Mathematical evaluation of in vitro release profiles of hydroxypropylmethylcellulose matrix tablets containing carbamazepine associated to β-cyclodextrin

Optimization of the different phases of the freeze-drying process of solid lipid nanoparticles using experimental designs

In this work, the effect of cryoprotectant type and concentration and freeze-drying process parameters were evaluated to determine an optimal freeze-drying process for celecoxib-loaded solid lipid nanoparticles. Different cryoprotectants were tested at different weight ratios (cryoprotectant:lipid). Trehalose, maltose, and sucrose at a 1:1 wt ratio were selected for further use in optimizing the freeze-drying process through experimental designs to accurately define the freezing, primary, and secondary drying conditions of the freeze-drying process. The optimal freeze-dried solid lipid nanoparticles were subjected to a 6-month stability study at either 4 °C or 25 °C/60% RH, resulting in significant growth when the nanoparticles were stored at 25 °C/60% RH. The best results were obtained with trehalose as a cryoprotectant and storage at 4 °C. Furthermore, the in vitro release data showed a significantly different release profile before and after optimization of the freeze-drying process, suggesting that the optimization of the freeze-drying process affected the quality of the freeze-dried cake. In conclusion, a successful lyophilization process was obtained due to rational cooperation between a good formulation and optimal conditions in the freezing and drying steps. This yielded an acceptable non-collapsed freeze-dried cake with good redispersibility, minimal changes in physicochemical properties, and long-term stability at 4 °C.

Spheronized drug microcarrier system from canola straw lignin

Inhomogeneous lignin from a canola (rapeseed) straw was isolated and valorized as regularly shaped spherical microparticles for drug delivery formulations. Lignin with a purity of 83% and broad molecular weight distribution (Ð > 5.0) was extracted by alkali pulping and acetylated to increase spheronization ability. Lignins with high degrees of acetylation (0.76 and 0.89) were successfully assembled into microparticles with uniform sizes (approximately 2 μm) and smooth spherical surfaces via solvent-antisolvent precipitation. Hydrophobic coumarin 153 and positively charged ciprofloxacin were used as model drugs to assess the encapsulation and release performance of lignin microparticles. Highly acetylated lignin microparticles displayed encapsulation efficiencies of 89.6% for coumarin 153% and 90.6% for ciprofloxacin. Scanning electron microscope images showed that coumarin 153 was encapsulated in the hydrophobic core, while ciprofloxacin was adsorbed on the less hydrophobic shell. The synthesis of lignin microcarriers not only provides a facile approach to utilizing waste canola straw lignin for drug delivery matrices but also has the potential to serve as an alternative lignin powder feedstock for bio-based materials.

The influence on the oral bioavailability of solubilized and suspended drug in a lipid nanoparticle formulation: in vitro and in vivo evaluation

The present study investigated the oral bioavailability of celecoxib when incorporated into solid lipid nanoparticles either dissolved or suspended. In vitro drug release in different media, in vivo performance, and in vitro-in vivo correlation were conducted. The results revealed that the compound was successfully encapsulated into the nanocarriers with good physicochemical properties for oral administration. The in vitro release profiles followed the Weibull model, with significant differences between the formulations containing the solubilized and the suspended compound. Furthermore, in vitro release data could be used to rank the observed in vivo bioavailability. The relative bioavailability of celecoxib from the solid lipid nanoparticles was 2.5- and 1.8-fold higher for the drug solubilized and suspended solid lipid nanoparticle formulation, respectively, when compared to the celecoxib reference. A significant difference was observed between the plasma concentration-time profiles and pharmacokinetic parameters for the three investigated formulations. Finally, this investigation displayed promising outcomes that both solubilized and suspended celecoxib in the lipid core of the solid lipid nanoparticles offers the potential to improve the compound's oral bioavailability and thereby reduce the dosing frequency.

