New preparation method of intestinal pressure-controlled colon delivery capsules by coating machine and evaluation in beagle dogs

pH-dependent pressure-sensitive colonic capsules for the delivery of aqueous bacterial suspensions

Microbiome-based therapies hold great promise for treating various diseases, but the efficient delivery of live bacteria to the colon remains a challenge. Furthermore, current oral formulations, such as lyophilized bacterial capsules or tablets, are produced using processes that can decrease bacterial viability. Consequently, high dosages are required to achieve efficacy. Herein, we report the design of pressure-sensitive colonic capsules for the encapsulation and delivery of aqueous suspensions of live bacteria. The capsules consisted of 2 functional thin-films (hydrophobic and enteric) of ethyl cellulose and Eudragit S100 dip-coated onto hydroxypropyl methylcellulose molds. The capsules could be loaded with aqueous media and provide protection against acidic fluids and, to some extent, oxygen diffusion, suggesting their potential suitability for delivering anaerobic bacterial strains. Disintegration and mechanical studies indicated that the capsules could withstand transit through the stomach and upper/proximal small intestinal segments and rupture in the ileum/colon. In vitro studies showed that bacterial cells (anaerobic and aerobic commensals) remained highly viable (74-98%) after encapsulation and exposure to the simulated GI tract conditions. In vivo studies with a beagle dog model revealed that 67% of the capsules opened after 3.5 h, indicating content release in the distal gastrointestinal tract. These data demonstrate that live aqueous bacterial suspensions comprised of both aerobic and anaerobic commensals can be encapsulated and in the future might be efficiently delivered to the distal gastrointestinal tract, suggesting the practical applications of these capsules in microbiome-based therapies.

In Vitro and In Vivo Evaluation of 3D Printed Capsules with Pressure Triggered Release Mechanism for Oral Peptide Delivery

In this study a 3D printed capsule designed to break from the physiological pressures in the antropyloric region was evaluated for its ability to deliver the synthetic octapeptide octreotide in beagle dogs when co-formulated with the permeation enhancer sodium caprate. The pressure sensitive capsules were compared to traditional enteric coated hard gelatin capsules and enteric coated tablets. Paracetamol, which is completely absorbed in dogs, was included in the formulations and used as an absorption marker to give information about the in vivo performance of the dosage forms. The pressure sensitive capsules released drug in 50% of the dogs. In the cases where drug was released, there was no difference in octreotide bioavailability or C_max compared to the enteric coated dosage forms. When comparing all dosage forms, a correlation was seen between paracetamol C_max and octreotide bioavailability, suggesting that a high drug release rate may be beneficial for peptide absorption when delivered together with sodium caprate.

In Vitro Methods to Study Colon Release: State of the Art and An Outlook on New Strategies for Better In-Vitro Biorelevant Release Media

The primary focus of this review is a discussion regarding in vitro media for colon release, but we also give a brief overview of colon delivery and the colon microbiota as a baseline for this discussion. The large intestine is colonized by a vast number of bacteria, approximately 1012 per gram of intestinal content. The microbial community in the colon is complex and there is still much that is unknown about its composition and the activity of the microbiome. However, it is evident that this complex microbiota will affect the release from oral formulations targeting the colon. This includes the release of active drug substances, food supplements, and live microorganisms, such as probiotic bacteria and bacteria used for microbiota transplantations. Currently, there are no standardized colon release media, but researchers employ in vitro models representing the colon ranging from reasonable simple systems with adjusted pH with or without key enzymes to the use of fecal samples. In this review, we present the pros and cons for different existing in vitro models. Furthermore, we summarize the current knowledge of the colonic microbiota composition which is of importance to the fermentation capacity of carbohydrates and suggest a strategy to choose bacteria for a new more standardized in vitro dissolution medium for the colon.

