A decongestant, also used by injection to raise blood pressure
Phenylephrine
A decongestant in cold remedies and nasal sprays, also given by injection to raise blood pressure during anaesthesia.
What is Phenylephrine?
Phenylephrine is used in two main ways. As a decongestant in cold and flu tablets and nasal sprays, it relieves a blocked nose by tightening blood vessels in the lining. As an injection given by an anaesthetist, it raises blood pressure that has dropped during anaesthesia. Because it tightens blood vessels, it can raise blood pressure, so it is used with caution in people with heart disease or high blood pressure. An important point with nasal sprays is that overusing them for more than a few days can cause 'rebound' congestion, where the blockage returns worse than before.
Education and reference only. This is a plain-language guide to Phenylephrine — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Phenylephrine is a medicine that narrows blood vessels. In everyday use it is found as a decongestant in many cold and flu remedies and in nasal sprays and drops, where it relieves a blocked or stuffy nose. In hospital, it has a quite different role: anaesthetists give it as an injection to bring up blood pressure that has fallen too low during an operation or with a spinal anaesthetic. So the same medicine works either to clear a stuffy nose or, in a controlled setting, to support the circulation. It is available as tablets, nasal sprays and drops, and as an injection.
How it works
Phenylephrine tightens the muscle in the walls of blood vessels, making them narrower. In the nose, this shrinks the swollen, blood-filled lining that causes a blocked feeling, so air flows more easily. Throughout the body, narrowing the vessels raises blood pressure, which is why an anaesthetist can use an injection of it to lift blood pressure that has dropped during anaesthesia. The same vessel-tightening action explains its cautions: it can raise blood pressure, and in the nose, over-using a spray can lead to rebound congestion as the lining reacts.
Company & origin
Originated / developed by: Various manufacturers.
A medicine used as a decongestant in cold and flu remedies and nasal sprays, and by injection to support blood pressure during anaesthesia.
What it treats
Conditions Phenylephrine is used for
Practical use
How to take Phenylephrine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- For a blocked nose, use the tablets, spray or drops exactly as directed on the product or by your pharmacist.
- Use decongestant nasal sprays for only a few days at a time to avoid 'rebound' congestion that makes the blockage worse.
- Check with a pharmacist before using it if you have heart disease, high blood pressure or an overactive thyroid.
- Do not use it with, or soon after, antidepressants of the MAOI type.
- The injection is given only by an anaesthetist or specialist in a monitored setting, not by you.
Weighing it up
Advantages & disadvantages of Phenylephrine
Advantages
- Relieves a blocked, stuffy nose during colds and flu.
- Available without prescription in tablets, sprays and drops for nasal congestion.
- By injection, gives anaesthetists a reliable way to support blood pressure during anaesthesia.
Disadvantages
- Can raise blood pressure, so it is used with caution in heart disease and high blood pressure.
- Nasal sprays can cause 'rebound' congestion if used for more than a few days.
- Can cause restlessness, a faster heartbeat or difficulty sleeping in some people.
Practical use
Good to know
Because phenylephrine tightens blood vessels, it can raise blood pressure, so it is used with caution in people with heart disease, high blood pressure, an overactive thyroid or certain other conditions; if you have these, check before using cold remedies that contain it. The most important practical tip with the nasal spray is to use it only for a few days at a time: using it for longer can cause 'rebound' congestion, where the nose becomes more blocked once the spray wears off, leading to a cycle of needing more of it. The injectable form is used only by anaesthetists and specialists in a monitored setting. It should not be used with, or soon after, antidepressants of the MAOI type. Tell your pharmacist about your other medicines and conditions before buying a decongestant that contains it.
Who should not take it / use with caution
- People who have had a serious allergic reaction to phenylephrine should not use it.
- It is used with caution, or avoided, in people with heart disease, high blood pressure or an overactive thyroid.
- It must not be used with, or soon after, antidepressants of the MAOI type.
- Decongestant products are used with care in children and should be checked with a pharmacist.
Monitoring
- For the injectable form, close monitoring of blood pressure and heart rate by the anaesthetist.
- For nasal sprays, reviewing how long they have been used to avoid rebound congestion.
- Checking blood pressure where there is a concern, particularly in people with heart conditions.
Side effects
- Restlessness, a faster heartbeat or a rise in blood pressure.
- Headache, dizziness or difficulty sleeping.
- With nasal sprays, stinging, dryness or, if overused, 'rebound' congestion.
- Rarely, palpitations or a marked rise in blood pressure, which need medical attention.
Key interactions
- It must not be used with, or soon after, antidepressants of the MAOI type, because of a dangerous rise in blood pressure.
- It can reduce how well some blood-pressure medicines work and add to the effects of other stimulants.
- Tell your pharmacist or prescriber about all medicines and conditions before using products that contain it.
Available as: Tablets, nasal sprays and drops, and a solution for injection given by a specialist.
Answers
Phenylephrine: frequently asked questions
What is phenylephrine used for?
It is used as a decongestant in cold and flu remedies and nasal sprays to relieve a blocked nose, and by injection by anaesthetists to raise blood pressure that has dropped during anaesthesia.
Can I use it if I have high blood pressure?
It can raise blood pressure, so it is used with caution in people with high blood pressure or heart disease. Check with a pharmacist before using a decongestant that contains it.
Why does my nose get more blocked after using the spray?
Using a decongestant nasal spray for more than a few days can cause 'rebound' congestion, where the nose becomes more blocked when the spray wears off. Use it only for a short time.
Is the injection the same medicine?
Yes, it is the same medicine, but the injection is used only by anaesthetists and specialists in a monitored setting to support blood pressure, not for a blocked nose.
Can I take it with antidepressants?
It must not be used with, or soon after, antidepressants of the MAOI type because of the risk of a dangerous rise in blood pressure. Always check with your pharmacist.
The wider class
About Decongestant / blood-pressure-raising medicine
Phenylephrine belongs to the decongestant / blood-pressure-raising medicine class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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