Effect of Simulated Gastrointestinal Conditions on Drug Release from Pectin/Ethylcellulose as Film Coating for Drug Delivery to the Colon

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.

Optimization study of combined enteric and time-dependent polymethacrylates as a coating for colon targeted delivery of 5-ASA pellets in rats with ulcerative colitis

Formulation design for colon-specific delivery of 5-aminosalicylic acid (5-ASA) could bring some therapeutic benefits in the treatment of ulcerative colitis (UC). In the current study, a 3² full factorial design was used to predict optimum coating composed of two enteric (poly methacrylic acid, methyl methacrylates 1:2 and 1:1) and time-dependent (poly ethyl acrylate, methyl methacrylate, trimethylammonio ethyl methacrylate chloride 1:2:0.1) polymethacrylates for colon-specific delivery of 5-ASA pellets. A unique coating composition and coating level predicted by the model was applied onto either inulin-free 5-ASA pellets or inulin-bearing 5-ASA pellets and the coated pellets were examined by dissolution test in-vitro. The coated pellets were also tested in a rat model of UC and compared with the a commercially available colonic delivery system of 5-ASA. The ratio of the two enteric polymethacrylates and time-dependet polymethacrylate of 16:64:20 w/w at a coating level of 15% was discovered as the optimum coating for delivery of 5-ASA pellets to the colon. In general, the coated pellets offered a better therapeutic outcome compared to commercially available colonic delivery system of 5-ASA and uncoated pellets in terms of colitis activity index and the colon's tissue enzymes of MDA and GSH. It seems that the coating composed of enteric and pH-dependent polymethacrylates could tune up the rate of drug release from 5-ASA-coated pellets and trigger drug release based on pH and time.

Budding Multi-matrix Technology-a Retrospective Approach, Deep Insights, and Future Perspectives

The human race is consistently striving for achieving good health and eliminate disease-causing factors. For the last few decades, scientists have been endeavoring to invent and innovate technologies that can substitute the conventional dosage forms and enable targeted and prolonged drug release at a particular site. The novel multi-matrix technology is a type of matrix formulation where the formulation is embraced to have a matrix system with multiple number of matrices. The MMX technology embraces with a combination of outer hydrophilic layer and amphiphilic/lipophilic core layer, within which drug is encapsulated followed by enteric coating for extended/targeted release at the required site. In comparison to conventional oral drug delivery systems and other drug delivery systems, multi-matrix (MMX) technology formulations afford many advantages. Additionally, it attributes for targeting strategy aimed at the colon and offers modified prolonged drug release. Thus, it has emerged rapidly as a potential alternative option in targeted oral drug delivery. However, the development of this MMX technology formulations is a exigent task and also has its own set of limitations. Due to its promising advantages and colon targeting strategy over the other colon targeted drug delivery systems, premier global companies are exploiting its potential. This article review deep insights into the formulation procedures, drug delivery mechanism, advantages, limitations, safety and efficacy studies of various marketed drug formulations of MMX technology including regulatory perspectives and future perspectives.

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.

Novel biorelevant dissolution medium as a prognostic tool for polysaccharide-based colon-targeted drug delivery system

To overcome the limitations of the conventionally used methods for evaluation of orally administered colon-targeted delivery systems, a novel dissolution method using probiotics has been recently reported. In the present study, universal suitability of this medium composed of five different probiotics is established. Different delivery systems - mini tablets, liquisolid compacts, and microspheres coated with different polysaccharides - were prepared and subjected to sequential dissolution testing in medium with and without microbiota. The results obtained from fluid thioglycollate medium (FTM)-based probiotic medium for all the polysaccharide-based formulations showed statistically similar dissolution profile to that in the rat and goat cecal content media. Hence, it can be concluded that the developed FTM-based probiotic medium, once established, may eliminate the need for further animal sacrifice in the dissolution testing of polysaccharide-based colon-targeted delivery system.

