Effects of enteral tube feeding on the absorption and pharmacokinetic profile of carbamazepine suspension.

In a randomized, two-period crossover clinical study, eight normal male volunteers received two separate 500-mg doses of carbamazepine (CBZ) suspension 1 week apart. One dose was administered orally after an overnight fast, and the other was administered by nasogastric feeding tube during a continuous enteral feeding infusion. Serial serum CBZ concentrations were determined by high-performance liquid chromatography (HPLC) to assess the effects of the enteral feeding on CBZ absorption. Noncompartmental methods were used to estimate pharmacokinetic data. One volunteer experienced a mild hypersensitivity reaction after his first CBZ dose and was withdrawn from the study. The other subjects tolerated both doses very well, although most experienced mild drowsiness or lightheadedness. Serum CBZ concentrations were lower during enteral feeding administration, but the differences were statistically significant only at 8 h (p = 0.044). Changes in pharmacokinetic data were not significant, although the decrease in maximum serum concentration approached significance (p = 0.052). The relative bioavailability of CBZ suspension with enteral feeding administration was 90.1% of that during fasting. There was a strong correlation between CBZ dose (mg/kg) and Cmax after oral administration (r = 0.97, Y = 1.88X - 4.49, p less than 0.001) but not during enteral feeding administration. Although absorption of CBZ suspension was generally slower and slightly diminished during nasogastric feeding, this interaction may lessen unwanted side effects.