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Pseudoephedrine - What is it & How Does it Work?

Pseudoephedrine is a decongestant that works by narrowing the blood vessels in the cavities of your nose. This can help you breathe more easily if you have a blocked or stuffy nose (nasal congestion). It can also be used to temporarily relieve sinus congestion and pressure.

While pseudoephedrine does not treat the underlying cause, or speed up recovery, it can provide relief from associated symptoms.

Here, we’ll explore how pseudoephedrine works, alongside dosage recommendations and potential side effects, to help you have a better understanding of pseudoephedrine.

In this guide:
  • What is pseudoephedrine used for?
  • How does pseudoephedrine work?
  • Who can take pseudoephedrine?
  • Potential pseudoephedrine side effects
  • Pseudoephedrine dosage recommendations
  • Pseudoephedrine FAQs
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What is pseudoephedrine used for?

Pseudoephedrine is commonly used to relieve nasal and sinus discomfort/congestion caused by cold and flu. It can also provide relief against certain symptoms arising from:

  • Sinusitis (a sinus infection)

  • Allergies, such as hay fever

Pseudoephedrine can either be taken in tablet or liquid form and can usually be purchased or prescribed at your local pharmacy. Sometimes, it may be formulated with additional ingredients to help treat colds, coughs, and other allergy symptoms.

How does pseudoephedrine work?

Pseudoephedrine works by narrowing the blood vessels in the nasal cavities to help decrease swelling and congestion caused by a cold, flu, infection, or allergies like hay fever. This allows mucus and air to flow more freely.

Who can take pseudoephedrine?

The majority of adults and children aged 12 years and over can take pseudoephedrine, although the age indication may differ depending on the medicine you’re taking. If you’re unsure about a dosage, contact your GP or pharmacist for more details about using the product.

Before use, always read the label and patient information leaflet. You should also get in touch with your pharmacist or GP before taking pseudoephedrine if you have:

  • Diabetes

  • Heart disease

  • High blood pressure (hypertension)

  • Liver or kidney problems

  • Have been taking medicines known as monoamine oxidase inhibitors (MAOIs) for depression in the last two weeks

  • Are on appetite suppressants or stimulants used to treat asthma and congestion (sympathomimetic drugs).

  • Are taking any other cold and cough medicines.

  • Have an enlarged prostate (this causes difficulty peeing or needing to pee more often)

  • Have glaucoma (increased pressure in the eye)

  • Have an overactive thyroid gland (hyperthyroidism)

  • Have had a previous allergic reaction to pseudoephedrine or any other medicine

Potential pseudoephedrine side effects

Like all medication, pseudoephedrine can cause side effects, although not everyone may experience them. Some potential side effects associated with SUDAFED® products that contain pseudoephedrine include:

  • Headaches

  • Dry mouth or nausea

  • Dizziness

  • Nervousness

  • Issues with sleeping

  • Anxiety, restlessness, and irritability

  • Vomiting

Be sure to check the leaflet inside your medicine packing for the full list of potential side effects.

Get in touch with your GP or pharmacist if you experience any of these side effects, or any not listed above, or if they persist. You can also report any other suspected side effects using the Yellow Card Scheme

In rare cases, some people may experience more serious side effects of pseudoephedrine. Contact 111 or seek immediate medical assistance if you have:

  • A fast, irregular, or pounding heartbeat that is continuous or keeps on coming back.

  • A sudden high temperature.

  • You get lots of pustules (small, fluid or pus-filled bumps), or your skin reddens.

Rarely, it is possible to have a serious allergic reaction to pseudoephedrine. Call 999 or seek immediate medical attention if:

  • Your throat feels tight, and/or you struggle to swallow.

  • Your tongue, throat, mouth, or lips suddenly become swollen.

  • Your skin, lips, or tongue turn pale, blue or grey.

  • Your breathing becomes more rapid, and you struggle to breathe.

  • ·You suddenly become, dizzy, drowsy, or very confused.

Pseudoephedrine dosage recommendations

Pseudoephedrine dosage instructions can vary depending on whether it’s prescribed, purchased from a pharmacy, or formulated with other ingredients. Always follow the instructions on the label or ask your pharmacist for advice if you buy pseudoephedrine from a pharmacy.

For example, SUDAFED® Decongestant Tablets come with an enclosed leaflet providing clear dosage instructions. These tablets contain pseudoephedrine hydrochloride and can be taken as one tablet every four to six hours up to four times a day (by adults and children over 12).

Pseudoephedrine FAQs

Store pseudoephedrine in the tightly closed container it came with, at room temperature and away from excess moisture and heat. Keep out of reach of children.

It is not recommended to consume alcohol whilst taking pseudoephedrine.

Both pseudoephedrine and phenylephrine are nasal decongestants, providing short-term relief from sinus pressure and congestion. However, there are differences in potential side effects.

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ALWAYS READ THE LABEL.

SUDAFED® Blocked Nose Spray (xylometazoline) (12+ years).

SUDAFED® Congestion & Headache Relief Max Strength Capsules (16+ years).

SUDAFED® Congestion & Headache Relief Day & Night Capsules (16+ years).

SUDAFED® Decongestant Tablets (Pseudoephedrine) (12+ years).

SUDAFED® Sinus Ease 0.1% Nasal Spray (Xylometazoline) (12+ years).

SUDAFED® Sinus Max Strength Capsules (16+ years).

SUDAFED® Mucus Relief Triple Action Cold & Flu Tablets (12+ years).

SUDAFED® Sinus Pressure & Pain Film-Coated Tablets (15+ years).

SUDAFED® Decongestant Liquid (Pseudoephedrine) (6+ years).

SUDAFED® Blocked Nose and Sinus Capsules (16+ years).

SUDAFED® Plus Blocked Nose Nasal Spray Solution (12+ years).

SUDAFED® Natural Relief Blocked Nose Spray is a medical device (from Birth).

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Site last updated on: 29th of May 2026 (UK-SUD-2026-332017)

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