Ex-vivo evaluation of the mucoadhesive properties of Cedrela odorata and Khaya senegalensis gums with possible applications for veterinary vaccine delivery

Background

Few studies have investigated the interaction of bioadhesives with biologic tissues for veterinary application. Hence, this study evaluates the mucoadhesive property and vaccine delivery properties of polymers from phytogenic origin. Gums from Cedrela odorata and Khaya senegalensis were harvested, purified, dried and compressed into 500 mg tablets individually and in combined ratios. The time taken for these tablets, placed on freshly excised (5 × 5 cm) trachea and duodenal tissues of cattle, chicken, pig, sheep and goat and fastened to the basket end of a tablet dissolution machine probe set at 50 rev/min in a phosphate buffer 6.8 pH at 37 °C, to fall off the tissue was the peak adhesion time (PAT). Gum with best PAT was combined with Newcastle disease vaccine and the procedure repeated. Haemagglutination assay (HA) was conducted on the gum polymer-vaccine mix with gum and vaccine individually as controls.

Results

On intestinal and trachea tissues, Cedrela gum polymer averagely had prolonged PAT (≈1 h 30 min and 1 h respectively) while average PAT values of Khaya gums followed the same trend but too transient PAT (≈6 and 0.3 min respectively). However on combination, Cedrela–Khaya polymer mix (1:1) was best on chicken, cattle and sheep trachea and intestinal tissues (PAT of 1 h 30 min and 2 h 24 min respectively). On combination with vaccine, the PAT of the gums reduced slightly on cattle and sheep tissues while other animal tissue showed varied results. The HA results showed the gum polymer boosted the HA property of the vaccine (Log 10⁵), when compared to vaccine alone (Log 10⁴).

Conclusion

Hence, mucoadhesives from phytogenic sources have potential for non-invasive vaccine application.

A Novel Approach to Study Enzymatic Degradation of Ter-polymeric Beads for Gastrointestinal Drug Delivery: Synthesis and Characterization

The α-amylase induced enzymatic degradation of terpolymeric beads, composed of calcium alginate, starch and poly(ethylene) glycol, were studied for gastrointestinal drug delivery. The beads demonstrated faster degradation with increased enzyme activity in the range 0.64 to 2.24IU/mL. A linear relationship of the degradation rates and corresponding enzyme concentration indicate that degradation is governed by Michaelis-Menten kinetics. The degradation rate was enhanced with increases in starch content in the beads. The smaller value of KM (3.15 × 10−5 mol−1 dm−3) indicated higher enzyme-substrate affinity. The beads crosslinked with barium ions demonstrated slower degradation due to a higher degree of crosslinking in the beads. With increases in initial water content, the degradation was found to increase. In order to incorporate in vivo GI conditions, the degradation was also studied using a flow through diffusion cell (FTDC). The hydrogel beads exhibited slower degradation by FTDC compared to traditional in vitro methods and the degradation was dependent on the nature of the filler particles used in the diffusion cell.

Optimization of an aqueous tablet-coating process containing carboxymethylated Cassia fistula gum

The present investigation was aimed at developing and optimizing a simple aqueous tablet-coating formulation and its process. 5-Fluorouracil (5-FU) was used to ascertain the relative lipophilic/hydrophilic behavior of the coating system. Optimization was performed by evaluating the adhesive force strength and cohesive force strength of the tablet coat using a texture analyzer. The in vitro release of 5-FU was found to decrease with an increase in (tablet surface-coat) adhesive force strength. The (tablet-tablet) cohesive force strength was reduced by the addition of magnesium silicate to the coating solution. The addition of magnesium silicate (0.2% w/v) to the carboxymethyl Cassia fistula gum-chitosan (CCG-CH) coating surface significantly inhibited the release of 5-FU possibly due to an increase in the hydrophobic character of the coated tablet surface. This was possible by coating cohesive force strength reduction coating compositions (CCG-CH (70:30) and 0.3% magnesium silicate). Further, the FTIR-ATR and DSC analyses suggested the pivotal role of magnesium silicate in modifying the release of 5-FU from CCG-CH-coated tablets due to hydrogen bonding of its Si-O-Si or Mg-O groups with -OH moieties of CCG-CH.

