Hiromu Kondo

Common solubilizers to estimate the Caco-2 transport of poorly water-soluble drugs

Solubilizers are often used to enhance the bioavailability of drugs with poor aqueous solubility. This study focuses on the use of the Caco-2 system containing solubilizers to predict the absorption of poorly water-soluble drugs in humans. First, the effects of propylene glycol (PG), hydroxypropyl-beta-cyclodextrin (HP-beta-CD), polyethylene glycol 400 (PEG 400), and Tween 80 on the viability (transepithelial electrical resistance, TEER) of 3-day cultured Caco-2 monolayers were evaluated. These solubilizers, even at the low concentration, reduce the viability of Caco-2 monolayers; these results indicate the impossibility for 3-day cultured Caco-2 monolayers to be used for this test. Next, the effects of PG, Tween 80, PEG 400, HP-beta-CD, Pluronic F-68 (Pluronic), HCO-40, sodium lauryl sulfate (SLS), Gelucire 44/14, Transcutol P, and extract gall powder on the viability of 21-day cultured Caco-2 monolayers and the apparent permeability (P(app)) of propranolol (PPL), Nadolol (NDL), and FITC-dextran 4000 (FD-4) were investigated. Five different solubilizing methods (20% PG, 5% Tween 80, 5% PEG 400, 5% HP-beta-CD, and 5% Tween 80+5% PEG 400) did not affect the viability of 21-day cultured Caco-2 monolayers. Furthermore, the P(app) values of the three compounds containing these solubilizers did not differ from the values for control formulations (without solubilizers). These results clearly suggest that the use of PG, Tween 80, PEG 400, or HP-beta-CD as solubilizing excipients and the testing of these formulations on 21-day cultured Caco-2 monolayers can predict intestinal absorption of poorly water-soluble drugs in humans.

Extended release of a large amount of highly water-soluble diltiazem hydrochloride by utilizing counter polymer in polyethylene oxides (PEO)/polyethylene glycol (PEG) matrix tablets.

The purpose of this study was to evaluate the feasibility of using a counter polymer in polyethylene oxide (PEO)/polyethylene glycol (PEG) polymeric matrices for the sustained release of a large amount of highly water-soluble drug. PEO/PEG matrix tablets (CR-A) containing four drugs with different water solubilities were prepared to investigate the effect of drug solubility on the drug-release and diffusion properties of PEO/PEG matrices. Cross-linked carboxyvinyl polymer (CVP)/PEO/PEG matrix tablets (CR-B) containing a water-soluble drug, diltiazem hydrochloride (DTZ), were also prepared, and their in vitro characteristics were compared with those of CR-A. Their in vitro drug release properties were evaluated using a dissolution test, and the polymeric erosion and drug diffusion properties of the matrices were also calculated. Drugs with higher solubility in water were released faster for the CR-A. The drug-release rate also increased with the amount of drug loaded. CR-A containing 50% DTZ (by weight) extended drug release by only 6h. This confirms the difficulty experienced when trying to formulate PEO/PEG matrices for the sustained release of a large amount of highly water-soluble drugs due to large drug diffusion. In an attempt to control this issue, a polymer bearing a charge opposite that of the drug was used to effectively decrease the diffusion of DTZ, resulting in sustained release for 24h or longer. These results suggested that including counter polymer in the PEO/PEG matrix tablet is a useful tool for achieving the sustained release of a large amount of highly water-soluble drug.

Evaluation of Factors Affecting Gastrointestinal Absorption of a Novel Anticoagulant FX-93 for Development of Oral Formulation

To find out factors causing the low bioavailability of FX-93, a novel anticoagulant, its solubility, membrane permeability, and the effect of bile salt on the absorption of FX-93 were investigated. The solubility of FX-93 under physiological conditions ranged from 0.3 to 18.3 mg/mL and the dose number was calculated to be 0.02-0.27, suggesting that the intrinsic solubility of FX-93 should not be a limiting factor for oral absorption. Apparent permeability of FX-93 across Caco-2 cell monolayer suggested that its fraction of dose absorbed would range between 30% and 40% in humans. Furthermore, FX-93 was substantially absorbed from each segment of rat intestine. However, the decrease in the gastrointestinal transit rate significantly decreased maximum plasma concentration and area under the plasma concentration-time curve of FX-93 after oral dosing in dogs, suggesting that FX-93 absorption would be suppressed by some components in the small intestinal lumen. An in situ rat administration study indicated that bile significantly decreased the intestinal absorption of FX-93 by two-thirds, which could be attributed to the decrease in FX-93 solubility by the interaction with bile or bile acid. Nuclear magnetic resonance spectroscopy analysis suggested that FX-93 would interact with bile salt between the naphthalene ring of FX-93 and steroidal backbone of bile salt.

