Feasibility, stability and release performance of a time-dependent insulin delivery system intended for oral colon release

Perspectives of colon-specific drug delivery in the management of morning symptoms of rheumatoid arthritis

Rheumatoid arthritis is a chronic condition that is characterized by joint pain and inflammation. It is an autoimmune disorder in which the body tissues are erroneously attacked by the immune system of the host itself. It has been evident that rheumatoid arthritis symptoms follow a 24 h circadian rhythm and exhibit high thresholds of pain, functional disability, and stiffness predominantly early in the morning. Colon-specific drug delivery systems can be utilized in the formulations to be used in the treatment of rheumatoid arthritis. The colon-specific drug delivery system has shown promising results in the treatment of different diseases at the colonic site like Crohn's disease, ulcerative colitis, colon cancer, etc. The colon-specific drug delivery is capable of delivering the formulation at the predetermined location and predetermined time. The early morning symptoms of rheumatoid arthritis like pain and inflammation can be treated using the various approaches of the colon-specific drug delivery system because it will lead to patient compliance as the patient will not require administering the formulation immediately after waking up in the morning. This review also explains the immunological factors which may trigger rheumatoid arthritis in human beings. It further explores conventional approaches like pH-dependant, microorganisms-driven, pressure-controlled, and time-dependant formulations. By employing two or more conventional approaches given above the various novel approaches have been designed to eliminate the drawbacks of individual techniques.

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.

Evaluation of powder-layering vs. spray-coating techniques in the manufacturing of a swellable/erodible pulsatile delivery system

A swellable/erodible system for oral time-dependent release, demonstrated to provide consistent pulsatile and colonic delivery performance, has been manufactured through a range of coating techniques to achieve the functional hydroxypropyl methylcellulose (HPMC) layer. Although aqueous spray-coating has long been preferred, the processing times and yields still represent open issues, especially in view of the considerable amount of polymer required to give in vivo lag phases of proper duration. To make manufacturing of the delivery system more cost-efficient, different coating modes were thus evaluated, namely top and tangential spray-coating as well as powder-layering, using a fluid bed equipment. To this aim, disintegrating tablets of 5 mm in diameter, containing a tracer drug, were coated up to 50% weight gain with low-viscosity HPMC, either as a water solution or as a powder formulation. In all cases, process feasibility was assessed following setup of the operating conditions. Irrespective of the technique employed, the resulting dosage forms exhibited uniform coating layers able to defer the onset of release as a function of the amount of polymer applied. The structure and thickness of such layers differed depending on the deposition modes. With respect to top spray-, both tangential spray-coating and powder-layering were shown to remarkably ameliorate the process time, which was reduced to approximately 1/3 and 1/6, and to enhance the yield by almost 20 and 30%, respectively. Clear advantages associated with such techniques were thus highlighted, particularly with respect to powder-layering here newly proposed for application of a swellable hydrophilic cellulose derivative.

Advances in orally targeted drug delivery to colon

Colon-specific drug delivery is critical for treating diseases of colon, such as colon cancer, amoebiasis, irritable bowel syndrome, and inflammatory bowel disease. This study reviews the effects of targeted oral drug delivery on patient by measuring the accurate administration of the drug to specific disease spot, thus enhancing the therapeutic efficacy and provides better therapeutic outcomes. Medically targeted delivery to colon produces local effect on the diseases and hinders the systemic toxic effects of drugs. The delivery of therapeutics to the specific diseased part of colon has its merits over systemic drug delivery, albeit has some obstacles and problems. Colon drug delivery can be used to create both systemic and local effects. Many advanced approaches are used, such as conventional methods for drug release to colon, delayed release dosage forms, nanoparticles, carbon nanotubes, dendrimers, and alginate coated microparticles. This concise review summarizes and elaborates the details of different techniques and strategies on targeted oral drug delivery to colon as well as studies the advantages, disadvantages, and limitations to improve the application of drug in the part of the affected colon.