Colon targeted drug delivery systems: a review on primary and novel approaches

The colon is a site where both local and systemic delivery of drugs can take place. Local delivery allows topical treatment of inflammatory bowel disease. However, treatment can be made effective if the drugs can be targeted directly into the colon, thereby reducing the systemic side effects. This review, mainly compares the primary approaches for CDDS (Colon Specific Drug Delivery) namely prodrugs, pH and time dependent systems, and microbially triggered systems, which achieved limited success and had limitations as compared with newer CDDS namely pressure controlled colonic delivery capsules, CODESTM, and osmotic controlled drug delivery which are unique in terms of achieving in vivo site specificity, and feasibility of manufacturing process.

Colon delivery of budesonide: evaluation of chitosan-chondroitin sulfate interpolymer complex

The present study was aimed at formulating tablets comprising of coating susceptible to microbial enzyme degradation for releasing budesonide in the colon. Tablets prepared by using Avicel pH 102 as diluent and Eudragit L100-55 as binder were coated to a weight gain of 10% w/w employing aqueous mixtures containing chitosan (CH) and chondroitin sulfate (CS). The interpolymer complex between CH and CS was characterized using Fourier transform infrared (FTIR) and differential scanning calorimetery (DSC) studies. The tablets were evaluated for release of budesonide through in vitro in vivo studies. Formation of bonds between -COO(-) and -OSO3(-) groups of CS and -NH3+ groups of CH was evident in the FTIR spectra of these interpolymer complexed (IPC) films. The DSC thermograms of these films revealed one endothermic transition between 190 degrees C and 205 degrees C, suggesting the formation of new bonds in the IPC. The pH sensitive swelling exhibited by these films was observed to be a function of CH concentration. Tablets coated with aqueous mixtures containing 40:60 or 50:50 ratio of CH/CS totally prevented the release of budesonide in pH 1.2 buffer. The peaks (FTIR) and endothermic transitions (DSC) characteristic of interpolymer complexation were observed to remain unaffected after sequential exposure of the films to pH 1.2 and pH 7.4 buffer IP. This proved the versatility of these IPC films for colon delivery. C (max) of 1,168.99 and 1,174.2 ng/mL, respectively, at 12 and 8 h post-oral dosing of tablets coated with 40:60 or 50:50 ratio of CH/CS was observed in rats. The aqueous CH/CS (40:60) coating could provide a facile method for delivering budesonide to the colon.

In-vitro and in-vivo studies of pectin/ethylcellulosefilm-coated pellets of 5-fluorouracil for colonic targeting

The aim of the present study was to define in-vitro and in-vivo characteristics of pectin/ethylcellulose-film-coated pellets of 5-fluorouracil (5-FU) for colonic targeting. The pellet cores were coated to different film thicknesses with three different pectin/ethylcellulose formulations using a fluidized bed coater. The gastrointestinal (GI) transit of coated pellets was determined by counting the percentage of coated pellets in the GI lumen by celiotomy at certain times after oral administration. 5FU was administered to rats at a dose of 15 mg kg(-1). The toxicity of 5-FU in the GI tract was evaluated using histological examination. The 1:2 ratio pectin:ethylcellulose-coated pellets with 30% total weight gain (TWG-30%) produced more satisfactory drug-release profiles in the simulated gastric, intestinal and colonic fluids. Most of the coated pellets were eliminated from the stomach in 2 h, moved into the small intestine after 2-4 h, and reached the large intestine after 4 h. After oral administration of coated pellets, 5-FU started appearing in the plasma at 7 h, and reached peak plasma concentration (Cmax) of 3.21+/-2.01 microg mL(-1) at 16 h (Tmax); the Cmax for uncoated pellets was 22.21+/-2.60 microg mL(-1) at Tmax 0.75 h. The TWG-30% formulation showed delayed Tmax, decreased Cmax and prolonged mean residence time compared with uncoated pellets. Marked pathological features in the colon were seen in rats given coated pellets, but no injuries were observed in the upper GI tract. The formulation of TWG-30% could deliver 5-FU to the colon for local action.

