Relationship between theophylline concentration in plasma and saliva of man.

Abstract

The concentration of theophylline in the plasma and saliva of 7 normal adults receiving single oral doses of 200 mg theophylline per square meter of body surface area (BSA) was determined spectrophotometrically over 8 hours. There was an excellent linear relationship between theophylline concentrations in plasma and saliva, over a plasma concentration range of 4 to 14 µg per milliliter. Theophylline concentrations in the saliva were about 48% lower than in the plasma and are similar to the concentration of free (not protein‐bound) drug in the plasma. There is very little intersubiect and intrasubiect variation of theophylline blank values in plasma and saliva, in the recovery of theophylline from plasma and saliva, and in the proportionality factor that relates saliva to plasma concentrations of the drug. These observations suggest that theophylline determination in saliva may be a convenient, painless, and noninvasive method for routine monitoring of theophylline levels.