Pulsatile drug delivery to ileo-colonic segments by structured incorporation of disintegrants in pH-responsive polymer coatings

Solidification and oral delivery of biologics to the colon- A review

The oral delivery of biologics such as therapeutic proteins, peptides and oligonucleotides for the treatment of colon related diseases has been the focus of increasing attention over the last years. However, the major disadvantage of these macromolecules is their degradation propensity in liquid state which can lead to the undesirable and complete loss of function. Therefore, to increase the stability of the biologic and reduce their degradation propensity, formulation techniques such as solidification can be performed to obtain a stable solid dosage form for oral administration. Due to their fragility, stress exerted on the biologic during solidification has to be reduced with the incorporation of stabilizing excipients into the formulation. This review focuses on the state-of-the-art solidification techniques required to obtain a solid dosage form for the oral delivery of biologics to the colon and the use of suitable excipients for adequate stabilization upon solidification. The solidifying processes discussed within this review are spray drying, freeze drying, bead coating and also other techniques such as spray freeze drying, electro spraying, vacuum- and supercritical fluid drying. Further, the colon as site of absorption in both healthy and diseased state is critically reviewed and possible oral delivery systems for biologics are discussed.

Surface Engineering Methods for Powder Bed Printed Tablets to Optimize External Smoothness and Facilitate the Application of Different Coatings

In a previous attempt to achieve ileo-colonic targeting of bovine intestinal alkaline phosphatase (BIAP), we applied a pH-dependent coating, the ColoPulse coating, directly on powder bed printed (PBP) tablets. However, the high surface roughness necessitated an additional sub-coating layer [Nguyen, K. T. T., Pharmaceutics 2022]. In this study, we aimed to find a production method for PBP tablets containing BIAP that allows the direct application of coating systems. Alterations of the printing parameters, binder content, and printing layer height, when combined, were demonstrated to create visually less rough PBP tablets. The addition of ethanol vapor treatment further improved the surface's smoothness significantly. These changes enabled the direct application of the ColoPulse, or enteric coating, without a sub-coating. In vitro release testing showed the desired ileo-colonic release or upper-intestinal release for ColoPulse or enteric-coated tablets, respectively. Tablets containing BIAP, encapsulated within an inulin glass, maintained a high enzymatic activity (over 95%) even after 2 months of storage at 2-8 °C. Importantly, the coating process did not affect the activity of BIAP. In this study, we demonstrate, for the first time, the successful production of PBP tablets with surfaces that are directly coatable with the ColoPulse coating while preserving the stability of the encapsulated biopharmaceutical, BIAP.

Microbiota-sensitive drug delivery systems based on natural polysaccharides for colon targeting

Colon targeting is an ongoing challenge, particularly for the oral administration of biological drugs or local treatment of inflammatory bowel disease (IBD). In both cases, drugs are known to be sensitive to the harsh conditions of the upper gastrointestinal tract (GIT) and, thus, must be protected. Here, we provide an overview of recently developed colonic site-specific drug delivery systems based on microbiota sensitivity of natural polysaccharides. Polysaccharides act as a substrate for enzymes secreted by the microbiota located in the distal part of GIT. The dosage form is adapted to the pathophysiology of the patient and, thus, a combination of bacteria-sensitive and time-controlled release or pH-dependent systems can be used for delivery.

Capsules with Ileocolonic-Targeted Release of Vitamin B2, B3, and C (ColoVit) Intended for Optimization of Gut Health: Development and Validation of the Production Process

The ileocolonic-targeted delivery of vitamins can establish beneficial alterations in gut microbial composition. Here, we describe the development of capsules containing riboflavin, nicotinic acid, and ascorbic acid covered with a pH-sensitive coating (ColoVit) to establish site-specific release in the ileocolon. Ingredient properties (particle size distribution, morphology) relevant for formulation and product quality were determined. Capsule content and the in vitro release behaviour were determined using a HPLC-method. Uncoated and coated validation batches were produced. Release characteristics were evaluated using a gastro-intestinal simulation system. All capsules met the required specifications. The contents of the ingredients were in the 90.0-120.0% range, and uniformity requirements were met. In the dissolution test a lag-time in drug release of 277-283 min was found, which meets requirements for ileocolonic release. The release itself is immediate as shown by dissolution of the vitamins of more than 75% in 1 h. The production process of the ColoVit formulation was validated and reproducible, it was shown that the vitamin blend was stable during the production process and in the finished coated product. The ColoVit is intended as an innovative treatment approach for beneficial microbiome modulation and optimization of gut health.

