Development of pectin matrix tablets for colonic delivery of model drug ropivacaine

Influence of pH Modulation on Dynamic Behavior of Gel Layer and Release of Weakly Basic Drug from HPMC/Wax Matrices, Controlled by Acidic Modifiers Evaluated by Multivariate Data Analysis

The solubility of weakly basic drugs in passage through gastrointestinal tract leads to their pH-dependent release from extended release formulations and to lower drug absorption and bioavailability. The aim of this study was to modulate the micro-environmental pH of hypromellose/montanglycol wax matrices and to observe its influence on the release of weakly basic drug verapamil hydrochloride (VH) with a pH-dependent solubility with respect to gel layer formation and its dynamics. For this study, malic and succinic acids differing in their solubility and pKa were selected as pH modifiers. The dissolution studies were performed by the method of changing pH. Within the same conditions, pH, thickness, and penetration force of the gel layer were measured as well. From the PCA sub-model, it is evident that a higher acid concentration ensured lower gel pH and conditions for higher drug solubility, thus creating larger gel layer with smaller rigidity, resulting in higher VH release during the dissolution test. Incorporation of stronger and more soluble malic acid (100 mg/tablet) created the most acidic and the thickest gel layer through which a total of 74% of VH was released. Despite having lower strength and solubility, matrices containing succinic acid (100 mg/tablet) released a comparable 71% of VH in a manner close to zero-order kinetics. The thinner and less rigid gel layers of the succinic acid matrices allowed an even slightly faster VH release at pH 6.8 than from matrices containing malic acid. Thus acid solubility is more parametrically significant than acid pKa for drug release at pH 6.8.

A simple electrochemical platform based on pectin stabilized gold nanoparticles for picomolar detection of biologically toxic amitrole

Amitrole is a biologically toxic nonselective herbicide which contaminates surface and ground waters at unprecedented rates. All reported modified electrodes that detect amitrole within sub-micromolar to nanomolar levels were based on the electro-oxidation of amitrole. Herein, we developed a new conceptual idea to detect picomolar concentrations of amitrole based on calcium cross linked pectin stabilized gold nanoparticle (CCLP-GNP) film modified electrode which was prepared by electrodeposition. When the electrochemical behavior of amitrole was investigated at the CCLP-GNP film, the reduction peak current of the GNPs linearly decreased as the concentration of amitrole increases. We have designed a determination platform based on the amitrole dependent decrease of the GNP cathodic peak. The described concept and high sensitivity of square wave voltammetry together facilitate the great sensing ability; as a result the described approach is able to reach a low detection limit of 36 pM which surpassed the detection limits of existing protocols. The sensor presents a good ability to determine amitrole in two linear concentration ranges: (1) 100 pM-1500 pM with a detection limit of 36 pM; (2) 100 nM-1500 nM with a detection limit of 20 nM. The preparation of CCLP-GNPs is simple, rapid and does not require any reducing agents.

A composite polyelectrolytic matrix for controlled oral drug delivery

The purpose of this study was to formulate drug-loaded polyelectrolyte matrices constituting blends of pectin, chitosan (CHT) and hydrolyzed polyacrylamide (HPAAm) for controlling the premature solvation of the polymers and modulating drug release. The model drug employed was the highly water-soluble antihistamine, diphenhydramine HCl (DPH). Polyelectrolyte complex formation was validated by infrared spectroscopy. Matrices were characterized by textural profiling, porositometry and SEM. Drug release studies were performed under simulated gastrointestinal conditions using USP apparatus 3. FTIR spectra revealed distinctive peaks indicating the presence of -COO(-) symmetrical stretching (1,425-1,390 cm(-1)) and -NH (3) (+) deformation (1,535 cm(-1)) with evidence of electrostatic interaction between the cationic CHT and anionic HPAAm corroborated by molecular mechanics simulations of the complexes. Pectin-HPAAm matrices showed electrostatic attraction due to residual -NH(2) and -COO(-) groups of HPAAm and pectin, respectively. Textural profiling demonstrated that CHT-HPAAm matrices were most resilient at 6.1% and pectin-CHT-HPAAm matrices were the least (3.9%). Matrix hardness and deformation energy followed similar behavior. Pectin-CHT-HPAAm and CHT-HPAAm matrices produced type IV isotherms with H3 hysteresis and mesopores (22.46 nm) while pectin-HPAAm matrices were atypical with hysteresis at a low P/P(0) and pore sizes of 5.15 nm and a large surface area. At t (2 h), no DPH was released from CHT-HPAAm matrices, whereas 28.2% and 82.2% was released from pectin-HPAAm and pectin-CHT-HPAAm matrices, respectively. At t (4 h), complete DPH release was achieved from pectin-CHT-HPAAm matrices in contrast to only 35% from CHT-HPAAm matrices. This revealed the release-modulating capability of each matrix signifying their applicability in controlled oral drug delivery applications.

