Pharmacokinetics of a sustained-release theophylline preparation in healthy subjects.

A comparative pharmacokinetic study between a sustained-release theophylline tablet (Theona) and aminophylline powder following multiple oral administrations every 12 h at a 200 mg theophylline dose was performed in ten healthy adult volunteers. As the results, theophylline in Theona revealed almost completely absorbed as is aminophylline. A peak-trough difference with Theona was less than half of that with aminophylline powder. These results suggest that Theona has excellent characteristics as a sustained-release preparation. In addition, in order to investigate dose-dependent kinetics for theophylline, the relationship between average plasma level and dosage was examined with Theona. The plasma level showed proportional change at the low concentrations. When the plasma level was close to 10 micrograms/ml, however, dosage increment results in an increasingly greater change of plasma level, which may indicate a high risk of toxicity.