Exploring Different Strategies for Efficient Delivery of Colorectal Cancer Therapy

Colorectal cancer (CRC) is the third most common cancer and the fourth leading cause of cancer death in the world. Currently available chemotherapy of CRC usually delivers the drug to both normal as well as cancerous tissues, thus leading to numerous undesirable effects. Much emphasis is being laid on the development of effective drug delivery systems for achieving selective delivery of the active moiety at the anticipated site of action with minimized unwanted side effects. Researchers have employed various techniques (dependent on pH, time, pressure and/or bacteria) for targeting drugs directly to the colonic region. On the other hand, systemic drug delivery strategies to specific molecular targets (such as FGFR, EGFR, CD44, EpCAM, CA IX, PPARγ and COX-2) overexpressed by cancerous cells have also been shown to be effective. This review aims to put forth an overview of drug delivery technologies that have been, and may be developed, for the treatment of CRC.

New targeting strategies in drug therapy of inflammatory bowel disease: mechanistic approaches and opportunities

INTRODUCTION

Inflammatory bowel disease (IBD) is an exceptional scenario with regard to drug targeting, as oral administration has the potential to deliver the drug directly to the site(s) of action. Consequently, retention of the drug within the intestinal lumen and tissue, rather than systemic absorption, is frequently desirable.

AREAS COVERED

In this article, the traditional drug-delivery strategies used in IBD are briefly summarized. These include rectal dosage forms and oral systems that target the lower intestine/colon by pH-, time-, microflora-, and pressure-dependent mechanisms. Then, the article offers an updated overview of recently developed delivery systems aimed to achieve maximal drug concentrations in the inflamed intestinal tissues with minimal systemic side effects. These include antibodies, small molecules, Janus kinase inhibitors, particulate carrier systems, anti-inflammatory peptides, gene therapy, and transgenic bacteria. The various approaches are reviewed, and the challenges that still remain to be overcome are discussed.

EXPERT OPINION

The molecular revolution of the past decade profoundly influenced the treatment and management of IBD. In the coming years, this trend is expected to continue. Yet, many challenges are still ahead. A strong collaborative effort by experts from different fields is encouraged and necessary to maximize our success in IBD drug targeting.

Strategies of targeting oral drug delivery systems to the colon and their potential use for the treatment of colorectal cancer

Colorectal cancer (CRC) is the third most common cause of cancer-related death in both men and women. Often, surgical intervention remains the choice in treating CRC. Traditional dosage forms used for treating CRC deliver drug to wanted as well as unwanted sites of drug action resulting in several adverse side effects. Targeted oral drug delivery systems are being investigated to target and deliver chemotherapeutic and chemopreventive agents directly to colon and rectum. Site-specific delivery of a drug to colon increases its concentration at the target site, and thus requires a lower dose with reduced incidence of side effects. The major obstacle to be overcome for successful targeting of drug to colon through oral route is that drug absorption/degradation must be avoided in stomach and small intestine before the dosage form reaches colon. The review includes discussion of physiological factors that must be considered when targeting drugs directly to colorectal region, an outline on drugs used for treatment and prevention of CRC, and a brief description of various types of colon-targeted oral drug delivery systems. The focus is on the assessment of various formulation approaches being investigated for oral colon-specific delivery of drugs used in the treatment and prevention of CRC.

Oral colon delivery of insulin with the aid of functional adjuvants

Oral colon delivery is currently considered of importance not only for the treatment of local pathologies, such as primarily inflammatory bowel disease (IBD), but also as a means of accomplishing systemic therapeutic goals. Although the large bowel fails to be ideally suited for absorption processes, it may indeed offer a number of advantages over the small intestine, including a long transit time, lower levels of peptidases and higher responsiveness to permeation enhancers. Accordingly, it has been under extensive investigation as a possible strategy to improve the oral bioavailability of peptide and protein drugs. Because of a strong underlying rationale, most of these studies have focused on insulin. In the present review, the impact of key anatomical and physiological characteristics of the colon on its viability as a protein release site is discussed. Moreover, the main formulation approaches to oral colon targeting are outlined along with the design features and performance of insulin-based devices.

Investigation into drug release from colon-specific azoreductase-activated steroid prodrugs using in-vitro models

OBJECTIVES

The aim of this study was to investigate drug release from a double steroid prodrug, OPN501, which incorporates a phenylpropionate linker, and its phenylacetate analogue. The prodrugs, which were designed to deliver prednisolone to the colon for the treatment of inflammatory bowel disease, are based on a novel design that requires sequential azoreductase activity and cyclization of an amino ester to trigger drug release. We sought to explain the divergent effects of the two compounds in anti-inflammatory models and to justify the selection of OPN-501 for clinical development.

