Rational theophylline use in older asthmatics.

In the sick adult, the variability of clearance from patient to patient may be greater than 50%. A given dose of theophylline that is predicted to result in a serum concentration of 15 micrograms/ml may result in an actual range of serum concentrations from 6.6 to 33 micrograms/ml. Respiratory infections, both acute and chronic, seem to have an adverse effect on theophylline clearance. Studies in adults with acute viral upper respiratory infections, pneumonia, and chronic obstructive pulmonary disease show a significant decrease in clearance.