Formulation of a 3D Printed Biopharmaceutical: The Development of an Alkaline Phosphatase Containing Tablet with Ileo-Colonic Release Profile to Treat Ulcerative Colitis

Powder bed printing is a 3D-printing process that creates freeform geometries from powders, with increasing traction for personalized medicine potential. Little is known about its applications for biopharmaceuticals. In this study, the production of tablets containing alkaline phosphatase using powder bed printing for the potential treatment of ulcerative colitis (UC) was investigated, as was the coating of these tablets to obtain ileo-colonic targeting. The printing process was studied, revealing line spacing as a critical factor affecting tablet physical properties when using hydroxypropyl cellulose as the binder. Increasing line spacing yielded tablets with higher porosity. The enzymatic activity of alkaline phosphatase (formulated in inulin glass) remained over 95% after 2 weeks of storage at 45 °C. The subsequent application of a colonic targeting coating required a PEG 1500 sub-coating. In vitro release experiments, using a gastrointestinal simulated system, indicated that the desired ileo-colonic release was achieved. Less than 8% of the methylene blue, a release marker, was released in the terminal ileum phase, followed by a fast release in the colon phase. No significant impact from the coating process on the enzymatic activity was found. These tablets are the first to achieve both biopharmaceutical incorporation in powder bed printed tablets and ileo-colonic targeting, thus might be suitable for on-demand patient-centric treatment of UC.

Clinical translation of advanced colonic drug delivery technologies

Targeted drug delivery to the colon offers a myriad of benefits, including treatment of local diseases, direct access to unique therapeutic targets and the potential for increasing systemic drug bioavailability and efficacy. Although a range of traditional colonic delivery technologies are available, these systems exhibit inconsistent drug release due to physiological variability between and within individuals, which may be further exacerbated by underlying disease states. In recent years, significant translational and commercial advances have been made with the introduction of new technologies that incorporate independent multi-stimuli release mechanisms (pH and/or microbiota-dependent release). Harnessing these advanced technologies offers new possibilities for drug delivery via the colon, including the delivery of biopharmaceuticals, vaccines, nutrients, and microbiome therapeutics for the treatment of both local and systemic diseases. This review details the latest advances in colonic drug delivery, with an emphasis on emerging therapeutic opportunities and clinical technology translation.

Effects of colon-targeted vitamins on the composition and metabolic activity of the human gut microbiome- a pilot study

An increasing body of evidence has shown that gut microbiota imbalances are linked to diseases. Currently, the possibility of regulating gut microbiota to reverse these perturbations by developing novel therapeutic and preventive strategies is being extensively investigated. The modulatory effect of vitamins on the gut microbiome and related host health benefits remain largely unclear. We investigated the effects of colon-delivered vitamins A, B2, C, D, and E on the gut microbiota using a human clinical study and batch fermentation experiments, in combination with cell models for the assessment of barrier and immune functions. Vitamins C, B2, and D may modulate the human gut microbiome in terms of metabolic activity and bacterial composition. The most distinct effect was that of vitamin C, which significantly increased microbial alpha diversity and fecal short-chain fatty acids compared to the placebo. The remaining vitamins tested showed similar effects on microbial diversity, composition, and/or metabolic activity in vitro, but in varying degrees. Here, we showed that vitamins may modulate the human gut microbiome. Follow-up studies investigating targeted delivery of vitamins to the colon may help clarify the clinical significance of this novel concept for treating and preventing dysbiotic microbiota-related human diseases. Trial registration: ClinicalTrials.gov, NCT03668964. Registered 13 September 2018 - Retrospectively registered, https://clinicaltrials.gov/ct2/show/NCT03668964.

Formulation and In Vitro Evaluation of Pellets Containing Sulfasalazine and Caffeine to Verify Ileo-Colonic Drug Delivery

The ColoPulse coating is a pH-dependent coating that can be used to target drug release to the ileo-colonic region. ColoPulse coated tablets and capsules have demonstrated their targeting capabilities in vivo in more than 100 volunteers and patients. However, so far the ColoPulse coating has not been used for multi-particulate pellet formulations. The sulfasalazine-caffeine method can be used to confirm ileo-colonic drug delivery in vivo. Caffeine serves as a release marker in this method, while sulfasalazine serves as a marker for colonic arrival. In this study, extrusion-spheronization was used to produce microcrystalline cellulose based pellets containing both caffeine and sulfasalazine. Dissolution tests revealed that a superdisintegrant, i.e., croscarmellose sodium or sodium starch glycolate, should be incorporated in the formulation to achieve acceptable release profiles for both sulfasalazine and caffeine. However, acceptable release profiles were only obtained when the pelletizing liquid consisted of ethanol/water 1/1 (v/v) but not with pure water. This phenomenon was ascribed to the differences in the degree of swelling of the superdisintegrant in the pelletizing liquid during the granulation process. The pellets were coated with the ColoPulse coating and showed the desired pH-dependent pulsatile release profile in vitro. In future clinical studies, ileo-colonic targeting should be verified.

