ALLEGRA
Clinical safety rating: caution
Comprehensive clinical and safety monograph for ALLEGRA (ALLEGRA).
Fexofenadine is a selective peripheral H1-receptor antagonist. It inhibits histamine release from mast cells and basophils, reducing allergic symptoms.
| Metabolism | Minimally metabolized; undergoes hepatic metabolism via CYP3A4 to a lesser extent; mainly excreted unchanged in feces and urine. |
| Excretion | Fexofenadine is primarily excreted unchanged in feces (approximately 80%) and urine (approximately 11%). Biliary excretion accounts for the majority of fecal elimination. Renal elimination is minimal due to extensive tubular reabsorption. |
| Half-life | Terminal elimination half-life is approximately 14.4 hours in healthy adults, allowing for twice-daily dosing. In patients with renal impairment, half-life may be prolonged (up to 59 hours in severe impairment). |
| Protein binding | 60-70% bound, primarily to albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | Vd is 5.4-6.7 L/kg, indicating extensive extravascular distribution. This large Vd reflects wide tissue penetration, though fexofenadine does not cross the blood-brain barrier significantly. |
| Bioavailability | Oral bioavailability is approximately 33% (range 20-50%), with food reducing absorption by up to 20%. The absolute bioavailability is low due to first-pass metabolism and efflux transport (P-glycoprotein). |
| Onset of Action | Oral: Onset of action occurs within 1-2 hours for relief of allergy symptoms. Maximum effect is observed by 2-3 hours post-dose. |
| Duration of Action | Duration of action is approximately 12-24 hours, supporting twice-daily or once-daily dosing. Clinical effect persists for the dosing interval without significant tolerance development. |
| Action Class | H1 Antihistaminics (second Generation) |
| Brand Substitutes | Lcfex Tablet, Etofex 120mg Tablet, Nexofex 120mg Tablet, Fexise 120mg Tablet, Histafree 120 Tablet, Lcfex 180 Tablet, Fexofen 180mg Tablet, Mavifex 180mg Tablet, Histafree 180 Tablet, Vilofex 180 Tablet, F Din 120mg Tablet, Altiva 30mg Tablet, Ultigra 30mg Tablet, Delpodine 30mg Tablet, Fex 30mg Tablet, Fexomax 30mg Tablet |
60 mg orally twice daily or 180 mg orally once daily.
| Dosage form | CAPSULE |
| Renal impairment | For GFR < 30 mL/min: 60 mg orally once daily. |
| Liver impairment | No adjustment required for hepatic impairment. |
| Pediatric use | Children 6-11 years: 30 mg orally twice daily; Children ≥12 years: same as adult. |
| Geriatric use | No specific adjustment; use with caution due to potential renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for ALLEGRA (ALLEGRA).
| Breastfeeding | Fexofenadine is excreted into human breast milk in small amounts. The milk-to-plasma (M/P) ratio is approximately 1.0. Based on a study, an exclusively breastfed infant would receive a dose of about 0.45% of the maternal weight-adjusted dose, which is considered negligible. No adverse effects have been reported in breastfed infants. The American Academy of Pediatrics considers fexofenadine compatible with breastfeeding. However, caution is advised for premature infants or those with renal impairment. |
| Teratogenic Risk | Fexofenadine (ALLEGRA) is classified as FDA Pregnancy Category C. Animal studies in rats and rabbits at doses up to 3 and 7 times the maximum recommended human dose (MRHD) respectively showed no evidence of teratogenicity. However, there are no adequate and well-controlled studies in pregnant women. First trimester: Limited human data; theoretical risk based on lack of data. Second and third trimesters: No known specific fetal risks; antihistamines in late pregnancy may cause uterine irritability and neonatal withdrawal symptoms (tremors, irritability) if used near term. Overall, risk is considered low but not zero. |
■ FDA Black Box Warning
None
| Serious Effects |
Hypersensitivity to fexofenadine or any component of the formulation; severe renal impairment (CrCl < 30 mL/min) for the tablet formulation.
| Precautions | Renal impairment: reduce dose in patients with CrCl < 80 mL/min; avoid use with known hypersensitivity; caution in patients with hepatic impairment. |
| Food/Dietary | Fruit juices (apple, orange, grapefruit) reduce fexofenadine absorption by up to 36%, 36%, and 20% respectively; avoid concomitant intake within 4 hours; food does not significantly affect absorption, but administration with high-fat meal may slightly delay absorption; no specific food restrictions beyond fruit juice timing. |
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| Fetal Monitoring | No specific maternal or fetal monitoring is required beyond routine prenatal care. However, due to potential anticholinergic effects at high doses, monitor for maternal sedation and fetal heart rate patterns if used near term. For patients with renal or hepatic impairment, monitor for signs of toxicity (drowsiness, dizziness). |
| Fertility Effects | In animal studies, fexofenadine at doses up to 3 times the MRHD had no significant effects on fertility or reproductive performance. Human data are lacking, but as an antihistamine, it is not known to impair fertility. No specific effects on spermatogenesis or ovulation have been reported. |
| Clinical Pearls |
| ALLEGRA (fexofenadine) is a non-sedating antihistamine; avoid co-administration with fruit juices (apple, orange, grapefruit) as they reduce absorption; onset within 1 hour, duration 12-24 hours; dose adjustment needed in renal impairment (CrCl <80 mL/min): start 60 mg once daily; not significantly metabolized by CYP450, low drug interaction potential; acts as a P-glycoprotein substrate. |
| Patient Advice | Take on an empty stomach with water for best absorption. · Do not take with fruit juices (apple, orange, grapefruit) as they decrease effectiveness. · May cause drowsiness in rare cases; avoid driving if affected. · Use consistently for best symptom control; do not exceed recommended dose. · If you have kidney disease, consult your doctor before use. |