Weibull Modeling of Controlled Drug Release from Ag-PMA Nanosystems

Traditional pharmacotherapy suffers from multiple drawbacks that hamper patient treatment such as antibiotic resistances or low drug selectivity and toxicity during systemic applications. Some functional hybrid nanomaterials are designed to handle the drug release process under remote-control. More attention has recently been paid to synthetic polyelectrolytes for their intrinsic properties which allow them to rearrange into compact structures, ideal to be used as drug carriers or probes influencing biochemical processes. The presence of Ag nanoparticles (NPs) in the Poly methyl acrylate (PMA) matrix leads to an enhancement of drug release efficiency, even using a low-power laser whose wavelength is far from the Ag Surface Plasmon Resonance (SPR) peak. Further, compared to the colloids, the nanofiber-based drug delivery system has shown shorter response time and more precise control over the release rate. The efficiency and timing of involved drug release mechanisms has been estimated by the Weibull distribution function, whose parameters indicate that the release mechanism of nanofibers obeys Fick's first law while a non-Fickian character controlled by diffusion and relaxation of polymer chains occurs in the colloidal phase.

Formulation of Chewable Tablets Containing Carbamazepine-β-cyclodextrin Inclusion Complex and F-Melt Disintegration Excipient. The Mathematical Modeling of the Release Kinetics of Carbamazepine

Due to its low solubility, carbamazepine (CBZ) exhibits slow and incomplete release in the gastrointestinal tract and, hence, variable pharmacokinetics and pharmacodynamic effect. Lots of methods have been devised to improve its solubility, the large number of proposed solutions being a sign that the problem is not yet satisfactorily solved. The persistent problem is that predictable release kinetics, an increased rate but within defined limits, are required to avoid high absorption variability. This paper presents a synthesis of a carbamazepine-β-cyclodextrin inclusion complex (CBZ-β-CD), the characterization of the physical mixture, CBZ, β-CD and the CBZ-β-CD inclusion complex using Fourier transform infrared spectroscopy, scanning electron microscopy, simultaneous thermal analysis and X-ray diffraction, formulation of chewable tablets, determination of the dissolution of carbamazepine in medium containing 1% sodium lauryl sulfate (LSS), and in simulated saliva (SS), mathematical modeling of release kinetics. The kinetics of total CBZ release from tablets containing CBZ-β-CD and super-disintegrant F-Melt in both SS and LSS followed two steps: a burst release in the first minutes and a slower release in intervals up to 60 min. The release in the second phase has been well described by the Higuchi and Peppas models, which advocate a controlled release by combined diffusion and with some phenomena of swelling and relaxation of the matrix generated by the crospovidone component of the F-Melt excipient.

Application of solid lipid nanoparticles as a long-term drug delivery platform for intramuscular and subcutaneous administration: In vitro and in vivo evaluation

The purpose of this work was to evaluate solid lipid nanoparticles (SLNs) as a long acting injectable drug delivery platform for intramuscular and subcutaneous administration. SLNs were developed with a low (unsaturated) and high (supersaturated) drug concentration at equivalent lipid doses. The impact of the drug loading as well as the administration route for the SLNs using two model compounds with different physicochemical properties were explored for their in vitro and in vivo performance. Results revealed that drug concentration had an influence on the particle size and entrapment efficiency of the SLNs and, therefore, indirectly an influence on the C_max/dose and AUC/dose after administration to rats. Furthermore, the in vitro drug release was compound specific, and linked to the affinity of the drug compounds towards the lipid matrix and release medium. The pharmacokinetic parameters resulted in an increased t_max, t_1/2 and mean residence time (MRT) for all formulations after intramuscular and subcutaneous dosing, when compared to intravenous administration. Whereas, the subcutaneous injections performed better for those parameters than the intramuscular injections, because of the higher blood perfusion in the muscles compared with the subcutaneous tissues. In conclusion, SLNs extend drug release, need to be optimized for each drug, and are appropriate carriers for the delivery of drugs that require a short-term sustained release in a timely manner.

