Difference between Pseudoephedrine and Phenylephrine

Updated on February 15, 2018

Pseudoephedrine and phenylephrine are nasal decongestants most people recognize as active ingredients in Sudafed, a popular brand of decongestant. This article seeks to explain the differences between the two.


Pseudophedrine in tablet form

Pseudoephedrine, also known as PSE, is a decongestant administered for the treatment of nasal congestion caused by colds, allergies, and sinus infections, to name a few. It is also used as a stimulant and a “eugeroic,” a type of drug that enhances alertness.

Pseudoephedrine is a stimulant that acts on the sympathetic nervous system, which is the system responsible for an individual’s fight or flight response. This reaction involves dilation of the pupils, increased heart rate, and enhanced energy. In addition to being a stimulant, pseudoephedrine is best known as an effective decongestant as it can shrink swollen mucous membranes.

Pseudoephedrine is administered orally and as a topical decongestant. Its stimulating properties can induce adverse effects such as sweating, hypertension, anxiety, insomnia, and urinary problems. Some studies claim that pseudoephedrine may be effective as a cough suppressor (i.e. antitussive).

Some common side effects associated with a pseudoephedrine therapy include the stimulation of the central nervous system, insomnia, excitability, anxiety, and dizziness. Occasional use of this drug is known to induce palpitations. Studies have also found rare side effects such as hypertension, hallucinations, and seizures.

Phenylephrine in liquid form

Phenylephrine is administered mainly as a decongestant and to increase blood pressure. It is offered as an alternative for pseudoephedrine, but studies suggest that phenylephrine taken orally at the prescribed dose is ineffective. It is also topically applied to treat symptoms of hemorrhoids as it supposedly narrows swollen veins and relieves the pain associated with it.

Phenylephrine is available as an oral medicine or nasal spray and is a common ingredient in over-the-counter decongestants in the US. Phenylephrine is also used as a substitute for pseudoephedrine in decongestants as PSE is used in the illegal manufacture of methamphetamine. In 2006, Leslie Hendeles, along with Randy Hatton, two pharmacists from the University of Florida, cited phenylephrine as being ineffective as a nasal decongestant in its 10-mg form. Many studies followed, but the US Food and Drug Administration upheld its 1976 decision approving phenylephrine as a nasal decongestant.

Pseudoephedrine vs Phenylephrine

So what’s the difference between pseudoephedrine and phenylephrine? Both are active ingredients in decongestant medicines such as Sudafed. However, the sale of pseudoephedrine is regulated as it is an ingredient in the illegal production of methamphetamine. A prescription is required to be able to purchase medication containing pseudoephedrine. In contrast, phenylephrine is an over-the-counter medication. Phenylephrine is used as an alternative to pseudoephedrine for this very reason.

The decongestant effect of pseudoephedrine, when taken in tablet or liquid form, can last for 4 to 6 hours. An extended-release tablet can last 24 hours. Phenylephrine can last up to 4 hours. Pseudoephedrine acts on the sympathetic nervous system and can induce heightened alertness, enhanced energy, and increased heart rate. Phenylephrine can only act as a nasal decongestant. The stimulant property of pseudoephedrine can cause side effects such as nervousness, insomnia, anxiety, and palpitations. Phenylephrine is known to cause side effects such as headaches, excitability, and cardiac arrhythmias or irregular heartbeat.

Comparison Chart

Nasal decongestant with stimulant propertiesPrimarily a nasal decongestant
Depending on the dosage, effect can last from 4-24 hoursEffect lasts for 4 hours
Side effects include insomnia, nervousness, anxiety, etc.Side effects include headaches, irregular heartbeat, and excitability
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