Standards of Laboratory Practice: Theophylline and Caffeine Monitoring (Nacb Symposium‪)‬

Obstructive lung disease is a common problem, and the incidence of asthma among children in westernized countries has been estimated to be 6-12% (1, 2). The immunological basis of asthma has been well documented (3). Theophylline is one of the therapeutic agents used to treat asthma and chronic obstructive pulmonary disease (COPD) (4-8). The effects on respiration can be assessed through peak lung flow and other lung function tests that provide immediate overall assessment. Patients in respiratory distress can readily die; thus it is important to assess whether the patient has achieved a theophylline blood concentration expected to produce a therapeutic effect. When drug monitoring is performed, the therapeutic range that has been established should be used only as a guide. However, theophylline has a narrow therapeutic index; high concentrations may be toxic, and the drug must be carefully monitored for adult therapy (5-7). The mechanism of pharmacologic action of theophylline has been studied for half a century (5-7). Theophylline has been shown to have intracellular effects on phosphodiesterases, calcium concentration, and adenosine receptors. The original concept that theophylline relaxes the smooth muscles of the bronchi does not explain its entire pharmacologic effect.