Entrapment of drug-loaded ion-exchange particles within polymeric microparticles

Preparation of Sustained Release Formulation of Verapamil Hydrochloride Using Ion Exchange Resins

The purpose of this investigation was to formulate and evaluate the interaction between cation exchange resins and verapamil hydrochloride. The uptake studies were conducted using the rotating bottle apparatus. The Langmuir-like equation was applied to the experimental data and the maximum drug loading was determined from the Langmuir-like parameters. The drug-resin complexes were evaluated using XRD, SEM, and particle size analysis. Release studies were performed using USP dissolution apparatus 2. The resin with the lowest percentage of cross-linking had the highest uptake capacity. The percent increase in particle size due to complexation was found to be associated with drug loading; the highest drug loading had the highest increase in particle size. The X-ray diffraction patterns of the resins and the drug-resin complexes showed that they were both amorphous. The maximum drug release was approximately 40% when conventional dissolution testing was used. Results showed that sink conditions could not be maintained using conventional dissolution methods. Maximum drug release increased dramatically by increasing the volume of samples withdrawn and fresh dissolution medium added. Excellent correlation was obtained between sample volume and drug release rate with an R-value of 0.988. Particle diffusion-controlled model and film diffusion-controlled model were both applied to the experimental data. The results indicated that the rate-limiting step is the diffusion of the exchanging cations through the liquid film. The modified release formulation was prepared successfully and correlated very well with the USP monograph for verapamil hydrochloride extended release capsules.

Polymer-amino-functionalized silica composites for the sustained-release multiparticulate system

This study presents an interesting and promising strategy for producing an oral multiparticulate formulation of the sustained-release of diclofenac sodium (DS) consisting of subunits closed inside hard gelatin capsules (each capsule contains ~50mg of diclofenac sodium). The subunits in the form of beads were produced through the encapsulation of diclofenac sodium dispersed within a nondisintegrating polymer carrier by a silica gel functionalized with the 3-aminopropyl groups. The hybrid silica gel, which plays the role of enteric coating, was fabricated by the gelation of the liquid silica precursors mixture (i.e. tetraethoxysilane (TEOS) and (3-aminopropyl)triethoxysilane (APTES)) in the vapor phase of ammonia. The conducted studies reveal that the introduction of the hybrid silica gel into the solid DS dispersion facilitates prolonged release in the neutral environment of the intestine. Since the ability of the multiparticulate formulation to control the release of the drug depends on the properties of its subunits, studies involving the low temperature N₂ sorption, DSC analysis together with spectroscopic techniques (XRD, SEM, ²⁹Si MAS NMR) were conducted.

Vapour-phase method in the synthesis of polymer-ibuprofen sodium-silica gel composites

The study discusses the synthesis of polymer-silica composites comprising water soluble drug (ibuprofen sodium, IBS). The polymers selected for this study were poly(TRIM) and poly(HEMA-co-TRIM) produced in the form of permanently porous beads via the suspension-emulsion polymerization method. The acid and base set ternary composites were prepared by the saturation of the solid dispersions of drug (poly(TRIM)-IBS and/or poly(HEMA-co-TRIM)-IBS) with TEOS, and followed by their exposition to the vapour mixture of water and ammonia, or water and hydrochloric acid, at autogenous pressure. The conducted analyses reveal that the internal structure and total porosity of the resulting composites strongly depend on the catalyst which was used for silica precursor gelation. The parameters characterizing the porosity of both of the acid set composites are much lower than the parameters of the base set composites. Moreover, the basic catalyst supplied in the vapour phase does not affect the ibuprofen sodium molecules, whereas the acid one causes transformation of the ibuprofen sodium into the sodium chloride and a derivative of propanoic acid, which is poorly water soluble. The release profiles of ibuprofen sodium from composites demonstrate that there are differences in the rate and efficiency of drug desorption from them. They are mainly affected by the chemical character of the polymeric carrier but are also associated with the restricted swelling of the composites in the buffer solution after precipitation of silica gel.