Dynamics of the enterohepatic circulation of bile acids in healthy humans

Regulation of bile acid metabolism is normally discussed as the regulation of bile acid synthesis, which serves to compensate for intestinal loss in order to maintain a constant pool size. After a meal, bile acids start cycling in the enterohepatic circulation. Farnesoid X receptor-dependent ileal and hepatic processes lead to negative feedback inhibition of bile acid synthesis. When the intestinal bile acid flux decreases, the inhibition of synthesis is released. The degree of inhibition of synthesis and the mechanism and degree of activation are still unknown. Moreover, in humans, a biphasic diurnal expression pattern of bile acid synthesis has been documented, indicating maximal synthesis around 3 PM and 9 PM. Quantitative data on the hourly synthesis schedule as compensation for intestinal loss are lacking. In this review, we describe the classical view on bile acid metabolism and present alternative concepts that are based on the overlooked feature that bile acids transit through the enterohepatic circulation very rapidly. A daily profile of the cycling and total bile acid pool sizes and potential controlled and uncontrolled mechanisms for synthesis are predicted. It remains to be elucidated by which mechanism clock genes interact with the Farnesoid X receptor-controlled regulation of bile acid synthesis. This mechanism could become an attractive target to enhance bile acid synthesis at night, when cholesterol synthesis is high, thus lowering serum LDL-cholesterol.

Current Film Coating Designs for Colon-Targeted Oral Delivery

Colon-targeted oral delivery has recently attracted a substantial number of studies on both systemic and local treatments. Among approaches for colonic delivery, film coatings have been demonstrated as effective elements of the drug delivery systems because they can integrate multiple release strategies, such as pH-controlled release, time-controlled release and enzyme-triggered release. Moreover, coating layer modulations, natural film materials and nanoparticle coatings have been vigorously investigated with promising applications. This review aims to describe the primary approaches for improving drug delivery to the colon in the last decade. The outstanding importance of current developments in film coatings will advance dosage form designs and lead to the development of efficient colon-targeted oral delivery systems.

Ileo-Colon Targeting of the Poorly Water-Soluble Drug Celecoxib Using a pH-Dependent Coating in Combination with Self-Emulsifying Drug Delivery or Solid Dispersion Systems

Targeting celecoxib to the ileo-colonic region could be beneficial for the treatment and prevention of colon cancer. Ileo-colonic targeting can be achieved by using pH-dependent coating systems such as ColoPulse. Celecoxib has poor aqueous solubility, which may jeopardize optimal treatment. Therefore, we combined a pH-dependent coating with self-emulsifying drug delivery systems (SEDDS) or with solid dispersion systems (SD); two approaches that are often used to improve the dissolution behavior of lipophilic drugs. The dissolution behavior of various formulations of both systems was investigated. Optimized formulations with and without precipitation inhibitors were coated with the ColoPulse and the release of celecoxib was tested under non-sink conditions using an in vitro dissolution system, simulating the pH gradient of the gastrointestinal tract. The dissolution behavior of SDs with and without precipitation inhibitor (sodium dodecyl sulfate) and the SEDDS without precipitation inhibitor was negatively impacted by the coating. Control experiments indicated that components of the coating released in the dissolution medium acted as precipitation mediators. However, the SEDDS formulation with HPMC 4000 cps as a precipitation inhibitor showed excellent dissolution behavior. We hypothesize that HPMC accumulates at the oil/water interface of the emulsion thereby stabilizing the emulsion resulting in maintenance of the supersaturated state.

A Comprehensive Review on Pharmaceutical Film Coating: Past, Present, and Future

Pharmaceutical film coating is considered a key part in the production of solid pharmaceutical dosage forms since it gives superior organoleptic properties products. In addition, it can improve the physical and chemical stability of dosage forms, and modify the release characteristics of the drug. Several troubleshooting problems such as twinning mottling, chipping, etc., may arise during or after or even during the shelf life of the film coated dosage forms. These troubleshooting problems may be due to tablet core faults, coating formulation faults and/or coating process faults. These problems must be overcome to avoid unnecessary product problems. Film coating as well as other parts of the pharmaceutical technology is subjecting to continuous innovation. The innovation may be at different levels including pharmaceutical excipients, processes, software, guidelines and equipment. In fact, of particular note is the growing interest in process analytical technology, quality by design, continuous coating processing and the inclusion of new ready for use coating formulations. In this review, we tried to explore and discuss the status of pharmaceutical film coating, the challenges that face this manufacturing process and the latest technological advances in this important manufacturing process.

A sodium alginate-based sustained-release IPN hydrogel and its applications

Interpenetrating polymer network (IPN) hydrogels are crosslinked by two or more polymer networks, providing free volume space in the three-dimensional network structure, and providing conditions for the sustained and controlled release of drugs. The IPN hydrogels based on the natural polymer sodium alginate can form a stable porous network structure. Due to its excellent biocompatibility, the loaded drug can be sustained to the maximum extent without affecting its pharmacological effect. Sodium alginate-based IPN hydrogels have broad application prospects in the field of sustained and controlled drug release. This paper begins with an overview of the formation of alginate-based IPN hydrogels; summarizes the types of alginate-based IPN hydrogels; and discusses the pharmaceutical applications of alginate-based IPN hydrogels. We aim to give an overview of the research on IPN hydrogels based on sodium alginate in sustained and controlled drug release systems.

pH-dependent ileocolonic drug delivery, part I: in vitro and clinical evaluation of novel systems

After the pH dependency of novel pH-dependent ileocolonic drug delivery systems is confirmed in vitro, their performance should be evaluated in human volunteers.

