Combination of co-amorphization with SNEDDS outperforms Ofev® in the oral absorption of nintedanib.

Nintedanib (NTD), approved for the treatment of idiopathic pulmonary fibrosis and advanced non-small cell lung cancer, is one of brick dusts with high melting point. Although NTD has been marketed as Ofev®, a soft capsule of NTD ethanesulfonate (NTD-ESA) suspended in oil components, the oral bioavailability is quite low and highly variable. To improve the oral absorption behavior of NTD, we prepared SNEDDS formulation containing NTD-(+)-10-camphorsulfonic acid (CSA) complex with 2% HPMCP-50. CSA disrupted the high crystallinity of NTD-ESA and the formed complex, NTD-CSA, was found to be amorphous by DSC and XRPD. NTD-CSA provided solubilities in various vehicles much higher than NTD-ESA. Under the gastric luminal condition, NTD-CSA SNEDDS with or without 2% HPMCP-50 and NTD-CSA powder indicated very good dissolution of NTD from early time periods, while NTD was gradually dissolved until around 60 min from NTD-ESA and Ofev®. Under the small intestinal luminal condition, in contrast, both NTD-CSA SNEDDS formulations almost completely dissolved NTD throughout the experiments, while Ofev®, NTD-CSA, and NTD-ESA exhibited a very poor dissolution of NTD. In the in vivo absorption study, NTD-CSA SNEDDS with 2% HPMCP-50 significantly improved NTD absorption and reduced the inter-individual variation in oral absorption behavior compared with Ofev®.

Possible Regulation of P-Glycoprotein Function by Adrenergic Agonists II: Study with Isolated Rat Jejunal Sheets and Caco-2 Cell monolayers.

To clarify the regulation of drug absorption by the enteric nervous system, we investigated how adrenergic agonists (adrenaline (ADR), clonidine (CLO), dobutamine (DOB)) and dibutyryl cAMP (DBcAMP) affected P-glycoprotein (P-gp) function by utilizing isolated rat jejunal sheets and Caco-2 cell monolayers. ADR and CLO significantly decreased the secretory transport (Papptotal) of rhodamine-123 and tended to decrease the transport via P-gp (PappP-gp) and passive transport (Papppassive). In contrast, DBcAMP significantly increased and DOB tended to increase Papptotal and both tended to increase PappP-gpand Papppassive. Changes in P-gp expression on brush border membrane by adrenergic agonists and DBcAMP were significantly correlated with PappP-gp, while P-gp expression was not changed in whole cell homogenates, suggesting that the trafficking of P-gp would be responsible for its functional changes. Papppassive was inversely correlated with transmucosal or transepithelial electrical resistance, indicating that adrenergic agonists affected the paracellular permeability. Adrenergic agonists also changed cAMP levels, which were significantly correlated with PappP-gp. Furthermore, protein kinase A (PKA) or PKC inhibitor significantly decreased PappP-gp in Caco-2 cell monolayers, suggesting that they would partly contribute to the changes in P-gp activity. In conclusion, adrenergic agonists regulated P-gp function and paracellular permeability, which would be caused via adrenoceptor stimulation.

Development of Sustained Release System Based on High Water-Absorbable Gel Formation Using Croscarmellose Sodium, Alkaline Excipients and HPMC (ACSH SR System); Novel Application of Croscarmellose Sodium as a Gel Former.

