Release Behaviour of Propranolol HCl from Hydrophilic Matrix Tablets Containing Psyllium Powder in Combination with Hydrophilic Polymers

The objective of this study was to investigate the release behaviour of propranolol hydrochloride from psyllium matrices in the presence hydrophilic polymers. The dissolution test was carried out at pH 1.2 and pH 6.8. Binary mixtures of psyllium and hydroxypropyl methylcellulose (HPMC) used showed that an increase in the percentage of HPMC in the binary mixtures caused a significant decrease in the release rate of propranolol. Psyllium–alginate matrices produced lower drug release as compared to when the alginate was the matrix former alone. When sodium carboxy methyl cellulose (NaCMC) was incorporated into the psyllium, the results showed that matrices containing the ratio of psyllium–NaCMC in the 1:1 ratio are able to slow down the drug release significantly as compared to matrices made from only psyllium or NaCMC as retardant agent suggesting that there could be a synergistic effect between psyllium and NaCMC. The double-layered tablets showed that the psyllium and HPMC in the outer shell of an inner formulation of psyllium alone had the greatest effect of protecting the inner core and thus producing the lowest drug release (DE = 38%, MDT = 93 min). A significant decrease in the value of n in Q = kt ⁿ from 0.70 to 0.51 as the psyllium content was increased from 50 to 150 mg suggests that the presence of psyllium in HPMC matrices affected the release mechanism. Psyllium powder had the ability in the combination with other hydrophilic polymers to produce controlled release profiles. Care and consideration should as such be taken when formulating hydrophilic matrices in different combinations.     

Synthesis and Characterization of Pectin/PVP Hydrogel Membranes for Drug Delivery System

The purpose of the present study was to develop and design pectin and polyvinyl pyrrolidone (PVP) blended hydrogel membranes (PEVP), with different pectin: PVP ratios (1:0.2, 1:0.4, 1:0.6, 1:0.8 and 1:1 w/w), which were prepared by using a conventional solution casting technique. An attempt has been made to characterize the hydrogel membranes by various instrumental techniques like, FTIR (Fourier transform infrared) spectroscopy, X-ray diffraction (XRD), Differential scanning calorimetry (DSC), tensile strength test and scanning electron microscopy (SEM). The release patterns of the drug (salicylic acid) from the hydrogel membrane were done in three different release mediums (pH 1.4, pH 7.4 and distilled water) and samples were analyzed spectrophotometrically at 294 nm wavelength on a UV Vis spectrophotometer. MTT assay was done to ensure cytocompatibility of the pectin/PVP hydrogel membranes using B16 melanoma cells. FTIR spectroscopy indicated the presence of secondary amide (I) absorption bands. The XRD study shows decrease in crystallinity of the hydrogel membranes with increase in PVP ratio. DSC study shows an increase in T _g of pectin after blending with PVP. It was found that tensile strength increases with increasing PVP ratios in the hydrogel membranes. The prepared hydrogel membranes were found to be biocompatible with B16 melanoma cells.     

A Design and Evaluation of Layered Matrix Tablet Formulations of Metoprolol Tartrate

The aim of this paper was to evaluate the performance of different swellable polymers in the form of layered matrix tablets to provide controlled therapeutic effect of metoprolol tartrate for twice daily administration. Seven different swellable polymers (carrageenan, hydroxypropylmethyl cellulose, pectin, guar gum, xanthan gum, chitosan, and ethyl cellulose) were evaluated alone or in combination as release-retardant layer. Tablets were tested for weight variation, hardness, diameter/thickness ratio, friability, and drug content uniformity and subjected to in vitro drug-release studies. In addition, the target-release profile of metoprolol tartrate was plotted using its clinical pharmacokinetic data, and the release profiles of the tablets were evaluated in relation to the plotted target release profile. Carrageenan was determined as the best polymer in two-layered matrix tablet formulations due to its better accordance to the target release profile and was selected for preparing three-layered matrix tablets. Carrageenan formulations exhibited super case II release mechanism. Accelerated stability testing was performed on two- and three-layered matrix tablet formulations of carrageenan. The tablets were stored at 25°C/60% relative humidity and 40°C/75% relative humidity for 6 months and examined for physical appearance, drug content, and release characteristics. At the end of the storage time, formulations showed no change either in physical appearance, drug content, or drug-release profile. These results demonstrated the suitability of three-layered tablet formulation of carrageenan to provide controlled release and improved linearity for metoprolol tartrate in comparison to two-layered tablet formulation.     

