Indications
Phenylephrine Hydrochloride eye drops are used to widen (dilate) the pupil before an eye examination, before some eye operations and for certain eye tests. The drops are often used together with another dilating drop such as Tropicamide for a wider and quicker effect. Phenylephrine is also found in some nasal and oral cold medicines as a decongestant, but this entry describes the eye drop form.
How It Works
Phenylephrine stimulates alpha receptors in the small muscle of the iris that pulls the pupil open. This makes the pupil larger so the doctor can see the back of the eye. It also narrows small blood vessels on the surface of the eye. It does not stop the eye from focusing, so vision for reading is usually only mildly affected.
Dosage and Administration
The drops are usually put in by an eye doctor, nurse or optometrist in the clinic. Usually one drop is placed in the eye, sometimes repeated after a few minutes, as directed by the eye specialist. The stronger strength (10%) is used with extra care. Press gently on the inner corner of the eye for one to two minutes after the drop to reduce absorption into the body. Do not use at home unless your eye doctor has told you how.
Interactions
Tell your doctor if you take MAO inhibitors (such as Selegiline), tricyclic antidepressants (such as Amitriptyline), beta blockers (such as Propranolol), other blood pressure medicines or medicines for heart rhythm, because the drops can raise blood pressure or affect the heart in sensitive people. Strong eye drops can add to the effect of other dilating drops.
Contraindications
- Allergy to Phenylephrine or any ingredient of the drops.
- Narrow angle glaucoma (a type of glaucoma where dilating the pupil can trigger a sudden rise in eye pressure).
- The 10% strength should be avoided in babies, in people with severe high blood pressure, serious heart disease, aneurysm or an overactive thyroid.
Side Effects
Common effects are stinging or burning when the drop goes in, blurred vision, sensitivity to bright light for a few hours and redness of the eye. Less often there may be headache, a racing or pounding heartbeat, raised blood pressure, paleness or sweating, especially with the stronger strength.
Get urgent medical help if you have chest pain, a severe headache, a very fast or irregular heartbeat, sudden eye pain with blurred vision, seeing haloes, or nausea and vomiting after the drops, as this may be a rise in eye pressure.
Pregnancy and Lactation
Only small amounts reach the body from eye drops, but safety in pregnancy has not been fully proven. Tell your eye doctor if you are pregnant or breastfeeding so they can decide whether the drops are needed and choose the lowest strength.
Precautions and Warnings
Your vision will be blurred and light will feel very bright for several hours after dilation. Do not drive or operate machines until your vision is clear, and wear sunglasses outdoors. Use with care in older people, in people with heart disease, high blood pressure, diabetes or an overactive thyroid, and in babies. Remove soft contact lenses before use. Do not touch the dropper tip to the eye.
Overdose
Too many drops or accidental swallowing, especially by a child, can cause high blood pressure, a fast or slow heartbeat, headache, vomiting or tremor. Seek medical help straight away.
Therapeutic Class
Mydriatic (pupil dilating) agent; alpha adrenergic agonist (sympathomimetic) eye preparation.
Storage
Store below 30°C in a dry place, away from light and out of the reach of children. Do not freeze. Discard the bottle within 4 weeks of opening, or as directed on the pack.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.