FEXOFENADINE HYDROCHLORIDE; PSEUDOEPHEDRINE HYDROCHLORIDE
Clinical safety rating: safe
MAOIs can cause hypertensive crisis Can cause insomnia and tachycardia.
Fexofenadine is a selective peripheral H1-receptor antagonist; pseudoephedrine is a sympathomimetic amine that acts as a decongestant by stimulating alpha-adrenergic receptors in the respiratory tract mucosa, causing vasoconstriction.
| Metabolism | Fexofenadine: minimally metabolized (5%) by CYP3A4; pseudoephedrine: partially metabolized by N-demethylation (liver), mostly excreted unchanged. |
| Excretion | Fexofenadine: 80% unchanged in feces, 11% in urine. Pseudoephedrine: 70-90% unchanged in urine. |
| Half-life | Fexofenadine: 14.4 hours. Pseudoephedrine: 5-8 hours, prolonged in renal impairment. |
| Protein binding | Fexofenadine: 60-70% (albumin and α1-acid glycoprotein). Pseudoephedrine: 20-30% (albumin). |
| Volume of Distribution | Fexofenadine: 5.4-5.8 L/kg. Pseudoephedrine: 2.6-3.5 L/kg. |
| Bioavailability | Fexofenadine: 30-40% (oral). Pseudoephedrine: 100% (oral, well absorbed). |
| Onset of Action | Fexofenadine: 1-2 hours. Pseudoephedrine: 30 minutes (oral). |
| Duration of Action | Fexofenadine: 24 hours. Pseudoephedrine: 4-6 hours. |
| Molecular Weight | 501.67 |
| Action Class | Antihistamine (second-generation) and sympathomimetic decongestant |
One tablet (fexofenadine HCl 60 mg / pseudoephedrine HCl 120 mg) orally every 12 hours. Maximum 2 tablets per day.
| Dosage form | TABLET, EXTENDED RELEASE |
| Renal impairment | Contraindicated in severe renal impairment (CrCl <60 mL/min). For moderate impairment (CrCl 60-90 mL/min): use with caution; consider reducing dose interval to every 24 hours. No specific dose reduction established; use not recommended in CrCl <60 mL/min. |
| Liver impairment | No specific dose adjustment required for mild to moderate hepatic impairment (Child-Pugh A or B). Not studied in severe hepatic impairment (Child-Pugh C); use with caution. |
| Pediatric use | Children ≥12 years: same as adult dose (one tablet every 12 hours). For children <12 years: safety and efficacy not established; alternative formulations recommended. |
| Geriatric use | Elderly patients may be more sensitive to CNS and anticholinergic effects of pseudoephedrine. Use with caution; consider lower starting dose or extended dosing interval. Contraindicated if CrCl <60 mL/min (common in elderly). |
| 1st trimester | Avoid due to potential risk of vascular disruption; pseudoephedrine is associated with gastroschisis in first trimester. |
| 2nd trimester | Use with caution; pseudoephedrine may reduce uterine blood flow and cause fetal tachycardia. |
| 3rd trimester | Avoid near term; pseudoephedrine can cause uterine contraction and fetal heart rate changes. |
Clinical note
MAOIs can cause hypertensive crisis Can cause insomnia and tachycardia.
| FDA category | Animal |
| Placental transfer | Pseudoephedrine crosses placenta; fexofenadine is likely to cross minimally based on molecular weight and properties. |
| Breastfeeding |
■ FDA Black Box Warning
None
| Common Effects | Insomnia |
| Serious Effects | Cardiac arrhythmias (e.g., QT prolongation, ventricular tachycardia), Hypertensive crisis, Stroke or myocardial infarction, Seizures, Severe allergic reactions (e.g., anaphylaxis), Urinary retention |
Severe hypertensionCoronary artery diseaseNarrow-angle glaucomaUrinary retentionConcurrent MAO inhibitor usePseudoephedrine hypersensitivity
| Precautions | Cardiovascular effects (hypertension, arrhythmias, palpitations), CNS stimulation (insomnia, nervousness, dizziness), Risk of urinary retention (especially in males with prostatic hypertrophy), Increased intraocular pressure (angle-closure glaucoma), Severe cutaneous reactions (rare), Drug interactions: MAOIs, beta-blockers, digoxin, antacids. |
| Food/Dietary |
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| Fexofenadine is excreted into breast milk in low amounts; pseudoephedrine is concentrated in breast milk and may cause irritability and disturbed sleep in infants. Limited data suggest caution, especially in preterm or jaundiced infants. |
| Lactation Rating | L3 (Moderate Safety) |
| Teratogenic Risk | FDA Pregnancy Category C. Inadequate human studies; animal studies show fetal harm, including reduced fetal weight and skeletal variations. First trimester: risk of neural tube defects? insufficient data. Second/third trimester: risk of premature closure of ductus arteriosus (pseudoephedrine). Avoid use, especially in first trimester and near term. |
| Fetal Monitoring | Monitor fetal heart rate and uterine activity if used near term due to pseudoephedrine. Assess fetal growth with ultrasound if prolonged use. Monitor maternal blood pressure and heart rate. |
| Fertility Effects | Pseudoephedrine may impair spermatogenesis in animal studies; fexofenadine no known fertility effects. Human data insufficient. |
| Avoid high-tyramine foods (aged cheese, cured meats, fermented products) as pseudophedrine may increase blood pressure. Grapefruit juice may reduce absorption of fexofenadine; take with water. Caffeine-containing products may exacerbate stimulant effects. |
| Clinical Pearls | Fexofenadine is a second-generation antihistamine with minimal CNS penetration; pseudophedrine is a sympathomimetic. Avoid in severe hypertension, coronary artery disease, or concurrent MAOI use. Caution in BPH, glaucoma, hyperthyroidism. Onset of action is ~1 hour; duration ~12 hours. Use with caution in renal impairment (CrCl <30 mL/min): fexofenadine dosing interval should be increased to 24 hours; pseudophedrine should be avoided. Not recommended in children <6 years. |
| Patient Advice | Do not crush or chew extended-release tablets; swallow whole. · May cause drowsiness in some patients; avoid driving or operating machinery until you know how you react. · Avoid caffeine or other stimulants; pseudophedrine can increase heart rate and blood pressure. · Avoid alcohol while taking this medication. · If you miss a dose, take it as soon as you remember; if it is near the time of the next dose, skip the missed dose. · Tell your doctor about all medications you are taking, especially MAOIs, blood pressure medications, and other antihistamines. · For pregnant or breastfeeding women: consult a healthcare provider before use. |