Design of taste-masked swellable drug particles using dry-coating technology with mechanical curing

A novel dry coating technique for fine particles that does not require any liquids has been developed. Swellable ordered-mixed drug particles (Swell-OM-spheres, SOS), using a modified starch as the core particle and a drug coating layer have been previously developed. In the present work, SOS particles were further processed to generate 100-μm taste-masking particles using an all dry coating processes. SOS particles were coated with a gastric-soluble powder using a mechanical powder processor. The coated particles (CPs) were subsequently heated while rotating in the same powder processor, completing film formation by a process termed dynamic curing. As a control, conventional film formation (static curing) was performed using a drying oven. The CPs obtained by these two curing processes had distinct appearances, but exhibited equivalent dissolution suppression effects in a medium at pH 6.8 (the pH of the oral cavity). The suppression effect was further improved by adding a plasticizer to the coating powder, even though a lower heating temperature was required. Orally disintegrating tablets incorporating these CPs exhibited excellent taste-masking performance, i.e., suppressing taste in saliva while accelerating dissolution in gastric juice. The dissolution behavior indicated that the CPs can provide an ON/OFF switching function in drug release.

Mathematical Models as Tools to Predict the Release Kinetic of Fluorescein from Lyotropic Colloidal Liquid Crystals

In this study, we investigated the release kinetic of fluorescein from colloidal liquid crystals made from monoglyceride and different non-ionic surfactants. The crystals were physicochemically characterized and the release experiments were carried out under the sink conditions, while mathematical models were described as extrapolations from solutions of the diffusion equation, in different initial and boundary conditions imposed by pharmaceutical formulations. The diffusion equation was solved using Laplace and Fourier transformed functions for release kinetics from infinite reservoirs in a semi-infinite medium. Solutions represents a general square root law and can be applied for the release kinetic of fluorescein from lyotropic colloidal liquid crystals. Akaike, Schwartz, and Imbimbo criteria were used to establish the appropriate mathematical model and the hierarchy of the performances of different models applied to the release experiments. The Fisher statistic test was applied to obtain the significance of differences among mathematical models. Differences of mathematical criteria demonstrated that small or no significant statistic differences were carried out between the various applied models and colloidal formulations. Phenomenological models were preferred over the empirical and semi-empirical ones. The general square root model shows that the diffusion-controlled release of fluorescein is the mathematical models extrapolated for lyotropic colloidal liquid crystals.

Ibuprofen Release from Poly(ethyl cyanoacrylate) Nanoparticles Prepared by Semicontinuous Heterophase Polymerization

Ibuprofen-loaded poly(ethyl cyanoacrylate) nanoparticles were prepared by semicontinuous heterophase polymerization of ethyl cyanoacrylate in the presence of ibuprofen; different surfactant concentration, pH, and temperature were used. Particle size was measured by quasi-light scattering and transmission electron microscopy, while the amount of drug released was determined by UV spectroscopy. Nanoparticles with diameters between 10 and 58 nm, loaded with ibuprofen, were obtained. The smallest particles and the higher drug loading were obtained at the highest pH tested. The analysis of the release data showed that the drug release profiles correspond to the Weibull model. Moreover, it was found that most of the ibuprofen is released within the first 80–120 min; initially the release rate is slow, but then it increases to finally decrease. This behavior contrasts with the reported burst of drug concentration in the plasma after oral administration of IB.

The influence of different long-circulating materials on the pharmacokinetics of liposomal vincristine sulfate

PURPOSE

This study was designed to improve the in vivo pharmacokinetics of long-circulating vincristine sulfate (VS)-loaded liposomes; three different long-circulating materials, chitosan, poly(ethylene glycol)-1,2-distearoyl sn-glycero-3-phosphatidylethanolamine (PEG-DSPE), and poly(ethylene glycol)-poly-lactide-co-glycolide (PEG-PLGA), were evaluated at the same coating molar ratio with the commercial product Marqibo(®) (vincristine sulfate liposome injection [VSLI]).

MATERIALS AND METHODS

VS-loaded liposomes were prepared by a pH gradient method and were then coated with chitosan, PEG-DSPE, or PEG-PLGA. Physicochemical properties, including the morphology, particle size, zeta potential, encapsulation efficiency (EE%), pH, drug loading, and in vitro release, were determined. Preservation stability and pharmacokinetic studies were performed to compare the membrane-coated liposomes with either commercially available liposomes or the VS solution.