METHODS

The compounds were incubated in mouse colonic contents (10%) fermented in brain heart infusion under anaerobic conditions. The disappearance of the prodrugs and release of prednisolone was monitored by HPLC. We then developed a method for assessment of prodrug activation using suspensions of Clostridium perfringens, an anaerobe from the human colon. The cyclization of the compounds was studied in various media, assessing the influence of pH and bulk solvent polarity on cyclization rate using HPLC and NMR.

KEY FINDINGS

The prodrugs were activated via multiple pathways releasing prednisolone in mouse colonic ferment. The compounds released prednisolone by reduction-cyclization in C perfringens suspension. The active OPN-501 generated a stoichiometric amount of prednisolone following azoreductase activation, whereas its analogue did not. The pH rate profile for the cyclization of the amino intermediates of the two compounds revealed significant differences in rate at pH values relevant to the inflamed colon, which explain in part the different amounts of drug produced.

CONCLUSIONS

The steroid prodrug OPN-501 has optimal drug release characteristics for colon targeting because of a kinetic advantage of a six-membered ring formation in the aminolysis reactions of anilides. The results are relevant to the development of OPN-501 but also to cyclization strategies in prodrug design especially for colon targeting.

Film coated tablets (ColoPulse technology) for targeted delivery in the lower intestinal tract: influence of the core composition on release characteristics

The design of a film coating technology which allows a tablet to deliver the drug in the ileocolonic segment would offer new treatment possibilities. The objective is to develop a platform technology that is suitable for a broad range of drug compounds. We developed a coated tablet with a delayed, pulsatile release profile based on a pH-sensitive coating technology (ColoPulse). The production process was validated, and the effect of core composition on the in vitro release and water uptake investigated. The release profile of the standard tablet core composition, based on the use of cellulose as a filler, was independent of the coat thickness in a range of 9.0-13.2 mg/cm(2). The release profile of a coated tablet was strongly influenced when cellulose was partly replaced by the model substance glucose (loss of sigmoidal release), citric acid (stabilization), sodium bicarbonate (destabilization) or sodium benzoate (destabilization). The film coating takes up water when below the pH-threshold. However, this did not cause early disintegration of the coating. The ColoPulse technology is successfully applied on tablets. The in vitro release characteristics of the coated tablets are influenced by the composition of the core.

Engineering strategies to enhance nanoparticle-mediated oral delivery

Oral delivery is the most preferred route of drug administration due to convenience, patient compliance and cost-effectiveness. Despite these advantages it remains difficult to achieve satisfactory bioavailability levels via oral administration due to the harsh environment of the gastrointestinal (GI) tract, particularly for biomacromolecules. One promising method to increase the bioavailability of macromolecular drugs such as proteins and nucleic acids is to encapsulate them in nanoparticles before oral administration. This review describes innovative strategies for increasing the efficacy of nanoparticle-mediated delivery to the GI tract. Approaches to optimize nanoparticle formulation by exploiting mucoadhesion, environmental responsiveness and external delivery control mechanisms are discussed. The application of recent advances in nanoparticle synthesis using supercritical fluids, microfluidics and imprint lithography to oral delivery are also presented, as well as possible strategies for incorporating nanoparticles into micro- and macroscale oral delivery devices.

Design of Nanohydrogel-Incorporated Microcapsules for Appropriate Controlled-Release of Peptide Drugs