Formulation and evaluation of meloxicam oral disintegrating tablet with dissolution enhanced by combination of cyclodextrin and ion exchange resins

CONTEXT

The bitter taste of drug is masked by the exchange of ionized drugs with counter ions of ion exchange resin, forming "resinate". Cyclodextrin reduces the unpleasant taste and enhances the drug solubility by encapsulating drug molecules into its central cavity.

OBJECTIVE

Oral disintegrating tablets (ODTs) using the combination of ion exchange resin and cyclodextrin was developed, to mask the bitter taste and enhance drug dissolution.

METHODS

Meloxicam (MX) was selected as a model drug. Formulations containing various forms of MX (free drug, MX-loaded resin or resinate, complexes of MX and 2-hydroxypropyl-β-cyclodextrin (HPβCD) or MX/HPβCD complexes, and a mixture of resinate and MX/HPβCD complexes) were made by direct compression. The ODTs were evaluated for weight variation, thickness, diameter, hardness, friability, disintegration time, wetting time, MX content, MX release, degree of bitter taste and stability.

RESULTS AND DISCUSSION

The tablet hardness was ∼3 kg/in(2), and the friability was <1%. Tablets formulated with resinate and the mixture of resinate and MX/HPβCD complexes disintegrated rapidly within 60 s, which is the acceptable limit for ODTs. These results were corresponded to the in vivo disintegration and wetting times. However, only tablets containing the mixture of resinate and MX/HPβCD complexes provided complete MX dissolution and successfully masked the bitter taste. In addition, this tablet was stable at least 6 months.

CONCLUSIONS

The combination of ion exchange resin and cyclodextrin could be used in ODTs to mask the bitter taste and enhance the dissolution of drugs that are weakly soluble in water.

Meloxicam taste-masked oral disintegrating tablet with dissolution enhanced by ion exchange resins and cyclodextrin

The purpose of this study was to develop taste-masked oral disintegrating tablets (ODTs) using the combination of ion exchange resin and cyclodextrin, to mask the bitter taste and enhance drug dissolution. Meloxicam (MX) was selected as a model drug with poor water solubility and a bitter taste. Formulations containing various forms of MX (free drug, MX-loaded resin or resinate, complexes of MX and 2-hydroxypropyl-β-cyclodextrin (HPβCD) or MX/HPβCD complexes, and a mixture of resinate and MX/HPβCD complexes) were made and tablets were prepared by direct compression. The ODTs were evaluated for weight variation, thickness, diameter, hardness, friability, disintegration time, wetting time, MX content, MX release, degree of bitter taste, and stability. The results showed that thickness, diameter, weight, and friability did not differ significantly for all of these formulations. The tablet hardness was approximately 3 kg/in.(2), and the friability was less than 1%. Tablets formulated with resinate and the mixture of resinate and MX/HPβCD complexes disintegrated rapidly within 60 s, which is the acceptable limit for ODTs. These results corresponded to the in vivo disintegration and wetting times. However, only tablets containing the mixture of resinate and MX/HPβCD complexes provided complete MX dissolution and successfully masked the bitter taste of MX. In addition, this tablet was stable at least 6 months. The results from this study suggest that the appropriate combination of ion exchange resin and cyclodextrin could be used in ODTs to mask the bitter taste of drug and enhance the dissolution of drugs that are weakly soluble in water.

Improvement of drug loading onto ion exchange resin by cyclodextrin inclusion complex

CONTEXT

Ion exchange resins have ability to exchange their counter ions for ionized drug in the surrounding medium, yielding "drug resin complex." Cyclodextrin can be applied for enhancement of drug solubility and stability.

OBJECTIVE

Cyclodextrin inclusion complex of poorly water-soluble NSAIDs, i.e. meloxicam and piroxicam, was characterized and its novel application for improving drug loading onto an anionic exchange resin, i.e. Dowex® 1×2, was investigated.

METHODS

β-Cyclodextrin (β-CD) and hydroxypropyl β-cyclodextrin (HP-β-CD) were used for the preparation of inclusion complex with drugs in solution state at various pH. The inclusion complex was characterized by phase solubility, continuous variation, spectroscopic and electrochemistry methods. Then, the drug with and without cyclodextrin were equilibrated with resin at 1:1 and 1:2 weight ratio of drug and resin.