PURPOSE: Croscarmellose sodium, generally used as a superdisintegrant in pharmaceutical formulations, is hydrolyzed to form the gel structure under basic pH conditions. Utilizing this property of croscarmellose sodium, we developed a novel sustained release (SR) system. METHODS: Immediate release (IR) and SR tablets containing croscarmellose sodium, alkaline excipients and/or hydroxypropyl methylcellulose (HPMC) were prepared and examined for wet strength and in vitro drug release behavior. In vivo oral drug absorption was evaluated for IR tablets, HPMC tablets and our novel SR tablets in fasted Beagle dogs. RESULTS: To form the gel structure even under the physiological condition, alkaline excipients were added into the formulation containing croscarmellose sodium. Furthermore, HPMC was used to make the gel structure strong enough against mechanical destructive forces. The novel alkalized croscarmellose sodium-HPMC (ACSH) SR tablet, consisting of croscarmellose sodium, alkaline excipients, and HPMC, successfully sustained the release of acetaminophen, ibuprofen, or nicardipine hydrochloride, compared with the IR tablets. The ACSH SR system provided a better release of acetaminophen than the HPMC tablet without croscarmellose sodium in the release study using a small volume of liquid, suggesting that substantial release and subsequent absorption would be expected in the distal intestinal segments after oral dosing. The in vivo oral absorption study revealed that the ACSH SR system successfully suppressed and prolonged the plasma concentrations of acetaminophen. CONCLUSION: This novel ACSH SR system prepared with croscarmellose sodium, alkaline excipients, and HPMC, would be a promising SR formulation for enabling substantial drug absorption in the distal intestinal segments.

Characterization and Interconversion of Two Crystal Forms of NEt-3IB, a Retinoid X Receptor Agonist.

Retinoid X receptor (RXR) agonist NEt-3IB (1) is a candidate for the treatment of inflammatory bowel disease (IBD), and we have established a process synthesis of 1 in which the final product is obtained by recrystallization from 70% EtOH. However, we found that there are two crystal forms of 1. Here, to characterize and clarify the relationship between them, we conducted thermogravimetry, powder X-ray diffraction, and single crystal X-ray diffraction. The crystal forms were identified as the monohydrate form I and anhydrate form II. The crystal form I, obtained as a stable form by our established synthesis, was easily dehydrated simply by drying to afford the form II', which was similar to the crystal form II obtained by recrystallization from anhydrous EtOH. Storage of the form II' in air regenerated the form I. The molecular conformations of 1 in the crystals of the two forms are similar, and they can be reversibly interconverted. The solubility of the monohydrate form I and anhydrate form II was examined and the former was found to be less soluble than the latter. Thus, form I may be superior to form II for targeting IBD, because of higher delivery to the lower gastrointestinal tract and reduction of systemic side effects associated with lower absorption due to lower water solubility.

Improvement and characterization of oral absorption behavior of clofazimine by SNEDDS: Quantitative evaluation of extensive lymphatic transport.

Clofazimine, an anti-leprosy drug, has been anticipated for a candidate to treat tuberculosis, cryptosporidiosis, and coronavirus infection, but its low oral bioavailability is considered a reason for its limited activity. In the current study, we have tried to improve the oral bioavailability of clofazimine by several SNEDDS formulations and characterized the absorption behavior from various aspects. Among four SNEDDS formulations prepared, SNEDDS A, prepared with castor oil as an oil component, provided the highest bioavailability (around 61%) and SNEDDS D, prepared with Capryol 90, gave the second highest bioavailability. SNEDDS A formed the finest nanoparticles, which were maintained under gastric and intestinal luminal conditions. The comparison in oral bioavailability between the SNEDDS formulation and its corresponding preformed nanoemulsion suggested that SNEDDS A would efficiently form nanoemulsion in the gastrointestinal tract after oral administration. AUC of mesenteric lymph node concentration was the highest for SNEDDS A, which would be one of the reasons for SNEDDS A to reveal the highest oral bioavailability. A cycloheximide-treated oral absorption study and single-pass perfusion study by utilizing a vascular-luminal perfused small intestine-liver preparation clearly indicated that over 90% of clofazimine absorbed to systemic circulation should be derived from lymphatic transport for both SNEDDS A and D. Furthermore, the fraction of dose absorbed was around 65% for SNEDDS D, but SNEDDS A achieved around 94%, indicating the excellent performance of SNEDDS A.

Establishment of a novel in vitro co-culture system of enteric neurons and Caco-2 cells for evaluating the effect of enteric nervous system on transepithelial transport of drugs.

