High absorbency and subchronic morphologic effects on the nasal epithelium of a nasal insulin powder dosage form with a soybean-derived sterylglucoside mixture in rabbits

Performance and toxicity of different absorption enhancers used in the preparation of Poloxamer thermosensitive in situ gels for ketamine nasal administration

The purpose of this study was to investigate the nasal absorption rate and nasal mucosal toxicity of thermosensitive ketamine in situ gels containing various absorption enhancers. The optimal composition ratio for the gel matrix was determined to be 17.2% Poloxamer 407 and 2% Poloxamer 188, as this combination resulted in solutions with a gelation point within the range found in the nasal cavity. Ketamine gels containing the tested enhancers, namely, ethylenediaminetetraacetic acid disodium salt, hydroxypropyl-β-cyclodextrin, propylene glycol, or Tween-80, were compared with enhancer-free counterparts to determine the absorption of the drug, in vivo by measuring its plasma levels in rats and in vitro using a Franz diffusion cell. Moreover, the toxicity of each gel type was assessed by microscopic observation of the morphology of rat nasal mucosa as well as by determining the mobility of the mucosal cilia using an established toad model. The results showed that gels containing hydroxypropyl-β-cyclodextrin could promote the absorption of ketamine without added toxicity compared to enhancer-free gels. Thus, we consider hydroxypropyl-β-cyclodextrin as the most promising absorption enhancer for the nasal administration of ketamine using in situ gels.

Absorption enhancers for nasal drug delivery

This paper describes the basic concepts for the transmucosal delivery of drugs, and in particular the use of the nasal route for delivery of challenging drugs such as polar low-molecular-weight drugs and peptides and proteins. Strategies for the exploitation of absorption enhancers for the improvement of nasal delivery are discussed, including consideration of mechanisms of action and the correlation between toxic effect and absorption enhancement. Selected enhancer systems, such as cyclodextrins, phospholipids, bioadhesive powder systems and chitosan, are discussed in detail. Examples of the use of these enhancers in preclinical and clinical studies are given. Methods for assessing irritancy and damage to the nasal membrane from the use of absorption enhancers are also described. Finally, the mucosal use of absorption enhancers (chitosan) for the improved nasal delivery of vaccines is reported with reference to recent phase I/II clinical studies.

Regional intestinal absorption of FITC-dextran 4,400 with nanoparticles based on beta-sitosterol beta-D-glucoside in rats

Nanoparticles (NP) are potential carriers for drug delivery to the targeted intestine. NP based on beta-sitosterol beta-D-glucoside (Sit-G) enhanced the colon-specific absorption of FITC-dextran 4,400 (FD-4), because the concentration-dependent increase of bioavailability appeared in only the colon. In a permeation study, the absorption enhancement in the colon was suppressed in the following conditions: (1) the addition of Sit-G NP to serosa; (2) a permeation study at 4 degrees C; (3) the addition of endocytosis inhibitor, cytochalasin B. NP based on sitosterol, the aglycon of Sit-G, did not increase the FD-4 colonic permeation. The addition of Sit-G NP to the mucosal side induced a decrease of transepithelial resistance (TEER), but this phenomenon was suppressed by an inhibitor of Na(+)-dependent specific glucose transporter, phrolidzin, which did not affect FD-4 permeation. These findings suggested that absorption enhancement by Sit-G NP may not be due to opening of a tight junction, but might be related to endocytosis via glucose residue of Sit-G.

Poly-L-arginine predominantly increases the paracellular permeability of hydrophilic macromolecules across rabbit nasal epithelium in vitro

PURPOSE

The purpose of this work was to characterize the main transport pathway of hydrophilic macromolecules induced by poly-L-arginine (poly-L-Arg; molecular weight 42.4 kDa) across the excised rabbit nasal epithelium.