RESULTS

The sphere-like morphology of the vesicles was confirmed by transmission electron microscope. Increased particle size, especially for the chitosan formulation, was observed after the coating process. However, the EE% was ~99.0% with drug loading at 2.0 mg/mL, which did not change after the coating process. The coating of long-circulation materials, except for chitosan, resulted in negatively charged and stable vesicles at physiological pH. The near-zero zeta potential exhibited by the PEG-DSPE formulation leads to a longer circulation lifetime and improved absorption for VS, when compared with the PEG-PLGA formulation. Compared with the commercial product, PEG was responsible for a higher plasma VS concentration and a longer half-life.

CONCLUSION

PEG-DSPE coating may be related to better absorption, based on the stability and a pharmacokinetic improvement in the blood circulation time.

Structural and silver/vanadium ratio effects on silver vanadium phosphorous oxide solution formation kinetics: Impact on battery electrochemistry

This study contains the first kinetic analyses of silver and vanadium solution formation from Ag_0.48VOPO₄·1.9H₂O and Ag₂VP₂O₈, in a non-aqueous battery electrolyte. The results presented here provide a framework for the quantitative and kinetic analyses of the dissolution of cathode materials which will aid the broader community in more fully understanding this battery failure mechanism.

Amphiphilic quasi-block copolymers and their self-assembled nanoparticles via thermally induced interfacial absorption in miniemulsion polymerization

A facile and nontoxic strategy for the preparation of amphiphilic quasi-block copolymers and nanoparticles has been developed utilizing miniemulsion polymerization.

Pulse release of doxazosin from hydroxyethylcellulose compression coated tablet: mechanistic and in vivo study

Chronotherapeutically programmed hydroxyethylcellulose (HEC) based compression coated doxazosin tablets were prepared and the influence of disintegrants croscarmellose sodium, L-hydroxypropylcellulose (L-HPC), gellan gum on drug release and in vivo performance were investigated. Infrared spectroscopy and differential scanning calorimetric studies did not indicate any excipient incompatibility in the tablets. The disintegrants induced a continuous water influx resulting in a rapid expansion of the membrane. The subsequent formation of fractures into the coats leads to a fast drug release after an initial lag time. Release rates indicated that croscarmellose sodium and L-HPC were directly proportional to their concentration in the formulations. In vitro optimized croscarmellose sodium-HEC matrix showed significantly faster (p < 0.05) drug release (t90% = 46 min) after an initial lag of 243 min. Disintegrant-HEC blended matrices were found significantly superior (p < 0.05) in terms of in vitro release and bioavailability in comparison to plain HEC matrices. Drug release kinetics followed modified power law and Weibull model (r > 0.99). The mechanism involved in release was anomalous transport and super case II transport with matrix swelling. The pulsatile tablets showed no changes either in physicochemical appearance, drug content or in dissolution pattern during its accelerated stability studies.

Pharmacokinetic delivery and metabolizing rate of nicardipine incorporated in hydrophilic and hydrophobic cyclodextrins using two-compartment mathematical model

The dispersion routes of cyclodextrin complexes with nicardipine (NC), such as hydrophilic hydroxypropyl-β-cyclodextrin (NC/HPβCD) and hydrophobic triacetyl-β-cyclodextrin (NC/TAβCD), through the body for controlled drug delivery and sustained release have been examined. The two-compartment pharmacokinetic model described the mechanisms of how the human body handles with ingestion of NC-cyclodextrin complexes in gastrointestinal tract (GI), distribution in plasma, and their metabolism in the liver. The model showed that drug bioavailability was significantly improved after oral administration of cyclodextrin complexes. The mathematical significance of this study to predict nicardipine delivery using pharmacokinetic two-compartment mathematical model with linear ordinary differential equations (ODE) approach represents a valuable tool to emphasize its effectiveness and metabolizing rate and diminish the side effects.