The gastrointestinal tract is innervated by extrinsic autonomic nerves and intrinsic enteric nervous system (ENS). However, the role of ENS in drug absorption has remained to be clarified. To investigate the effect of ENS on drug transport across the intestinal epithelial cells, we established a novel co-culture system of Caco-2 cells and enteric neurons differentiated from neural crest stem (NCS)-like cells isolated from mouse longitudinal muscle/myenteric plexus (LMMP). Immunostaining analysis revealed that the proportions of neuron, glia, and NCS-like cells were only <5 % at population in the primary culture of LMMP cells. Therefore, we proliferated NCS-like cells and differentiated them into neuronal cells and successfully increased the neuronal cell population upto about 40 %. Then, the differentiated neuronal cells were co-cultured with Caco-2 cell monolayers, and we found that the co-culture significantly decreased the transepithelial electrical resistance and enhanced the transport of fluorescein isothiocyanate-labeled dextran-4 across Caco-2 cell monolayers, suggesting that the enteric neurons would function to open the tight junction and facilitate the drug transport via the paracellular route. On the other hand, no changes in the permeability of antipyrine were observed, suggesting that the enteric neurons would not affect the passive transport via the transcellular pathway.

Analysis of absorption-enhancing mechanisms for combinatorial use of spermine with sodium taurocholate in Caco-2 cells.

Previously, we reported that the combined use of spermine (SPM) and sodium taurocholate (STC) (SPM-STC) significantly improves the oral absorption of rebamipide (BCS class IV) and pulmonary absorption of interferon-α without any harmful histopathological changes in the gastrointestinal tract and lungs, respectively. In the present study, we examined the effect of SPM-STC on the transport of fluorescein isothiocyanate-labeled dextrans (FDs) across Caco-2 cell monolayers and attempted to clarify the mechanisms underlying the transport enhancement caused by SPM-STC. SPM-STC were found to significantly enhance the transport of FDs, while the treatment with SPM-STC was not harmful, and the decrease in transepithelial electrical resistance was transient and reversible. The voltage-clamp study clearly indicated that the opening of the paracellular route could be mainly responsible for the enhanced transport of FD-4. As for the mechanisms, it was found that SPM-STC caused a significant increase in membrane fluidity, which would lead to the enhanced transport of small-molecule drugs such as rebamipide. Since SPM-STC increased intracellular Ca2+ via Ca2+ uptake through Ca2+ channels and Ca2+ release from the endoplasmic reticulum stimulated by the IP3 pathway, the subsequent possible activation of the MLCK signaling pathway would have led to the contraction of the actin-myosin ring. The rearrangement of tight junction-constituting proteins induced through the MAPK pathway has also been suggested as a possible mechanism for opening tight junctions. Claudin-4, a key protein constituting the tight junction, merged with F-actin along with the plasma membrane, was significantly decreased, which would be at least partial structural evidence for the tight-junction opening.

Effect of Excessive Serotonin on Pharmacokinetics of Cephalexin after Oral Administration: Studies with Serotonin-Excessive Model Rats.

PURPOSE: Serotonin (5-HT) is important for gastrointestinal functions, but its role in drug absorption remains to be clarified. Therefore, the pharmacokinetics and oral absorption of cephalexin (CEX) were examined under 5-HT-excessive condition to understand the role of 5-HT. METHODS: 5-HT-excessive rats were prepared by multiple intraperitoneal dosing of 5-HT and clorgyline, an inhibitor for 5-HT metabolism, and utilized to examine the pharmacokinetics, absorption behavior and the intestinal permeability for CEX. RESULTS: Higher levels of 5-HT in brain, plasma and small intestines were recognized in 5-HT-excessive rats, where the oral bioavailability of CEX was significantly enhanced. The intestinal mucosal transport via passive diffusion of CEX was significantly increased, while its transport via PEPT1 was markedly decreased specifically in the jejunal segment, which was supported by the decrease in PEPT1 expression on brush border membrane (BBM) of intestinal epithelial cells. Since no change in antipyrine permeability and significant increase in FITC dextran-4 permeability were observed in 5-HT-excessive rats, the enhanced permeability for CEX would be attributed to the opening of tight junction, which was supported by the significant decrease in transmucosal electrical resistance. In 5-HT-excessive rats, furthermore, total body clearance of CEX tended to be larger and the decrease in PEPT2 expression on BBM in kidneys was suggested to be one of the reasons for it. CONCLUSIONS: 5-HT-excessive condition enhanced the oral bioavailability of CEX in rats, which would be attributed to the enhanced permeability across the intestinal mucosa via passive diffusion through the paracellular route even though the transport via PEPT1 was decreased.