METHODS

Excised rabbit nasal epithelium was mounted in an Ussing-type chamber for measurement of fluorescein isothiocyanate-labeled dextran (FD-4; molecular weight 4.4 kDa) transport and transepithelial electrical resistance (TEER). The main transport pathway of FD-4 enhanced by poly-L-Arg was evaluated using confocal laser scanning microscopy. Immunolocalization of junction proteins (ZO-1, occludin, and E-cadherin) after treatment with poly-L-Arg was also observed.

RESULTS

After apical application of a poly-L-Arg (0.05, 0.5, and 5 mg/mL), the permeability coefficient of FD-4 increased by 1.6-, 2.9-, and 5.2-fold, respectively, compared with the control of 5.2 +/- 1.3 x 10(-7) cm/s. Consistent with the increase in transport, there was a concurrent reduction in TEER. At a concentration of 0.05 mg/mL poly-L-Arg. both FD-4 transport and TEER returned to the control level. A good correlation was obtained between the FD-4 permeability coefficient and 1/TEER. Basolateral application of poly-L-Arg at 5 mg/mL, however, did not increase FD-4 transport. Marked FD-4 fluorescence was located in the paracellular spaces after treatment with apical poly-L-Arg compared with that in the absence of poly-L-Arg. Immunofluorescence of ZO-1, occludin, and E-cadherin in cell-to-cell junctions was reduced and distributed into the cytoplasm by apical application of poly-L-Arg, suggesting that poly-L-Arg regulates the junction proteins to enhance paracellular permeability across the nasal epithelium. After pretreatment with either 2,4-dinitrophenol or ouabain, the enhancing effect of apical poly-L-Arg was abolished, indicating the contribution of metabolic energy (cell viability) to the poly-L-Arg-mediated enhancing effect.

CONCLUSION

In the nasal epithelium, apical poly-L-Arg appears to increase predominantly the paracellular transport of hydrophilic macromolecules via disorganization of tight- and adherens-junction proteins. The regulatory mechanism of the poly-L-Arg effect is likely to be dependent on energy-requiring cellular processes.

Analysis of transient and reversible effects of poly-L-arginine on the in vivo nasal absorption of FITC-dextran in rats

We have investigated whether poly-L-arginine, with a mean molecular weights of 8.9 and 45.5 kDa (poly-L-Arg (10) and poly-L-Arg (50)), can induce transient and reversible effects involving enhancement of the nasal absorption of fluorescein isothiocyanate-labeled dextran (MW 4.4 kDa, FD-4) and determined the main pathway for the increased transport of FD-4 in rats in vivo. Pre-administration and repeated administration studies were conducted involving the selection of different time intervals between intranasal administration of poly-L-Arg and administration of FD-4, with and without poly-L-Arg, to characterize these transient and reversible effects. The degradation of poly-L-Args in a diluted nasal drip was determined from the fluorescence of degraded poly-L-Arg-fluorescamine products. In the pre-administration study, poly-L-Arg exhibited a transient effect on the increased nasal FD-4 absorption depending on its molecular weight, associated with the degradation rate of poly-L-Arg in mucus. In the repeated administration study, additional poly-L-Arg produced similarly enhanced FD-4 absorption. Confocal laser scanning microscopy showed that fluorescence of FD-4 after co-administration of poly-L-Arg (50) was confined mainly to the paracellular spaces. In conclusion, poly-L-Arg exhibited molecular weight-dependent transient and reversible effects on the enhancement of nasal FD-4 absorption paracellularly in rats in vivo. The enzymatic degradation of poly-L-Arg is one of the key determinants of the transient effect on in vivo enhanced absorption of FD-4.

The enhancing effect of nasal absorption of FITC-dextran 4,400 by beta-sitosterol beta-D-glucoside in rabbits

The effect and mechanism of action of beta-sitosterol beta-D-glucoside (Sit-G) on the in vitro and in vivo nasal absorption of FITC-dextran (molecular weight, 4400; FD-4) in rabbits were studied in comparison with beta-sitosterol (Sit). The FD-4 permeation in the powder dosage form was increased by Sit-G and Sit and related to the uptake of Sit-G and Sit with no changes in the amount of cholesterol in the excised nasal mucosa. The application of Sit and Sit-G increased FD-4 permeation with and without a decrease in transepithelial resistance (TEER), respectively. These results suggested that the mechanism of the enhancement by Sit-G was different from those of Sit and sodium caprate; Sit-G may exert its effects mainly via the transcellular pathway due to perturbation of the mucosal membrane.