RESULTS AND DISCUSSION

Solubility of the drugs was found to increase with increasing cyclodextrin concentration and pH. The increased solubility was explained predominantly due to the formation of inclusion complex at low pH and the increased ionization of drug at high pH. According to characterization studies, the inclusion complex was successfully formed with a 1:1 stoichiometry. The presence of cyclodextrin in the loading solution resulted in the improvement of drug loading onto resin.

CONCLUSIONS

Enhancing drug loading onto ion-exchange resin via the formation of cyclodextrin inclusion complex is usable in the development of ion-exchange based drug delivery systems, which will beneficially reduce the use of harmful acidic or basic and organic chemicals.

Simple preparation of coated resin complexes and their incorporation into fast-disintegrating tablets

Even though ion-exchange resins are good drug carriers to get sustained release properties, it may not be good enough only with themselves. For further sustained release effect, a diffusion barrier or coating on the resins' surface can be utilized. Initially, microencapsulation using a w/o/w double emulsion method was used to apply ethylcellulose (EC) onto the drug/resin complexes. Typical pharmaceutical waxes can be alternative materials to delay the drug release from the complex. After the coating, the coated resin particles were incorporated into fast-disintegrating tablets to get an idea regarding the effects of wet granulation and compression on the release. Among the different grades of ECs tested (Ethocel 20, 45, and 100), more viscous EC resulted in better morphologies and sustained release effects. Because the drug release rate was significantly dependent on the coating level, the release rate can be modified easily by changing different levels of the coating. The drug release rate was also strongly dependent on the granulation and compaction process as the coated particles were incorporated into the tablet dosage form. Among the tested waxes, stearic acid had an effect on the sustained release together with lubrication and wetting properties. Even though microencapsulation or wax coating may not be practical for real manufacturing, the results may give valuable information how to formulate sustained release dosage forms and their properties on the tablet preparation.

Preparation and evaluation of differently sulfonated styrene-divinylbenzene cross-linked copolymer cationic exchange resins as novel carriers for drug delivery

The differently sulfonated styrene-divinylbenzene cross-linked copolymer cationic exchange resins were prepared by oil-in-water polymerization and varied degrees of sulfonation. Several characteristics of the obtained resins were evaluated, i.e., Fourier transform infrared spectra, the ion-exchange capacity, microscopic morphology, size, and swelling. The resin characteristics were altered in relation to the degree of sulfonation, proving that differently sulfonated resins could be prepared. The behavior of chlorpheniramine (CPM) loading and in vitro release in the USP simulated gastric (SGF) and intestinal fluids (SIF) of the obtained resins were also evaluated. The CPM loaded in the resinates (drug-loaded resins) increased with the increasing degree of sulfonic group and hence the drug binding site in the employed resins. The CPM release was lower from the resins with the higher degree of sulfonic group due to the increase in the diffusive path depth. The CPM release was obviously lower in SGF than SIF because CPM, a weak base drug, ionized to a greater extent in SGF and then preferred binding with rather than releasing from the resins. In conclusion, the differently sulfonated resins could be utilized as novel carriers for drug delivery.

Taste masking by spray-drying technique

The purpose of this research was to develop the taste-masked microspheres of intensely bitter drug ondansetron hydrochloride (OSH) by spray-drying technique. The bitter taste threshold value of OSH was determined. Three different polymers viz. Chitosan, Methocel E15 LV, and Eudragit E100 were used for microsphere formation, and the effect of different polymers and drug-polymer ratios on the taste masking and release properties of microspheres was investigated. The microspheres were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, Drug loading, in vitro bitter taste evaluation, and drug-release properties. The taste masking was absent in methocel microspheres at all the drug-polymer ratios. The Eudragit microspheres depicted taste masking at 1:2 drug-polymer ratio whereas with Chitosan microspheres the taste masking was achieved at 1:1 drug-polymer ratio. The drug release was about 96.85% for eudragit microspheres and 40.07% for Chitosan microspheres in 15 min.