Efficient Evaluation of In Vivo Performance in Human for Generic Formulation by Novel Dissolution-Absorption Prediction (DAP) Workflow.

PURPOSE: The pharmaceutical bioequivalence of generic medicines must be confirmed with corresponding original drugs. Although the in vitro dissolution tests are required, results of the mandatory in vitro study do not necessarily reflect the in vivo performance after oral administration. Then, we have tried to develop the novel "Dissolution-Absorption Prediction (DAP) workflow" to evaluate the in vivo performance of generic medicines. METHODS: The DAP workflow consists of an "In vitro two-cell connected dissolution (TCCD) system" mimicking the changes in the luminal pH associated with gastrointestinal transit of medicines, "Evaluation of pharmacokinetics of active pharmaceutical ingredient (API)" and "Prediction of plasma concentration-time profile". TCCD system-evaluated dissolution kinetics of APIs from generic formulations and pharmacokinetic parameters based on human data regarding the original drugs were used to calculate the plasma concentration-time profiles of APIs after the oral administration of generic medicines. RESULTS: The mandatory in vitro dissolution tests indicated that the dissolution properties of valsartan (BCS class II) and fexofenadine (BCS class III/IV) in generic formulations did not coincide with those in the corresponding original formulations. The TCCD system provided the very similar dissolution kinetics for the generic and original formulations for the two APIs. Plasma concentration-time profiles evaluated utilizing the dissolution profiles obtained by the TCCD system were in good agreement with the observed profiles for both the generic and original formulations for each API. CONCLUSIONS: The DAP workflow would be valuable for estimating the in vivo performance of generic formulation and deducing their bioequivalence with the original formulation.

Effects of particle size and release property of paclitaxel-loaded nanoparticles on their peritoneal retention and therapeutic efficacy against mouse malignant ascites.

Malignant ascites accounts for abdominal pain, dyspnea and anorexia, all of which decrease quality of life in cancer patients. Intraperitoneal chemotherapy is a useful method for managing malignant ascites and nanoparticulate drug delivery system makes it more effective by increasing peritoneal retention of anti-cancer drugs. In this study, we prepared paclitaxel-loaded emulsions and liposomes with different particle sizes and drug release properties, and evaluated their peritoneal retention and therapeutic efficacy in Ehrlich's ascites carcinoma (EAC)-bearing mice. Liposomes with the size of 100 nm were rapidly absorbed from peritoneal cavity into blood after intraperitoneal injection into EAC-bearing mice, whereas 1000-nm liposomes were highly retained in peritoneal cavity. Accordingly, 1000 nm liposomes significantly prolonged survival time of EAC-bearing mice but did not inhibit the ascites accumulation because of too poor paclitaxel release. On the other hand, although peritoneal retention of emulsions themselves was similar irrespective of their sizes, 270-nm emulsions showed the higher PTX retention in ascites than other emulsions, and resulted in significantly prolonged survival time and lower accumulation of ascites in EAC-bearing mice. These results indicate that not only particle size but drug release property is one of key determinants of the biodisposition and therapeutic efficacy of intraperitoneally injected nanoparticulate PTX against malignant ascites.

Extensive improvement of oral bioavailability of mebendazole, a brick dust, by polymer-containing SNEDDS preparation: Disruption of high crystallinity by utilizing its counter ion.

