Theophylline is used to treat lung diseases such as asthma and COPD (bronchitis, emphysema). It must be used regularly to prevent wheezing and shortness of breath. This medication belongs to a class of drugs known as xanthines. It works by relaxing the muscles around the airways so that they open up and you can breathe more easily. It also decreases the lungs' response to irritants. Controlling symptoms of breathing problems can decrease time lost from work or school.

This medication must be used regularly to be effective. It does not work right away and should not be used to relieve sudden breathing problems. If sudden shortness of breath occurs, use your quick-relief inhaler as prescribed.

Take this medication by mouth as directed by your doctor, usually once or twice daily. Since different manufacturers have different ways to take this medication, ask your doctor or pharmacist about the best time(s) to take your brand of theophylline and if you should take the drug with or without food.

Do not crush or chew the capsules or tablets. Doing so can release all of the drug at once, increasing the risk of side effects. Also, do not split the tablets unless they have a score line and your doctor or pharmacist tells you to do so. Swallow the whole or split tablet without crushing or chewing.

The dosage is based on your medical condition, response to treatment, age, weight, lab tests (theophylline blood levels), and other medications you may be taking. Be sure to tell your doctor and pharmacist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). To reduce your risk of side effects, your doctor may direct you to start this medication at a low dose and gradually increase your dose. Follow your doctor's instructions carefully.

Certain diets (such as high protein/low carbohydrate or high carbohydrate/low protein) may change the effect of theophylline. Tell your doctor if you have any major changes in your diet. Your doctor may need to adjust your dose.

Take this medication regularly to get the most benefit from it. To help you remember, take it at the same time(s) each day. Keep taking this medication even if you feel well. Do not increase your dose, take this drug more often, or stop taking it without first consulting your doctor.

Get medical help right away if your asthma symptoms worsen or if you are using your quick-relief inhaler more than usual or more often than prescribed.

Nausea/vomiting, stomach/abdominal pain, headache, trouble sleeping, diarrhea, irritability, restlessness, nervousness, shaking, or increased urination may occur. If any of these effects last or get worse, tell your doctor or pharmacist promptly.

Remember that this medication has been prescribed because your doctor has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects.

Tell your doctor right away if you have any serious side effects, including:

• nausea/vomiting that doesn't stop
• fast/slow/irregular heartbeat
• muscle cramps
• fainting
• confusion
• dizziness

Get medical help right away if you have any very serious side effects, including:

• seizures

A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including:

• rash
• itching/swelling (especially of the face/tongue/throat)
• severe dizziness
• trouble breathing

This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist.

In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch.

In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

Before using theophylline, tell your doctor or pharmacist if you are allergic to it; or to other xanthine drugs (such as aminophylline, oxtriphylline, caffeine); or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details.

Before using this medication, tell your doctor or pharmacist your medical history, especially of:

• stomach/intestinal ulcer
• seizures
• thyroid disease
• heart problems (such as heart failure, irregular heartbeat)
• liver disease
• high blood pressure

If you get sick or have a fever while taking this medication, tell your doctor right away. The dose of your medicine may need to be adjusted.

Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products).

Older adults may be more sensitive to the side effects of this drug, especially fast/irregular heartbeat, or trouble sleeping. Careful monitoring of side effects and drug blood levels is recommended.

Children may be more sensitive to the side effects of this drug. Careful monitoring of side effects and drug blood levels is recommended.

During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. Changes in your body during the last 3 months of pregnancy may affect the amount of this drug in your blood. Your doctor should carefully monitor the amount of drug in your blood, as well as any side effects, so that your dose may be changed if needed.

This drug passes into breast milk and may have undesirable effects on a nursing infant. Consult your doctor before breastfeeding.

Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval.

A product that may interact with this drug is:

• riociguat

Other medications can affect the removal of theophylline from your body, which may affect how theophylline works. Examples include cimetidine, disulfiram, fluvoxamine, interferon, mexiletine, rifampin, drugs used to treat seizures (such as carbamazepine, phenytoin), St. John's wort, ticlopidine, viloxazine, among others.

Cigarette/marijuana (cannabis) smoking decreases blood levels of this medication. Tell your doctor if you smoke or if you have recently stopped smoking.

Caffeine and alcohol can increase the side effects of this medication. Avoid drinking large amounts of beverages containing alcohol or caffeine (such as coffee, tea, colas), eating large amounts of chocolate, or taking nonprescription products that contain caffeine.

Theophylline is very similar to aminophylline and oxtriphylline. Do not take medications containing aminophylline or oxtriphylline while using theophylline.

This medication may interfere with certain lab tests (such as blood sugar, cholesterol, uric acid, dipyridamole-thallium imaging tests), possibly causing false test results. Make sure lab personnel and all your doctors know you use this drug.

If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call 1-800-222-1222. Canada residents can call 1-844-764-7669. Symptoms of overdose may include: nausea/vomiting that doesn't stop, seizures, muscle cramps, fast/irregular heartbeat, mental/mood changes (such as agitation, confusion), vomit that looks like coffee grounds.

Do not share this medication with others.

Lab and/or medical tests (such as theophylline blood levels) should be done while you are taking this medication. Keep all medical and lab appointments. Consult your doctor for more details.

If you miss a dose, skip the missed dose. Take your next dose at the regular time. Do not double the dose to catch up.

Store at room temperature away from light and moisture. Do not store in the bathroom. Keep all medications away from children and pets.

Do not flush medications down the toilet or pour them into a drain unless instructed to do so. Properly discard this product when it is expired or no longer needed. Consult your pharmacist or local waste disposal company.

Your condition can cause complications in a medical emergency. For information about enrolling in MedicAlert, call 1-888-633-4298 (US) or 1-800-668-1507 (Canada).