Theophylline can help to relieve breathlessness by relaxing muscles in your airways so they open up. This means the air can flow through them more easily.

How does theophylline help asthma?

Some people with asthma are prescribed theophylline as an ‘add on’ treatment, to take as well as their usual reliever and preventer asthma inhalers. It is not a steroid.

“Theophylline relaxes the smooth muscles in your airways so they open up and can let air flow through them more easily,” says Asthma UK’s in-house GP Dr Andy Whittamore.

  • When you take theophylline at home it’s usually as a tablet or capsule that lasts all day. It helps manage day-to-day asthma symptoms by keeping your airways open and making breathing easier. It works alongside your preventer inhaler to reduce your risk of an asthma attack.
  • Theophylline is also used in hospital emergencies. It’s given directly into a vein (intravenously) to help relieve your asthma symptoms if an attack of breathlessness or an asthma attack has started. You’ll only ever be given theophylline intravenously if you’re in hospital. The doctor or nurse who gives it to you will make sure you get the correct dose and be able to answer any questions you may have.


Phyllocontin® drug discontinued

Phyllocontin® (aminophylline) tablets are being discontinued in the UK. If you’re prescribed Phyllocontin® for your asthma, your GP or asthma nurse will contact you about your options, which may include switching to theophylline tablets.


“Theophylline is not a steroid. If you do get any side effects, or you’re worried about anything at all, speak to your GP, asthma nurse or pharmacist as soon as possible. Keep taking the medicine until you’ve had that conversation,” says Dr Andy. “If you suddenly stop taking theophylline, your asthma symptoms may return, which could lead to a potentially fatal asthma attack.”

Keep taking your other asthma medicines if you take theophylline

“If you’re given theophylline to take at home, it’s an ‘add-on’ to your usual medicine and does not take the place of any other treatment you’re taking unless otherwise instructed to by your healthcare professional,” says Dr Andy. “If you find that your asthma improves after you start taking it, it’s important that you don’t stop taking any of your other medicines, as this will cause your symptoms to get worse again.”

You should always continue to take the preventer inhaler (corticosteroids) that you take regularly (usually twice daily) when you use long-acting bronchodilators such as theophylline.

Who might theophylline help?

Theophylline to take at home is usually prescribed by a specialist for adults and children whose asthma isn’t well managed with other medicines. 

Theophylline isn’t suitable for everyone, including people with certain health conditions or people who are taking some medicines (see below).

“It is very important that the person prescribing you medicines to help manage your asthma knows your full medical history and understands what other medicines you’re taking,” says Dr Andy. “Theophylline can be affected by this list of things: 

  • Smoking
  • Over-the-counter medicines or remedies
  • Recreational drugs
  • Alcohol
  • What you usually eat and drink.

“If any of these are likely to change you need to let your GP, asthma nurse or pharmacist know because it may affect how the drug works for you and whether it is still safe for you to take it. If you take theophylline every day at home, this type of it will not be useful during an asthma attack,” says Dr Andy. “Make sure you keep your fast-acting blue reliever inhaler with you at all times so you can use it if you have an asthma attack.”

How often do you need to take theophylline?

If you’re given theophylline to help manage your asthma every day, it needs to be taken regularly – usually every 12 hours, as prescribed by your doctor. It is very important that you take this medicine exactly as it’s prescribed. If you don’t, you may not be getting all its benefits.

“Your GP, asthma nurse or hospital doctor will tell you how often you need to take it – and will write it down on your written asthma action plan,” says Dr Andy. “This information is also written on the prescription label on the box of your medicine.”

If you’re unsure, make an appointment to see your GP or asthma nurse as soon as possible so you can ask. You can also ask your pharmacist.

If you’re taking theophylline to help manage your asthma every day, what else do you need to know?

