Nanostructured reverse hexagonal liquid crystals sustain plasma concentrations for a poorly water-soluble drug after oral administration

Reverse hexagonal (H-2) liquid crystals formed from selachyl alcohol were demonstrated to sustain the absorption of the poorly water-soluble drug cinnarizine (CZ) after oral administration to rats. When CZ was administered as a bolus lipid solution in selachyl alcohol, the T-max was observed to be 23.5 +/- 5.9 h, significantly longer than the control suspension (1 h). Administration of selachyl alcohol as dispersed nanoparticles (hexosomes) also resulted in a sustained plasma profile, with drug concentrations maintained from 20 to 40 ng/mL over the first 24 h after administration. Sustained absorption of CZ from the selachyl alcohol hexosomes led to a significant enhancement (p<0.05) in oral bioavailability (F%=17%) compared to the control CZ suspension (9%). Analysis of selachyl alcohol hexosomes using small-angle x-ray scattering indicated that neither the presence of CZ (7 mg/g) nor simulated intestinal fluid altered the H-2 nanostructure. Selachyl alcohol is not susceptible to digestion. Prolonged absorption from the selachyl alcohol-based H-2 systems was attributed to the non-digestible nature of the lipid, similar to non-digestible phytantriol cubic (V-2) systems previously reported. Furthermore, the likely presence of non-sink conditions in the gastric compartment provides a drug reservoir requiring gastric emptying to stimulate drug release from the formulation. This study highlights the potential use of non-digestible liquid crystalline systems generally and nanostructured liquid crystalline particles in particular as novel sustained oral drug delivery systems.