Pectin matrix as oral drug delivery vehicle for colon cancer treatment

Colon cancer is the fourth most common cancer globally with 639,000 deaths reported annually. Typical chemotherapy is provided by injection route to reduce tumor growth and metastasis. Recent research investigates the oral delivery profiles of chemotherapeutic agents. In comparison to injection, oral administration of drugs in the form of a colon-specific delivery system is expected to increase drug bioavailability at target site, reduce drug dose and systemic adverse effects. Pectin is suitable for use as colon-specific drug delivery vehicle as it is selectively digested by colonic microflora to release drug with minimal degradation in upper gastrointestinal tract. The present review examines the physicochemical attributes of formulation needed to retard drug release of pectin matrix prior to its arrival at colon, and evaluate the therapeutic value of pectin matrix in association with colon cancer. The review suggests that multi-particulate calcium pectinate matrix is an ideal carrier to orally deliver drugs for site-specific treatment of colon cancer as (1) crosslinking of pectin by calcium ions in a matrix negates drug release in upper gastrointestinal tract, (2) multi-particulate carrier has a slower transit and a higher contact time for drug action in colon than single-unit dosage form, and (3) both pectin and calcium have an indication to reduce the severity of colon cancer from the implication of diet and molecular biology studies. Pectin matrix demonstrates dual advantages as drug carrier and therapeutic for use in treatment of colon cancer.

Solid dispersions in the development of a nimodipine floating tablet formulation and optimization by artificial neural networks and genetic programming

The present study investigates the use of nimodipine-polyethylene glycol solid dispersions for the development of effervescent controlled release floating tablet formulations. The physical state of the dispersed nimodipine in the polymer matrix was characterized by differential scanning calorimetry, powder X-ray diffraction, FT-IR spectroscopy and polarized light microscopy, and the mixture proportions of polyethylene glycol (PEG), polyvinyl-pyrrolidone (PVP), hydroxypropylmethylcellulose (HPMC), effervescent agents (EFF) and nimodipine were optimized in relation to drug release (% release at 60 min, and time at which the 90% of the drug was dissolved) and floating properties (tablet's floating strength and duration), employing a 25-run D-optimal mixture design combined with artificial neural networks (ANNs) and genetic programming (GP). It was found that nimodipine exists as mod I microcrystals in the solid dispersions and is stable for at least a three-month period. The tablets showed good floating properties and controlled release profiles, with drug release proceeding via the concomitant operation of swelling and erosion of the polymer matrix. ANNs and GP both proved to be efficient tools in the optimization of the tablet formulation, and the global optimum formulation suggested by the GP equations consisted of PEG=9%, PVP=30%, HPMC=36%, EFF=11%, nimodipine=14%.

Predictable pulsatile release of tramadol hydrochloride for chronotherapeutics of arthritis

The present investigation deals with the development of a pH and time-dependent press-coated pulsatile drug delivery system for delivering drugs into the colon. The system consists of a drug containing core, coated by a combination of natural polymer Delonix regia gum (DRG) and hydroxypropyl methylcellulose (HPMC K4M) in various proportions, which controls the onset of release. The whole system was coated with methacrylic acid copolymers, which not only prevents the drug release in the stomach, but also prolongs the lag time. Tramadol HCl was used as a model drug and varying combinations of DRG and HPMC K4M were used to achieve the desired lag time before rapid and complete release of the drug in the colon. It was observed that the lag time depends on the coating ratio of DRG to HPMC and also on press coating weight. Drug release was found to be increased by 15-30% in the presence of colonic microbial flora. The results showed the capability of the system in achieving pulsatile release for a programmable period of time and pH-dependent release to attain colon-targeted delivery.