Poorly water-soluble and poorly lipid-soluble drugs are called as "brick dust" and it is very hard for them to be formulated as some dosage form which can provide an effective bioavailability after oral administration. Mebendazole (MBZ), an anti-helminthic drug having anti-cancer properties, is one of the brick dusts and its poor bioavailability has been well known. The strategy of the current study was to improve the oral absorption of MBZ by SNEDDS formulation prepared by utilizing an MBZ-counter ion complex, of which the formation would disrupt the high crystallinity of MBZ. Among five different counter ions examined, (+)-10-camphorsulfonic acid (CSA), 2-naphthalene-sulfonic acid (NSA) and p-toluenesulfonic acid (TSA) largely improved MBZ solubility in the SNEDDS vehicle by forming the complex with MBZ. The solid state of these complexes, MBZ-CSA, MBZ-NSA and MBZ-TSA, was suggested to be amorphous by XRPD and DSC. SNEDDS formulations of the three complexes extensively improved MBZ dissolution under gastric and intestinal luminal conditions, compared with MBZ crystalline powder. However, since the dissolved concentrations of MBZ were time-dependently decreased so much by precipitation, we tried to maintain the high dissolution property by applying some polymer for SNEDDS preparation of MBZ-CSA which provided the highest solubility in the SNEDDS vehicle. Among ten different polymers examined, HPMCP-50 successfully maintained the high dissolution property of MBZ-CSA SNEDDS under both gastric and intestinal luminal conditions. In the in vivo oral administration study, SNEDDS preparations for the three MBZ complexes significantly improved MBZ absorption compared with MBZ crystalline powder, but 2% HPMCP-50-containing SNEDDS of MBZ-CSA provided further improvement of MBZ absorption, resulting in around 10-fold of crystalline powder in AUC.

Effect of Doxorubicin Release Rate From Polyethylene Glycol-Modified Liposome on Anti-tumor Activity in B16-BL6 Tumor-Bearing Mice.

To investigate the effect of doxorubicin (DOX) release rates from polyethylene glycol (PEG)-liposomes on the anti-tumor activity, several in-vitro and in-vivo studies were performed by utilizing three types of DOX-PEG-liposomes showing the slow (L-Slow), middle (L-Mid) and fast (L-Fast) release rates of DOX. L-Mid provided the highest anti-tumor activity in B16-BL6 tumor-bearing mice, although the largest amount of DOX distribution into the tumor tissue was observed in L-Slow-administered mice and the lowest was in L-Fast-administered mice. To elucidate the reason for this discrepancy, DOX distribution into cancer cells constituting the tumor tissue was determined and the highest DOX distribution into cancer cells was observed in L-Mid-administered mice. These results clearly indicate that the adequate drug release rate from liposome should make it possible to deliver the substantial amounts of drugs into cancer cells, leading to the actual anti-tumor activity.

Formation of a Stable Co-Amorphous System for a Brick Dust Molecule by Utilizing Sodium Taurocholate with High Glass Transition Temperature.

Brick dust molecules are usually poorly soluble in water and lipoidal components, making it difficult to formulate them in dosage forms that provide efficient pharmacological effects. A co-amorphous system is an effective strategy to resolve these issues. However, their glass transition temperatures (Tg) are relatively lower than those of polymeric amorphous solid dispersions, suggesting the instability of the co-amorphous system. This study aimed to formulate a stable co-amorphous system for brick dust molecules by utilizing sodium taurocholate (NaTC) with a higher Tg. A novel neuropeptide Y5 receptor antagonist (AntiY5R) and NaTC with Tg of 155 °C were used as the brick dust model and coformer, respectively. Ball milling formed a co-amorphous system for AntiY5R and NaTC (AntiY5R-NaTC) at various molar ratios. Deviation from the theoretical Tg value and peak shifts in Fourier-transform infrared spectroscopy indicated intermolecular interactions between AntiY5R and NaTC. AntiY5R-NaTC at equal molar ratios resulting in an 8.5-fold increase in AntiY5R solubility over its crystalline form. The co-amorphous system remained amorphous for 1 month at 25 °C and 40 °C. These results suggest that the co-amorphous system formed by utilizing NaTC as a coformer could stably maintain the amorphous state and enhance the solubility of brick dust molecules.