Biphasic release of indomethacin from HPMC/pectin/calcium matrix tablet: II. Influencing variables, stability and pharmacokinetics in dogs

The pectin/calcium interaction, which is the basis for biphasic release of indomethacin from the HPMC/pectin/calcium chloride matrix tablet, is susceptible to influence of a variety of variables that is supposed to be encountered by the oral route. In this study, the effect of influencing variables on biphasic release characteristics, the stability and the pharmacokinetics of the hybrid matrix tablet were investigated. An increasing tendency of the overall release rate was observed from pH 1.2 to 7.4. The power law correlation n values increased with pH, while the release lag time or 10% release time (T0.1) decreased at pH 6.8 and 7.4. Ionic strength in the release media also influenced the biphasic release significantly at sodium chloride levels of over 0.5%. Obvious increase in overall release rate was observed at sodium chloride level of 0.9% with an n value of 1.20 and a T0.1 of 3.4h. At sodium chloride levels of over 2%, the pectin/calcium interaction was disrupted resulting in very fast release of indomethacin. Release in gradient pH media was similar to that in pH 6.8 citrate buffer. When pectinase (Pectinex Ultra SP-L) was added into the release medium in 22.2 pg/ml or over, obvious triggering on drug release was observed. The stress testing showed increased release at extreme relative humidity of 92.5%. Both accelerated testing for 6m and long-term testing for 12 m affirmed fine stability, especially in release characteristics. Pharmacokinetic study in dogs gave Tmax/Cmax of 4h/604 ng/ml and 3h/1662 ng/ml for HPMC/pectin/calcium and HPMC/pectin tablet, respectively. The plasma indomethacin level of the calcium-containing tablet was maintained at a much lower level for 3h with a MRT of 7.13 h, longer than 3.97 and 5.61 h for indomethacin crude drug and HPMC/pectin tablet, confirming delayed absorption. The AUC of the HPMC/pectin/calcium tablet was lower than that of the HPMC/pectin tablet and indomethacin crude drug showing incomplete absorption. It is concluded that the HPMC/pectin/calcium matrix tablet is potentially useful for colon-specific drug delivery.

Release of 5-aminosalicylate from an MMX mesalamine tablet during transit through a simulated gastrointestinal tract system

5-Aminosalicylate (5-ASA; mesalamine) is the current first-line treatment for mild to moderate ulcerative colitis, a chronic inflammatory condition that most commonly affects the distal part of the colon. MMXtrade mark mesalamine (Lialdatrade mark [US]; Mezavanttrade mark XL [UK and Ireland]; Mezavanttrade mark [elsewhere]; Shire Pharmaceuticals Inc., Wayne, Pa, under license from Giuliani SpA, Milan, Italy) was created to be a novel, once-daily 5-ASA formulation. MMX mesalamine in tablet form has a pH-dependent, gastroresistant coating and is designed to delay the release of 5-ASA during transit through the upper gastrointestinal tract; it consists of hydrophilic and lipophilic excipients that are designed to prolong the release of 5-ASA throughout the colon. The release kinetics of 5-ASA from an MMX mesalamine tablet were assessed with the use of a dynamic in vitro gastrointestinal tract system (TNO GastroIntestinal Model) that simulates physiologic conditions in the adult human gastrointestinal tract under standardized fed and fasted conditions. This system incorporates removal of released drug via dialysis and automated sampling taken at various sections of the system. Less than 1% of 5-ASA was found to be released from the tablet in the simulated stomach and small intestine (before introduction into the simulated colon). Most of the 5-ASA within each tablet was released in the simulated colon (fasted state conditions: 78.0%; fed state conditions: 68.5%). Substantial quantities were released during the 8- to 18-hour sampling period (49.6 mg/h[fasted] and 40.7 mg/h [fed]). In conclusion, with the use of an in vitro system, the investigators showed that 5-ASA release from an MMX mesalamine tablet was delayed until the tablet reached the simulated colon. Throughout the simulated colon, release of 5-ASA from an MMX mesalamine tablet was prolonged.