A multiple-dose study of sustained-release theophylline and aminophylline

This study evaluated the relative bioavailability of a sustained-release capsule of theophylline, an elixir of theophylline, and a sustained-release tablet of aminophylline. Twelve healthy, nonsmoking, adult male subjects received nine doses of each of the three products in a crossover study conducted over a ten-day period. Each dosage form contained approximately 250 mg of theophylline and was administered every eight hours. Concentrations of theophylline in the plasma at steady state demonstrated the equivalence of the three dosage forms in terms of the percent of drug absorbed, including the tablet which had exhibited reduced bioavailability in an earlier single-dose study of only five subjects. The steady-state average concentrations of theopylline in the plasma were 9.8 micrograms/ml, 10.3 micrograms/ml and 10.8 micrograms/ml for the tablet, capsulse, and elixir, respectively. The areas under the curves of the plasma level vs time for the three dosage forms were within 9 percent of each other. These data indicate that a significant reduction in fluctuations of the plasma level of theophylline was achieved with the two sustained-release dosage forms, compared to the elixir.