Biologically active peptides for therapeutic use have relatively short half-lives in general, requiring appropriate controlled-release systems for better therapy. Controlled release of peptides is, however, not as easy as that of conventional drugs because their large molecular size is much more dramatic in hindering the diffusion and release from polymeric devices. From this perspective, we have been developing two types of microcapsular devices containing new acrylate-based nanogels with a specific solute-permeability for delayed- or thermosensitive-release of peptide drugs. The microcapsule preparation was accomplished by an air suspension coating process. A nanogel-particle of acrylic terpolymer, ethyl acrylate-methyl methacrylate-2-hydroxyethyl methacrylate, was newly synthesized by emulsion polymerization to construct delayed-release microcapsules. By spray-coating the insulin-loaded lactose particles with the acrylic terpolymers, microcapsules showing a pH-independent delayed-release profile can be obtained. Oral administration of the microcapsules with the lag time of 6 hours to beagle dogs resulted in significantly reduced blood glucose concentration, leading to colon-specific insulin delivery with pharmacological availability of 5%. Meanwhile, poly(N-isopropylcarylamide) (p(NIPAAm)) nanogel-particles with a reversible temperature-dependent swelling property were prepared by dispersion polymerization to fabricate microcapsular membranes with thermosensitively changeable permeability. The microcapsules constructed by coating of drug-loaded CaCO(3) particles with a blend mixture of the p(NIPAAm) nanogels and ethylcellulose pseudo-latex exhibited an 'on-off' positively thermosensitive drug-release; the release rate was remarkably enhanced at higher temperatures possibly due to the formation of voids through the shrinkage of p(NIPAAm) nanogels in the membrane. A possible application of this type of microcapsules can be found in externally temperature-activated pulsatile peptide delivery.

Time-controlled oral delivery systems for colon targeting

In recent years, many research efforts have been spent in the achievement of selective delivery of drugs into the colon following oral administration. Indeed, colonic release is regarded as a beneficial approach to the pharmacological treatment or prevention of widespread large bowel pathologies, such as inflammatory bowel disease and adenocarcinoma. In addition, it is extensively explored as a potential means of enhancing the oral bioavailability of peptides, proteins and other biotechnological molecules, which are known to be less prone to enzymatic degradation in the large, rather than in the small, intestine. Based on these premises, several formulation strategies have been attempted in pursuit of colonic release, chiefly including microflora-, pH-, pressure- and time-dependent delivery technologies. In particular, this review is focused on the main design features and release performances of time-controlled devices, which rely on the relative constancy that is observed in the small intestinal transit time of dosage forms.

New oral delivery systems for treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) is often localized to specific sites in the gastrointestinal tract (GIT). As a result, this disease can be treated with oral site-specific (targeted) drug delivery systems. Targeted delivery systems for treatment of IBD are designed to increase local tissue concentrations of antiinflammatory drugs from lower doses compared with systemic administration. This review addresses the impact disease has or may have on oral targeted delivery for treatment of IBD as well as a number of delivery approaches currently used in marketed products or under investigation. Delivery systems reviewed rely on temporal control, changes in pH along the GIT, the action of local enzymes to trigger drug release, and changes in intraluminal pressure. Dissolution of enteric polymer coatings due to a change in local pH and reduction of azo-bonds to release an active agent are both used in commercially marketed products. Newer approaches showing promise in treating IBD are based on polysaccharides. These materials are most effective when used as compression coatings around core tablets, which contain the active agent. More complex polymeric prodrugs systems are also under investigation. If the dose of the drug is sufficiently low, this approach may also prove useful in improving treatment of IBD.

Analysis of the Release Process of Phenylpropanolamine Hydrochloride from Ethylcellulose Matrix Granules II. Effects of the Binder Solution on the Release Process

The release properties of phenylpropanolamine hydrochloride (PPA) from ethylcellulose (EC) matrix granules prepared by an extrusion granulation method were examined. The release process could be divided into two parts; the first and second stages were analyzed by applying square-root time law and cube-root law equations, respectively. The validity of the treatments was confirmed by the fitness of a simulation curve with the measured curve. In the first stage, PPA was released from the gel layer of swollen EC in the matrix granules. In the second stage, the drug existing below the gel layer dissolved and was released through the gel layer. The effect of the binder solution on the release from EC matrix granules was also examined. The binder solutions were prepared from various EC and ethanol (EtOH) concentrations. The media changed from a good solvent to a poor solvent with decreasing EtOH concentration. The matrix structure changed from loose to compact with increasing EC concentration. The preferable EtOH concentration region was observed when the release process was easily predictable. The time and release ratio at the connection point of the simulation curves were also examined to determine the validity of the analysis.