A Novel Approach to Flurbiprofen Pulsatile Colonic Release: Formulation and Pharmacokinetics of Double-Compression-Coated Mini-Tablets

A significant plan is executed in the present study to study the effect of double-compression coating on flurbiprofen core mini-tablets to achieve the pulsatile colonic delivery to deliver the drug at a specific time as per the patho-physiological need of the disease that results in improved therapeutic efficacy. In this study, pulsatile double-compression-coated tablets were prepared based on time-controlled hydroxypropyl methylcellulose K100M inner compression coat and pH-sensitive Eudragit S100 outer compression coat. Then, the tablets were evaluated for both physical evaluation and drug-release studies, and to prove these results, in vivo pharmacokinetic studies in human volunteers were conducted. From the in vitro drug-release studies, F6 tablets were considered as the best formulation, which retarded the drug release in the stomach and small intestine (3.42 ± 0.12% in 5 h) and progressively released to the colon (99.78 ± 0.74% in 24 h). The release process followed zero-order release kinetics, and from the stability studies, similarity factor between dissolution data before and after storage was found to be 88.86. From the pharmacokinetic evaluation, core mini-tablets producing peak plasma concentration (C max) was 14,677.51 ± 12.16 ng/ml at 3 h T max and pulsatile colonic tablets showed C max = 12,374.67 ± 16.72 ng/ml at 12 h T max. The area under the curve for the mini and pulsatile tablets was 41,238.52 and 72,369.24 ng-h/ml, and the mean resident time was 3.43 and 10.61 h, respectively. In conclusion, development of double-compression-coated tablets is a promising way to achieve the pulsatile colonic release of flurbiprofen.

The in vivo fate of nanoparticles and nanoparticle-loaded microcapsules after oral administration in mice: Evaluation of their potential for colon-specific delivery

Anti-cancer drug loaded-nanoparticles (NPs) or encapsulation of NPs in colon-targeted delivery systems shows potential for increasing the local drug concentration in the colon leading to improved treatment of colorectal cancer. To investigate the potential of the NP-based strategies for colon-specific delivery, two formulations, free Eudragit® NPs and enteric-coated NP-loaded chitosan-hypromellose microcapsules (MCs) were fluorescently-labelled and their tissue distribution in mice after oral administration was monitored by multispectral small animal imaging. The free NPs showed a shorter transit time throughout the mouse digestive tract than the MCs, with extensive excretion of NPs in faeces at 5h. Conversely, the MCs showed complete NP release in the lower region of the mouse small intestine at 8h post-administration. Overall, the encapsulation of NPs in MCs resulted in a higher colonic NP intensity from 8h to 24h post-administration compared to the free NPs, due to a NP 'guarding' effect of MCs during their transit along mouse gastrointestinal tract which decreased NP excretion in faeces. These imaging data revealed that this widely-utilised colon-targeting MC formulation lacked site-precision for releasing its NP load in the colon, but the increased residence time of the NPs in the lower gastrointestinal tract suggests that it is still useful for localised release of chemotherapeutics, compared to NP administration alone. In addition, both formulations resided in the stomach of mice at considerable concentrations over 24h. Thus, adhesion of NP- or MC-based oral delivery systems to gastric mucosa may be problematic for colon-specific delivery of the cargo to the colon and should be carefully investigated for a full evaluation of particulate delivery systems.