Possible Regulation of P-glycoprotein Function by Adrenergic Agonists in a Vascular-luminal Perfused Preparation of Small Intestine.

Although the functions of small intestine are largely regulated by enteric nervous system (ENS), an independent intrinsic innervation, as well as central nervous system (CNS), the neural regulation of drug absorption from the small intestine still remains to be clarified. To obtain some information on it, the effect of adrenergic agonists on P-glycoprotein (P-gp) function was investigated by utilizing a vascular-luminal perfused rat small intestine. Adrenaline significantly decreased the secretion of rhodamine-123 (R-123) into the intestinal lumen, but dibutyryl cAMP (DBcAMP) significantly enhanced R-123 secretion. The inhibition study with quinidine clearly indicated that the decrease in secretory clearance of R-123 by adrenaline or the increase by DBcAMP would be attributed to the decrease or increase in P-gp activity, respectively. Expression levels of P-gp in whole mucosal homogenates were not changed at all by any chemicals examined, but those on brush border membrane (BBM) of intestinal epithelial cells were significantly decreased or increased by adrenaline or DBcAMP, respectively. Furthermore, changes in P-gp activity caused by adrenergic agonists and DBcAMP were significantly correlated with changes in expression level of P-gp in BBM, suggesting that the trafficking of P-gp from cytosolic pool to BBM would be regulated by adrenergic agonists and DBcAMP.

Sequential administration of PEG-Span 80 niosome enhances anti-tumor effect of doxorubicin-containing PEG liposome.

To improve the anti-tumor effect of polyethylene glycol-modified liposome containing doxorubicin (DOX-PEG liposome), the effect of sequential administration of PEG-Span 80 niosome was investigated for Colon-26 cancer cells (C26)-bearing mice. The concept of the current study is as follows: Since both particulates would be accumulated in the tumor tissue due to the enhanced permeability and retention (EPR) effect, PEG-Span 80 niosome, mainly composed of synthetic surfactant (Span 80), would interact with DOX-PEG liposome and be a trigger to induce the release of DOX from the liposome within the tumor tissue, leading to the improvement of anti-tumor effect of DOX-PEG liposome. To find out an adequate liposome for this strategy, several PEG liposomes with different compositions were examined in terms of drug release enhancement and it was found that PEG-Span80 niosome could significantly enhance the release of calcein and DOX from a PEG liposome composed of 90% hydrogenated soybean phosphatidylcholine (HSPC) and 10% cholesterol. The sequential administration of PEG-Span 80 niosome at 24 or 48 h after dosing of DOX-PEG liposome provided a higher anti-tumor effect than the single dose of DOX-PEG liposome in the C26-bearing mice. Particularly, the 24 h-later dosing of PEG-Span 80 niosome has been found to be more effective than the 48 h-later dosing. It was also confirmed that the coexistence of PEG-Span 80 niosome with DOX-PEG liposome in 50% serum or in 50% supernatant of tumor tissue homogenate significantly increased DOX release from PEG liposome, suggesting that DOX release from DOX-PEG liposome within tumor tissue would be enhanced via the interaction with PEG-Span 80 niosome. This strategy would lead to the safer and more inexpensive chemotherapy, since it could make it possible to provide the better anti-tumor effect by utilizing the lower dose of DOX.

Spermine with Sodium Taurocholate Enhances Pulmonary Absorption of Macromolecules in Rats.

