Effect of an enteral nutrient formula on sustained-release theophylline absorption

The effect of an enteral nutrient formula (Osmolite) on the absorption of a single oral dose of sustained-release theophylline (Slo-bid) was studied in healthy men. In a randomized, crossover design, subjects received the enteral nutrient diet (2,400 ml/day) or food diet (F) of similar caloric, fat, carbohydrate, protein, and sodium content for 7 days. On day 6 of each diet, volunteers received a single oral dose (600 mg) of sustained-release theophylline (SRT) after fasting or with hourly oral boluses (100 ml) of enteral nutrient formula (ENF). Serial blood samples were collected for 48 h and serum concentrations were analyzed by enzyme multiplied immunoassay. Slight differences (p less than 0.01; paired t test) in Cmax (7.1 +/- 1.2 versus 8.2 +/- 1.3 mg/L) and Tmax (10.7 +/- 2.4 vs. 7.1 +/- 1.1 h) were observed between the ENF and F diets, respectively. However, areas under the curve values were similar (215 +/- 72 versus 211 +/- 70 mg h/L). This study suggests that ENF does not affect the extent of absorption of SRT when administered as a single oral dose.