A review of biodegradable polymeric systems for oral insulin delivery

Currently, repeated routine subcutaneous injections of insulin are the standard treatment for insulin-dependent diabetic patients. However, patients' poor compliance for injections often fails to achieve the stable concentration of blood glucose. As a protein drug, the oral bioavailability of insulin is low due to many physiological reasons. Several carriers, such as macromolecules and liposomes have been used to deliver drugs in vivo. In this review article, the gastrointestinal barriers of oral insulin administration are described. Strategies for increasing the bioavailability of oral insulin, such absorption enhancers, enzyme inhibitors, enteric coatings are also introduced. The potential absorption mechanisms of insulin-loaded nanoparticles across the intestinal epithelium, including intestinal lymphatic route, transcellular route and paracellular route are discussed in this review. Natural polymers, such as chitosan and its derivates, alginate derivatives, γ-PGA-based materials and starch-based nanoparticles have been exploited for oral insulin delivery; synthetic polymers, such as PLGA, PLA, PCL and PEA have also been developed for oral administration of insulin. This review focuses on recent advances in using biodegradable natural and synthetic polymers for oral insulin delivery along with their future prospects.

pH-sensitive poly(lactide-co-glycolide) nanoparticle composite microcapsules for oral delivery of insulin

This study proposes a new concept of pH-sensitive poly(lactide-co-glycolide) (PLGA) nanoparticle composite microcapsules for oral delivery of insulin. Firstly, insulin–sodium oleate complex was prepared by the hydrophobic ion pairing method and then encapsulated into PLGA nanoparticles by the emulsion solvent diffusion method. In order to reduce the burst release of insulin from PLGA nanoparticles and deliver insulin to specific gastrointestinal regions, hence to enhance bioavailability of insulin, the PLGA nanoparticles were further encapsulated into Eudragit^® FS 30D to prepare PLGA nanoparticle composite microcapsules by organic spray-drying method. The preparation was evaluated in vitro and in vivo, and the absorption mechanism was discussed. The in vitro drug release studies revealed that the drug release was pH dependent, and the in vivo results demonstrated that the formulation of PLGA nanoparticle composite microcapsules was an effective candidate for oral insulin delivery.

Film coatings for oral pulsatile release

Pulsatile delivery is generally intended as a release of the active ingredient that is delayed for a programmable period of time to meet particular chronotherapeutic needs and, in the case of oral administration, also target distal intestinal regions, such as the colon. Most oral pulsatile delivery platforms consist in coated formulations wherein the applied polymer serves as the release-controlling agent. When exposed to aqueous media, the coating initially performs as a protective barrier and, subsequently, undergoes a timely failure based on diverse mechanisms depending on its physico-chemical and formulation characteristics. Indeed, it may be ruptured because of the gradual expansion of the core, swell and/or erode due to the glassy-rubbery polymer transition or become permeable thus allowing the drug molecules to diffuse outwards. Otherwise, when the coating is a semipermeable membrane provided with one or more orifices, the drug is released through the latter as a result of an osmotic water influx. The vast majority of pulsatile delivery systems described so far have been prepared by spray-coating, which offers important versatility and feasibility advantages over other techniques such as press- and dip-coating. In the present article, the design, manufacturing and performance of spray-coated pulsatile delivery platforms is thus reviewed.

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.

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.

A novel injection-molded capsular device for oral pulsatile delivery based on swellable/erodible polymers

The feasibility of injection molding was explored in the preparation of a novel capsular device for oral pulsatile/delayed delivery based on swellable/erodible polymers. For this purpose, a mold intended to be coupled with a bench-top injection-molding press was designed. This was expected to enable the preparation of matching capsule cap and body items within a single manufacturing cycle and the selection of differing shell thicknesses (300, 600, and 900 μm). Hydroxypropylcellulose (Klucel(®) EF, LF, and GF) was employed as the release-controlling polymer in admixture with polyethylene glycol 1500 (10%, w/w) as the plasticizer. After preliminary trials aimed at the setup of operating conditions, Klucel(®) EF and LF capsule shells with satisfactory technological properties were manufactured. The performance of capsular devices filled with a tracer drug powder was studied by means of a modified USP31 disintegration apparatus. Typical in vitro delayed release patterns were thereby obtained, with lag time increasing as a function of the wall thickness. A good correlation was found between the latter parameter and t (10%), i.e., the time to 10% release, for both polymer grades employed. On the basis of the overall results, the investigated technique was proven suitable for the manufacturing of an innovative pulsatile release platform.