Preparation of Codeine-Resinate and Chlorpheniramine-Resinate Sustained-Release Suspension and its Pharmacokinetic Evaluation in Beagle Dogs

Using ion exchange resins (IERs) as carriers, a dual-drug sustained release suspension containing codeine, and chlorpheniramine had been prepared to elevate drug safety, effectiveness and conformance. The codeine resinate and chlorpheniramine resinate beads were prepared by a batch process and then impregnated with Polyethylene glycol 4000 (PEG 4000), respectively. The PEG impregnated drug resinate beads were coated with ethylcellulose as the coating polymer and di-n-butyl-phthalate as plasticizer in ethanol and methylene chloride mixture by the Wurster process. The coated PEG impregnated drug resinate beads were dispersed in an aqueous suspending vehicle containing 0.5% w/w xanthan gum and 0.5% w/w of hydroxypropylmethylcellulose of nominal viscosity of 4000 cps, obtaining codeine resinate and chlorpheniramine resinate sustained-release suspension (CCSS). Codeine phosphate and chlorpheniramine maleate were respectively loaded onto AMBERLITE IRP 69, and PEG 4000 was used to impregnate drug resinate beads to maintain their geometry. Ethylcellulose with di-n-butyl-phthalate in ethanol and methylene chloride mixture for the coating of drug resinate beads was performed in Glatt fluidized bed coater, where the coating solution flow rate was 8-12 g/min, the inlet air temperature was 50-60 degrees C, the outlet air temperature was 32-38 degrees C, the atomizing air pressure was 2.0 bar and the fluidized air pressure was adjusted as required. Few significant agglomeration of circulating drug resinate beads was observed during the operation. The film weight gained 20% w/w and 15% w/w were suitable for the PEG impregnated codeine resinate and chlorpheniramine resinate beads, respectively. Residual solvent content increased with coating level, but inprocess drying could reduce residual solvent content. In the present study, the rates of drug release from both drug resinate beads were measured in 0.05 M and 0.5M KCl solutions. The increased ionic strength generally accelerated the release rate of both drugs. But the release of codeine from its resinate beads was much more rapid than chlorpheniramine released from its resinate beads in the same ionic strength release medium. The drug release specification of the CCSS, where release mediums were 0.05 M KCl solution for codeine and 0.5 M KCl solution for chlorpheniramine, was established to be in conformance with in vivo performance. Relative bioavailability and pharmacokinetics evaluation of the CCSS, using commercial immediate-release tablets as the reference preparation, were performed following a randomized two-way crossover design in beagle dogs. The drug concentrations in plasma were measured by a validated LC-MS/MS method to determine the pharmacokinetic parameters of CCSS. This LC-MS/MS method demonstrated high accuracy and precision for bioanalysis, and was proved quick and reliable for the pharmacokinetic studies. The results showed that the CCSS had the longer value of Tmax and the lower value of Cmax, which meant an obviously sustained release effect, and its relative bioavailability of codeine and chlorpheniramine were (103.6 +/- 14.6)% and (98.1 +/- 10.3)%, respectively, compared with the reference preparation. These findings indicated that a novel liquid sustained release suspension made by using IERs as carriers and subsequent fluidized bed coating might provide a constant plasma level of the active pharmaceutical ingredient being highly beneficial for various therapeutic reasons.

Sustained release of propranolol hydrochloride based on ion-exchange resin entrapped within polystyrene microcapsules

Propranolol-HCl, a water soluble drug, was bound to Indion 254, a cation exchange resin, and the resulting resinate was microencapsulated with polystyrene using an oil-in-water emulsion-solvent evaporation method with a view to achieve prolonged drug release in simulated gastric and intestinal fluid. The effect of various formulation parameters on the characteristics of the microcapsules was studied. The diameter of the resinate-loaded polystyrene microcapsules increased with increase in the concentration of emulsion stabilizer and coat/core ratio and decreased with increase in the volume of organic disperse phase. The variation in the size of the microcapsules appeared to be related with the inter-facial viscosity which was influenced by the viscosity of both the aqueous dispersion medium and the organic disperse phase. The resinate encapsulation efficiency and hence the drug entrapment efficiency of the microcapsules increased with increase in the concentration of emulsion stabilizer and coat/core ratio and decreased with increase in the volume of organic disperse phase. These characteristics were found to depend on the extent of formation of fractured microcapsules and subsequent partitioning of the resinate into the aqueous dispersion medium. The degree of fracture on the microcapsules depended on the viscosity of the aqueous dispersion medium and the organic disperse phase. The uncoated resinate discharged the drug quite rapidly following the typical particle diffusion process. Although the desorption of the drug from the resinate was independent of pH of the dissolution media, increase in ionic strength increased the drug desorption. On the other hand, release of drug from the coated resinate was considerably prolonged and followed a diffusion controlled model. The prolongation of drug release was dependent on the uniformity of coating which was influenced by the formulation parameters. The drug release from the microcapsules was also found to be independent of pH of the dissolution media and increased with increase in ionic strength. The pH-independent release of the drug from both the uncoated and microencapsulated resinate was due to pH-independent solubility of the drug and high equilibrium concentration of the resinate in both the dissolution media. Polystyrene appeared to be a suitable polymer to provide prolonged release of propranolol independent of pH of the dissolution media.