Oral tacrolimus oil formulations for enhanced lymphatic delivery and efficient inhibition of T-cell's interleukin-2 production.

Oral oil formulations have been reported to deliver drugs into the lymph. Lymphatic delivery of immunomodulatory drugs can more efficiently expose the drugs to T-cells in lymph, consequently induce higher efficacy and lower side effects. In this study, effects of tacrolimus oral oil formulations on drug blood exposure, and on inhibition of T-cells interleukin-2 (IL-2) production were investigated in rats. Oil formulations (sunflower oil, cacao butter, medium chain triglyceride, and palm oil) dissolving tacrolimus showed lower drug blood concentration than a solid dispersion formulation (SDF). The sunflower oil, and cacao butter formulations suppressed drug blood exposure to 50% of the SDF, and inhibited T-cells IL-2 production similar to the SDF. In vitro digestion tests indicated that slower digestion of the oils might reduce amount and rate of tacrolimus blood absorption. The cacao butter formulations showed 3.0 times more rapid tacrolimus absorption to lymphatic fluid than the SDF. Ratio of the rate constants of absorption into lymph to that into blood was higher in oil formulations (15 times in cacao butter, 15 times sunflower oil, and 3.5 times palm oil) than in the SDF. These results indicated that the oral oil formulations might be suitable for reduced tacrolimus blood concentration for low systemic side effects, and keep high lymph concentration for high efficacy in organ transplantation patients.

Application of water-insoluble polymers to orally disintegrating tablets treated by high-pressure carbon dioxide gas

The phase transition of pharmaceutical excipients that can be induced by humidifying or heating is well-known to increase the hardness of orally disintegrating tablets (ODTs). However, these conditions are not applicable to drug substances that are chemically unstable against such stressors. Here, we describe a system which enhances the hardness of tablets containing water-insoluble polymers by using high-pressure carbon dioxide (CO2). On screening of 26 polymeric excipients, aminoalkyl methacrylate copolymer E (AMCE) markedly increased tablet hardness (+155N) when maintained in a high-pressure CO2 environment. ODTs containing 10% AMCE were prepared and treatment with 4.0MPa CO2 gas at 25°C for 10min increased the hardness to +30N, whose level corresponded to heating at 70°C for 720min. In addition, we confirmed the effects of CO2 pressure, temperature, treatment time, and AMCE content on the physical properties of ODTs. Optimal pressure of CO2 gas was considered to be approximately 3.5MPa for an AMCE formula, as excessive pressure delayed the disintegration of ODTs. Combination of high-pressure CO2 gas and AMCE is a prospective approach for increasing the tablet hardness for ODTs, and can be conducted without additional heat or moisture stress using a simple apparatus.

Aminoalkylmethacrylate copolymer E improves oral bioavailability of YM466 by suppressing drug-bile interaction

The aim of this study was to find out polymeric compounds that can inhibit the interaction between YM466, a novel anticoagulant, and bile to improve its oral bioavailability. In vitro ultrafiltration method using extract gall powder was useful to detect the formation of insoluble complex of YM466 with bile and also used to select a polymer that can inhibit the interaction between YM466 and bile. The in vitro studies revealed that aminoalkylmethacrylate (AAM) copolymer E, a polymethacrylate, dose-dependently inhibited the interaction between YM466 and bile and that this polymer could interact with bile salt, but not with YM466, possibly by electrostatic and/or hydrophobic interactions. The coadministration of AAM copolymer E with YM466 to rats dose-dependently increased the plasma concentration of YM466 and it was found that the oral dose of the polymer three times of YM466 (polymer to drug ratio in weight, P-D ratio, 3) significantly increased AUC0-1 h of YM466 to 2.6-fold of that of YM466 alone. Considering the condition of therapeutic use of YM466 and the maximum tolerated dose of the polymer, the formulation of P-D ratio 3 would be clinically practical and promising from the viewpoint of safety.

Trade-offs in Oral Drug Product Development

Drug products are developed to meet multiple targets, thereby increasing their value. Pharmaceutical scientists encounter several trade-offs during the development of novel oral formulations. These trade-offs are generated by their desire to supply the highest possible quality products under the prevailing conditions of limited time and cost, and feasible options. When there are two incompatible factors, it is sometimes difficult to dismiss one element. This is because a quality target product profile (QTPP) is critical for each product being developed, and all elements should basically be satisfied with the criteria. Therefore, technological innovation becomes important to overcome the trade-offs. This article introduces examples of such innovations which have been successful in doing this, as well as some encountered in the oral formulation development and in the selection of proper dosage forms. Based on these examples, points to be considered in order to produce the drug product are thoroughly discussed.