1. Clinical Overview
A fixed-dose combination (FDC) medication primarily used for symptomatic relief of allergic rhinitis and the common cold. Fexofenadine is a second-generation, non-sedating H1-antihistamine that blocks histamine effects. Phenylephrine is a selective α1-adrenergic receptor agonist that acts as a nasal decongestant by vasoconstriction. Paracetamol (Acetaminophen) is a centrally-acting analgesic and antipyretic that inhibits cyclooxygenase (COX) pathways in the CNS. This combination addresses multiple symptoms: allergy, congestion, pain, and fever.
| Onset | Duration | Bioavailability |
|---|---|---|
| Fexofenadine: 1-2 hours; Phenylephrine: 15-30 minutes (nasal decongestion); Paracetamol: 30-60 minutes. | Fexofenadine: ~24 hours; Phenylephrine: ~4 hours; Paracetamol: 4-6 hours. | Fexofenadine: ~33%; Phenylephrine: ~38% (oral); Paracetamol: ~88%. |
2. Mechanism of Action
The combination exerts a multi-target symptomatic effect. Fexofenadine competitively and selectively inhibits peripheral H1 receptors, preventing histamine-mediated allergic responses (vasodilation, increased capillary permeability, itching). Phenylephrine stimulates post-synaptic α1-adrenergic receptors in vascular smooth muscle of the respiratory tract mucosa, causing vasoconstriction, reduced edema, and decreased nasal congestion. Paracetamol acts centrally by inhibiting prostaglandin synthesis (COX-1 and COX-2 inhibition in CNS), raising the pain threshold, and acting on the hypothalamic heat-regulating center to produce antipyresis.
3. Indications & Uses
- Symptomatic relief of Allergic Rhinitis (seasonal/perennial)
- Symptomatic relief of Common Cold
- Symptomatic relief of Influenza (flu)
4. Dosage & Administration
Adult Dosage: One tablet (Fexofenadine 60mg + Phenylephrine 10mg + Paracetamol 500mg) every 8 to 12 hours. Maximum: 2 tablets in 24 hours.
Administration: Administer orally with a full glass of water. Can be taken with or without food. However, avoid taking with fruit juices (orange, apple, grapefruit) as they can significantly reduce fexofenadine absorption. Do not crush or chew. Space doses evenly. Do not use for more than 7 days for pain or 3 days for fever without consulting a doctor.
5. Side Effects
Common side effects may include:
- Headache
- Drowsiness (uncommon with fexofenadine but possible)
- Nausea
- Dry mouth
- Dizziness
- Insomnia (due to phenylephrine)
- Nervousness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Monoamine Oxidase Inhibitors (MAOIs) - e.g., Phenelzine, Selegiline | Risk of severe hypertensive crisis due to potentiation of phenylephrine's vasopressor effects. | Contraindicated |
| Beta-blockers (e.g., Propranolol) | Unopposed alpha-adrenergic stimulation can lead to severe hypertension and bradycardia. | Major |
| Other sympathomimetics (e.g., Pseudoephedrine, Decongestants) | Additive pressor effects, increasing risk of hypertension, tachycardia, and arrhythmias. | Major |
| Antihypertensives (e.g., Alpha-blockers, Beta-blockers, ACE inhibitors) | Phenylephrine may antagonize the hypotensive effect. | Moderate |
| Alcohol | Increased risk of hepatotoxicity with paracetamol; CNS depression may be additive with fexofenadine (rare). | Moderate |
| Drugs inducing CYP2E1 (e.g., Isoniazid, Rifampicin, Carbamazepine) | Increased conversion of paracetamol to toxic metabolite NAPQI, raising hepatotoxicity risk. | Major |
| Warfarin | Paracetamol may potentiate anticoagulant effect, increasing INR risk, especially with high doses (>2g/day). | Moderate |
| Anticholinergics (e.g., Atropine, Tricyclic Antidepressants) | Additive anticholinergic effects with fexofenadine (mild), risk of urinary retention, dry mouth. | Moderate |
| Erythromycin, Ketoconazole | May increase fexofenadine plasma levels via P-glycoprotein inhibition, but clinical significance is low. | Minor |
7. Patient Counselling
- DO take with a full glass of water, not with fruit juice.
- DO inform your doctor about all other medications, including OTC drugs and herbal supplements.
- DO not exceed the recommended dose or duration (max 7 days for pain, 3 days for fever).
- DO not take with other paracetamol-containing products (e.g., cough syrups, other pain relievers).
- DO not use to make a child sleepy.
- DO not crush or chew the tablet.
8. Toxicology & Storage
Overdose: Paracetamol: Stage 1 (0-24h): Nausea, vomiting, anorexia, malaise. Stage 2 (24-72h): Right upper quadrant pain, elevated LFTs. Stage 3 (72-96h): Peak hepatotoxicity, jaundice, coagulopathy, encephalopathy, potentially fatal hepatic necrosis. Phenylephrine: Severe hypertension, headache, palpitations, tachycardia, arrhythmias, cerebral hemorrhage, pulmonary edema. Fexofenadine: Dizziness, drowsiness, dry mouth (generally low toxicity).
Storage: Store below 30°C, in a cool, dry place. Protect from light and moisture. Keep out of reach of children. Do not use after the expiry date printed on the pack.