What is Phenylephrine?

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  • Written By: Alex Tree
  • Edited By: Melissa Wiley
  • Last Modified Date: 22 October 2019
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Phenylephrine is a medication often used to relieve nasal or sinus congestion caused by the common cold, seasonal allergies, and other conditions. This decongestant is normally available over the counter in many countries around the world, meaning it can be purchased without a prescription. It comes in a variety of forms, though nasal spray is an especially common form, and can be taken about every four hours to temporarily lessen or eliminate symptoms of minor ailments. Phenylephrine can temporarily worsen some conditions, like epilepsy and hypertension, in addition to having other, more common side effects. Less common uses of the drug are to increase blood pressure and pupil dilation.

The medication as a decongestant is typically taken in the forms of a tablet, nasal spray, or soluble film placed on the tongue. Nasal spray is a particularly popular form of phenylephrine in several countries. The effectiveness of the drug to relieve congestion is a subject of debate and research because some studies have found that it is no more effective than a placebo, in direct contradiction to other studies. To dilate the pupils, usually for a health professional to better exam the eye, the drug takes the form of eye drops. As a way to increase blood pressure, phenylephrine can be especially useful because it does not increase heart rate as well.


Phenylephrine, no matter how it is administered, can increase the risk of epileptic seizures in those who have epilepsy, but its most common side effect is high blood pressure, also known as hypertension. Abdominal cramping, vomiting, and an upset stomach may also be the fault of phenylephrine. Less severe side effects are temporary insomnia, nervousness, and dizziness. Around one week after taking phenylephrine in a nasal spray, a patient may experience even more congestion, which is called rebound congestion and should not be treated with further sprays. If a person already has high blood pressure, he or she will usually be advised by his or her health professional to not take this medication.

This medication is available in popular cold remedies around the world. For example, in the United States, Tylenol®, DayQuil®, and Benadryl® commonly use phenylephrine as an ingredient in some of their products. The brands Decolgen and Bioflu in the Philippines may also contain the drug. Italy, India, and the United Kingdom are also among the countries that have products containing the drug. Even with its effectiveness being questioned, the medication has a strong market.


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