The Influence of Enteral Feedings on Sustained‐Release Theophylline Absorption

In a randomized, crossover study the influence of enteral feedings (Ensure) on the absorption of theophylline from a sustained‐release preparation (Theo‐24) was evaluated. Six healthy, male subjects, age 22 to 37 years, participated. In phase 1 the subjects received a single oral dose of Theo‐24 6 mg/kg with 100 ml of water at 8:00 a.m. In phase 2, they received 100 ml boluses of Ensure hourly, beginning 3 hours prior to the oral dose and continuing for a total of 1000 ml. In phase 3, subjects received a single 30‐minute intravenous infusion of an equivalent dose of aminophylline. After each dose, serial blood samples were collected for 72 hours. No statistically significant differences in area under the curve (AUC^∞₀) (126.0 vs 127.3 μg hr/ml), maximum concentration (3.80 vs 4.08 μg/ml), or time to peak plasma level (13 vs 11 hrs) were found between phases 1 and 2. Mean AUC^∞₀ for the intravenous phase (161.4 μg hr/ml) was significantly higher than the AUC for either oral study (p < 0.05). The mean bioavailability was 81 % for phase 1 and 80% for phase 2. Percent absorbed versus time plots revealed no difference in rate of absorption between treatments. We conclude that short‐term administration of the enteral feeding Ensure does not influence the absorption of theophylline when administered as the sustained‐release product Theo‐24. 1990 Pharmacotherapy Publications Inc.