Time-dependent loss of radioactivity counts associated with paracellular markers in the presence of cyclodextrin

Influence of the intermediate digestion phases of common formulation lipids on the absorption of a poorly water‐soluble drug

The influence of different model intestinal phases (modelled on those likely to be produced in vivo after the digestion of commonly used formulation lipids) on the absorption profile of cinnarizine has been studied. Combinations of C8, C12, or C18:1 fatty acid and monoglyceride and simulated endogenous intestinal fluid were formulated to provide examples of liquid (L1), lamellar (L(alpha)), and cubic (C) liquid crystalline phases. Phases containing cinnarizine were dosed intraduodenally and absorption was assessed in an anesthetized rat model. Bile duct ligation was performed to inhibit the effects of digestion/dilution on the phase structure. Absorption from the L(alpha) phases (C8 and C12 lipids) was statistically higher (p < 0.05) than a cinnarizine suspension: however, a statistically significant difference was not observed from the L1 and C phases. The rigid C18:1 C phase showed evidence of providing for sustained drug absorption. Experiments in bile intact rats with the C8 L(alpha) and C18:1 C phase highlighted that the absorption-modifying properties of these phases were influenced by dilution in the endogenous bile milieu, with absorption from L(alpha) phase reducing (possibly through precipitation of solubilized drug) and increasing in the case of the C18:1 C phase, possibly through the coexistence of L1 and C upon dilution permitting more efficient transfer of solubilized drug.

Cytotoxicity evaluation of enzyme inhibitors and absorption enhancers in Caco-2 cells for oral delivery of salmon calcitonin

The usefulness of enzyme inhibitors and absorption enhancers with least mucosal cell cytotoxicity was evaluated on Caco-2 cell monolayers. The temporal cytotoxicity of several protease inhibitors at 500 microg/mL (e.g., turkey and chicken ovomucoids, aprotinin, and Protease Inhibitor Cocktail) and absorption enhancers [e.g., cholate (3%), glycocholate (3%), glycosursodeoxycholate (3%), ethylenediaminetetraacetic acid (EDTA, 0.1%), hydroxypropyl-beta-cyclodextrin (HP-beta-CD, 5%), hydroxypropyl-gamma-cylcodextrin (HP-gamma-CD, 5%), gamma-cylcodextrin (gamma-CD, 5%), tetradecyl-beta-D-maltoside (0.25%), octylglucoside (0.25%), citric acid (10%), glycyrrhetinic acid (0.34 mM), and Tween-80 (0.1%)] was measured by monitoring their effect on Caco-2 cell viability. Cell viability was measured by mannitol permeability measurements, transepithelial electrical resistance (TEER) measurements, DNA-propidium iodide staining assay, and WST-1 assay (tetrazolium salt based assay). Sodium dodecyl sulfate (0.1%), a potent surfactant, was used as a positive control. Chicken and turkey ovomucoids were nontoxic to cells as evaluated by all the methods used. Aprotinin decreased the TEER, whereas plasma membrane damage was seen with Protease Inhibitor Cocktail after a 24-h period. With respect to the absorption enhancers, the toxicity increased directly as a result of an increase in the time of incubation. The enhancers EDTA and HP-beta-CD can be used safely for a short period of time, whereas glycosursodeoxycholate, glycyrrhetinic acid, octylglucoside, HP-gamma-CD, and gamma-CD can be used for a longer period.