OPTICORE™, an innovative and accurate colonic targeting technology

Inflammatory bowel disease (IBD) is a debilitating condition, estimated to affect 7 million people worldwide. Current IBD treatment strategies are substandard, relying on colonic targeting using the pH gradient along the gastrointestinal tract. Here, we describe an innovative colonic targeting concept, OPTICORE™ coating technology. OPTICORE™ combines two release triggers (pH and enzyme: Phloral™) in the outer layer, with an inner layer promoting a release acceleration mechanism (Duocoat™). The technology comprises an inner layer of partially neutralized enteric polymer with a buffer agent and an outer layer of a mixture of Eudragit® S and resistant starch. 5-aminosalicylic acid (5-ASA) tablets were coated with different inner layers, where the type of polymer, buffer salt concentration and pH of neutralization, were investigated for drug release acceleration. Buffer capacity of polymethacrylate neutralized polymer significantly contributes to the buffer capacity of the inner layer formulation, while buffer salt concentration is a major contributor to dispersion buffer capacity in the case of hypromellose enteric polymer formulations. An interplay between buffer capacity, pH and ionic strength contributes to an accelerated drug release. Resistant starch does not impact the enteric properties but allows for drug release mediated by colonic bacterial enzymes, ensuring complete drug release. Therefore, OPTICORE™ technology is designed to offer significant advantages over standard enteric coatings, particularly allowing for more accurate colonic drug delivery in ulcerative colitis patients.

A heat-stable microparticle platform for oral micronutrient delivery

Micronutrient deficiencies affect up to 2 billion people and are the leading cause of cognitive and physical disorders in the developing world. Food fortification is effective in treating micronutrient deficiencies; however, its global implementation has been limited by technical challenges in maintaining micronutrient stability during cooking and storage. We hypothesized that polymer-based encapsulation could address this and facilitate micronutrient absorption. We identified poly(butylmethacrylate-co-(2-dimethylaminoethyl)methacrylate-co-methylmethacrylate) (1:2:1) (BMC) as a material with proven safety, offering stability in boiling water, rapid dissolution in gastric acid, and the ability to encapsulate distinct micronutrients. We encapsulated 11 micronutrients (iron; iodine; zinc; and vitamins A, B2, niacin, biotin, folic acid, B12, C, and D) and co-encapsulated up to 4 micronutrients. Encapsulation improved micronutrient stability against heat, light, moisture, and oxidation. Rodent studies confirmed rapid micronutrient release in the stomach and intestinal absorption. Bioavailability of iron from microparticles, compared to free iron, was lower in an initial human study. An organotypic human intestinal model revealed that increased iron loading and decreased polymer content would improve absorption. Using process development approaches capable of kilogram-scale synthesis, we increased iron loading more than 30-fold. Scaled batches tested in a follow-up human study exhibited up to 89% relative iron bioavailability compared to free iron. Collectively, these studies describe a broad approach for clinical translation of a heat-stable ingestible micronutrient delivery platform with the potential to improve micronutrient deficiency in the developing world. These approaches could potentially be applied toward clinical translation of other materials, such as natural polymers, for encapsulation and oral delivery of micronutrients.

A review on 5-aminosalicylic acid colon-targeted oral drug delivery systems

Site-specific colon drug delivery is a practical approach for the treatment of local diseases of the colon with several advantages such as rapid onset of action and reduction of the dosage of the drug as well as minimization of harmful side effects. 5-aminosalicylic acid (5-ASA) is a drug of choice in the treatment of inflammatory bowel disease and colitis. For the efficient delivery of this drug, it is vital to prevent 5-ASA release in the upper part of the gastrointestinal tract and to promote its release in the proximal colon. Different approaches including chemical manipulation of drug molecule for production of prodrugs or modification of drug delivery systems using pH-dependent, time-dependent and/or bacterially biodegradable materials have been tried to optimize 5-ASA delivery to the colon. In the current review, the different strategies utilized in the design and development of an oral colonic delivery dosage form of 5-ASA are presented and discussed.

A Novel Ileocolonic Release Peppermint Oil Capsule for Treatment of Irritable Bowel Syndrome: A Phase I Study in Healthy Volunteers

INTRODUCTION

Peppermint oil (PO) has been shown to reduce abdominal pain in patients with irritable bowel syndrome (IBS). PO is assumed to induce intestinal smooth muscle relaxation and desensitization of nociceptive nerve afferents. To increase colonic PO concentration, an ileocolonic release peppermint oil (IC-PO) capsule has been developed. The aim of this study was to compare pharmacokinetic parameters of the currently available small intestinal release PO (SI-PO) and the novel IC-PO.

METHODS

In this randomized, double-blind, crossover study, subjects received 182 mg of either SI-PO or IC-PO in a crossover design with a washout period of more than 14 days. Blood samples were collected to determine menthol glucuronide concentrations.