Preparation, in vitro and in vivo evaluation of algino-pectinate bioadhesive microspheres: An investigation of the effects of polymers using multiple comparison analysis

Ionotropic gelation was used to entrap aceclofenac into algino-pectinate bioadhesive microspheres as a potential drug carrier for the oral delivery of this anti-inflammatory drug. Microspheres were investigated in vitro for possible sustained drug release and their use in vivo as a gastroprotective system for aceclofenac. Polymer concentration and polymer/drug ratio were analyzed for their influence on microsphere properties. The microspheres exhibited good bioadhesive property and showed high drug entrapment efficiency. Drug release profiles exhibited faster release of aceclofenac from alginate microspheres whereas algino-pectinate microspheres showed prolonged release. Dunnet's multiple comparison analysis suggested a significant difference in percent inhibition of paw edema when the optimized formulation was compared to pure drug. It was concluded that the algino-pectinate bioadhesive formulations exhibit promising properties of a sustained release form for aceclofenac and that they provide distinct tissue protection in the stomach.

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.

Direct compression behavior of low- and high-methoxylated pectins

The objective of this study was to evaluate possible usefulness of pectins for direct compression of tablets. The deformation behavior of pectin grades of different degree of methoxylation (DM), namely, 5%, 10%, 25%, 35%, 40%, 50%, and 60% were, examined in terms of yield pressures (YP) derived from Heckel profiles for both compression and decompression and measurements of elastic recovery after ejection. All pectin grades showed a high degree of elastic recovery. DM 60% exhibited most plastic deformation (YP 70.4 MPa) whereas DM 5% (104.6 MPa) and DM 10% (114.7 MPa) least. However, DM 60% gave no coherent tablets, whereas tablet tensile strengths for DM 5% and DM 10% were comparable to Starch 1500^®. Also, Heckel profiles were similar to Starch 1500^®. For sieved fractions (180–250 and 90–125 μm) of DM 25% and DM 40% originating from the very same batch, YPs were alike, indicating minor effects of particle size. These facts indicate that DM is important for the compaction behavior, and batch-to-batch variability should also be considered. Therefore, pectins of low degree of methoxylation may have a potential as direct compression excipients.

Polysaccharides for Colon Targeted Drug Delivery

Colon targeted drug delivery has the potential to deliver bioactive agents for the treatment of a variety of colonic diseases and to deliver proteins and peptides to the colon for their systemic absorption. Various strategies, currently available to target the release of drugs to colon, include formation of prodrug, coating of pH-sensitive polymers, use of colon-specific biodegradable polymers, timed released systems, osmotic systems, and pressure controlled drug delivery systems. Among the different approaches to achieve targeted drug release to the colon, the use of polymers especially biodegradable by colonic bacteria holds great promise. Polysaccharidases are bacterial enzymes that are available in sufficient quantity to be exploited in colon targeting of drugs. Based on this approach, various polysaccharides have been investigated for colon-specific drug release. These polysaccharides include pectin, guar gum, amylose, inulin, dextran, chitosan, and chondroitin sulphate. This family of natural polymers has an appeal to drug delivery as it is comprised of polymers with a large number of derivatizable groups, a wide range of molecular weights, varying chemical compositions, and, for the most part, low toxicity and biodegradability yet high stability. The most favorable property of these materials is their approval as pharmaceutical excipients.

Development of Enteric-coated Pectin-based Matrix Tablets for Colonic Delivery of Theophylline