  • You’ll need blood tests. Your GP or asthma nurse will arrange for you to have a blood test five days after you first start taking theophylline and at least three days after any dose adjustment. You’ll also need regular blood tests to check that you’re taking the correct dose. “It is important you always go for these tests, even if you are well, because it means your GP or asthma nurse can make sure that the level of theophylline in your blood stays at a safe level,” says Dr Andy. “Depending on the results of the tests, your dose may be adjusted.”
  • Sticking to the same brand is important. Make sure you get the same brand of theophylline each time you pick up a new prescription. “This is because the amount of theophylline absorbed by your body varies between brands,” says Dr Andy. “If you start taking a different brand to the one you normally have, you may be getting too much or too little of the medicine you need.”
  • Six weeks is long enough to tell if it works. “If theophylline has had no effect after you’ve been taking it for six weeks, then it’s probably not the right medicine for you,” says Dr Andy. “You and your GP or asthma nurse will need to discuss other treatment options.”
  • It can become unsuitable. “Over time, it is possible that theophylline can become unsuitable for some people even if it’s been suitable in the past,” says Dr Andy. “If you think that taking this medicine is causing you to become unwell, speak to your specialist, GP or asthma nurse straightaway. You also need to tell your specialist, GP or asthma nurse if you are pregnant, planning to get pregnant or breast feeding as theophylline may not be suitable for you.”
  • You’ll need to tell your GP about your lifestyle. Theophylline can interact with various everyday things that can mean the levels of it in your blood can go up − potentially to harmful levels.

If you’re taking theophylline, it’s really important to be aware that it can interact with:

    • Alcohol − ask your GP or asthma nurse if you can drink alcohol
    • Tobacco − tell your GP or asthma nurse if you smoke, or if you start or give up smoking
    • Caffeine − speak to your GP or asthma nurse if you drink lots of caffeinated drinks, such as tea, coffee, hot chocolate or energy drinks (caffeine is also found in chocolate, both milk and dark)
    • A herbal medicine called St John’s wort − tell your GP or asthma nurse if you’re taking any herbal medicines
    • There are lots of medicines that can affect how theophylline works and how safe it is. This is why if you are prescribed any new medicines such as antibiotics, vaccines or oral contraceptives, or have to have an anaesthetic, you need to let your doctor or dentist know as it may affect the medicines they can prescribe.

Possible side effects of theophylline

Like all medicines, theophylline can cause side effects for some people. “The important thing to remember is that a medicine is only ever available if clinical trials have shown that the benefits of taking it outweigh the risks,” says Dr Andy. “And talking to your GP or asthma nurse if you have any concerns or side effects means you can take steps to reduce your risks.”

If you’re taking theophylline to help manage your asthma every day, there’s a list of all potential side effects in the patient information leaflet in the box with your medicine. This can seem worrying when you read through it, but everyone who takes theophylline will respond to it differently. “It’s difficult to predict who will get side effects and who won’t,” says Dr Andy. “You may get some, or you may get none.”

It’s unlikely that you’ll experience any of the following symptoms, but if you do, seek medical attention immediately by calling your GP or 111:

  • Vomiting
  • Increased or rapid heart rate
  • Irregular heartbeat
  • Seizures
  • Skin rash.

Other possible side effects, which are more common, include:

  • Headache
  • Insomnia
  • Nausea
  • Irritability
  • Stomach upset.

You may find that there are some simple things you can do to help prevent or reduce these side effects. We also have a useful Q&A about the common concerns people have about taking asthma medicine here.

If you’re given theophylline in a hospital emergency, via your vein (intravenously), another possible short-term side effect is an irregular heartbeat. “This is why your healthcare professional may decide to keep an eye on your heart with a heart monitor,” says Dr Andy. “This is a painless process. You’ll have electrodes placed on your chest so your heart rate and rhythm show up on a screen.”

Get the best from your theophylline

You need to take theophylline exactly as it’s prescribed to get all its benefits. Here’s how:

  • Get into a good routine so that you don’t forget to take it at the right time(s) every day. You can try linking it to a habit − for example, taking it when you take your other asthma medicines. Or if you need to take it once a day, take it while you’re having breakfast. You may also find it helpful to set a reminder in your phone or make a note in your diary or on your calendar.
  • If you’re taking theophylline as tablets, swallow them whole with a drink of water. Crushing or chewing them may mean they can’t work as well. Each brand has different instructions on the best ways and times to take it, so check this with your GP, asthma nurse or pharmacist.
  • If you’re taking theophylline as capsules, swallow them whole with a drink of water. Or you (or your child) might find it easier to open the capsule and sprinkle the granules into some soft food, such as yoghurt. The granules should not be chewed as they’re swallowed, however. Each brand has different instructions on the best ways and times to take it, so check this with your GP, asthma nurse or pharmacist.
  • If you forget to take a dose, speak to your pharmacist about it.
  • As well as going for your usual regular blood tests, book an annual asthma review with your GP or asthma nurse so they can check how you or your child are doing.

To talk to our asthma nurse specialists, call the Asthma UK Helpline on 0300 222 5800 or message them via WhatsApp on 07378 606 728 (Monday-Friday, 9am-5pm).


Last updated September 2019

Next review due September 2022

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