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Generic name: theophylline (oral) [ thee-OFF-i-lin ]
Brand names: Elixophyllin, Theo-24
Drug class: Methylxanthines

Medically reviewed by on Aug 31, 2022. Written by Cerner Multum.

What is Theo-24?

Theo-24 is a bronchodilator that is used to treat symptoms of asthma, bronchitis, emphysema, and other breathing problems.

Theo-24 may also be used for purposes not listed in this medication guide.


Never use Theo-24 in larger amounts, or for longer than prescribed. Seek medical attention if your breathing problems get worse quickly, or if you think your medications are not working as well.

Overdose can occur if you take too much Theo-24 at one time, or if your daily doses are too high.

Tell your doctor about all your current medicines and any you start or stop using. Many drugs can interact with Theo-24.

Before taking this medicine

You should not use Theo-24 if you are allergic to it.

Tell your doctor if you have ever had:

Tell your doctor if you drink alcohol, or if you smoke or have recently quit smoking cigarettes or marijuana.

Also tell your doctor if you have been sick with a high fever (102 degrees or higher) for 24 hours or longer.

Tell your doctor if you are pregnant or breastfeeding.

Do not give Theo-24 to a child without medical advice.

How should I take Theo-24?

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Never use Theo-24 in larger amounts, or for longer than prescribed.

Theo-24 is not a rescue medicine for asthma or bronchospasm attacks. Use only fast-acting inhalation medicine for an attack. Seek medical attention if your breathing problems get worse quickly, or if you think your medications are not working as well.

Swallow the capsule or tablet whole and do not crush or chew it. You may break a scored tablet in half if needed to get the correct dose.

Some tablets are made with a shell that is not absorbed or melted in the body. Part of this shell may appear in your stool. This is normal and will not make the medicine less effective.

Measure liquid medicine carefully. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

Your dose and the number of times you take Theo-24 daily will depend on the reason you are taking this medication.

Follow your doctor's instructions about whether to take your medication with food or on an empty stomach.

Your dose needs may change if you are ill, or if you switch to a different brand, strength, or form of this medicine. Avoid medication errors by using only the form and strength your doctor prescribes.

You will need regular medical tests to be sure you are using the right dose. Do not change your dose or dosing schedule without your doctor's advice.

Theo-24 doses are based on weight in children. Your child's dose needs may change if the child gains or loses weight.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using Theo-24.

Store at room temperature away from moisture, heat, and light.

What happens if I miss a dose?

Skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. Seizures caused by a Theo-24 overdose can cause death or permanent brain damage.

Theo-24 overdose can occur if you accidentally take too much at one time. Overdose can also occur slowly over time if your daily doses are too high. To be sure you are using the correct dose, your blood will need to be tested often.

Overdose symptoms may include severe nausea and vomiting, seizure, slow heart rate, weak pulse, or fainting.

What should I avoid while using theophylline?

Do not start or stop smoking without first talking to your doctor. Smoking changes the way your body uses Theo-24, and you may need to use a different dose.

Avoid taking an herbal supplement containing St. John's wort.

Avoid driving or hazardous activity until you know how Theo-24 will affect you. Your reactions could be impaired.

Theo-24 side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Theo-24 may cause serious side effects. Call your doctor at once if you have:

  • severe or continued vomiting;

  • ongoing headache, trouble sleeping;

  • rapid heartbeats;

  • a seizure;

  • new signs of illness (especially fever);

  • low potassium level--leg cramps, constipation, irregular heartbeats, fluttering in your chest, increased thirst or urination, numbness or tingling, muscle weakness or limp feeling; or

  • high blood sugar--increased thirst, increased urination, dry mouth, fruity breath odor.

Serious side effects may be more likely in older adults.

Common side effects of Theo-24 may include:

  • nausea, vomiting, diarrhea;

  • headache;

  • sleep problems (insomnia);

  • tremors;

  • sweating; or

  • feeling restless or irritable.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

What other drugs will affect Theo-24?

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

If you take St. John's wort regularly, do not stop taking it without first asking your doctor. Starting or stopping St. John's wort can affect your blood levels of theophylline.

Many drugs can affect Theo-24. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.

Further information

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.