People's Pharmacy

Theo-dur

Generic Name:theophylline

Revised:4/1/2000

Table of Contents

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, Cartrol, Inderal, 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.