Cyclodextrin-crosslinked poly(acrylic acid): adhesion and controlled release of diflunisal and fluconazole from solid dosage forms

The controlled release of diflunisal and fluconazole from tablets made of novel polymers, poly(acrylic acid) (PAA) crosslinked with either β-cyclodextrin (βCD) or hydroxypropyl-βCD (HPβCD), was investigated and Carbopol 934P (Carbopol) was used as a highly crosslinked PAA for comparison. Diflunisal strongly associates with βCD-PAA and HPβCD-PAA polymers (Ka of 486 and 6,055 M(-1) respectively); thus, it was physically mixed into the conjugates and also precomplexed to identify whether decomplexation has any influence on release kinetics. Fluconazole has poor complexing ability (Ka of 34 M(-1) with HPβCD-PAA); thus, it was only tested as a physical mixture. Swelling and adhesion studies were conducted on all tablet combinations and adhesivity of the CD-PAA polymer tablets was maintained. Diflunisal release was much slower from HPβCD-PAA tablets than from βCD-PAA, suggesting that a higher degree of complexation retards release. The precomplexed diflunisal release was also slower than the physically mixed diflunisal of the corresponding conjugate. The release closely followed zero-order kinetics for HPβCD-PAA, but was more sigmoidal for βCD-PAA and especially Carbopol. Conversely, poorly associating fluconazole released in almost exactly the same way across both polymers and Carbopol, indicating that the release kinetics of poorly associating drugs are not influenced by the presence of cyclodextrins. In view of the varying profiles and release rates shown with diflunisal for the different polymers, the fluconazole data support the concept that adequate complexation can indeed modulate the release kinetics of drugs.

Comparative in vitro dissolution study of carbamazepine immediate-release products using the USP paddles method and the flow-through cell system

Dissolution profiles of four carbamazepine immediate-release generic products (200 mg tablets) and the reference product Tegretol® were evaluated using the USP paddles method and an alternative method with the flow-through cell system, USP Apparatus 4. Under official conditions all products met the Q specification, dissolution profiles of generic products were similar to the dissolution profile of the reference product (f 2 > 50) and model-independent parameters showed non significant differences to the reference product except mean dissolution time for product A (p < 0.05). On the other hand, when the flow-through cell system was used, none of the products met the pharmacopeial specification at 15 min and product A did not reach dissolution criteria at 60 min, dissolution profiles of all generic products were not similar to the reference product profile (f 2 < 50) and all model-independent parameters showed significant differences compared to the reference product (p < 0.05). Weibull's model was more useful for adjusting the dissolution data of all products in both USP apparatuses and Td values showed significant differences compared to the reference product (p < 0.05) when USP Apparatus 4 was used. These results indicate that the proposed method, using the flow-through cell system, is more discriminative in evaluating both, rate and extent of carbamazepine dissolution process from immediate-release generic products.

Alginate/hydrophobic HPMC (60M) particulate systems: new matrix for site-specific and controlled drug delivery

This study aimed to obtain site-specific and controlled drug release particulate systems. Some particulates were prepared using different concentrations of sodium alginate (Na-Alg) alone and others were formulated using different proportions of Na-Alg with hydroxypropyl methylcellulose (HPMC) stearoxy ether (60M viscosity grade), a hydrophobic form of conventional HPMC, using diclofenac potassium (DP) by ion-exchange methods. Beads were characterized by encapsulation efficiency, release profile, swelling, and erosion rate. The suitability of common empirical (zero-order, first-order and Higuchi) and semi-empirical (Ritger-Peppas and Peppas-Sahlin) models was studied to describe the drug release profile. The Weibull model was also studied. Models were tested by non-linear least-square curve fitting. A general purpose mathematical software (MATLAB) was used as an analysis tool. In addition, instead of the widely used linear fitting of log-transformed data, direct fitting was used to avoid any sort of truncation or transformation errors. The release kinetics of the beads indicated a purely relaxation-controlled delivery, referred to as case II transport. Weibull distribution showed a close fit. The release of DP from Na-Alg particulates was complete in 5-6 hours, whereas from Na-Alg hydrophobic HPMC particulate systems, release was sustained up to 10 hours. Hydrophobic HPMC with Na-Alg is an excellent matrix to formulate site-specific and controlled drug release particulate systems.

