A Practical Guide to Interactions Involving Theophylline Kinetics

Abstract

A practical guide to the drug interactions involving theophylline kinetics is presented. The text is classified into three categories--pharmacokinetics, pharmacodynamics, and miscellaneous drug interactions. In the discussion of pharmacokinetics, interactions are classified according to site; in vitro, intestinal, metabolic, protein binding, and renal mechanisms are considered. The pharmacodynamic section concentrates on possible additive effects of theophylline and other commonly used bronchodilators, while in the miscellaneous section, discussion is devoted to those interactions involving allergic skin testing and changed results of commonly used assay methods for theophylline. Increased awareness of possible interactions should lead to a more critical approach to theophylline prescribing, particularly in those cases where an unexpected therapeutic effect (or theophylline serum concentration) is obtained during the treatment of asthmatic patients.

Effect of Exercise and Environmental Heat on Theophylline Kinetics

“…On the other hand, the clear ance of indocyanine green, which is highly extracted by the liver, was found to be markedly influenced by exercise [Rowellet al, 1965]. In the present study the elimina tion of theophylline, in spite of a relatively low hepatic extraction ratio [McElnay et al, 1982], was affected by exercise.…”