Problems with generic theophylline and indiscriminate brand switching.

Theophylline is a very efficacious medication for the treatment of bronchospastic disorders: however, it has a narrow therapeutic range of 10 to 20 micrograms/mL. Pharmacokinetics of theophylline can be affected by diverse factors, such as viral infections, fever, circadian rhythms, food ingestion, and a large number of medications. Theophylline is monitored through a serum theophylline level, which is dependent both on the amount of medication taken, the specific preparation ingested, as well as the amount of time between medication ingestion and serum level. The physician must know specific pharmacokinetic data to ascertain the preparation to use and the proper time to draw levels. This paper also discusses the toxic effects that a patient could incur if one theophylline preparation is indiscriminately substituted for another.