The improvement effect of the combined use of spermine (SPM), a polyamine, with sodium taurocholate (STC) on the pulmonary drug absorption was investigated utilizing poorly absorbable drugs with various molecular sizes in rats. The pulmonary absorption of rebamipide, a low molecular but poorly absorbable drug after oral administration, was significantly improved by the combined use of SPM with STC (SPM-STC formulation), while poly- L-lysine did not show a significant change in rebamipide absorption from the lungs. Furthermore, the safety of the SPM-STC formulation for the lungs was assessed in rats by the histopathological study and any local toxicity was not observed while poly-L-lysine, a typical chemical causing the toxicity for the epithelial cells, provided several histopathological changes. In addition, the SPM-STC formulation significantly improved the pulmonary absorption of fluorescein isothiocyanate dextran 4 (FD-4, Mw ca 4000) and interferon-α (IFN-α, Mw ca 25,000) as well. Our present results clearly indicated that the SPM-STC formulation significantly improved the pulmonary absorption of poorly absorbable small and large molecular drugs without any harmful effects on the lungs. Therefore, the SPM-STC formulation would be a useful one for the pulmonary absorption of drugs, specifically macromolecular ones, which are very difficult to be absorbed after oral administration.

Improvement of lipid solubility and oral bioavailability of a poorly water- and poorly lipid-soluble drug, rebamipide, by utilizing its counter ion and SNEDDS preparation.

Among drugs in development and/or in market, there are poorly water-soluble and poorly lipid-soluble compounds. Rebamipide, classified into BCS class IV, is one of those drugs which provide very low bioavailability and/or the difficulty of formulation for oral administration. Because of its low solubility in available lipoidal excipients, it was impossible to prepare an adequate SNEDDS formulation of rebamipide. Then, we tried to increase the solubility of rebamipide in lipoidal excipients for preparing a more practical SNEDDS formulation by making the complex with its counter ion, tetrabutylphosphonium hydroxide (TBPOH) or NaOH. Rebamipide concentration in ethanol was proportionally increased with the increment of TBPOH or NaOH added, indicating that the formation of complex with a counter ion should contribute to the solubilization of rebamipide in ethanol. Both Rebamipide-TBPOH complex (Reb-TBPOH) and Rebamipide-NaOH complex (Reb-NaOH) obtained by lyophilization showed no endothermic peak in DSC and no diffraction peak in XRPD, suggesting that the solid state of both complexes should be amorphous. Reb-TBPOH maintained the dissolution of rebamipide in SNEDDS vehicle (Capryol 90:Cremophor EL:Transcutol P = 4:3:3) at 20 mg/g at least for 28 days, while Reb-NaOH did it at 10 mg/g. In vitro dissolution study showed that Reb-TBPOH SNEDDS and Reb-NaOH SNEDDS containing rebamipide at 10 mg/g maintained the complete dissolution of rebamipide in FaSSIF (intestinal luminal condition). In the gastric luminal condition (pH3.9 acetate buffer), the high concentration, close to the complete dissolution, was transiently observed and quickly decreased to one-sixth of the maximum, but it was still around 70 times higher than that of the crystalline powder. The additional utilization of Eudragit EPO for SNEDDS preparations of both complexes successfully maintained the high concentrations of rebamipide in the gastric luminal condition. In vivo oral absorption studies clearly indicated that SNEDDS preparations utilizing Reb-counter ion complex successfully improved rebamipide absorption.

Pharmacokinetic analysis of new synthetic antimalarial N-251.

BACKGROUND: With the emergence and growing number of drug-resistant Plasmodium falciparum, a new drug for malaria control must be urgently developed. The new antimalarial synthetic compound N-251 was recently discovered. As an endoperoxide structure in the body, the compound shows high antimalarial activity and curative effects. We performed a pharmacokinetic (PK) analysis of N-251 under various conditions using mice to understand the inhibitory effect of N-251 in parasite-infected mice. RESULTS: PK study of N-251 after intravenous and oral administration in mice showed plasma concentration of N-251 was decreased drastically by intravenous route. C max was reached in 2 h after oral administration of N-251, and the level decreased to a level similar to that obtained after intravenous administration. The area under the curves (AUCs) of the plasma concentration of N-251 increased dose-proportionally in both administrations, and bioavailability (F) was approximately 23%. Additionally, T max, C max, AUC, and F increased in fasted mice compared to normal-fed mice after the administration of N-251, indicating the influence of diet on the absorption kinetics of N-251. Furthermore, in parasite-infected fasted mice, the plasma concentration-time profile of N-251 was similar to that in normal-fasted mice. Based on the PK parameters of single oral administration of N-251, we investigated the effect of multiple oral doses of N-251 (68 mg/kg three times per day for 2 days) in normal-fed mice. The plasma concentration of N-251 was between 10 and 1000 ng/mL. The simulation curve calculated based on the PK parameters obtained from the single-dose study well described the plasma concentrations after multiple oral dosing, indicating that N-251 did not accumulate in the mice. Multiple oral administrations of N-251 in mice were required to completely eliminate parasites without accumulation of N-251. CONCLUSIONS: N-251 has been selected as a potent antimalarial candidate. We found that N-251 showed short half-life in plasma, and AUCs increased proportionally to dose. With multiple doses of N-251, the plasma level of N-251 was greater than 10 ng/mL in normal-fed mice, and accumulation of N-251 was not observed; however, multiple treatments with N-251 are required for the complete cure of parasite-infected mice. Determining the appropriate dosage was an important step in the clinical applications of N-251.

