Altered theophylline pharmacokinetics during acute respiratory viral illness.

The plasma half-life of theophylline was determined during and 1 month after serologically confirmed upper-respiratory-tract viral illness in six children with chronic asthma. In this group the plasma-theophylline half-life (mean = 419.8 min) was significantly longer during the acute stage of their illness than 1 month later (mean 249.9 min). There was no appreciable change in half-life in 4 patients who were febrile but in whom seroconversion did not occur. These preliminary results suggest that certain upper-respiratory-tract viral infections may affect theophylline metabolism.