Preparation and In-vivo Pharmacokinetic Study of a Novel Extended Release Compression Coated Tablets of Fenoterol Hydrobromide

The aim of this study was to formulate extended release compression coated core tablets of fenoterol hydrobromide, a selective beta(2) adrenergic receptor agonist, in an attempt to prevent nocturnal asthma. Two hydrophilic polymers viz Kollidon SR, Polyox WSR 303 and a hydrophobic one (Precirol ATO5) were employed. Compression coated tablets were formulated by preparing a core tablet containing 7.5 mg drug and various amounts of polymer and Emcompress then compressed coated with the same polymeric materials. For comparison purpose different matrix tablets were also prepared employing the same polymers. In-vitro release studies were carried out at different pH (1.2 and 6.8). Pharmacokinetics of extended release tablets as well as commercially available immediate release tablets (Berotec) were studied after oral administration to beagle dogs using a new developed LC-MS/MS method with a lower limit of quantification of 1 ng/ml. Fenoterol release from compression coated tablets was significantly lower than matrix tablets. The mechanism of release was changed with the nature and content of polymer. The release pattern of drug from F16 containing 40 mg Kollidon SR divided in the core tablet (15 mg) and the rest in the compressed coat (25 mg) showed a typical zero order release kinetic that could extend drug release >10 h and reasonable time for 75% to be released (t(75)) (8.92 h). When compared to immediate release Berotec tablet the MRT was significantly extended from 7.03 +/- 0.76 to 10.93 +/- 1.25 h (P < 0.001) and HVD(t 50%Cmax) was also significantly extended from 2.71 +/- 0.68 to 6.81 +/- 0.67 h with expected prevention of nocturnal asthma.     

Pectin microspheres for oral colon delivery: Preparation using spray drying method and<Emphasis Type="Italic">in vitro</Emphasis> release of indomethacin

Drug delivery systems that are based on pectin have been studied for colon specific delivery using the specific activity of colon microflora. The aim of this study was to design a novel method of manufacturing pectin microspheres without oils and surfactants and to investigate the potential use of the pectin microsphere as an oral colon-specific drug carrier. The pectin microspheres were successfully formed using the spray drying method and crosslinking with calcium chloride. From the crosslinked pectin microspheres, indomethancin (IND) release was more supressed than its release from non-crosslinked microspheres. In a low pH (pH 1.4) environment, the pectin microspheres released IND at an amount of about 18±2% of the total loaded weight for 24h while the release rate of IND was stimulated at neutral pH (pH 7.4). IND release from the pectin microspheres was increased by the addition of pectinase. The results clearly demonstrate that the pectin microspheres that were prepared by the spray drying and crosslinking methods are potential carriers for colon-specific drug deliveries.     