Suspensions of prolonged-release diclofenac-Eudragit® and ion-exchange resin microcapsules: II. Improved dissolution stability

PURPOSE

The stability of prolonged release 100 microm -size ion-exchange resin (IER) diclofenac microcapsules (prepared by the Wurster process) and coated with Eudragit RS30D was evaluated using dissolution analysis.

METHODS

The IER microcapsules were suspended in 0.1% methylcellulose and stored at 23 and 37 degrees C and the dissolution study conducted over a 6-month period. The surface morphology of the microcapsules was examined using scanning electron microscopy (SEM).

RESULTS

The dissolution of the suspensions stored at 23 degrees C on day 1 or 7 and was similar to that of day 30 with slightly faster dissolution on day 60. In contrast, release from suspensions stored at 37 degrees C decreased with storage. The decrease in dissolution with increased temperature was possibly due to the polymer relaxation (micromelting) that was enough to seal the drug within the matrix, resulting in slow dissolution. SEM of the suspended microcapsules correlated with the dissolution data, i.e. the surfaces of microcapsule stored at 37 degrees C showed decreased roughness or smoothening and closing of pores with time and, hence, retardation of drug release, compared with samples stored at 23 degrees C. The dissolution kinetics (shown by the linearity of Bt vs. time profiles) indicated that release mechanism was diffusion.

CONCLUSIONS

The suspensions of diclofenac IER microcapsules were stable up to 30 days at ambient temperature, which makes the formulation potentially useful as reconstitutable product.

Development and evaluation of polyethyleneimine-treated calcium alginate beads for sustained release of diltiazem

The objective of this investigation is to develop a multi-unit sustained release dosage form of a water soluble drug from a completely aqueous environment avoiding the use of any organic solvent. The drug was complexed with resin and calcium alginate or polyethyleneimine-treated calcium alginate beads loaded with the resinate were prepared by a ionic/polyelectrolyte complexation method. The effect of different formulation variables on the characteristics of the beads was investigated. Although the drug release from spherical and smooth-surfaced calcium alginate beads in both acidic and alkaline dissolution media were slower than those obtained from plain resinate, none of the variables were found to prolong the drug release considerably due to rapid swelling and disintegration of calcium alginate beads in alkaline medium. On the other hand, drug release from polyethyleneimine-treated calcium alginate beads in acidic medium did not increase appreciably following a burst release. However, in alkaline medium, the drug release was found to increase gradually and extend over a different period of time depending on the intensity of polyethyleneimine treatment. Scanning electron micrographs revealed the formation of a dense membrane around the resinate-loaded calcium alginate matrix. The membrane appeared to be responsible for reduced swelling and protracted disintegration of the beads resulting in slow release of the drug. The results indicate that sustained release of a water soluble drug from polyethyleneimine-treated calcium alginate beads could be achieved by adjusting the formulation variables.