RESULTS

Eight healthy volunteers (50% female, median age 22) were included. The time to reach the maximum concentration (T_max) of IC-PO was significantly longer compared to SI-PO with a median (IQR) of 360 (360-405) versus 180 (120-180) min. The lag time (T_lag) was significantly longer with a median (IQR) of 225 (204-284) for IC-PO compared to 37 (6-65) min for SI-PO. The areas under the menthol glucuronide plasma concentration-time curves were significantly smaller with a median (IQR) of 2331 μg h/L (2006-2510) for IC-PO compared to 2623 μg h/L (2471-2920) for SI-PO. No significant differences were found in peak concentrations and elimination half-lives.

CONCLUSION

IC-PO has a significantly delayed peak menthol glucuronide concentration and T_lag, both pointing to the release of PO in the more distal part of the intestine. This may enhance therapeutic efficacy as it results in increased exposure of colonic mucosal afferents to the PO. A randomized controlled trial investigating the efficacy of SI and IC-PO in IBS is currently ongoing.

TRIAL REGISTRATION

ClinicalTrials.gov identifier, NCT02291445, EudraCT database 2014-004195-32.

Local delivery of macromolecules to treat diseases associated with the colon

Current treatments for intestinal diseases including inflammatory bowel diseases, irritable bowel syndrome, and colonic bacterial infections are typically small molecule oral dosage forms designed for systemic delivery. The intestinal permeability hurdle to achieve systemic delivery from oral formulations of macromolecules is challenging, but this drawback can be advantageous if an intestinal region is associated with the disease. There are some promising formulation approaches to release peptides, proteins, antibodies, antisense oligonucleotides, RNA, and probiotics in the colon to enable local delivery and efficacy. We briefly review colonic physiology in relation to the main colon-associated diseases (inflammatory bowel disease, irritable bowel syndrome, infection, and colorectal cancer), along with the impact of colon physiology on dosage form design of macromolecules. We then assess formulation strategies designed to achieve colonic delivery of small molecules and concluded that they can also be applied some extent to macromolecules. We describe examples of formulation strategies in preclinical research aimed at colonic delivery of macromolecules to achieve high local concentration in the lumen, epithelial-, or sub-epithelial tissue, depending on the target, but with the benefit of reduced systemic exposure and toxicity. Finally, the industrial challenges in developing macromolecule formulations for colon-associated diseases are presented, along with a framework for selecting appropriate delivery technologies.

Deuterium- and Tritium-Labelled Compounds: Applications in the Life Sciences

Hydrogen isotopes are unique tools for identifying and understanding biological and chemical processes. Hydrogen isotope labelling allows for the traceless and direct incorporation of an additional mass or radioactive tag into an organic molecule with almost no changes in its chemical structure, physical properties, or biological activity. Using deuterium-labelled isotopologues to study the unique mass-spectrometric patterns generated from mixtures of biologically relevant molecules drastically simplifies analysis. Such methods are now providing unprecedented levels of insight in a wide and continuously growing range of applications in the life sciences and beyond. Tritium (³ H), in particular, has seen an increase in utilization, especially in pharmaceutical drug discovery. The efforts and costs associated with the synthesis of labelled compounds are more than compensated for by the enhanced molecular sensitivity during analysis and the high reliability of the data obtained. In this Review, advances in the application of hydrogen isotopes in the life sciences are described.

A Three-Pulse Release Tablet for Amoxicillin: Preparation, Pharmacokinetic Study and Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Amoxicillin is a commonly used antibiotic which has a short half-life in human. The frequent administration of amoxicillin is often required to keep the plasma drug level in an effective range. The short dosing interval of amoxicillin could also cause some side effects and drug resistance, and impair its therapeutic efficacy and patients' compliance. Therefore, a three-pulse release tablet of amoxicillin is desired to generate sustained release in vivo, and thus to avoid the above mentioned disadvantages.

METHODS

The pulsatile release tablet consists of three pulsatile components: one immediate-release granule and two delayed release pellets, all containing amoxicillin. The preparation of a pulsatile release tablet of amoxicillin mainly includes wet granulation craft, extrusion/spheronization craft, pellet coating craft, mixing craft, tablet compression craft and film coating craft. Box-Behnken design, Scanning Electron Microscope and in vitro drug release test were used to help the optimization of formulations. A crossover pharmacokinetic study was performed to compare the pharmacokinetic profile of our in-house pulsatile tablet with that of commercial immediate release tablet. The pharmacokinetic profile of this pulse formulation was simulated by physiologically based pharmacokinetic (PBPK) model with the help of Simcyp®.

RESULTS AND DISCUSSION

Single factor experiments identify four important factors of the formulation, namely, coating weight of Eudragit L30 D-55 (X1), coating weight of AQOAT AS-HF (X2), the extrusion screen aperture (X3) and compression forces (X4). The interrelations of the four factors were uncovered by a Box-Behnken design to help to determine the optimal formulation. The immediate-release granule, two delayed release pellets, together with other excipients, namely, Avicel PH 102, colloidal silicon dioxide, polyplasdone and magnesium stearate were mixed, and compressed into tablets, which was subsequently coated with Opadry® film to produce pulsatile tablet of amoxicillin. In vitro release study firstly indicated a three-pulse release profile of the tablet. Later the pulse tablet was found to generate the sustained release of amoxicillin in beagle dogs. Furthermore, the Simcyp® software was used to simulate the in vivo concentration time curve model of the three-pulse release tablet for amoxicillin in both human and beagle dog. The prediction by PBPK model nicely fitted the observation in human and beagle dog.