Preliminary Investigation on the Development of Diltiazem Resin Complex Loaded Carboxymethyl Xanthan Beads

The objective of this study was to develop a multiunit sustained release dosage form of diltiazem using a natural polymer from a completely aqueous environment. Diltiazem was complexed with resin and the resinate-loaded carboxymethyl xanthan (RCMX) beads were prepared by interacting sodium carboxymethyl xanthan (SCMX), a derivatized xanthan gum, with Al⁺³ ions. The beads were evaluated for drug entrapment efficiency (DEE) and release characteristics in enzyme free simulated gastric fluid (SGF, HCl solution, pH 1.2) and simulated intestinal fluid (SIF, USP phosphate buffer solution, pH 6.8). Increase in gelation time from 5 to 20 min and AlCl₃ concentration from 1 to 3% decreased the DEE respectively from 95 to 79% and 88.5 to 84.6%. However, increase in gum concentration from 1.5 to 2.5% increased the DEE from 86.5 to 90.7%. The variation in DEE was related to displacement of drug from the resinate by the gel forming Al⁺³ ions. While 75–82% drug was released in 2 h in SGF from various beads, 75 to 98% drug was released in 5 hour in SIF indicating the dependence of drug release on pH of dissolution media. Although the beads maintained their initial integrity throughout the dissolution process in both media, as evident from scanning electron microscopic studies, the faster release in SGF was accounted for higher swelling of the beads in SGF than in SIF. When release data (up to 60%) was fitted in power law expression, the drug release was found to be controlled by diffusion with simultaneous relaxation phenomena.     

Development and Evaluation of Artemether Taste Masked Rapid Disintegrating Tablets with Improved Dissolution Using Solid Dispersion Technique

The purpose of this research was to mask the intensely bitter taste of artemether (ARM) and to formulate a rapid-disintegrating tablet (RDT) of the taste-masked drug. Taste masking was done by solid dispersion with mono amino glycyrrhyzinate pentahydrate (GLY) by solvent evaporation method. To characterize and formulate taste masked rapid disintegrating tablets (RDTs) of ARM, the 1:1M solid dispersion was selected based on bitterness score. Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), and X-ray powder diffraction (XRPD) were performed to identify the physicochemical interaction between drug and carrier, hence its effect on dissolution. RDTs were evaluated for weight variation, disintegration time, hardness and friability. In vitro drug release studies were performed for RDTs at pH 1.2 and 6.8. Bitterness score was evaluated using mini-column method and compared with gustatory sensation test. FTIR spectroscopy and DSC showed no interaction while XRPD showed amorphization of ARM in GLY solid dispersion. RDTs prepared using solid dispersion, (RDT3), showed faster disintegration (within 28 s) and complete bitter taste masking of ARM. In addition, RDT3 exhibited better dissolution profile at both pH 1.2 and 6.8, than RDTs prepared from pure ARM (RDT5). Taste evaluation of RDTs in human volunteers rated tasteless with a score of 0 to RDT3 and 3 to RDT5. Mini-column revealed that RDT5 showed increase in number of persons who sensed bitterness with increased amount of ARM release while RDT3 sensed no bitterness. Thus, results conclusively demonstrated successful masking of taste and rapid disintegration of the formulated tablets in the oral cavity with improved dissolution.     

A Novel Anti-HIV Dextrin–Zidovudine Conjugate Improving the Pharmacokinetics of Zidovudine in Rats

The aim of this study was to investigate a newly synthesized dextrin–zidovudine (AZT) conjugate designed as a sustained release prodrug of AZT for parenteral administration. AZT was first reacted with succinic anhydride to form a succinoylated AZT which was subsequently coupled with dextrin to yield the dextrin–AZT conjugate. The structure of the conjugate was characterized by FT-IR and ¹H-NMR spectroscopy. The drug content of the conjugate was 18.9 wt.%. The release in vitro of free AZT and succinoylated AZT was investigated in buffer solutions at pH 5.5 and 7.4 and in human plasma. AZT and succinoylated AZT release from the conjugate was 1.4% (pH 5.5), 41.7% (pH 7.4) and 78.4% in human plasma after 24 h. Release was complete in human plasma after 48 h. A pharmacokinetic study in rats following intravenous administration of the conjugate showed prolonged plasma levels of AZT compared to free AZT. The use of the conjugate extended the plasma half-life of AZT from 1.3 to 19.3 h and the mean residence time from 0.4 to 23.6 h. Furthermore, the conjugate provided a significant greater area under the plasma concentration-time curve and reduced the systemic clearance of AZT. This study suggested the potential of this novel dextrin–AZT conjugate as a new intravenous preparation of AZT.     

