Effect of Dietary Fiber, Glucomannan, on Absorption of Sulfonylurea in Man

Abstract

In order to clarify whether a dietary fiber has any effect upon the intestinal absorption of sulfonylurea, changes in plasma concentration of glibenclamide were determined during a six-hour period in nine healthy volunteers who took 2.5 mg of glibenclamide together with a breakfast and 3.9 g of glucomannan in a form of konjac powder and were compared with those of the control experiment in which the same amount of the hypoglycemic agent was given without the dietary fiber. In the control, mean plasma glibenclamide level increased rapidly, reaching a peak at 60 min and decreased gradually thereafter, whereas an increase in plasma glibenclamide level was blunted in the test experiment, thus plasma concentration of glibenclamide being lower at 30, 60, 90 and 150 min compared with the corresponding value of the control (31.7 +/- 24.5 ng/ml vs 76.4 +/- 25.0 ng/ml at 30 min; 51.3 +/- 35.5 ng/ml vs 120.9 +/- 56.0 ng/ml at 60 min; 60.0 +/- 38.8 ng/ml vs 117.4 +/- 53.1 ng/ml at 90 min; 54.0 +/- 31.5 ng/ml vs 100.7 +/- 46.5 ng/ml at 150 min). Mean plasma glucose concentration was significantly lower at 30 min in the test experiment than in the control despite the lower level of plasma glibenclamide in the former. The results suggest that glucomannan may influence the intestinal absorption of glibenclamide. A dietary fiber must be prescribed in due consideration of these facts.

Effect of glucomannan and the dosage form on ethinylestradiol oral absorption in rabbits

“…In addition, the results of these studies are variable, reporting increases, decreases or even no modification in the drug concentrations after the fiber administration [15][16][17][18][19][20][21][22][23][24]. Even when the same drug and dietary fiber were used, the data obtained can be contradictory [25][26][27][28]. We found only one study about the interaction of glucomannan with other drugs [29].…”

“…There are not many studies regarding this aspect, and the results obtained are controversial: several studies show that fiber can increase the bioavailability of other drugs, other authors find a decrease, or no modification is observed [15][16][17][18][19][20][21][22][23][24][25][26][27][28][29]. The main mechanism of interaction may be that the fiber retains by adsorption part of the administered dose, which would be higher with a very viscous fiber.…”

Clinical Pharmacology of Sulfonylureas

“…In addition, dietary fibers such as glucomannan and guar may have different effects depending on the formulation administered. With nonmicronized formulations they delay absorption, whereas with micronized formulations they do not (NEUGEBAUER et al 1983;SHIMA et al 1983). All these different effects have not been systematically explored with respect to their inftuence on postprandial glycemia.…”

“…Increased nonmicronized glibenclamide absorption is reported for magnesium hydroxide, sodium bicarbonate and antacids (NEUVONEN and KIVISTÖ 1991;KIVISTÖ et al 1993;ZUCCARO et al 1989), but not with micronized glibenclamide (NEUVONEN and KIVlSTÖ 1991). The absorption rate of nonmicronized but not of micronized glibenclamide is decreased by glucomannan and guar (SHIMA et al 1983;NEUGEBAUER et al 1983;UUSITUPA et al 1990) and may be accelerated by erythromycin (FLEISHAKER and PHILLIPS 1991). Absorption is decreased by the glucosidase inhibitor miglitol (SALVATORE et al 1990).…”

“…Dietary tibers such as konjac mannan and guar gum appear to have only little inftuence on gliclazide absorption (SHIMA et al 1982). No other specitic studies with the aim of evaluating the interaction potential of gliclazide seem to exist.…”