Chitosan dispersed system for colon-specific drug delivery

A chitosan dispersed system (CDS), which was composed of active ingredient reservoir and the outer drug release-regulating layer dispersing chitosan powder in hydrophobic polymer, was newly developed for colon-specific drug delivery. An aminoalkyl methacrylate copolymer RS (Eudragit) RS) was selected as a hydrophobic polymer because it is hardly dissolved in acidic medium in which easily dissolves chitosan. In order to obtain the bi-functional releasing characteristics, i.e. time dependent and site specific, capsules containing the active ingredient (Drug Capsules) were coated by the chitosan dispersed hydrophobic polymer, resulting in CDS Capsules. The release rate could be controlled by changing the thickness of the layer. Furthermore, for colon-specific drug delivery, an additional outer enteric coating was necessary to prevent the drug release from CDS Capsules in the stomach, since chitosan dispersed in the layer dissolves easily under acidic conditions. Resultant enteric-coated CDS Capsules reached the large intestine within 1-3 h after oral administration and they were degraded at the colon in beagle dogs.

Analysis of the release process of phenylpropanolamine hydrochloride from ethylcellulose matrix granules

The release properties of phenylpropanolamine hydrochloride (PPA) from ethylcellulose (EC, ethylcellulose 10 cps (EC#10) and/or 100 cps (EC#100)) matrix granules prepared by the extrusion granulation method were examined. The release process could be divided into two parts, and was well analyzed by applying square-root time law and cube root law equations, respectively. The validity of the treatments was confirmed by the fitness of the simulation curve with the measured curve. At the initial stage, PPA was released from the gel layer of swollen EC in the matrix granules. At the second stage, the drug existing below the gel layer dissolved, and was released through the gel layer. Also, the time and release ratio at the connection point of the simulation curves was examined to determine the validity of the analysis. Comparing the release properties of PPA from the two types of EC matrix granules, EC#100 showed more effective sustained release than EC#10. On the other hand, changes in the release property of the EC#10 matrix granule were relatively more clear than that of the EC#100 matrix granule. Thus, it was supposed that EC#10 is more available for controlled and sustained release formulations than EC#100.

Synthesis of an enzyme-dependent prodrug and evaluation of its potential for colon targeting

AIM: To synthesize dexamethasone-succinate-dextran (DSD) conjugate and to evaluate the potentiality of DSD for the treatment of inflammatory bowel diseases.

METHODS: Dexamethasone was attached to dextran (average molecular weight = 70400 Dalton) using succinate anhydride in an anhydrous environment catalyzed by 4-dimethylaminopyridine and 1,1’-carbonyldiimidazole. The chemical structure of DSD was identified by UV, IR and NMR, and the in vivo drug release behavior of this prodrug was investigated after oral administration of DSD suspension.

RESULTS: The DSD conjugate was obtained in two steps and the content of dexamethasone in DSD was 11.28%. The dextran prodrug was stable in rat stomach and small intestine and negligibly absorbed from these tracts. Four to nine hours after the oral administration, most of the prodrug (> 95%) had moved to the cecum and colon, and was easily hydrolyzed by an endodextranase. Recover of dexamethasone from colon and cecum after administration of DSD conjugate was 6-12 folds higher than the recovery after administration of unmodified dexamethasone (t = 2.74, P < 0.05). The preferential release of free dexamethasone in cecum and colon over that in the small intestine was statistically significant (t = 2.27, P < 0.05).

CONCLUSION: The results of this study indicate that dextran conjugates may be useful in selectively delivering glucocorticoids to the colon.

Colon-specific drug delivery: new approaches and in vitro/in vivo evaluation

The necessity and advantages of colon-specific drug delivery systems have been well recognized and documented. In the past, the primary approaches to obtain colon-specific delivery achieved limited success and included prodrugs, pH- and time-dependent systems, and microflora-activated systems. Precise colon drug delivery requires that the triggering mechanism in the delivery system only respond to the physiological conditions particular to the colon. Hence, continuous efforts have been focused on designing colon-specific delivery systems with improved site specificity and versatile drug release kinetics to accommodate different therapeutic needs. Among the systems developed most recently for colon-specific delivery, four systems were unique in terms of achieving in vivo site specificity, design rationale, and feasibility of the manufacturing process (pressure-controlled colon delivery capsules (PCDCs), CODES, colonic drug delivery system based on pectin and galactomannan coating, and Azo hydrogels). The focus of this review is to provide detailed descriptions of the four systems, in particular, and in vitro/in vivo evaluation of colon-specific drug delivery systems, in general.