Eudragit-coated pectin microspheres of 5-fluorouracil for colon targeting

An objective of the present investigation was to prepare and evaluate Eudragit-coated pectin microspheres for colon targeting of 5-fluorouracil (FU). Pectin microspheres were prepared by emulsion dehydration method using different ratios of FU and pectin (1:3 to 1:6), stirring speeds (500–2000 rpm) and emulsifier concentrations (0.75%–1.5% wt/vol). The yield of preparation and the encapsulation efficiencies were high for all pectin microspheres. Microspheres prepared by using drug:polymer ratio 1:4, stirring speed 1000 rpm, and 1.25% wt/vol concentration of emulsifying agent were selected as an optimized formulation. Eudragit-coating of pectin microspheres was performed by oil-in-oil solvent evaporation method using coat: core ratio (5:1). Pectin microspheres and Eudragit-coated pectin microspheres were evaluated for surface morphology, particle size and size distribution, swellability, percentage drug entrapment, and in vitro drug release in simulated gastrointestinal fluids (SGF). The in vitro drug release study of optimized formulation was also performed in simulated colonic fluid in the presence of 2% rat cecal content. Organ distribution study in albino rats was performed to establish the targeting potential of optimized formulation in the colon. The release profile of FU from Eudragit-coated pectin microspheres was pH dependent. In acidic medium, the release rate was much slower; however, the drug was released quickly at pH 7.4. It is concluded from the present investigation that Eudragit-coated pectin microspheres are promising controlled release carriers for colon-targeted delivery of FU. Published: February 16, 2007     

Evaluation of Matrix Tablets Based on Eudragit?E100/Carbopol?971P Combinations for Controlled Release and Improved Compaction Properties of Water Soluble Model Drug Paracetamol

The purpose of this work was to investigate the influence of Eudragit®E100 polymer in modifying the release rates and compaction properties of water soluble model drug paracetamol from Carbopol®971P NF polymer matrix tablets prepared by direct compression. The effects of the ratio of the two polymers, the total polymeric content, and the tablets mechanical strength on paracetamol release rates were investigated. Dissolution studies were conducted using USP XX Π rotating paddle apparatus at 50 rpm and 37°C at three different stages (pH 1.2, 4.8, and 6.8). Results showed that the polymers combination improved significantly the compaction properties of paracetamol tablets as evident by the higher crushing strengths (8.3 ± 0.4 Kp) compared to polymer-free tablets (3.4 ± 0.2 Kp) at intermediate compression pressure of 490 MPa. When combined with Carbopol®971P NF, Eudragit®E100 was found to be capable of extending paracetamol release for more than 12 h compared to 1 h for polymers-free tablets. The combined polymers were able to control paracetamol release in a pH independent pattern. The f2 (similarity factor) analysis showed that the ratio between the polymers and the total polymer concentration exhibited significant impact on drug release rates. In conclusion, Eudragit®E100 when combined with Carbopol®971P NF was capable of improving the compaction and sustained release properties of paracetamol. Korsmeyer–Peppas model was found to be the most suitable for fitting drug release data. The polymer combinations can potentially be used to control the release rates of highly water soluble drugs.KEY WORDS: Carbopol®971P NF, Eudragit®E100, matrix tablet, pH-independent release, sustained     

Rheological Characterization and Drug Release Studies of Gum Exudates of Terminalia catappa Linn

