Indications
Phenylephrine is mainly used to relieve a blocked or runny nose caused by colds, flu, sinusitis and allergies. In Bangladesh it is most often found in cough and cold syrups combined with an antihistamine and a cough suppressant. Eye drops containing phenylephrine are used to relieve minor eye redness, and stronger eye drops are used by eye doctors to widen the pupil for eye examinations. An injection form is used in hospital to raise low blood pressure during anaesthesia.
How It Works
Phenylephrine is a decongestant. It acts on alpha receptors in blood vessels and makes them narrow. In the nose this reduces swelling and opens the airway; in the eye it reduces redness and widens the pupil; in the bloodstream it raises blood pressure.
Dosage and Administration
Cough and cold products: follow the dose on the product label or as advised by the doctor or pharmacist, because the strength differs between products. For adults, the total phenylephrine from all products should usually not be more than 60 mg a day. Children: only use a product made for children, at the labelled dose for their age; do not give cough and cold medicines to children under 6 years without a doctor’s advice.
Eye drops for redness: usually 1 drop in the affected eye up to 4 times a day for no more than 2 to 3 days. Eye drops for pupil widening and the injection are given by a doctor or nurse.
Interactions
- Do not take it with MAO inhibitors (such as Phenelzine, Selegiline or Linezolid) or within 14 days of stopping them; a dangerous rise in blood pressure can happen.
- Other decongestants and stimulants, including Pseudoephedrine and Ephedrine, increase side effects.
- It can weaken blood pressure medicines and beta-blockers.
- Tricyclic antidepressants such as Amitriptyline and Digoxin can increase heart effects.
Contraindications
- Severe high blood pressure or serious heart disease.
- Taking an MAO inhibitor now or in the last 14 days.
- Overactive thyroid.
- Closed-angle glaucoma (for eye drops).
- Allergy to phenylephrine or any ingredient of the product.
Side Effects
Common effects are headache, restlessness, nervousness, trouble sleeping, fast or pounding heartbeat and a rise in blood pressure. Eye drops can cause stinging, blurred vision and, with overuse, redness that comes back worse.
Get urgent medical help for a severe headache, chest pain, a very fast, slow or irregular heartbeat, fainting, eye pain or sudden change in vision, or signs of allergy such as swelling of the face or difficulty breathing.
Pregnancy and Lactation
Avoid in pregnancy, especially in the first three months, unless a doctor advises it. Avoid while breastfeeding unless a doctor advises it.
Precautions and Warnings
- Use with care and ask a doctor first if you have high blood pressure, heart disease, diabetes, thyroid disease, an enlarged prostate or glaucoma.
- Do not take more than one cough and cold product at a time, because many contain the same ingredients.
- Use for short periods only. If symptoms last more than 7 days or come with high fever, see a doctor.
- Combination syrups that contain an antihistamine can cause drowsiness; do not drive if affected.
Overdose
Too much can cause very high blood pressure, severe headache, slow or irregular heartbeat, vomiting, anxiety and fits. Seek medical help straight away, especially if a child has swallowed it.
Therapeutic Class
Sympathomimetic decongestant (alpha-adrenergic agonist).
Storage
Store below 30°C in a dry place, away from light and out of the reach of children. Use eye drops within 4 weeks of opening, or as stated on the pack.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.