Evaluation of an intestinal pressure-controlled colon delivery capsules prepared by a dipping method

A new method for preparation of large amounts of empty pressure-controlled colon delivery capsules (PCDCs) by a dipping method has been developed. Empty PCDCs are composed of two polymer membranes. The inner one was a water-insoluble polymer membrane, ethylcellulose (EC). The outer one was an enteric polymer membrane, hydroxypropylmethylcellulose phthalate (HPMCP) or hydroxypropylmethylcellulose acetate succinate (HPMCAS). By consequently dipping into an ethanolic EC solution and an alkalized enteric polymer solution, empty PCDCs were obtained after both the capsule body and cap were adjusted to the size of #2 capsules. With each enteric polymer, two types of empty PCDCs of different thickness were prepared. Fluorescein (FL) was formulated with suppository base, PEG1000, and used as a model drug. FL/PEG1000 suspension was introduced into empty PCDCs which were then sealed with enteric polymer solution. The PCDCs were evaluated by an in vivo experiment using beagle dogs. After oral administration of the test PCDC preparations containing 30 mg of FL, blood samples were obtained from the jugular vein and serum FL levels were measured. The thickness of the EC membrane layer varied in both the capsule body and cap. HPMCAS PCDCs had 62.1+/-5.0 (S.E.) microm (body) and 49.7+/-3.3 microm (cap) with thicker ones and 55.7+/-6.6 microm (body) and 46.8+/-6.2 microm (cap) with thinner ones. HPMCP PCDCs had 28.1+/-3.3 microm (body), 30.9+/-1.0 microm (cap) with thinner ones and 43.1+/-9.8 microm (body), 42.4+/-8.2 microm (cap) with thicker ones. The mean T(i) values, the first appearance time, of FL in the serum of HPMCAS PCDCs were 2.0+/-0.7 h for thicker ones and 3.8+/-0.5 h for thinner ones, while the mean T(i) values of HPMCP PCDCs were 2.0+/-0.0 h for thinner ones and 3.5+/-0.7 h for thicker ones. Since the colon arrival time in beagle dogs was 3.5+/-0.3 h as determined by a sulfasalazine test, thinner HPMCAS PCDCs and thicker HPMCP PCDCs were thought to deliver FL to the colon.

Colon delivery efficiencies of intestinal pressure-controlled colon delivery capsules prepared by a coating machine in human subjects

Large quantities of pressure-controlled colon delivery capsules (PCDCs) were prepared by a Hicoater-mini pharmaceutical coating machine and colon delivery efficiencies were evaluated in man. Caffeine powder as a model drug was suspended with a polyethylene glycol (PEG) 1000 suppository base at 50 degrees C, and was hardened in no. 0- and no. 2-sized capsular shapes. The capsule-shaped suppositories were coated with 5% w/v ethanolic ethylcellulose (7G grade) solution using the coating machine. By increasing the coating weight of ethylcellulose from 28.6 +/- 1.1 mg to 45.3 +/- 0.2 mg, the mean coating thickness of no. 0 PCDCs increased from 56 +/- 1 microm to 64 +/- 1 microm. With no. 2 PCDCs, the mean coating thickness increased from 50 micro +/- 1 microm to 57 +/- 1 microm by increasing the coating weight of ethylcellulose from 8.1 +/- 0.5 mg to 11.2 +/- 0.3 mg. The no. 0 PCDCs, having a mean ethylcellulose coating membrane thicknesses of 56 +/- 1 microm (type 1) and 64 +/- 1 microm (type 2), as well as no. 2 PCDCs, having thicknesses of 50 +/- 1 microm (type 3) and 57 +/- 1 microm (type 4), were used for in-vivo evaluation in man. After oral administration of test preparations containing 75 mg of caffeine, saliva samples were obtained and salivary caffeine levels were measured by an HPLC method. The first appearance time, Ti, of caffeine in the saliva was used as a parameter for the estimation of the release time of caffeine from PCDCs in the gastrointestinal tract. The mean Ti values of no. 0 PCDCs were 3.3 +/- 0.3 h for type- 1 and 5.3 +/- 0.3 h for type-2 preparations while the mean Ti values of no. 2 PCDCs were 4.3 +/- 0.5 h for type 3 and 5.3 +/- 0.3 h for type 4. There were good correlations between ethylcellulose coating membrane thicknesses and in-vivo Ti values. A colon arrival time of 5 h was reported in our subjects by gastrointestinal magnetomarkergraphy. PCDCs having a mean coating thickness of 64 +/- 1 microm for no. 0 capsules and of 57 +/- 1 microm for no. 2 capsules were thought to deliver caffeine to the human colon efficiently.

