1. Clinical Overview
A fixed-dose combination of a second-generation, non-sedating antihistamine (Fexofenadine) and a sympathomimetic decongestant (Phenylephrine). It is primarily indicated for the symptomatic relief of allergic rhinitis and the common cold, providing relief from sneezing, rhinorrhea, nasal congestion, and itchy/watery eyes. Fexofenadine is a selective peripheral H1-receptor antagonist, while Phenylephrine is a selective α1-adrenergic receptor agonist that causes vasoconstriction in the nasal mucosa.
| Onset | Duration | Bioavailability |
|---|---|---|
| Fexofenadine: 1-3 hours; Phenylephrine: 15-30 minutes (for nasal decongestion). | Fexofenadine: Approximately 24 hours; Phenylephrine: 4-6 hours. | Fexofenadine: ~30-40% (oral); Phenylephrine: ~38% (oral, but highly variable due to extensive first-pass metabolism). |
2. Mechanism of Action
Fexofenadine competitively inhibits histamine binding at the H1-receptor in the respiratory tract, blood vessels, and gastrointestinal tract, preventing allergic symptoms. Phenylephrine acts as a direct sympathomimetic agonist on α1-adrenergic receptors in the vascular smooth muscle of the nasal mucosa, causing vasoconstriction, reduced edema, and decreased nasal congestion.
3. Indications & Uses
- Symptomatic relief of Allergic Rhinitis (seasonal and perennial)
- Symptomatic relief of the Common Cold
4. Dosage & Administration
Adult Dosage: 10 ml (2 teaspoonfuls) orally twice daily. Each 5ml contains Fexofenadine 30mg and Phenylephrine 2.5mg.
Administration: Shake the bottle well before use. Use the measuring cup/spoon provided. Can be taken with or without food. Avoid taking with fruit juices (apple, orange, grapefruit) as they can reduce Fexofenadine absorption. Maintain adequate fluid intake.
5. Side Effects
Common side effects may include:
- Headache
- Drowsiness (less common than with older antihistamines)
- Dizziness
- Nausea
- Dry mouth
- Insomnia (due to Phenylephrine)
- Nervousness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase Inhibitors (MAOIs) - e.g., Phenelzine, Selegiline | Markedly potentiates pressor effects of Phenylephrine, leading to hypertensive crisis. | Contraindicated |
| Beta-blockers (e.g., Propranolol) | Unopposed alpha-adrenergic activity may lead to severe hypertension and bradycardia. | Major |
| Other Sympathomimetics (e.g., Pseudoephedrine, Decongestant cold remedies) | Additive adrenergic effects, increasing risk of hypertension, tachycardia, and CNS stimulation. | Major |
| Antihypertensives (e.g., Alpha-blockers, Beta-blockers, Diuretics) | Phenylephrine may antagonize the hypotensive effect. | Moderate |
| Erythromycin, Ketoconazole | May increase Fexofenadine plasma levels via P-glycoprotein inhibition, potentially increasing side effects. | Moderate |
| Anticholinergics (e.g., Atropine, TCAs) | Additive anticholinergic effects (dry mouth, urinary retention, blurred vision). | Moderate |
| Alcohol, CNS Depressants | Although Fexofenadine is non-sedating, additive sedation may occur in sensitive individuals. | Moderate |
7. Patient Counselling
- Do take the exact dose as prescribed by your doctor.
- Do shake the bottle well before measuring the dose.
- Do use the measuring device provided with the syrup.
- Do inform your doctor about all other medicines you are taking.
- Don't take with fruit juices (apple, orange, grapefruit). Take with water.
- Don't exceed the recommended dose to avoid side effects.
- Don't use if the seal is broken or the syrup appears discolored.
8. Toxicology & Storage
Overdose: Fexofenadine: Dizziness, drowsiness, dry mouth. Phenylephrine: Predominant symptoms - severe hypertension, headache, palpitations, tachycardia, reflex bradycardia, anxiety, tremor, insomnia, urinary retention. In severe cases: cardiac arrhythmias, cerebral hemorrhage, convulsions.
Storage: Store at a temperature not exceeding 30°C. Protect from light and moisture. Keep the bottle tightly closed. Keep out of reach and sight of children. Do not use after the expiry date printed on the label.