Improved nasal absorption of drugs using poly-L-arginine: effects of concentration and molecular weight of poly-L-arginine on the nasal absorption of fluorescein isothiocyanate-dextran in rats

The effects of the concentration and molecular weight of poly-L-arginine (poly-L-Arg) on the in vivo nasal absorption of fluorescein isothiocyanate-labeled dextran (MW, 4 kDa, FD-4) in rats were studied. When poly-L-Arg with a range of different molecular weights (MW, 8.9, 45.5 and 92.0 kDa) was applied intranasally at various concentrations, the bioavailability (F(0-9 h)) of FD-4 increased with the increasing concentration of poly-L-Arg. The enhanced absorption was also dependent on the molar concentration, in that the poly-L-Arg with a higher molecular weight increased F(0-9 h) at a lower molar concentration. In addition, for each applied concentration, the poly-L-Arg exhibited a molecular weight-dependence as far as the enhancement of FD-4 absorption was concerned. On the other hand, the maximum absorption rate (MAR) of FD-4, calculated by means of a deconvolution method, tended to reach a maximum plateau level at a lower applied concentration for the poly-L-Arg with the highest molecular weight, but this plateau level was almost the same for poly-L-Arg with molecular weights of 45.5 and 92.0 kDa. Moreover, the simulated absorption profiles of FD-4 indicate that the degree of enhancement (the level of MAR and the subsequent reduction in the absorption rate) was dependent on the molecular weight of poly-L-Arg, while the effect of poly-L-Arg was maintained for a longer period, depending on the applied concentration, although the MAR was relatively similar. These results indicate that the molecular weight of poly-L-Arg appears to affect both the enhancing efficiency (absorption rate) and the time-frame of this enhancing effect, whereas the concentrations of each poly-L-Arg system applied only have an effect on the time-frame. These effects may also be associated with the charge density of a poly-L-Arg molecule.

Estimation of absorption rate of alpha-human atrial natriuretic peptide from the plasma profile and diuretic effect after intranasal administration to rats

The absorption rate of alpha-human atrial natriuretic peptide (alpha-hANP) after intranasal (i.n.) administration to rats was estimated from the plasma profile and pharmacological effect (diuretic effect) using a pharmacokinetic (PK) model and a PK-pharmacodynamic (PD) model involving data obtained after intravenous (i.v.) bolus injection. The plasma concentrations of alpha-hANP after i.v. administration at different doses were fitted to a two-compartment PK model with zero-order excretion and input of endogenous alpha-rat atrial natriuretic peptide (alpha-rANP) and two elimination processes represented by Michaelis-Menten and first-order kinetics. However, the saturable process was ignored at low doses. The plasma concentrations after low doses via the i.n. route could also be expressed by this model, but with first-order absorption, so that an absorption rate constant was calculated using a deconvolution method. In addition, the diuretic effect plotted against the i.v. dose was represented by the Hill equation and showed an anti-clockwise hysteresis loop versus the plasma concentration. These results suggest that the diuretic effect could be estimated by a PK-PD model having an 'effect' compartment or a homeostatic system. Such a PK-PD model accurately expressed the diuretic effect of alpha-hANP at all doses after i.v. and i.n. administrations. The resulting absorption rate constant calculated using the PK-PD model agreed closely with that obtained by the PK model alone. The absorption rate and simulated diuretic effect suggest that, for i.n. administration of alpha-hANP, a higher absorption rate constant causes a more potent diuretic effect (a dramatic effect over the early period), whereas greater bioavailability is associated with a better hypotensive effect (sustained effect).