Preparation and In Vitro Release of Dual-Drug Resinates Containing Equivalent Content Dextromethorphan and Diphenhydramine

The dual-drug resinate containing equivalent content of dextromethorphan hydrobromide (DTM) and diphenhydramine hydrochloride (DPH) was developed and characterized. To achieve this specific resinate, a procedure of simultaneous dual-drug loading using loading solutions composed of different proportions of DTM and DPH was performed and a dual-drug loading diagram was constructed to determine the equivalent drug loading solution (ELS) and also the estimated equivalent drug content (EQC). The effects of resin crosslinkage, overall drug concentration of the loading solution, and temperature during drug loading on the values of ELS and EQC were assessed. The increased overall drug concentration from 0.25 to 1.0% w/v elevated the EQC values from 18 to 35% w/w for low crosslinked resins (Dowex 50 W x 2 and x 4), and from 18 to 27% w/w for high crosslinked resin (Dowex 50 W x 8). It also changed the values of ELS from 0.50 to 0.48 for the low crosslinked resins, and 0.50 to 0.55 for the high crosslinked resin. For the high crosslinked resin, the applied heat from 35 to 65 degrees C further increased the values of EQC from 27 to 32% w/w, and changed the values of ELS in the reverse direction from 0.55 to 0.48. However, the heat did not exert significant effects on the values of EQC and ELS for the low crosslinked resins. Different batches of dual-drug resinates prepared from the determined ELS provided the resultant resinates with equivalent contents of DTM and DPH which were very close to the estimated EQC. The drug release from the resinates was performed in 0.05, 0.1, 0.2, and 0.4 N of KCl solutions. The increased ionic strength generally accelerated the release of both drugs except for 0.4 N KCl solution in which the drug release from the resinates of high crosslinkage was decreased. The congestion on the outward movement of drugs through the high crosslinked matrix might cause the delay of drug release. In conclusion, the release study demonstrated that the dual-drug resinate using a suitable crosslinked resin could be used for extended delivery of two combined drugs with the equivalent therapeutic dose.

Taste mask, design and evaluation of an oral formulation using ion exchange resin as drug carrier

The purpose of this research was to mask the bitter taste of Diphenhydramine Hydrochloride (DPH) using cation exchange resins. Indion 234 and Tulsion 343 that contained crosslinked polyacrylic backbone were used. The drug resin complexes (DRC) were prepared by batch process by taking drug: resin ratios 1:1, 1:2, and 1:3. The optimum drug: resin ratio and the time required for maximum complexation was determined. The drug resinates were evaluated for the drug content, taste, micromeritic properties drug release and X-ray diffraction (PXRD). Effervescent and dispersible tablets were developed from optimum drug: resin ratios of 1:2 and 1:1. The formulations were evaluated for uniformity of dispersion, disintegration time, and in vitro dissolution. The X-ray diffraction study confirmed the monomolecularity of entrapped drug in the resin beads. The taste evaluation depicted the successful taste masking of DPH with drug resin complexes. The drug release of 95% in 15 min was observed for effervescent and dispersible tablets.

Wet granulation as innovative and fast method to prepare controlled release granules based on an ion‐exchange resin

The goal of this work was to evaluate the suitability of wet granulation as an innovative and fast method for the preparation of granules containing a drug-resin complex (resinate), having cholestyramine as resin and potassium diclofenac (KD) as drug. Resinate and granules were prepared directly by steam granulation in high shear mixer (method A), using two different amount of resin (granules 1 and 2). For comparison granules 1 were also prepared by conventional batch method followed by steam granulation (method B). All granules showed quite irregular shape, main size fractions between 75 and 500 microm, good flowability and uniform KD distribution. Granules 1A exhibited controlled release profiles at pH 7.4, while granules 2A showed a burst effect due to KD free crystals. FT-IR studies confirmed the complete complexation between resin and KD during the granulation process with method A for granules 1. Finally, the dissolution test of granules 1A in different media revealed a controlled drug release in 12 h, providing the utility of this system for enteric drug delivery. Granules 1B evidenced similar characteristics to those of granules 1A; the drawback of the multistep procedure was related to the long processing time.

