Evaluation of the Oral Bioavailability of Low Molecular Weight Heparin Formulated With Glycyrrhetinic Acid as Permeation Enhancer

Abstract

Low molecular weight heparin (LMWH) is the agent of choice for anticoagulant therapy and prophylaxis of thrombosis and coronary syndromes. However, its therapeutic use is limited due to poor oral bioavailability. The aim of this study was to investigate the oral delivery of LMWH, ardeparin formulated with 18-beta glycyrrhetinic acid (GA), as an alternative to currently used subcutaneous (sc) delivery. Drug transport through Caco-2 cell monolayers was monitored in the presence and absence of GA by scintillation counting and transepithelial electrical resistance. Regional permeability studies using rat intestine were performed using a modified Ussing chamber. Cell viability in the presence of various concentrations of enhancer was determined by MTT assay. The absorption of ardeparin after oral administration in rats was measured by an anti-factor Xa assay. Furthermore, the eventual mucosal epithelial damage was histologically evaluated. Higher ardeparin permeability (~7-fold) compared to control was observed in the presence of 0.02 % GA. Regional permeability studies indicated predominant absorption in the duodenal segment. Cell viability studies showed no significant cytotoxicity below 0.01 % GA. Ardeparin oral bioavailability was significantly increased (F(relative)/(S.C). = 13.3%) without causing any damage to the intestinal tissues. GA enhanced the oral absorption of ardeparin both in vitro and in vivo. The oral formulation of ardeparin with GA could be absorbed in the intestine. These results suggest that GA may be used as an absorption enhancer for the oral delivery of LMWH.

Fig. 1

Chemical structure of 18-β glycyrrhetinic acid (GA).

Fig. 2

Caco-2 cell viability after exposure to various concentrations of glycyrrhetinic aicd for 6 and 12 h. The values are means of three independent experiments. *Significantly different compared to control (P<0.05).

Fig. 3

Regional permeability of ardeparin (2,400 IU/kg) across rat gastrointestinal membrané, *Significantly different as compared to control. Data are shown as the mean concentration, and error bars represent the SEM (n - 3)

Fig. 4

Anti-factor Xa activity-time profiles of ardeparin in rats after oral administration of formulations. Data are shown as the mean concentration, and error bars represent the SEM (n = 4–6).

Fig. 5

H & E photomicrographs of gastric and intestinal tissue sections after oral administration of glycyrrhetinic (100 mg/kg and LMWH 1,200 IU/kg). All panels represent cross-sections of gastric and intestinal tissues. The original magnification was 100× for all panels. A: stomach (control); B: stomach (test); C: duodenum (control); D: duodenum (test); E: jejunum (control); F: jejunum (test); G: ileum (control); H: ileum (test); I: colon (control); J: colon (test).