The enhancing effect of soybean-derived sterylglucoside and beta-sitosterol beta-D-glucoside on nasal absorption in rabbits

The aim of this study was to elucidate the efficiency of soybean-derived sterylglucoside (SG) and its main component beta-sitosterol beta-D-glucoside (Sit-G), as nasal absorption enhancers. Nasal administration of verapamil with SG and Sit-G showed the higher bioavailabilities (60.4 and 90.7%, respectively) than that with lactose (39.8%). It was clear that SG and Sit-G promoted the absorption of verapamil through nasal mucosa. To elucidate the mechanism, we measured the calcein leakage from liposomes by incubation with SG, Sit-G, oleic acid, soybean-derived sterol, and beta-sitosterol to investigate transcellular absorption and measured the changes in intracellular Ca2+ concentrations ([Ca2+]i) by Sit-G to analyze paracellular absorption. The large amount of calcein leakage induced by enhancers was consistent with an enhancement of bioavailability of verapamil and insulin following nasal administration (oleic acid < SG < Sit-G). Moreover, Sit-G increased [Ca2+]i in the medium containing Ca2+, but not in Ca2+ free medium. This result suggested that Sit-G increases the fluidity of the mucosal membrane and facilitates Ca2+ influx from extracellular sources. In conclusion, a possible explanation for SG and Sit-G to promote drug absorption, is that they may affect both paracellular pathway and transcellular pathways caused by pertubation of lipid.

Screening of cationic compounds as an absorption enhancer for nasal drug delivery

Several cationic compounds were screened as potential nasal absorption enhancers to increase intranasal absorption of a model drug, fluorescein isothiocyanate labeled dextran (MW 4.4 kDa, FD-4), without nasal membrane damage in rats. Their effects were compared with those of classical enhancers. Various cationic compounds (poly-L-arginines with different molecular weights (MW 8.9, 45.5 and 92.0 kDa, poly-L-Arg (10), (50) and (100), respectively), L-arginine (L-Arg), L-lysine (L-Lys), and cetylpyridinium chloride (CPCL) were evaluated. Of the cationic compounds, poly-L-Arg and CPCL greatly enhanced the intranasal absorption of FD-4, as did chitosan, a cationic polysaccharide which has been reported to show a great effect on the transnasal delivery of peptide and protein drugs. The enhancing intensity by poly-L-Arg was dependent on its molecular weight. Rank order of the enhancing ratio, calculated from the AUC ratio for the enhancer treatment against the untreatment, was 0.5% poly-L-Arg (100) congruent with0.5% sodium dodecylsulfate congruent with0.5% CPCL?0.5% poly-L-Arg (50)?0.5% sodium deoxycholate congruent with0.5% sodium taurodihydrofusidate?0.5% polyoxyethylene-9-lauryl ether congruent with0.5% lysophosphatidylcholine?0.5% chitosan congruent with0.5% poly-L-Arg (10)>/=10% L-Arg congruent with10% L-Lys?0.5% sodium glycocholate congruent with0.5% sodium taurocholate congruent with0.5% EDTA. Only the poly-L-Args represented almost the same degree of hemolysis of cationic compounds compared with pH 7.0 phosphate buffered saline in the rat erythrocyte lysis experiment. The enhancing ratio by classical enhancers correlated with leaching of protein, phospholipids and LDH from isolated rabbit nasal mucosa. CPCL also fell on the regression lines between the enhancing ratio and their degree of leaching from classical enhancers. In contrast, the enhancing intensities by poly-L-Arg (10), (50) and (100) were greatly shifted from the regression line: the amount of leaching was markedly low in spite of a great enhancement of FD-4 absorption. These findings suggest that of the assessed enhancers only the poly-L-Args enhance the transnasal delivery of high molecular substances without severe damage to the nasal mucosal membrane. Poly-L-Arg is therefore a promising candidate having a good balance between enhancing activity and safety for nasal peptide and protein delivery.