Comparative absorption of theophylline from theophylline-guaifenesin tablets and liquid and from a reference theophylline liquid.

This single-dose, three-way crossover study in 18 healthy adults compared the oral absorption of theophylline from a theophylline-guaifenesin tablet and from a theophylline-guaifenesin liquid with absorption from a theophylline liquid. Each dose form contained 500 mg theophylline and, when indicated, 400 mg guaifenesin. The extents of theophylline absorption from the formulations were within 10% of each other. The absolute differences in the areas under the curve among the formulations were small and, although significantly higher statistically for the theophylline-guaifenesin tablet, are without therapeutic consequence. The theophylline plasma level curves from each of the three formulations were similar. Comparable theophylline absorption and elimination characteristics were seen.