Abstract

Twelve patients with chronic airways obstruction took part in a bioavailability study of a sustained-release preparation of theophylline (Nuelin SR). Each patient took a Nuelin SR (250 mg) tablet after an overnight fast and, next day, after a light breakfast. On the third day, six patients took two halves of a 250 mg Nuelin SR tablet after breakfast; six subjects took one-half of a 500 mg Nuelin SR tablet after an overnight fast. There were marked interindividual variations in the plasma theophylline concentrations on all study days. The effect of food was equally variable, and appeared to delay the peak plasma concentration in four subjects; in another four, the peak plasma theophylline concentration occurred earlier, and no change was observed in the remaining four. Overall, no significant differences either in the amount of theophylline absorbed, or in its bioavailability were observed. We suggest that patients should be instructed to take theophylline at the same time every day in relation to food intake; however, theophylline assay is essential for the appropriate use of the drug.