ALLEGRA ALLERGY
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ALLEGRA ALLERGY (ALLEGRA ALLERGY).
Fexofenadine is a selective peripheral H1-receptor antagonist. It inhibits histamine-induced vasodilation and bronchoconstriction by blocking the H1 receptor, thereby reducing allergic symptoms.
| Metabolism | Fexofenadine undergoes minimal hepatic metabolism; approximately 5% of the dose is metabolized by CYP3A4. It is primarily excreted unchanged in feces and urine. |
| Excretion | Primarily eliminated in feces (80%) and urine (approximately 15%) as unchanged drug. Biliary secretion contributes significantly. |
| Half-life | Terminal elimination half-life is 14.4 hours (range 8–16 hours) in healthy adults. In renal impairment, half-life may be prolonged; dose adjustment recommended for CrCl <30 mL/min. |
| Protein binding | 60-70% bound to plasma proteins (mainly albumin and α1-acid glycoprotein). |
| Volume of Distribution | Steady-state volume of distribution (Vdss) is 5.4–16 L/kg (mean ~12 L/kg). The large Vd indicates extensive tissue distribution. |
| Bioavailability | Oral bioavailability is approximately 30% (range 25–40%) due to first-pass metabolism. Bioavailability is reduced by fruit juices (e.g., grapefruit, apple, orange). |
| Onset of Action | Oral: 1–3 hours for symptom relief (histamine-induced wheal and flare). Peak effect occurs at 2–4 hours. |
| Duration of Action | 24 hours; once-daily dosing provides sustained suppression of histamine-induced wheal and flare for at least 24 hours. |
| Molecular Weight | 501.54 |
Fexofenadine 180 mg orally once daily.
| Dosage form | TABLET |
| Renal impairment | GFR 40-59 mL/min: 60 mg once daily; GFR 15-39 mL/min: 60 mg every other day; GFR <15 mL/min: not recommended. |
| Liver impairment | No dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Insufficient data for severe (Child-Pugh C). |
| Pediatric use | Children 2-11 years: 30 mg orally twice daily; Children 12 years and older: same as adult dosing. |
| Geriatric use | No specific dose adjustment, but elderly patients may be more sensitive to anticholinergic effects; consider starting at lower end of dosing range. No renal adjustment needed if renal function normal. |
| 1st trimester | Limited human data; animal studies have not shown fetal harm. Use only if clearly needed. |
| 2nd trimester | No known risk based on available data; considered safe for use. |
| 3rd trimester | No known risk; safe for use in third trimester. |
Clinical note
Comprehensive clinical and safety monograph for ALLEGRA ALLERGY (ALLEGRA ALLERGY).
| Placental transfer | Fexofenadine undergoes minimal placental transfer based on animal studies; human data limited but suggests low transfer. |
| Breastfeeding | Fexofenadine is excreted into breast milk in low amounts. No adverse effects observed in infants. Consider risk-benefit; generally considered compatible with breastfeeding. |
| Lactation Rating |
■ FDA Black Box Warning
None.
| Serious Effects |
Hypersensitivity to fexofenadine or any component of the formulation
| Precautions | Use with caution in patients with renal impairment (CrCl < 80 mL/min) as exposure is increased; consider dose adjustment., Avoid concurrent use with aluminum- and magnesium-containing antacids, which reduce fexofenadine absorption by up to 40%., Potential for QT prolongation at high doses (rare); caution in patients with pre-existing QT prolongation or electrolyte imbalances., Not recommended for severe hepatic impairment due to lack of data. |
| Food/Dietary | Fruit juices (apple, orange, grapefruit) significantly decrease absorption of fexofenadine; avoid concurrent consumption. No other significant food interactions. |
Loading safety data…
| L2 (Safer) |
| Teratogenic Risk | Fexofenadine (ALLEGRA ALLERGY) is classified as FDA Pregnancy Category C. Animal studies have shown no teratogenicity at doses up to 2-3 times the human dose. There are no adequate, well-controlled studies in pregnant women. First trimester: Limited data suggest no increased risk of major malformations. Second and third trimesters: No known specific fetal risks from antihistamine use; however, use only if clearly needed due to lack of extensive human data. |
| Fetal Monitoring | No specific monitoring required beyond routine prenatal care. Monitor for maternal side effects such as drowsiness or dizziness. In the fetus, no specific monitoring is mandated, but observe for any unusual signs after delivery if used near term. |
| Fertility Effects | No adverse effects on fertility have been reported in animal studies or human data. Fexofenadine is not expected to impair male or female fertility. |
| Clinical Pearls | Fexofenadine is a second-generation antihistamine with minimal CNS penetration, causing less sedation than first-generation agents. Onset of action is within 1 hour; peak effect at 2-3 hours. Avoid in patients with severe renal impairment (CrCl <30 mL/min) due to reduced clearance. Antacids containing aluminum or magnesium reduce absorption; separate by at least 2 hours. No significant QT prolongation at therapeutic doses. |
| Patient Advice | Take with water; do not take with fruit juices (apple, orange, grapefruit) as they reduce absorption. · Do not use with antacids containing aluminum or magnesium; wait at least 2 hours between doses. · May cause mild drowsiness in some patients; avoid driving if affected. · Do not exceed recommended dose; overdose may cause dizziness, drowsiness, or dry mouth. · Store at room temperature away from moisture and heat. · Consult healthcare provider if symptoms persist >7 days or if fever occurs. |