The present work was aimed at developing a new colonic drug delivery system which takes advantage of the combined approaches of a specifically colon-biodegradable pectin matrix with a pH-sensitive Eudragit S100 polymeric coating. The developed system was able to suitably retard the onset of drug release and to provide a colon-specific delivery, thus overcoming the problems of pectin solubility in the upper gastrointestinal tract and low site-specificity of simple pH-dependent systems. Due to the poor compactability properties of pectin, it was used in mixture with Emdex, a hydrophilic directly-compressible material, in order to make it possible to prepare tablets by direct compression. Theophylline (TP) was used as model drug due to its suitable pharmacokinetic properties for colonic delivery and good absorption in the large intestine. The effects of varying the type of pectin (low and high methoxylated, or amidated), the pectin:Emdex ratio and the level of the pH-dependent polymeric coating on drug release behavior were investigated. Release tests were performed using sequential liquids simulating the physiological variation of pH and the effect of the presence or not of pectinolytic enzymes into the simulated colonic medium was evaluated. Thirty percent (w/w) was the the minimum content of Emdex for obtaining directly compressible tablets with sufficient hardness to withstand the coating process and 27% (w/w) was the minimum coating amount for obtaining an adequate lag time before the onset of drug release. After lag time, linear nearly zero-order profiles were obtained whose slope (i.e. the drug release rate) depended on both the Emdex content and the pectin type. Comparison of the results obtained in the presence or not of pectynolitic enzymes allowed selection of the high methoxylated pectin as the most interesting candidate for specific colonic delivery since it was the least water-soluble and the most susceptible to enzymatic degradation, thus assuring a greater site-specificity of drug release. Finally, the importance of using appropriate dissolution test conditions to adequately characterize the drug release profiles from delivery systems endowed with a microflora-activated drug release triggering mechanism has been demonstrated.

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

The aim of this work was to investigate the effect of acidic pH representative of gastric fluid on the release of 5-aminosalicylic acid from beads coated with pectin/ethylcellulose as film coating intended for drug delivery to the colon, in media mimicking the lower gastrointestinal (GI) tract and representative of colonic conditions. In this work, the in vitro incubation of the beads in acid medium was found to influence the hydration and the swelling characteristics of pectin after transfer into simulated intestinal fluid and simulated cecal fluid containing pectinolytic enzymes. Moreover, the drug release profiles from the beads in simulated intestinal fluid after incubation for 2 h or 30 min in simulated gastric fluid vs. no acid incubation were found to be very different. The in vitro degradation of pectin in the coat by pectinolytic enzymes in simulated cecal fluid depended on whether the beads were placed in simulated gastric fluid prior to testing in simulated intestinal fluid. The percentage drug release also depended on the ratio of pectin to ethylcellulose in the coat.

Colonic Drug Delivery: Influence of Cross-linking Agent on Pectin Beads Properties and Role of the Shell Capsule type

For colonic delivery, pectin beads obtained by ionotropic gelation method have been already reported as an interesting approach. This study investigated the influence of the cross-linking agent (calcium or zinc) and the type of shell capsule used (classical or enteric capsules) on pectin beads properties and on their performance to target the colon (in vitro dissolution studies with subsequent pH change to mimic overall gastro-intestinal tract). Zinc pectinate beads seemed to be relatively similar to calcium's ones in morphological point, except on the surface aspect. When beads were introduced in classical hard capsules, ketoprofen release was not significantly different between CPG and ZPG beads, and it was too premature and too quick due to a chemical erosion of the pectinate matrix (acid + basic attacks). However, zinc pectinate beads showed slower ketoprofen release compared with calcium pectinate beads when enteric hard capsules were used. This interesting finding could be due to the strength of the network formed during the process between the zinc cations and the LM-pectin following the "egg-box" model. This network was stronger and induced a reduction of swelling and hydration when contact with dissolution medium, then subsequently a decrease of drug release. Thus, the zinc pectinate beads could protect sufficiently drug entrapped from the upper gastro-intestinal conditions and drug release will be controlled by pectin degradation with colonic microflora. Finally, these zinc pectinate beads in enteric hard capsules are promising as a carrier for specific colonic delivery of drugs after oral administration.

Chitosan-based controlled porosity osmotic pump for colon-specific delivery system: Screening of formulation variables and in vitro investigation