Characteristics of intestinal absorption and disposition of glycyrrhizin in mice

As basic studies to apply an intestinal pressure-controlled colon delivery capsule (PCDC) for glycyrrhizin (GZ), the characteristics of intestinal absorption and disposition of GZ were investigated in mice. In the in vivo study, after intravenous (iv) administration of GZ, 10 mg/kg dose, plasma GZ disappeared from the systemic circulation with t(1/2(alpha)) of 0.0063 h, thereafter, it slowly declined with t(1/2(beta)) of 15.23 h. The area under the plasma drug concentration versus time curve (AUC) values of iv (10 mg/kg), intracolonic (50 mg/kg) and intraduodenum (50 mg/kg) administrations were 115.1, 16.7 and 2.7 microgh/mL, respectively. The AUC values of plasma glycyrrhetic acid (GA), a degradation product after intracolonic and intraduodenum administrations were 2.8 and 8.4 microgh/mL, respectively. In the in situ closed loop study, the concentrations of GZ in plasma and liver after intracolonic administration were significantly increased (p<0.05) in comparison with those after intrajejunum or intraileum administration, while the concentration of GA in plasma and liver after intracolonic administration had trends to increase. These observations clearly suggest that the intracolonic administration is a useful way to improve the oral bioavailability of GZ and to enhance its pharmacological efficacy. These pharmacokinetic results of GZ suggest that GZ is a subject drug to be applied for the PCDC system we previously developed. The PCDCs formulation of GZ will enable us to carry GZ to the colon and enhance the oral bioavailability of GZ.

Application of a biomagnetic measurement system (BMS) to the evaluation of gastrointestinal transit of intestinal pressure-controlled colon delivery capsules (PCDCs) in human subjects

PURPOSE

For determination of the transit time through various parts of the gastrointestinal (GI) tract, we developed a method that provides the location of disintegration and drug release. This method involves GI magnetomarkergraphy (GIMG) using a 129-channel Shimadzu vector biomagnetic measurement system (BMS).

METHODS

To magnetically label the pressure-controlled colon delivery capsule (PCDC) containing 75.0 +/- 0.5 mg of caffeine as a tracer drug, small capsule caps containing 90 mg of ferric oxide powdered magnetite (Fe2O3) were attached to PCDCs. After orally administration to fasted human volunteers, saliva samples were collected hourly and salivary caffeine concentration was measured. At the same time, locations of the magnetic PCDC were detected by BMS just after the PCDCs were magnetized with the coils of a magnetic resonance imaging (MRI) system. The magnetic field distributions were analyzed and the estimated positions were shown on the MRI picture of the same subject's abdominal structure.

RESULTS

We magnetized PCDC with permanent magnets or an electromagnet before ingestion and the estimated locations of PCDC in the GI tract exhibited high estimation error. In order to increase the precision of estimated localization of PCDCs, PCDCs were magnetized within the coils of the MRI. As a result, these PCDCs had strong magnetic dipoles that were parallel to the sensor unit of BMS in every measurement, and therefore the spatial resolution of the PCDC's two-dimensional positions in the organs of the GI tract was within a range of several millimeters.

CONCLUSIONS

GIMG is a powerful tool for the study of colon delivery efficiencies of PCDCs. The main advantage of GIMG is the capability to obtain even more detailed knowledge of the behavior and fate of solid pharmaceutical formulations during GI passage.