CONCLUSIONS

This study has demonstrated the interrelation of factors affecting the pulsatile formulation of amoxicillin using a Box-Behnken design. The three-pulse release tablets of amoxicillin were proven to generate pulsatile release in vitro and sustained release in vivo. This formulation was also found to extend the effective plasma concentration in human compared to the tablet of immediate release based on the simulation data by PBPK modeling. This study provides an example of using PBPK to guide the development of pulsatile dosage forms.

Development of a zero-order sustained-release tablet containing mesalazine and budesonide intended to treat the distal gastrointestinal tract in inflammatory bowel disease

Ulcerative colitis (UC) and Crohn's disease (CD) are diseases affecting the gastrointestinal tract. Treatment depends on the severity of the disease, site of inflammation, and patient's response. The aim of this study was to develop a zero-order sustained-release tablet containing both the anti-inflammatory drugs mesalazine and budesonide as a new treatment option for ileo-colonic CD and UC. Tablets were attained by wet granulation with hydroxypropyl methylcellulose and direct compression. Our newly developed tablet core was coated with different ColoPulse® coating thicknesses and the mesalazine and budesonide release profiles were investigated in a 600-min gastrointestinal simulation system (GISS) experiment, together with commercially available MMX®-mesalazine and MMX®-budesonide. Lag-time, release rate (k0), completeness of release, and zero-order correlation coefficient (R(2)0) could be manipulated by varying ColoPulse® coating thickness. Our newly developed combination preparation (C[4.92]) complied with all conducted European Pharmacopoeia tests as well as an accelerated 6-month stability test and had a lag-time of 250min (simulated ileum targeted), a linear release profile (mesalazine R(2)0=0.9002; budesonide R(2)0=0.9481), and drug release of 100% mesalazine and 77% budesonide. Like C[4.92], MMX®-mesalazine had a linear (R(2)0=0.9883) and complete release profile (96%). However, C[4.92] lag-time was longer (250 vs. 210min), assuring simulated ileum specificity. Remarkably, MMX®-budesonide lag-time was 480min and release was only 7% with a linear character (R(2)0=0.9906). The in vitro results suggest that MMX®-budesonide effectiveness may be improved if budesonide release in the aqueous phase would be increased and that C[4.92] is a potential, new treatment option for ileo-colonic CD and UC.

Design of experiment approach for formulating multi-unit colon-targeted drug delivery system: in vitro and in vivo studies

OBJECTIVE

The objective of the present investigation was to develop systematically optimized multiunit formulation for colon targeted delivery of metronidazole (MTZ) by employing design of experiment (DoE) and evaluate it for in vitro as well as in vivo drug release study.

METHODS

Core of mini-tablets of MTZ was prepared using drug along with suitable swelling agents to provide pH sensitive pulsatile drug delivery. Eudragit® S 100 (ES) and ethyl cellulose (EC) were used as coating polymers to prevent initial drug release in gastric region. The coating composition was systematically optimized using 3(2)-full factorial design and optimized formulation was evaluated in vitro and then in vivo, to confirm colon targeting ability of the developed system. Stability study of optimized formulation was performed for 6 months as per ICH guidelines.

RESULTS

The optimized coating composition was selected from the results of design batches. The optimized formulation showed 6.99 ± 1.5% drug release up to 5 h and 100% drug release within 7.2 ± 0.2 h indicating pH sensitive pulsatile behavior of formulation. Similar drug release profile was observed while performing in vivo study in rabbits with a lag time of 4 h and Cmax of 190 ± 4.9 ng/ml being achieved after 7 h. Stability study indicated insignificant difference in properties of tablets and their drug release patterns.

CONCLUSION

Optimization of coating composition (EC and ES) and thickness could offer pH sensitive pulsatile release of drugs at colon. Furthermore, in vivo results confirmed the successful development of colon targeted formulation of MTZ.

Patented pulsatile drug delivery technologies for chronotherapy

INTRODUCTION

Oral-controlled and modified-release drug delivery systems with zero-order sustained-release kinetics have been developed and proven suitable for meeting increasingly sophisticated therapeutic needs. Nevertheless, the impact of basic chronobiology concepts on the practice of medicine is still ongoing and to address chronotherapy needs, various types of pulsatile drug delivery systems have been innovated. The purpose of this review is to highlight these innovations in the field of chronotherapy.

AREAS COVERED

The present review discusses in depth on recent patents and developments related to pulsatile drug delivery systems with eroding, soluble or rupturable barrier coatings, and systems with capsular structures. Besides focusing on all recent innovations, the review addresses the novelty and feasibility of all upcoming technologies being exploited considering pulsatile drug delivery systems.