Synthesis and characterization of amphiphilic lipopolymers for micellar drug delivery

The objective of this study was to design lipopolymers for hydrophobic drug delivery. Poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate-graft-dodecanol) (PEG-PCD) lipopolymers were synthesized and characterized by (1)H NMR, FT-IR, GPC, and DSC. The critical micelle concentration (CMC) of PEG-PCD micelles was around 10(-8) M and decreased with increasing length of hydrophobic block. PEG-PCD micelles could efficiently load a model drug embelin into its hydrophobic core and significantly improve its solubility. The loading capacity was dependent on the polymer core structure, but the length of hydrophobic core had little effect. PEG-PCD formed both spherical and cylindrical micelles, which were dependent on the copolymer structure and composition. PEG-PCD lipopolymers with various hydrophobic core lengths showed similar drug release profiles, which were slower than that of poly(ethylene glycol)-block-poly(2-methyl-2-benzoxycarbonyl-propylene carbonate) (PEG-PBC) micelles. Embelin loaded PEG-PCD micelles showed significant inhibition of C4-2 prostate cancer cell proliferation, while no obvious cellular toxicity was observed for blank micelles.

Population in vitro-in vivo correlation model for pramipexole slow-release oral formulations

PURPOSE

To establish an in vitro-in vivo level A correlation (IVIVC) for pramipexole slow-release formulations.

METHODS

The IVIVC was developed based on data from an immediate-release (IR) and three slow-release (SR) formulations of pramipexole; a fourth SR formulation was used for validation purposes. In vitro dissolution profiles were obtained from all SR formulations. Fifteen volunteers received all pramipexole formulations in a randomized cross-over trial. Data were analyzed using the population modelling approach as implemented in NONMEM VI.

RESULTS

Dissolution profiles of the SR formulations were described by the Weibull model. The pharmacokinetics of the IR formulation were described by a two-compartment disposition model with first-order absorption. Difference between the in vivo and in vitro estimates of the release rate constants (k(d)) from the Weibull function suggests the release process occurs faster in vivo. Pharmacokinetic profiles for SR formulations were described based on the in vitro release model with k(d) increased in 0.058 h(-1) and the population pharmacokinetic model developed from the IR formulation.

CONCLUSION

A level A IVIVC was established and evaluated for the pramipexole SR formulations, which can be used in the future as a surrogate to avoid certain bioequivalence studies.

Influence of soluble and insoluble cyclodextrin polymers on drug release from hydroxypropyl methylcellulose tablets

BACKGROUND

The influence of beta-cyclodextrin (beta-CD) polymers on drug release from hydroxypropyl methylcellulose (HPMC) matrices has not been reported in the literature.

AIM

The influence of monomeric beta-CD and both soluble and insoluble beta-CD polymers on drug release from tablets containing either 30% or 50% hydroxypropyl methylcellulose has been studied using diflunisal (DF) as model drug.

METHOD

The DF-beta-CD inclusion complex (1:1 M) was prepared by coevaporation and characterised using X-ray diffraction, differential thermal analysis, and IR spectroscopy. The dissolution assays were performed according to the USP paddle method.

RESULTS

The incorporation of beta-CD in the complexed form increases drug release from hydroxypropyl methylcellulose tablets in comparison with the physical mixture because of the better solubilization of the drug. The soluble polymer promotes drug release to a higher extent than the physical mixture with monomeric beta-CD, but the insoluble polymer, which is itself a hydrogel, gives rise to the most retarded release profile, probably by retention of the drug in its structure. The formulations containing physical mixtures with either beta-CD or the soluble polymer present an optimum adjustment to zero-order release kinetics, and the inclusion complex followed non-Fickian diffusion according to the Korsmeyer-Peppas model.

CONCLUSION

The release profile of DF from a HPMC matrix can be modulated in different ways by the use of either monomeric or polymeric beta-CD.