The present study was undertaken to evaluate the gum exudates of Terminalia catappa Linn. (TC gum) as a release retarding excipient in oral controlled drug delivery system. The rheological properties of TC gum were studied and different formulation techniques were used to evaluate the comparative drug release characteristics. The viscosity was found to be dependent on concentration and pH. Temperature up to 60°C did not show significant effect on viscosity. The rheological kinetics evaluated by power law, revealed the shear thinning behavior of the TC gum dispersion in water. Matrix tablets of TC gum were prepared with the model drug dextromethorphan hydrobromide (DH) by direct compression, wet granulation and solid dispersion techniques. The dissolution profiles of the matrix tablets were compared with the pure drug containing capsules using the USP Basket apparatus with 500 ml phosphate buffer of pH 6.8 as a dissolution medium. The drug release from the compressed tablets containing TC gum was comparatively sustained than pure drug containing capsules. Even though all the formulation techniques showed reduction of dissolution rate, aqueous wet granulation showed the maximum sustained release of more than 8 h. The release kinetics estimated by the power law revealed that the drug release mechanism involved in the dextromethorphan matrix is anomalous transport as indicated by the release exponent n values. Thus the study confirmed that the TC gum might be used in the controlled drug delivery system as a release-retarding polymer.     

Modified Polysaccharides as Fast Disintegrating Excipients for Orodispersible Tablets of Roxithromycin

The purpose of this study was to develop a dosage form that was easy to administer and provides rapid release of the drug roxithromycin, using modified polysaccharides as rapidly disintegrating excipients. Modified polysaccharides co grinded treated agar (C-TAG) and co grinded treated guar gum (C-TGG) were prepared by subjecting pure polysaccharides namely agar and guar gum respectively to sequential processes of wetting, drying and co grinding with mannitol (1:1). The modified polysaccharides were characterized by Scanning Electron Microscopy and Diffuse Reflectance Spectroscopy and evaluated for particle size distribution, derived properties, swelling index and biodegradability. Optimization studies based on 2² factorial designs, with friability and disintegration time as response parameters were used to formulate orodispersible tablets of roxithromycin and evaluated for wetting time, water absorption ratio and in vitro drug release at salivary pH 6.4 and physiological pH 7.4. Results indicated that lower levels of modified polysaccharides namely C-TAG in F₃ and C-TGG in F₇ and higher levels of microcrystalline cellulose, exhibited least disintegration times without friability concerns. In vitro release of optimized formulations F₃ and F_7, both at salivary pH and physiological pH was found to be more than 90% within 30 min as compared to 27.82% at the same time point of conventional formulation. Stability studies carried out as per ICH Q1A guidelines suggested the formulations to be stable for a period of 6 months. Thus the approach of using modified polysaccharides as fast disintegrating excipient can be used to formulate a stable orodispersible formulation.     

A Model for Calcium Permeation into Small Intestine

An in vitro model was used to simulate the intestinal permeation of calcium ions depending on the type of salt (carbonate, fumarate, citrate, or gluconate), its concentration (1.0, 2.5, 5.0, or 10 mM/l), and pH (1.3, 4.2, 6.2, or 7.5). To simulate the conditions for calcium permeation in a patient in a fasting state, the solutions were placed in contact with segments of small intestine of pig: stomach, duodenum, jejunum, and ileum. The percent permeation, its rate, and half-time were measured in each case. In all cases, the maximum permeation was seen at 1 mM concentration, depending on pH: 100% for carbonate at pH 1.3; 82% for fumarate, pH 6.2; 79.5% for citrate at pH 4.2, and 81% for gluconate at pH 7.4. The maximum rate of permeation (% h⁻¹) was also observed at 1 mM: 2.16 for carbonate at pH 1.3, 0.29 for fumarate at pH 6.2, 0.26 for citrate at pH 4.2, and 0.28 for gluconate at pH 7.4. The shortest half-time permeation (t _1/2, h) for 1 mM solutions depended also on pH (in parentheses): carbonate 0.3 (1.3), fumarate 2.4 (6.2), citrate 2.6 (4.2), and gluconate 2.5 (7.4). The results suggest that calcium carbonate and citrate can be recommended to patients with normal gastric acidity and hyperacidity while fumarate and gluconate to patients with hypoacidity.     

