ALLEGRA HIVES
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ALLEGRA HIVES (ALLEGRA HIVES).
Fexofenadine is a non-sedating antihistamine (H1-receptor antagonist) that selectively inhibits peripheral H1 receptors, reducing histamine-mediated symptoms such as pruritus, urticaria, and vasodilation. It does not cross the blood-brain barrier significantly, minimizing CNS effects.
| Metabolism | Fexofenadine undergoes minimal hepatic metabolism; approximately 5% is metabolized by CYP3A4. The majority (up to 95%) is excreted unchanged in feces (80%) and urine (11-12%). |
| Excretion | Fexofenadine is primarily excreted unchanged in feces (80%) and urine (11%). The remainder undergoes minimal hepatic metabolism. Renal elimination accounts for about 11% of the dose. |
| Half-life | Terminal elimination half-life is approximately 14.4 hours (range 11–17 hours). This supports once-daily dosing in most patients; however, in moderate to severe renal impairment, half-life may be prolonged (e.g., ~22 hours), necessitating dosing adjustment. |
| Protein binding | Protein binding is approximately 60–70%, primarily to albumin and alpha1-acid glycoprotein. |
| Volume of Distribution | Volume of distribution is 5.4–5.8 L/kg. This relatively high Vd indicates extensive extravascular distribution, consistent with its peripheral antihistamine activity. |
| Bioavailability | Oral bioavailability is approximately 25–33% due to incomplete absorption and first-pass metabolism? Actually, fexofenadine has low presystemic metabolism, but absorption is incomplete; bioavailability is about 30% (range 25–33%). |
| Onset of Action | Oral: Onset of antihistamine effect is observed within 1–2 hours after a single dose, with peak effect at 2–4 hours. |
| Duration of Action | Duration of action is 24 hours, allowing once-daily dosing. However, symptom control may wane in the last few hours for some patients. |
Fexofenadine hydrochloride 60 mg orally twice daily or 180 mg orally once daily.
| Dosage form | TABLET |
| Renal impairment | For GFR < 15 mL/min: 60 mg orally once daily. For GFR 15-30 mL/min: 60 mg orally once daily. For GFR > 30 mL/min: no adjustment needed. |
| Liver impairment | No specific dose adjustment required for hepatic impairment; however, use caution in severe hepatic impairment due to limited data. |
| Pediatric use | Children 6 months to <2 years: 15 mg orally twice daily. Children 2-11 years: 30 mg orally twice daily. Children ≥12 years: same as adult dosing. |
| Geriatric use | No specific dose adjustment required; however, elderly patients may be more sensitive to adverse effects. Use lowest effective dose and monitor renal function. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ALLEGRA HIVES (ALLEGRA HIVES).
| Breastfeeding | Fexofenadine is excreted into human breast milk. The milk-to-plasma ratio (M/P) is approximately 0.5. The estimated daily infant dose via breast milk is less than 1% of the maternal weight-adjusted dose, which is considered low. However, caution is advised in lactating women, especially when breastfeeding preterm or low birth weight infants, due to potential anticholinergic effects. Monitor infant for drowsiness, irritability, or feeding difficulties. |
| Teratogenic Risk | ALLEGRA HIVES contains fexofenadine hydrochloride. In animal studies, no evidence of teratogenicity was observed at doses up to 3 times the maximum recommended human dose. Human data are limited; however, fexofenadine is not associated with increased risk of major congenital malformations. First trimester: insufficient data but current evidence suggests low risk. Second and third trimesters: no known fetal risks. Fexofenadine is classified as FDA Pregnancy Category C (pre-2015) and is not expected to increase teratogenic risk based on available studies. |
■ FDA Black Box Warning
None
| Serious Effects |
["Known hypersensitivity to fexofenadine or any component of the formulation"]
| Precautions | ["Severe renal impairment (CrCl < 30 mL/min): dose reduction recommended (initial dose 60 mg once daily)","Hypersensitivity reactions (rare)","Potential for reduced absorption with concomitant antacids containing aluminum or magnesium (separate by 2 hours)","Not recommended for use in patients with known hypersensitivity to fexofenadine or any component of the formulation"] |
| Food/Dietary | Fruit juices (apple, orange, grapefruit) reduce fexofenadine absorption significantly; separate ingestion by at least 4 hours. No other known food interactions. |
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| Fetal Monitoring | In pregnant patients using ALLEGRA HIVES, routine prenatal care is sufficient. No specific additional monitoring is required. Assess maternal blood pressure and heart rate if used in high doses due to possible anticholinergic effects. Fetal monitoring indicated only if signs of maternal toxicity or overdose occur. |
| Fertility Effects | Animal studies with fexofenadine showed no adverse effects on fertility at doses up to 3 times the maximum recommended human dose. Human data on fertility effects are lacking. Fexofenadine is not known to cause significant reproductive impairment. No clinical evidence of decreased fertility in men or women with use of antihistamines. |
| Clinical Pearls |
| ALLEGRA HIVES (fexofenadine 180 mg) is a non-sedating antihistamine approved for chronic idiopathic urticaria. Onset of action is within 1 hour; peak effect at 6 hours. Avoid use in severe renal impairment (CrCl <30 mL/min) due to increased exposure. May be taken with or without food, but fruit juices (apple, orange, grapefruit) decrease absorption by up to 36%; separate dosing by at least 4 hours. |
| Patient Advice | Take one tablet daily with water, avoiding fruit juices within 4 hours of dosing. · Drowsiness is uncommon but possible; caution with driving if sedated. · Do not exceed one tablet in 24 hours. · Notify your doctor if hives persist after 2 weeks or if symptoms worsen. · Store at room temperature away from moisture and heat. |