Quantitative Estimation of the Effect of Nasal Mucociliary Function on in Vivo Absorption of Norfloxacin after Intranasal Administration to Rats.

Nasal drug delivery has attracted significant attention as an alternative route to deliver drugs having poor bioavailability. Large-molecule drugs, such as peptides and central nervous system drugs, would benefit from intranasal delivery. Drug absorption after intranasal application depends on the nasal retention of the drug, which is determined by the nasal mucociliary clearance. Mucociliary clearance (MC) is an important determinant of the rate and extent of nasal drug absorption. The aim of the present study was to clarify the effect of the changes in MC on in vivo drug absorption after nasal application, and to justify the pharmacokinetic model to which the MC parameter was introduced, to enable prediction of bioavailability after intranasal administration. The pharmacokinetics of norfloxacin (NFX) after intranasal administration were evaluated following the modification of nasal MC by pretreatment with the MC inhibitors propranolol and atropine and the MC enhancers terbutaline and acetylcholine chloride. From the relationship between nasal MC and bioavailability after nasal application, prediction of drug absorption was attempted on the basis of our pharmacokinetic model. Propranolol and atropine enhanced the bioavailability of NFX by 90 and 40%, respectively, while the bioavailability decreased by 30% following terbutaline and 40% following acetylcholine chloride. As a result of changes in the MC function, nasal drug absorption was changed depending on the nasal residence time of the drug. On the basis of our pharmacokinetic model, the nasal drug absorption can be precisely predicted, even when the MC is changed. This prediction system allows the quantitative evaluation of changes in drug absorption due to changes in nasal MC and is expected to contribute greatly to the development of nasal formulations.

The relationship between in vivo nasal drug clearance and in vitro nasal mucociliary clearance: Application to the prediction of nasal drug absorption.

Drug absorption after nasal application is dependent on drug clearance from the nasal cavity, which is determined by nasal mucociliary clearance (MC). We previously developed an in vitro method to evaluate MC via the translocation velocity of fluorescent microspheres (VFMS) applied to excised rat nasal mucosa. In the present study, the relationship between in vivo nasal MC and in vitro VFMS was examined to optimize our PK model for the prediction of nasal drug absorption. Appropriate inhibitors (propranolol and atropine) and enhancers (terbutaline and acetylcholine chloride) of MC were utilized to modify MC. In vivo clearance of drug from the nasal cavity was determined from the disappearance of fluorescent microspheres (FMS) from the nasal cavity following nasal application to rats. The first order elimination rate constant, kmc, was determined from the disappearance profiles of FMS. kmc was decreased to 35.8% by propranolol and 52.6% by atropine, but increased to 117% by terbutaline and 168% by acetylcholine chloride. A significant linear correlation was observed between kmc and VFMS (r2 = 0.9745, p < 0.001). These results indicate that in vivo kmc can be estimated from the in vitro parameter, VFMS. By introducing linear correlation into our PK model, nasal drug absorption may be precisely estimated, even with changes in MC.