A microbially triggered colon-targeted osmotic pump (MTCT-OP) has been studied. The gelable property at acid condition and colon-specific biodegradation of chitosan were used to: (1) produce the osmotic pressure, (2) form the drug suspension and (3) form the in situ delivery pores for colon-specific drug release, respectively. The scanning electron microscopy (SEM) study and the calculation of membrane permeability were applied to elucidate the mechanism of MTCT-OP. The effects of different formulation variables, including the level of pH-regulating excipient (citric acid) and the amount of chitosan in the core, the weight gain of semipermeable membrane and enteric-coating membrane, and the level of pore former (chitosan) in the semipermeable membrane, have been studied. Results of SEM showed that the in situ delivery pores could be formed in predetermined time after coming into contact with dissolution medium, and the number of pore was dependent on the initial level of pore former in the membrane. The amount of budesonide release was directly proportional to the initial level of pore former, but inversely related to the weight of semipermeable membrane. The effects of variations in the level of citric acid and chitosan in the core formulation on drug release were studied. The different levels of enteric-coating membrane could prevent cellulose acetate membrane (containing chitosan as pore former) from forming pore or rupture before contact with simulated colonic fluid, but had no effect on the drug release. Budesonide release from the developed formulation was inversely proportional to the osmotic pressure of the release medium, confirming that osmotic pumping was the major mechanism of drug release. These results showed that MTCT-OP based on osmotic technology and microbially triggered mechanism had a high potential for colon-specific drug delivery.

Design and evaluation of colon specific drug delivery system containing flurbiprofen microsponges

The purpose of this study was to design novel colon specific drug delivery system containing flurbiprofen (FLB) microsponges. Microsponges containing FLB and Eudragit RS 100 were prepared by quasi-emulsion solvent diffusion method. Additionally, FLB was entrapped into a commercial Microsponge 5640 system using entrapment method. Afterwards, the effects of drug:polymer ratio, inner phase solvent amount, stirring time and speed and stirrer type on the physical characteristics of microsponges were investigated. The thermal behaviour, surface morphology, particle size and pore structure of microsponges were examined. The colon specific formulations were prepared by compression coating and also pore plugging of microsponges with pectin:hydroxypropylmethyl cellulose (HPMC) mixture followed by tabletting. In vitro dissolution studies were done on all formulations and the results were kinetically and statistically evaluated. The microsponges were spherical in shape, between 30.7 and 94.5microm in diameter and showed high porosity values (61-72%). The pore shapes of microsponges prepared by quasi-emulsion solvent diffusion method and entrapment method were found as spherical and cylindrical holes, respectively. Mechanically strong tablets prepared for colon specific drug delivery were obtained owing to the plastic deformation of sponge-like structure of microsponges. In vitro studies exhibited that compression coated colon specific tablet formulations started to release the drug at the 8th hour corresponding to the proximal colon arrival time due to the addition of enzyme, following a modified release pattern while the drug release from the colon specific formulations prepared by pore plugging the microsponges showed an increase at the 8th hour which was the time point that the enzyme addition made. This study presents a new approach based on microsponges for colon specific drug delivery.

Immersion coating of pellets with calcium pectinate and chitosan

This study has investigated the potential of immersion coating calcium containing pellet cores first with pectin, and then with two different cross-linkers, calcium or chitosan. The interaction between pectin and calcium, and between pectin and chitosan, are believed to slow down the drug release, and thereby, the coated pellets might possibly be used for colon specific drug delivery. Both the calcium coated pellets and the chitosan coated pellets had a reduced drug release compared to uncoated pellets in 0.1M HCl (1 h) and phosphate buffer pH 6.8 (4 h). The most successful combination had a drug release of only 17% during the entire test period in comparison to the uncoated pellets that had a drug release of 80%. When chitosan was used as a cross-linker, a higher reduction in drug release was obtained than by using calcium as the cross-linker. For the pellets coated with pectin in combination with chitosan, the type of pectin with a degree of methoxylation (DM) of 35 was superior to the pectin type with DM 17. The drug release was further slowed down by choosing a type of chitosan with a high degree of deacetylation (Dda) 89% and by coating at low concentrations (0.1%) in the immersion solution.

Pectin-based oral drug delivery to the colon

This review presents an overview of studies concerning oral formulations intended for site-specific drug delivery to the colon with pectin as the main excipient. The biological aspects covered include gastrointestinal transit and the enzymatic degradation of pectin. Scintigraphic methods demonstrating the functionality of pectin formulations are discussed. The main focus is on the various formulations reported, including matrix tablets, multiparticulate formulations as pellets and hydrogel beads, and pectin-based coatings. Also included is an evaluation of common excipients employed to improve colon specificity by crosslinking or increasing the hydrophobicity. Finally, properties of the pectin molecules that are important for successful formulations are examined. The conclusion is that the studies found in the literature provide an excellent platform for the development of pectin-based colon delivery systems.