The initial release of cisplatin from poly(lactide-co-glycolide) microspheres

PLGA microspheres loaded with cisplatin were produced using a single emulsion method. A semi-empirical model, with bi-exponential terms, was found to give a better fit to the drug release profiles compared to a mono-exponential model. This model suggests that there are two separate fractions of drug present in the depot. A fraction of the drug is located near/at the surface of the depot, and is readily released during immersion in buffer. A second fraction of drug is entrapped deeper within the depot and is subsequently released. It was also found that the initial release of cisplatin from PLGA microsphere is highly diffusion-controlled and the classical Higuchi model provides a good fit. From studies of water diffusion using PFG-NMR, results suggested that 50:50 PLGA microsphere was most susceptible to swelling and this might have promoted the faster initial drug release. Results from NMR cryoporometry also indicated that the developed PLGA microspheres could have "ink-bottle" pores.

Bio-dis and the paddle dissolution apparatuses applied to the release characterization of ketoprofen from hypromellose matrices

The purposes of this work were: (1) to comparatively evaluate the effects of hypromellose viscosity grade and content on ketoprofen release from matrix tablets, using Bio-Dis and the paddle apparatuses, (2) to investigate the influence of the pH of the dissolution medium on drug release. Furthermore, since direct compression had not shown to be appropriate to obtain the matrices under study, it was also an objective (3) to evaluate the impact of granulation on drug release process. Six formulations of ketoprofen matrix tablets were obtained by compression, with or without previous granulation, varying the content and viscosity grade of hypromellose. Dissolution tests were carried out at a fixed pH, in each experiment, with the paddle method (pH 4.5, 6.0, 6.8, or 7.2), while a pH gradient was used in Bio-Dis (pH 1.2 to 7.2). The higher the hypromellose viscosity grade and content were, the lower the amount of ketoprofen released was in both apparatuses, the content effect being more expressive. Drug dissolution enhanced with the increase of the pH of the medium due to its pH-dependent solubility. Granulation caused an increase in drug dissolution and modified the mechanism of the release process.

Detecting and identifying the complexation of nimodipine with hydroxypropyl-beta-cyclodextrin present in tablets by Raman spectroscopy

For CD-based formulations, it is important to directly monitor the complexation status of the drug present in final dosage form pharmaceuticals. In this work, Raman spectroscopy was explored for the detection and identification of the Nimodipine/hydroxypropyl-beta-cyclodextrin (NMD/HPbetaCD) complexation present in the tablet. The evident, consistent Raman spectral changes in the shift, height ratio and area ratio for the characteristic bands of NMD molecule were featured in the NMD/HPbetaCD complex, and employed to distinguish between complexed and uncomplexed NMD in tablets. A number of practical issues for the Raman measurements performed on the tablets were considered and addressed. The Raman approach and dissolution test were applied to different tablets prepared experimentally at variable granulations. The results demonstrated that the Raman approach can serve as a promising methodology for tablet identification on the complexation. Wet granulation facilitated the process-induced transformations in the complexation. The adequate ethanol in the granulating fluid appeared optimized for the complexation of the two components. The spectral characteristics for dissociation in the tablets were in full accordance with the observations of their diminished initial dissolution parameters. It implied the possibility that the tablet dissolution can be predicted from the Raman interpretation.

Formulation and pharmacodynamic evaluation of captopril sustained release microparticles

Cellulose propionate (CP) microparticles containing captopril (CAP) were prepared by solvent evaporation technique. The effects of polymer molecular weight, polymer composition and drug:polymer ratios on the particle size, flow properties, morphology, surface properties and release characteristics of the prepared captopril microparticles were examined. The anti-hypertensive effect of the selected CAP formulation in comparison with aqueous drug solution was also evaluated in vivo using hypertensive rats. The formulation containing drug:polymer blend ratio 1:1.5 (1:1 low:high molecular weight CP), namely F7, was chosen as the selected formulation with regard to the encapsulation efficiency (75.1%), flow properties (theta=24 degrees, Carr index=5%, Hausner ratio=1.1, packing rate=0.535) and release characteristics. Initial burst effect was observed in the release profile of all examined formulations. DSC and SEM results indicated that the initial burst effect could be attributed to dissolution of CAP crystals present on the surface or embedded in the superficial layer of the matrix. The release kinetics of CAP from most microparticle formulations followed diffusion mechanism. After oral administration of the selected microparticle formulation (F7) to hypertensive rats, systolic blood pressure decreased gradually over 24 h compared to reference drug solution. These results may suggest the potential application of cellulose propionate microparticles as a suitable sustained release drug delivery system for captopril.

