Greatly enhanced bioavailability of theophylline on postprandial administration of a sustained release tablet

The bioavailability of theophylline after oral administration of a new sustained release tablet Theograd-250 mg was studied in 7 healthy volunteers, under fasting and non-fasting conditions. Whilst fasting the bioavailability was moderate at 64 +/- 22% (mean +/- SD), whereas in the non-fasting state the relatively high bioavailability of 90 +/- 13% was found. The drug appeared to be significantly more slowly absorbed when a tablet was taken after a meal, than when it was ingested on an empty stomach. In the former case, the peak level was reached after 6.9 +/- 1.0 h, whereas in the fasting state the maximum serum concentration occurred 4.0 +/- 1.7 h after administration of the drug. Despite the slow absorption, the peak non-fasting level of 4.4 +/- 1.4 mg . 1(-1) was significantly higher than the 3.1 +/- 1.0 mg . 1(-1) observed in the fasting state. The profiles of the serum concentration-time curves showed that the concentration remained above 75% of Cmax for 8.7 +/- 1.3 h in the fasting and 9.0 +/- 1.1 h in the non-fasting state. It was concluded that to define the optimal dosage regime for sustained release oral dosage forms of theophylline, the influence of food on absorption from these preparations should be taken into account. Based on the present results, Theograd-250 mg tablets have predictable absorption and a high (90%) bioavailability if taken after a meal.