Theophyllines are important drugs for patients with asthma as are inhaled bronchodilators and the corticosteroids discussed in earlier communications. Theophyllines are in a class of drugs called methylxanthines. They are closely related to caffeine. Theophyllines are potent bronchodilators, and they also stimulate clearance of mucus, just as the inhaled bronchodilators do. In addition to being bronchodilators, theophyllines strengthen the breathing muscles of the diaphragm and chest wall. Thus, they may help prevent muscle fatigue when air flow is quite limited. Theophyllines also have a mild beneficial effect in improving heart function, and they act as a mild stimulant to respiration by affecting the respiratory center in the brain. In addition, theophyllines may stimulate the secretion of gastric acid. This can cause heartburn if the connection between the stomach and esophagus becomes relaxed, another action of theophyllines. This can be undesirable in certain patients. The heart and brain stimulation may also be undesirable in some people. So you can see that theophyllines have a number of effects on the body, both good and bad.

The main side effects of theophyllines are from excessive blood levels. Even convulsions can occur from excessive doses. The stomach upset and central nervous system irritability are one of the main reasons why physicians measure blood levels so frequently. Most patients don’t need repeated blood level measurements if simple rules are followed. If your appetite remains good, heartburn is absent, and you sleep well, it is highly doubtful that you are getting too much theophylline. It may be important to determine if enough is being given. Thus, one or two blood levels are commonplace when theophyllines are first started.

Many things affect the metabolism of theophyllines. These include smoking and the use of barbiturates which speed up the metabolism or clearance of theophylline. Other drugs increase theophylline blood levels. Age and food have variable effects.

There are a lot of theophylline products on the market. The most popular are the long-acting, sustained release types, such as Uniphyll, and Theo-24 which are given once a day. Our studies indicate that once a day dosing gives very predictable blood levels and clinical responses. The dose must be determined by the physician, but 600 to 800 mg per day is an average.

Theophyllines are not the most potent bronchodilators. After full doses of theophylline, further bronchodilation still occurs with the use of an inhaled bronchodilator taken from a metered dose inhaler. Both drugs work well together. I’ll be writing more about strategies and therapy in future Newsletters.

Dr. Thomas Petty, Professor of Medicine University of Colorado Health Sciences Center; Consultant and Faculty at HealthONE Center Denver, CO.