Synthesis of an Amphiphilic Polysaccharide Derivative and Its Micellization for Drug Release

A new route for the synthesis of novel amphiphilic polysaccharides was developed, in which a synthetic biodegradable poly(ε-caprolactone) was capped with a phenylalanine group (PCL-phenylalanine). The ring-opening polymerization of ε-caprolactone (ε-CL) was carried out in the absence of a metal catalyst with L-phenylalanine as the initiator; this was followed by a coupling reaction with biodegradable dextran in the presence of carbonyldimidazole. The FTIR and 1H NMR analyses confirm the coupling reaction. Fluorescence, transmission electron microscopy (TEM), and dynamic light scattering (DLS) confirm that in aqueous solution the amphiphilic polysaccharides self-assemble into the nanoscale spherical micelles with good stability. The in vitro drug release behavior of the nonsteroidal indomethacin drug exhibits sustained drug release profile as described by the Higuchi model without a burst effect.

A drug release study from hydroxypropylmethylcellulose (HPMC) matrices using QSPR modeling

This investigation is aimed at characterization of the mode of release from two different substitution types of HPMC and the effect of chemical structure of drugs using the QSPR (Quantitative - Structure-Property Relationship) technique. To this end, release profiles of HPMC matrices of several drugs containing the same formulation and compressed at a constant pressure were studied. QSPR method was used to establish statistically significant relationships between release parameters and the structural descriptors. Structural descriptors consisted of molecular mechanical, quantum mechanical and graph-theoretical parameters, as well as the partition coefficient and the aqueous solubility of the drugs. The results showed that the most important factors determining the release profile from both HPMC K4M and HPMC E4M matrices were the aqueous solubility of drugs (which could be substituted efficiently by dipole moment) and the size of the drug molecules. Comparison of drug release from matrices prepared using the two grades of HPMC showed very distinct differences for some drugs, as evaluated by the similarity factor. The results indicated that the source of the difference could be sought in the drug properties (as exemplified by the aqueous solubility and surface area) as well as the rate of erosion (that depends mainly on the polymer type).

Practical considerations in development of solid dosage forms that contain cyclodextrin

The following is a review of the literature that addresses the use of cyclodextrin in solid dosage forms. Care was taken to exclude physical and chemical characteristics of cyclodextrin, which have been discussed in the literature. A flow diagram is provided to outline the decision-making steps that are involved in the development process. Both preparation of physical mixtures and inclusion complexes are considered. Analytical techniques to determine the presence of inclusion complexes, the effect of other excipients on complex formation, the effect of size limitation of solid dosages forms, powder processing, and storage of solid dosage forms are discussed.

On the use of the Weibull function for the discernment of drug release mechanisms

Previous findings from our group based on Monte Carlo simulations indicated that Fickian drug release from Euclidian or fractal matrices can be described with the Weibull function. In this study, the entire drug release kinetics of various published data and experimental data from commercial or prepared controlled release formulations of diltiazem and diclofenac are analyzed using the Weibull function. The exponent of time b of the Weibull function is linearly related to the exponent n of the power law derived from the analysis of the first 60% of the release curves. The value of the exponent b is an indicator of the mechanism of transport of a drug through the polymer matrix. Estimates for b< or =0.75 indicate Fickian diffusion in either fractal or Euclidian spaces while a combined mechanism (Fickian diffusion and Case II transport) is associated with b values in the range 0.75<b<1. For values of b higher than 1, the drug transport follows a complex release mechanism.