The pharmacokinetics of dihydroxypropyltheophylline: a basis for rational therapy.

Dihydroxypropyltheophylline (dyphylline) was administered in a single dose on 7 different days to 7 normal subjects; 5 mg/kg was given by intramuscular injection and oral tablet; 10 mg/kg was given by these routes and also in 3 different liquid formulations. Dyphylline is rapidly absorbed, and bioavailability is independent of route of administration or formulation. The pharmacokinetics of dyphylline do not appear to be dose-dependent in the dosage range studied. The mean half-life of dyphylline is 2.11 +/- 0.36 hr; because of its short half-life and unproved efficacy, current dosage recommendations for dyphylline must be revised greatly. Further efficacy trials utilizing the pharmacokinetic data from this study are essential.