adults with renal impairment: Start with 60 mg once daily (instead of twice daily or 180 mg) 1
• Children 6-11 years with renal impairment: Start with 30 mg once daily (instead of twice daily) 1
• No specific creatinine clearance threshold is provided in the FDA label, so apply these reductions for any documented renal dysfunction 1

Safety Profile and Drug Interactions

Fexofenadine is truly non-sedating and demonstrates no cardiotoxicity, making it safer than many alternative antihistamines. 6

• Unlike loratadine or cetirizine, fexofenadine shows no dose-related sedation even at high doses 6
• No clinically significant drug interactions have been identified 6
• The combined incidence of drowsiness/fatigue with fexofenadine (4%) is significantly lower than cetirizine (9%, p=0.02) 2
• Electrocardiogram monitoring in pediatric trials showed no QT prolongation or cardiac effects 4

Special Populations

Fexofenadine is well-tolerated across diverse patient populations without dose adjustment except for renal impairment:

• Safe in elderly patients without age-based dose reduction 6
• Well-tolerated in patients with hepatic impairment 6
• Approved and studied down to age 6 years 1, 5, 4
• Safety profile remains similar to placebo across all age groups 6, 4

Clinical Pearls

• The 180 mg once-daily dose shows a trend toward greater symptom relief compared to 120 mg, though not statistically significant 3
• Efficacy is maintained for the entire 24-hour dosing interval with once-daily administration 2
• Discontinuation rates due to adverse events are extremely low (<1%) and similar between fexofenadine and placebo 4
• Fexofenadine improves quality of life in patients with seasonal allergic rhinitis beyond just symptom control 6