Development and Gamma Scintigraphy Study of <Emphasis Type="Italic">Trigonella foenum-graecum</Emphasis> (Fenugreek) Polysaccharide-Based Colon Tablet

The major concern with the use of some synthetic excipients is their safety towards biological tissues, hence influencing the reliability of products. With the aim to minimize dependency on highly toxic synthetic excipients, the present study was designed to deliver metronidazole (MNZ) into the colonic region for localized treatment of amoebiasis using natural polysaccharide-based drug delivery. Compression-coated tablets were prepared using water extractable natural polysaccharide from Trigonella foenum-graecum (FG). Physical properties of the tablets were evaluated and dissolution study was performed at pH 1.2, 6.8, and 7.4 with rat cecal material. Results indicate that all batches demonstrated pH-dependent drug release and prevented release into the stomach, allowing traces into the intestine and highest availability into the colon. A significant correlation (r²?=?0.975) was found between the coating levels of extracted polysaccharide and lag time release of drug. Gamma scintigraphy images of in vivo study conducted on human volunteers showed a small intestinal transit time, i.e., 3–5 (4.2?±?0.4) h and confirmed that the tablets reached the colon within 6–8 h. The present study revealed that the FG polysaccharide-based double compression tablets may be promising colon-specific drug carriers with reduced toxic effects of commonly used synthetic excipients.     

Design and Development of Gliclazide Mucoadhesive Microcapsules: In Vitro and In Vivo Evaluation

In this study an attempt was made to prepare mucoadhesive microcapsules of gliclazide using various mucoadhesive polymers designed for oral controlled release. Gliclazide microcapsules were prepared using sodium alginate and mucoadhesive polymer such as sodium carboxymethyl cellulose (sodium CMC), carbopol 934P or hydroxy propylmethyl cellulose (HPMC) by orifice-ionic gelation method. The microcapsules were evaluated for surface morphology and particle shape by scanning electron microscope. Microcapsules were also evaluated for their microencapsulation efficiency, in vitro wash-off mucoadhesion test, in vitro drug release and in vivo study. The microcapsules were discrete, spherical and free flowing. The microencapsulation efficiency was in the range of 65–80% and microcapsules exhibited good mucoadhesive property in the in vitro wash off test. The percentage of microcapsules adhering to tissue at pH 7.4 after 6 h varied from 12–32%, whereas the percentage of microcapsules adhering to tissue at pH 1.2 after 6 h varied from 35–68%. The drug release was also found to be slow and extended for more than 16 h. In vivo testing of the mucoadhesive microcapsules in diabetic albino rats demonstrated significant antidiabetic effect of gliclazide. The hypoglycemic effect obtained by mucoadhesive microcapsules was for more than 16 h whereas gliclazide produced an antidiabetic effect for only 10 h suggesting that mucoadhesive microcapsules are a valuable system for the long term delivery of gliclazide.     

I n Vivo Evaluation of 5-ASA Colon-Specific Tablets Using Experimental-Induced Colitis Rat Animal Model

Colonic drug delivery is intended not only for local treatment in inflammatory bowel disease (IBD) but also for systemic delivery of therapeutics. Intestinal myeloperoxidase (MPO) determination could be used to estimate the average level of inflammation in colon as well as to determine the efficacy of drugs to be used in the treatment of inflammatory bowel diseases or study the specificity of dosage forms to be used for colonic targeting of anti-inflammatory drugs. Colonic prodrug sulfasalazine (SASP) gets metabolized to give 5-aminosalicylic acid (5-ASA), which is the active portion of SASP. However, when given orally, 5-ASA is absorbed in upper part of gastrointestinal tract (GIT) and not made available in colon. In the present study, colon-targeted delivery of 5-ASA was achieved by formulating tablets with two natural polymers namely guar gum and pectin using compression coating method. Colonic specificity of 5-ASA tablets (prepared using guar gum and pectin as polymers) was evaluated in vitro using simulated fluids mimicking in vivo environment as well as in vivo method using chemically (2,4,6-trinitrobenzenesulfonic acid and acetic acid)-induced colitis rat model. Both colon-specific formulations of 5-ASA (guar gum and pectin) were observed to be more effective in reducing inflammation in chemically induced colitis rat models when compared to colon-specific prodrug sulfasalazine as well as conventional 5-ASA administered orally.KEY WORDS: colitis, colon-specific drug delivery, myeloperoxidase     