EXPERT OPINION

There has been a growing interest in pulsatile delivery, which generally refers to the liberation of drugs following a programmable and well-defined lag phase from the time of administration. From 1981 until the present date, patent publications related to pulsatile drug delivery have shown more promising systems with numerous developments in arena of drug delivery. Future development of chronotherapeutic medications requires proper assessment and integration with other emerging disciplines such as hydrogel and transdermal delivery systems. The selection of the appropriate chronopharmaceutical technology should take into considerations with the ease of manufacturing and the cost-effectiveness.

A novel multilayered multidisk oral tablet for chronotherapeutic drug delivery

A Multilayered Multidisk Tablet (MLMDT) comprising two drug-loaded disks enveloped by three drug-free barrier layers was developed for use in chronotherapeutic disorders, employing two model drugs, theophylline and diltiazem HCl. The MLMDT was designed to achieve two pulses of drug release separated by a lag phase. The polymer disk comprised hydroxyethylcellulose (HEC) and ethylcellulose (EC) granulated using an aqueous dispersion of EC. The polymeric barrier layers constituted a combination of pectin/Avicel (PBL) (1st barrier layer) and hydroxypropylmethylcellulose (HPMC) (HBL1 and HBL2) as the 2nd and 3rd barrier layers, respectively. Sodium bicarbonate was incorporated into the diltiazem-containing formulation for delayed drug release. Erosion and swelling studies confirmed the manner in which the drug was released with theophylline formulations exhibiting a maximum swelling of 97% and diltiazem containing formulations with a maximum swelling of 119%. FTIR spectra displayed no interactions between drugs and polymers. Molecular mechanics simulations were undertaken to predict the possible orientation of the polymer morphologies most likely affecting the MLMDT performance. The MLMDT provided two pulses of drug release, separated by a lag phase, and additionally it displayed desirable friability, hardness, and uniformity of mass indicating a stable formulation that may be a desirable candidate for chronotherapeutic drug delivery.

Isotope-labelled urea to test colon drug delivery devices in vivo: principles, calculations and interpretations

This paper describes various methodological aspects that were encountered during the development of a system to monitor the in vivo behaviour of a newly developed colon delivery device that enables oral drug treatment of inflammatory bowel diseases. [(13)C]urea was chosen as the marker substance. Release of [(13)C]urea in the ileocolonic region is proven by the exhalation of (13)CO2 in breath due to bacterial fermentation of [(13)C]urea. The (13)CO2 exhalation kinetics allows the calculation of a lag time as marker for delay of release, a pulse time as marker for the speed of drug release and the fraction of the dose that is fermented. To determine the total bioavailability, also the fraction of the dose absorbed from the intestine must be quantified. Initially, this was done by calculating the time-dependent [(13)C]urea appearance in the body urea pool via measurement of (13)C abundance and concentration of plasma urea. Thereafter, a new methodology was successfully developed to obtain the bioavailability data by measurement of the urinary excretion rate of [(13)C]urea. These techniques required two experimental days, one to test the coated device, another to test the uncoated device to obtain reference values for the situation that 100 % of [(13)C]urea is absorbed. This is hampered by large day-to-day variations in urea metabolism. Finally, a completely non-invasive, one-day test was worked out based on a dual isotope approach applying a simultaneous administration of [(13)C]urea in a coated device and [(15)N2]urea in an uncoated device. All aspects of isotope-related analytical methodologies and required calculation and correction systems are described.

Characterization of soy polysaccharide and its in vitro and in vivo evaluation for application in colon drug delivery

The objective of the present investigation was to establish potential of commercially available soy polysaccharide (Emcosoy®) for colon drug delivery. The soy polysaccharide-ethyl cellulose films were fabricated and characterized. The effect of the pectinase enzyme on the tensile strength and surface morphology of the film was evaluated. The permeation of chlorpheniramine maleate (CPM), a model hydrophilic drug from pectinase enzyme treated and untreated films was measured in pH 7.4 buffer. The soy polysaccharide-ethyl cellulose films were also incubated with Lactobacillus sp. culture for a specific duration, and effect on the CPM permeation was evaluated. The CPM capsules were coated with the soy polysaccharide-ethyl cellulose mixture, and Eudragit S100 was applied as a secondary coat. The coated CPM capsules were radiolabelled, and their in vivo transit was evaluated in human volunteers on oral administration. The pectinase enzyme had a significant influence on the tensile strength and surface morphology of the soy polysaccharide-ethyl cellulose films. The permeability of pectinase enzyme-treated and Lactobacillus sp.-treated films was significantly higher than that of untreated films. The CPM capsules were coated with the soy polysaccharide-ethyl cellulose mixture and Eudragit S100 and were successfully radiolabelled by a simple method. Gamma scintigraphic studies in human volunteers showed that the radiolabelled capsules maintained integrity for at least 9 h after oral administration. Thus, the soy polysaccharide has a potential in colon drug delivery.

