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Theo-Dur is a commonly prescribed oral asthma medication that helps open the airways.

Theo-Dur is an extended-release formulation that enables patients to control breathing symptoms with one or two daily doses. Smokers and children may need more frequent doses. The doctor’s instructions on dose and timing should be followed carefully.

Side Effects and Interactions

Side effects of theophylline include nausea, vomiting, loss of appetite, stomach pain, diarrhea, headaches, insomnia, restlessness, nervousness, muscle twitching, heart palpitations, increased urination, hair loss, rash and increased blood sugar. Less common but more serious adverse reactions include seizures, heart rhythm disturbances, vomiting blood and dehydration. Report any symptoms to your physician promptly.

A blood test is extremely helpful in monitoring treatment and determining proper dose. Blood levels should not be higher than 20 micrograms per milliliter.

Theo-Dur interacts with many other drugs, including caffeine. Large amounts of coffee or cola can exacerbate side effects of theophylline. Be aware that some nonprescription pain relievers may also contain caffeine and exercise appropriate caution.

Although people with asthma may be more susceptible to respiratory tract infections, quinolone antibiotics such as Cipro, Noroxin or Penetrex may be dangerous in combination with Theo-Dur. They may raise blood levels of the drug gradually and insidiously to the point where serious adverse reactions such as convulsions or heart rhythm changes may occur.

A similar and equally dangerous interaction is possible with Tagamet, the ulcer medicine. Other drugs that may cause increased Theo-Dur toxicity include antibiotics like erythromycin or TAO, the antiseizure medicine Tegretol, and certain beta blockers (Blocadren, CartrolInderal, Levatol, Timoptic and Visken). (People with asthma should avoid beta blockers in the first place, as they often make breathing worse.)

Medications that require extra caution due to potential interactions with Theo-Dur include oral contraceptives, calcium blockers like Calan or Cardizem, the heart drug Mexitil, anticonvulsants like Dilantin or the barbiturates, and tuberculosis medicines. The herb St. John’s wort can speed elimination of theophylline from the body, which could reduce its effectiveness.

Excess nervous stimulation may occur if the herb ma huang is taken together with theophylline. Such a combination may provoke cardiovascular reactions. Capsaicin (cayenne) inhibits liver enzymes (CYP1A2) and thus slows the metabolism of Theo-Dur.

It’s a good idea to check with your pharmacist and physician before using any other medication or herbs in combination with Theo-Dur.

Special Precautions

Some people should not take Theo-Dur. They include those with peptic ulcers and anyone with a history of seizures. Those with liver problems, heart disease or high blood pressure should be monitored closely if they take Theo-Dur. An acute asthmatic attack in which a person is having difficulty breathing will not respond adequately to Theo-Dur and requires immediate medical attention. The patient should be taken for emergency treatment.

Taking the Medicine

There is some question about the best way to swallow Theo-Dur. Do not chew or crush the capsule. The manufacturer suggests that a high-fat breakfast does not interfere with absorption. Because theophylline may upset your stomach, you may wish to take this medicine with food to try and reduce digestive tract disturbances.

With Theo-Dur Sprinkle, the contents of the capsule may be sprinkled on applesauce or other soft food to make it easier for a child or elderly person to swallow. The food should not be chewed.

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About the Author
Joe Graedon is a pharmacologist who has dedicated his career to making drug information understandable to consumers. His best-selling book, The People’s Pharmacy, was published in 1976 and led to a syndicated newspaper column, syndicated public radio show and web site. In 2006, Long Island University awarded him an honorary doctorate as “one of the country's leading drug experts for the consumer.”.
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