Theophylline is used to treat or prevent the symptoms of bronchial asthma, chronic bronchitis, emphysema, and other diseases involving constriction of the airways. Theophylline helps to ease the cough, wheezing, shortness of breath, and troubled breathing associated with these conditions by allowing relaxation of the tubes (bronchi) of the airways, thereby permitting increased amounts of air to flow through them.

This medication may be available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms or approved for all of the conditions discussed here. As well, some forms of this medication may not be used for all of the conditions discussed here.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. If you have not discussed this with your doctor or are not sure why you are using this medication, speak to your doctor. Do not stop using this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to use this medication if their doctor has not prescribed it.

The dose of theophylline is carefully determined by your doctor based on your age and response to the medication. Sometimes blood tests are required in order to make sure the levels of theophylline are within the range that will be effective, yet not high enough to cause unwanted side effects.

Theophylline liquid should be taken with milk or food.

Use an oral syringe to measure each dose of the liquid, as it gives a more accurate measurement than household teaspoons.

Theophylline must be taken regularly as prescribed so that blood levels of the medication are always in the correct range for effectiveness. It is important that you don't take more theophylline than prescribed, even if your breathing does not get better, because levels at which signs of overdose take place are not as high as most medications. If your breathing does not improve, or gets worse, call your doctor at once.

Many things can affect the dose of medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are using the medication without consulting your doctor.

It is important to take this medication exactly as prescribed by your doctor. If you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

Store this medication at room temperature, protect it from light and moisture, and keep it out of the reach of children.

Do not use this medication if you:

• are allergic to theophylline or any ingredients of this medication
• are allergic to related medications (i.e., xanthines)
• have active or symptomatic coronary artery disease
• have a peptic ulcer

Do not give this medication to children less than 5 years old.

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent.

The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

• diarrhea
• fast heartbeat
• feeling of excitement
• flushing
• headache
• heartburn or stomach pain
• increased urination
• loss of appetite
• low blood pressure (dizziness or lightheadedness when rising from a lying or sitting position)
• nausea
• nervousness
• restlessness
• trembling
• trouble sleeping
• vomiting

Although most of the side effects listed below don't happen very often, they could lead to serious problems if you do not seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

• hives
• skin rash
• symptoms of irregular heartbeat (e.g., chest pain, dizziness, rapid, pounding heartbeat, shortness of breath)
• symptoms of toxicity:
• abdominal pain (continuing or severe)
• confusion or change in behaviour
• dark or bloody vomit
• diarrhea
• dizziness or lightheadedness
• extreme flushing or fever
• extreme thirst
• fast and/or irregular heartbeat
• nausea
• nervousness or restlessness (continuing)
• ringing or buzzing in the ears
• seizures
• trembling (continuing)
• unusual increase or decrease in urination (or passing of water)
• vision changes (e.g., seeing flashes of light)
• vomiting

Stop taking the medication and seek immediate medical attention if any of the following occur:

• convulsions (seizures)
• signs of bleeding in the stomach or intestines (e.g., bloody, black, or tarry stools, spitting up of blood, vomiting blood or material that looks like coffee grounds)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Changes in life: Changes in your life can sometimes affect the way theophylline affects you. Tell your doctor if any of the following occur:

• you start or stop smoking
• you start or stop another medication
• you change your diet for a long time
• you have a fever of 39°C (102°F) for at least 24 hours or higher than 38°C (100°F) for longer than 24 hours

Heart disease: Heart disease can affect how theophylline is used in the body, causing an increase in side effects. If you have high blood pressure, irregular heartbeat, or heart disease, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: Liver disease or reduced liver function may cause this medication to build up in the body, causing side effects. If you have liver problems, discuss with your doctor how this medication may affect your medical condition, how your medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Pregnancy: Theophylline crosses the placenta and may affect the development of the baby, if the mother takes it during pregnancy. This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.

Breast-feeding: This medication passes into breast milk. If you are a breast-feeding mother and are taking theophylline, it may affect your baby. Talk to your doctor about whether you should continue breast-feeding.

Seniors: Seniors may be more likely to experience side effects of this medication.

The stimulating effects of coffee and colas may be exaggerated with the use of this medication.

There may be an interaction between theophylline and any of the following:

• adalimumab
• acyclovir
• alcohol
• allopurinol
• amiodarone
• amphetamines (e.g., dextroamphetamine, lisdexamfetamine)
• antipsychotic medications (e.g., aripiprazole, cariprazine, chlorpromazine, clozapine, quetiapine, risperidone)
• atomoxetine
• "azole" antifungals (e.g., fluconazole, ketoconazole)
• barbiturates (e.g., butalbital, phenobarbital)
• benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
• beta-adrenergic blockers (e.g., atenolol, propranolol, sotalol)
• birth control pills
• fast-acting bronchodilators (e.g., salbutamol, terbutaline)
• long-acting bronchodilators (e.g., formoterol, indacaterol, salmeterol)
• bupropion
• caffeine
• cannabis
• cimetidine
• decongestant cold medications (e.g., phenylephrine, pseudoephedrine)
• decongestant eye drops and nose sprays (e.g., naphazoline, oxymetazoline, xylometazoline)
• deferasirox
• dexmethylphenidate
• dipivefrin
• epinephrine
• estrogens (e.g., conjugated estrogen, estradiol, ethinyl estradiol)
• influenza virus vaccine
• isoniazid
• leflunomide
• linezolid
• lithium
• macrolide antibiotics (e.g., clarithromycin, erythromycin)
• methotrexate
• methoxsalen
• methylphenidate
• mexiletine
• modafinil
• nabilone
• other theophyllines (e.g., aminophylline, oxtriphylline)
• pentoxifylline
• propafenone
• quinolone antibiotics (e.g., ciprofloxacin, ofloxacin)
• rifampin
• riociguat
• ritonavir
• seizure medication (e.g., carbamazepine, clobazam, phenytoin, primidone)
• stiripentol
• selective serotonin reuptake inhibitors (SSRIs; e.g., citalopram, fluoxetine, paroxetine, sertraline)
• teriflunomide
• thyroid medications (medications for overactive or underactive thyroid)
• tobacco
• valacyclovir
• vemurafenib
• verapamil
• zafirlukast

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

• stop taking one of the medications,
• change one of the medications to another,
• change how you are taking one or both of the medications, or
• leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.