Large intestine-targeted, nanoparticle-releasing oral vaccine to control genitorectal viral infection

Both rectal and vaginal mucosal surfaces serve as transmission routes for pathogenic microorganisms. Vaccination through large intestinal mucosa, previously proven protective for both of these mucosal sites in animal studies, can be achieved successfully by direct intracolorectal (i.c.r.) administration, but this route is clinically impractical. Oral vaccine delivery seems preferable but runs the risk of the vaccine's destruction in the upper gastrointestinal tract. Therefore, we designed a large intestine-targeted oral delivery with pH-dependent microparticles containing vaccine nanoparticles, which induced colorectal immunity in mice comparably to colorectal vaccination and protected against rectal and vaginal viral challenge. Conversely, vaccine targeted to the small intestine induced only small intestinal immunity and provided no rectal or vaginal protection, demonstrating functional compartmentalization within the gut mucosal immune system. Therefore, using this oral vaccine delivery system to target the large intestine, but not the small intestine, may represent a feasible new strategy for immune protection of rectal and vaginal mucosa.

Polymeric coatings for a multiple-unit pulsatile delivery system: preliminary study on free and applied films

In order to adapt a previously described swellable/erodible pulsatile delivery system to a multiple-unit configuration, insoluble films with adequate permeability and flexibility were proposed for application to its functional hydroxypropyl methylcellulose (HPMC) layer. By slowing down the penetration of water into the system, such films would be expected to improve the relevant effectiveness in delaying the onset of release without possibly impacting on the mechanism involved. Free films of Eudragit(®)NE containing differing amounts (10-20%) of a superdisintegrant, i.e. Explotab(®)V17, Ac-Di-Sol(®), Kollidon(®)CL or Kollidon(®)CL-M, were prepared by spraying technique and evaluated for hydration, permeability and tensile properties. The hydration and permeability characteristics were enhanced by the addition of the superdisintegrants, generally as a function of their concentration. Explotab(®)V17 was shown particularly useful to increase the film permeability. Moreover, it exerted a minor impact on the advantageous tensile properties of the acrylic polymer, especially in the wet state. Based on these results and on a preliminary release study performed with two-layer devices, the Eudragit(®)NE film with Explotab(®)V17 at the highest investigated percentage was identified as a potential formulation candidate for being applied to HPMC-coated cores thus allowing the onset of release to effectively be delayed by coatings of reduced thickness.

A non-invasive, low-cost study design to determine the release profile of colon drug delivery systems: a feasibility study

PURPOSE

Conventional bioavailability testing of dosage forms based on plasma concentration-time graphs of two products in a two-period, crossover-design, is not applicable to topical treatment of intestinal segments. We introduce an isotope dual-label approach ((13)C- and (15)N(2)-urea) for colon drug delivery systems that can be performed in a one-day, non-invasive study-design.

METHODS

Four healthy volunteers took an uncoated or a ColoPulse-capsule containing (13)C-urea and an uncoated capsule containing (15)N(2)-urea. In case of colon-release (13)C-urea is fermented and (13)C detected as breath (13)CO(2). Absorbed (13)C-urea and (15)N-urea are detected in urine.

RESULTS

C and (15)N in urine released from uncoated capsules showed a ratio of 1.01 ± 0.06. The (13)C/(15)N-recovery ratio after intake of a ColoPulse-capsule was constant and lower >12 h post-dose (median 0.22, range 0.13-0.48). The (13)C/(15)N-ratio in a single urine sample at t ≥ 12 h predicted the 24 h non-fermented fraction (13)C of <26 %. Breath (13)CO(2) indicated delayed (>3 h) release and a fermented fraction (13)C >54 %.

CONCLUSIONS

Breath and urine (13)C and (15)N data describe the release-profile and local bioavailability of a colon delivery device. This allows non-invasive bioavailability studies for evaluation of colon-specific drug delivery systems without radioactive exposure and with increased power and strongly reduced costs.

Applications of stable isotopes in clinical pharmacology

This review aims to present an overview of the application of stable isotope technology in clinical pharmacology. Three main categories of stable isotope technology can be distinguished in clinical pharmacology. Firstly, it is applied in the assessment of drug pharmacology to determine the pharmacokinetic profile or mode of action of a drug substance. Secondly, stable isotopes may be used for the assessment of drug products or drug delivery systems by determination of parameters such as the bioavailability or the release profile. Thirdly, patients may be assessed in relation to patient-specific drug treatment; this concept is often called personalized medicine. In this article, the application of stable isotope technology in the aforementioned three areas is reviewed, with emphasis on developments over the past 25 years. The applications are illustrated with examples from clinical studies in humans.

Needle-free influenza vaccination

Vaccination is the cornerstone of influenza control in epidemic and pandemic situations. Influenza vaccines are typically given by intramuscular injection. However, needle-free vaccinations could offer several distinct advantages over intramuscular injections: they are pain-free, easier to distribute, and easier to give to patients, and their use could reduce vaccination costs. Moreover, vaccine delivery via the respiratory tract, alimentary tract, or skin might elicit mucosal immune responses at the site of virus entry and better cellular immunity, thus improving effectiveness. Although various needle-free vaccination methods for influenza have shown preclinical promise, few have progressed to clinical trials-only live attenuated intranasal vaccines have received approval, and only in some countries. Further clinical investigation is needed to help realise the potential of needle-free vaccination for influenza.

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.