Preparation and in vitro evaluation of polystyrene-coated diltiazem-resin complex by oil-in-water emulsion solvent evaporation method

The purpose of this study was to examine the suitability of polystyrene-coated (PS-coated) microcapsules of drug-resin complex for achieving prolonged release of diltiazem-HCl, a highly water-soluble drug, in simulated gastric and intestinal fluid. The drug was bound to Indion 254, a cation-exchange resin, and the resulting resinate was microencapsulated with PS using an oil-in-water emulsion-solvent evaporation method. The effect of various formulation parameters on the characteristics of the microcapsules was studied. Mean diameter and encapsulation efficiency of the microcapsules rose with an increase in the concentration of emulsion stabilizer and the coat/core ratio, while the same characteristics tended to decrease with an increase in the volume of the organic disperse phase. The desorption of drug from the uncoated resinate was quite rapid and independent of the pH of the dissolution media. On the other hand, the drug release from the microcapsules was prolonged for different periods of time depending on the formulation parameters and was also found to be independent of the pH of the dissolution media. Both the encapsulation efficiency and the retardation of drug release were found to be dependent on the uniformity of coating, which in turn was influenced by the formulation parameters. Kinetic studies revealed that the desorption of drug from the resinate obeyed the typical particle diffusion process, whereas the drug release from the microencapsulated resinate followed the diffusion-controlled model in accordance with the Higuchi equation. PS appeared to be a suitable polymer to provide prolonged release of diltiazem independent of the pH of the dissolution media.

Effect of polysulfonate resins and direct compression fillers on multiple-unit sustained-release dextromethorphan resinate tablets

The purpose of this work was to investigate the effect of different polysulfonate resins and direct compression fillers on physical properties of multiple-unit sustained-release dextromethorphan (DMP) tablets. DMP resinates were formed by a complexation of DMP and strong cation exchange resins, Dowex 50 W and Amberlite IRP69. The tablets consisted of the DMP resinates and direct compression fillers, such as microcrystalline cellulose (MCC), dicalcium phosphate dihydrate (DCP), and spray-dried rice starch (SDRS). Physical properties of tablets, such as hardness, disintegration time, and in vitro release, were investigated. A good performance of the tablets was obtained when MCC or SDRS was used. The use of rod-like and plate-like particles of Amberlite IRP69 caused a statistical decrease in tablet hardness, whereas good tablet hardness was obtained when spherical particle of Dowex 50 W was used. The plastic deformation of the fillers, such as MCC and SDRS, caused a little change in the release of DMP. A higher release rate constant was found in the tablets containing DCP and Dowex 50 W, indicating the fracture of the resinates under compression, which was attributable to the fragmentation of DCP. However, the release of DMP from the tablets using Amberlite IRP69 was not significantly changed because of the higher degree of cross-linking of the resinates, which exhibited more resistance to deformation under compression. In conclusion, the properties of polysulfonate resin, such as particle shape and degree of cross-linking, and the deformation under compaction of fillers affect the physical properties and the drug release of the resinate tablets.

Cellulose acetate butyrate microcapsules containing dextran ion-exchange resins as self-propelled drug release system

Sulfopropylated dextran microspheres (SP-Ms), (Dm = 80 microm) loaded with a water soluble drug (Tetracycline HCl), were included in cellulose acetate butyrate (CAB) microcapsules. Spherical CAB microcapsules were obtained by oil in water (o/w) solvent evaporation method in the presence of an inert solvent as cyclohexane (CyH) or n-hexane (N-Hex), and different excipients (Phospholipon, Tween, Span, Eudragit RS 100). Chloroform was found to be the best solvent for the preparation of the microcapsules. Also, the sphericity as well as the porosity of the microcapsules was controlled by the presence of an inert solvent. The final concentration of the drug in CAB microparticles was up to 25% (w/w). The key factors for the successful preparation were also the viscosity of the polymer, while the wettability of the resulted microcapsules, the temperature of the preparation, and the porosity have modulated the release of the drug. The higher is the amount of encapsulated microspheres the thinner is the CAB wall between the compartments created by their incorporation. When these microspheres come in contact with the release medium, the pressure created by their swelling breaks the polymer film and the drug starts to be released. The more drug is released in phosphate buffer the higher is the swelling degree of the encapsulated ion exchange resins and the force created by their supplementary swelling will break the more resistants walls. In this way a self-propelled drug release is achieved, until almost all drug was eliberated.