Development and Validation of a Discriminating <Emphasis Type="Italic">In Vitro</Emphasis> Dissolution Method for a Poorly Soluble Drug,Olmesartan Medoxomil: Comparison Between Commercial Tablets

A dissolution test for tablets containing 40 mg of olmesartan medoxomil (OLM) was developed and validated using both LC-UV and UV methods. After evaluation of the sink condition, dissolution medium, and stability of the drug, the method was validated using USP apparatus 2, 50 rpm rotation speed, and 900 ml of deaerated H₂O + 0.5% sodium lauryl sulfate (w/v) at pH 6.8 (adjusted with 18% phosphoric acid) as the dissolution medium. The model-independent method using difference factor (f ₁) and similarity factor (f ₂), model-dependent method, and dissolution efficiency were employed to compare dissolution profiles. The kinetic parameters of drug release were also investigated. The obtained results provided adequate dissolution profiles. The developed dissolution test was validated according to international guidelines. Since there is no monograph for this drug in tablets, the dissolution method presented here can be used as a quality control test for OLM in this dosage form, especially in a batch to batch evaluation.     

Preparation and characteristics of high-amylose corn starch/pectin blend microparticles: A technical note

Summary and Conclusions  The HACS/pectin blend microparticles were prepared by spray-drying technique to obtain effective targeted drug release to the colon. The mean particle size of the micro-particles (plain and blend) that were prepared in the present study was between 5.8 and 7.3 μm. The microparticles were positively charged (ζ potential was in the range of 20.3 to 30.8), and the encapsulation efficiency was between 80.1% and 94.7%. The blending of HACS with pectin improved the encapsulation efficiency and decreased the drug dissolution in the gastric condition (pH 1.2) from the pectin-based microparticles. Results of the drug release study indicated that the colonic-controlled drug delivery could be obtained from spray-dried HACS/pectin blend microparticles, and the drug release mechanism was found to be by diffusion or erosion or a combination of both. Published: September 30, 2005.     

Effect of degree of esterification of pectin and calcium amount on drug release from pectin-based matrix tablets

The aim of this work was to assess the effect of 2 formulation variables, the pectin type (with different degrees of esterification [DEs]) and the amount of calcium, on drug release from pectin-based matrix tablets. Pectin matrix tablets were prepared by blending indomethacin (a model drug), pectin powder, and various amounts of calcium acetate and then tableting by automatic hydraulic press machine. Differential scanning calorimetry, powder x-ray diffraction, and Fourier transformed-infrared spectroscopy studies of the compressed tablets revealed no drug-polymer interaction and the existence of drug with low crystallinity. The in-vitro release studies in phosphate buffer (United States Pharmacopeia) and tris buffer indicated that the lower the DE, the greater the time for 50% of drug release (T₅₀). This finding is probably because of the increased binding capacity of pectin to calcium. However, when the calcium was excluded, the pectins with different DEs showed similar release pattern with insignificant difference of T₅₀. When the amount of calcium acetate was increased from 0 to 12 mg/tablet, the drug release was significantly slower. However, a large amount of added calcium (ie, 24 mg/tablet) produced greater drug release because of the partial disintegration of tablets. The results were more pronounced in phosphate buffer, where the phosphate ions induced the precipitation of calcium phosphate. In conclusion, both pectin type and added calcium affect the drug release from the pectin-based matrix tablets.