The amount of theophylline needed to prevent symptoms varies from patient to patient. Dosage is based on a number of factors, including the patient's:

• Age
• Weight
• Severity of asthma
• Diet
• Additional medications
• Rate of theophylline elimination in the body

In order to determine if a patient is receiving the proper amount, a physician may order a blood test to measure the level of theophylline in the blood. The blood level range for safe, effective levels of theophylline is very narrow. Maintaining the proper level of theophylline is important because too little does not work and too much can be toxic. Therefore, it is extremely important to have the levels monitored by the physician as directed.

Those who take theophylline should be aware that there is a very small difference between a proper dose of the medication and a dangerous, toxic dose. For this reason, extreme caution must be exercised by all patients using theophylline.

Theophylline is usually taken every 6, 8, 12 or 24 hours. Those who miss a dose should take theophylline as soon as they remember unless it is at a time near to the next regularly-scheduled dose. In the latter case, the missed dose should not be made up. Never take a double dose of the medication, as there is a very small difference between the proper dose of theophylline and an overdose that requires medical attention.

Patients who have been prescribed this drug should take it exactly as directed by their physician. They should continue to take it even if they feel well and are not experiencing symptoms. A patient should not stop taking the drug unless advised to do so by their physician. 

Minor side effects associated with theophylline (especially nervousness and headache) can be reduced by avoiding food and drinks high in caffeine (e.g., coffee, tea, cocoa, cola, chocolate). Theophylline and caffeine are chemically related and combined use of these substances can increase side effects. Side effects associated with the medication include:

• Upset stomach and heartburn
• Stomach pain
• Diarrhea
• Restlessness
• Nervousness or irritability
• Headache
• Slight nausea
• Vomiting
• Decreased appetite or weight loss
• Insomnia
• Lightheadedness or dizziness
• Slight tremor or shakiness
• Frequent urination (polyuria)

Other side effects might indicate toxic levels of theophylline in the bloodstream. Patients experiencing any of the following should consult a physician immediately:

• Seizures
• Low blood sugar
• Irregular heartbeat (arrhythmia)
• Rapid heart rate (tachycardia)
• Rapid breathing (tachypnea)
• Severe nausea or vomiting
• A fever of 102 degrees Fahrenheit (39 degrees Celsius) or higher develops and persists for more than 12 hours

In addition, patients experiencing signs and symptoms of an allergic reaction (e.g., skin rash) should consult their physician. Individuals experiencing signs and symptoms of anaphylaxis (a severe allergic reaction involving two or more body systems) should seek immediate medical attention. Without immediate emergency treatment, anaphylaxis can quickly progress to life-threatening anaphylactic shock, which is characterized by difficulty breathing and a dangerous drop in blood pressure. Signs and symptoms of anaphylaxis include:

• Breathing problems
  
• Closing of throat
  
• Hives (pink or white bumps that appear on or beneath the skin)
  
• Swelling of lips, tongue or face