FEXOFENADINE HYDROCHLORIDE ALLERGY
Clinical safety rating: safe
Aluminum and magnesium-containing antacids decrease absorption Rarely may cause headache or drowsiness.
Fexofenadine is a selective peripheral H1-receptor antagonist that inhibits histamine release from mast cells and basophils.
| Metabolism | Minimally metabolized; ~5% undergoes hepatic metabolism via CYP3A4; 95% excreted unchanged in feces and urine |
| Excretion | Primarily excreted unchanged in feces (80%) and urine (11%). Biliary excretion contributes to fecal elimination. |
| Half-life | Terminal elimination half-life is 14.4 hours in healthy adults. In renal impairment, half-life may be prolonged up to 59 hours. |
| Protein binding | 60-70% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein. |
| Volume of Distribution | 5.4-5.8 L/kg, indicating extensive tissue distribution. |
| Bioavailability | Oral: Approximately 33% (interindividual variability due to limited absorption and first-pass metabolism). |
| Onset of Action | Oral: 1-2 hours for antihistamine effect. |
| Duration of Action | Approximately 24 hours, allowing once-daily dosing. |
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. No adjustment for GFR ≥ 15 mL/min. |
| Liver impairment | No dosage adjustment required for hepatic impairment. |
| Pediatric use | Children 6 months to <2 years: 15 mg orally twice daily. Children 2 years to <12 years: 30 mg orally twice daily. Children ≥12 years: same as adult. |
| Geriatric use | No specific dose adjustment; start at lower end of dosing range due to potential renal impairment. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Aluminum and magnesium-containing antacids decrease absorption Rarely may cause headache or drowsiness.
| FDA category | Animal |
| Breastfeeding | Fexofenadine is excreted into human milk; M/P ratio not established. Peak milk concentrations occur 1-3 hours after maternal dose. Relative infant dose estimated <2% of maternal weight-adjusted dose. Caution with preterm or neonates, but considered compatible with breastfeeding by AAP. |
| Teratogenic Risk | Pregnancy Category C. First trimester: Limited human data; animal studies showed no teratogenicity at doses up to 3 times the MRHD. Second/third trimester: No evidence of fetal harm in animal studies; insufficient human data. Avoid unless clearly needed. |
■ FDA Black Box Warning
None
| Common Effects | Headache Drowsiness Dizziness Nausea |
| Serious Effects |
Hypersensitivity to fexofenadine or any component of the formulation
| Precautions | Use with caution in patients with renal impairment; may cause QT prolongation in overdose or with hepatic impairment; not recommended for pediatric patients <6 months |
Loading safety data…
| Fetal Monitoring | No specific fetal monitoring required. Monitor maternal response and adverse effects (e.g., dizziness, headache). Assess efficacy for allergic symptoms. |
| Fertility Effects | No impairment of fertility observed in animal studies at doses up to 10 times the MRHD. Human data lacking; no known effect on human fertility. |