Night-time pharmacokinetics of once a day theophylline: a steady state comparison of three preparations.

We have carried out a steady state pharmacokinetic comparison of three different theophylline preparations in nine healthy volunteers using a once a day dosage schedule of 600 mg theophylline given before bedtime for four days. The preparations tested were Retafyllin 200 mg depot tablet (R), Theo-Dur 200 mg depot tablet (T) and Uniphyllin 200 mg tablet (U). All preparations in steady state reached the serum level of 8.9-10.2 microg/ml after a single evening dose of theophylline 600 mg. The pharmacokinetic profile of these slow release theophylline preparations was such that there is no risk of exceeding the therapeutic range even after a rather high evening dose. Individual variation was also observed in the present study but nobody exceeded the therapeutic range. The pharmacokinetic profiles of R and U were quite similar and they seemed to have suitable pharmacokinetic properties for once a day dosage, and they showed a more sustained action than T. Only minimal gastrointestinal side effects were reported during this study.