Polymer microspheres for controlled drug release

Polymer microspheres can be employed to deliver medication in a rate-controlled and sometimes targeted manner. Medication is released from a microsphere by drug leaching from the polymer or by degradation of the polymer matrix. Since the rate of drug release is controlled by these two factors, it is important to understand the physical and chemical properties of the releasing medium. This review presents the methods used in the preparation of microspheres from monomers or from linear polymers and discusses the physio-chemical properties that affect the formation, structure, and morphology of the spheres. Topics including the effects of molecular weight, blended spheres, crystallinity, drug distribution, porosity, and sphere size are discussed in relation to the characteristics of the release process. Added control over release profiles can be obtained by the employment of core-shell systems and pH-sensitive spheres; the enhancements presented by such systems are discussed through literature examples.

Swelling and drug release behavior of tablets coated with aqueous hydroxypropyl methylcellulose phthalate (HPMCP) nanoparticles

Organic solvent-based enteric coating technology using hydroxypropyl methyl cellulose phthalate (HPMCP) has been developed for many years due to low water solubility of HPMCP. In this work, aqueous HPMCP nanoparticles (HPMCP-NPs) were prepared by neutralization emulsification method using HPMCP powder and ammonium hydroxide (NH(4)OH) in the absence of any organic solvent and emulsifier. Tablets for enteric use were coated with HPMCP-NP dispersions having different degree of neutralization that was manipulated by ion-exchange process. Disintegration and dissolution behavior of coated tablets were investigated using UV-visible spectrophotometer based on USP method (pH 1.2 and at 37 degrees C) and simulated intestinal fluid (pH 6.8 and at 37 degrees C for 60 min), respectively. The ion-exchange process, which was directly achieved by the protonation of dissociated carboxylic acid group of the aqueous HPMCP-NPs, was introduced as a useful way to control the release rate of drug and hydrophobic nature of HPMCP coating layer with a view for pharmaceutical application. The drug release and swelling were increased with increase in conductivity of aqueous HPMCP-NPs. On the other hand, particle size and polydispersity were decreased with increase in degree of neutralization.

Ion-exchange resins: carrying drug delivery forward

Ion-exchange resins (IER), or ionic polymer networks, have received considerable attention from pharmaceutical scientists because of their versatile properties as drug-delivery vehicles. In the past few years, IER have been extensively studied in the development of novel drug-delivery systems (DDSs) and other biomedical applications. Some of the DDSs containing IER have been introduced into the market. In this review, the applications of IER in drug delivery research are discussed.

Molecular properties of propranolol hydrochloride prepared as drug-resin complexes

Drug-resin complexes, as well as physical dispersions, containing varying contents of propranolol were prepared. The molecular properties of samples were investigated by differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), and infrared (IR) spectroscopy. In addition, the USP paddle method was used to determine the release behavior of drug from various formulations prepared from the samples. The data from DSC and XRPD indicated that the molecular state of drug in the complexes was amorphous, whereas that in the physical dispersions exhibited the crystalline state of pure drug. These results suggested that the molecule of drug prepared as drug-resin complexes was monomolecularly dispersed in the resin bead. The IR study provided evidence that demonstrated the interaction between the drug and resin in the complexes. The release behavior of drug from the complexes was governed by the cross-linkage structure and equilibrium treatment of drug exchange of resin.

Design and in vitro evaluation of adhesive matrix for transdermal delivery of propranolol

Propranolol hydrochloride, a water-soluble drug, was incorporated in three transdermal delivery systems using three polymers (hydroxypropylmethylcellulose, polyisobutylene and Ucecryl MC808). The influence of different factors (polymeric material, matrix thickness, drug content, thickness of the adhesive layer and presence of a dissolution enhancer) was investigated. Microscopic observations and DSC thermograms have permitted to demonstrate that propranolol was essentially dissolved in the HPMC matrix and dispersed in the two other matrix types. In vitro dissolution study was carried out according to European Pharmacopoeia. Release from HPMC matrices without adhesive coating was fast. Release from these matrices became more regular (reduction of the burst effect) and slow when they are coated with a 12 microm thick Ucecryl layer. Release from different PIB matrices was too slow to be suitable as TDDS for propranolol. The best release modulation was obtained from Ucecryl matrices. In all matrices types, propylene glycol accelerated propranolol release rate. The kinetic of drug release from most matrix types was more closely described by the square-root model (Higuchi).