Dissolution testing for sustained or controlled release oral dosage forms and correlation with in vivo data: Challenges and opportunities

Development of sustained-release pellets to modulate the in vivo processes of the main active components of Danshen: A pharmacokinetic and pharmacodynamic evaluation

BACKGROUND

Danshen is a first-line traditional Chinese medicine derived from Salvia miltiorrhiza Bunge consisting mainly of tanshinone IIA, tanshinol, protocatechuic aldehyde, and salvianolic acid B, it is widely used to treat cardiovascular diseases based on the synergistic effect of its multiple active components. Recent studies have indicated that the overall effect of traditional Chinese medicine is closely related to the in vivo coexistence of a variety of active components.

HYPOTHESIS

The prolongation of the coexistence of the four active components in Danshen in vivo by regulating their pharmacokinetic processes may contribute to better efficiency.

METHODS/STUDY DESIGNS

Individual sustained-release pellets of the four main active components in Danshen were respectively prepared according to the optimised formulations developed in our previous studies to modulate their in vivo processes, in which the desired release profiles of each kind of sustained-release pellets for formulation optimisation were calculated based on the point-area deconvolution and circadian rhythm of variant angina. The four kinds of sustained-release pellets were filled into capsules on the basis of the original weight ratio of the four active components in purified Salvia miltiorrhiza extract for further in vitro release and pharmacokinetic and pharmacodynamic investigations.

RESULTS

The release behaviours of the combined Danshen capsules composed of the four kinds of sustained-release pellets were evaluated in three media with different pH levels (pH 1.2, 6.8, and pure water). The release profiles of each kind of sustained-release pellets in pH 6.8 PBS and pH 1.2 HCl were similar to the release profile of those in pure water (similarity factors f₂ > 50). Pharmacokinetic studies revealed that the four kinds of sustained-release pellets in the combined Danshen capsules possessed the same T_max and similar and extended MRT. Moreover, pharmacodynamic studies indicated that the combined Danshen capsules had much better anti-angina effects than commercial Danshen capsules according to comprehensive evaluations via electrocardiogram, serum index (CK-MB, cTn-I, ET, and NO), myocardial oxidative damage, and myocardial pathologic biopsy.

CONCLUSION

Sustained-release preparations can markedly prolong the in vivo coexistence of multiple components in Danshen to enhance their overall effects, which provides a potent strategy for developing the combination therapy of traditional Chinese medicine.

Matrix systems for oral drug delivery: Formulations and drug release

In this current article matrix formulations for oral drug delivery are reviewed. Conventional dosage forms and novel applications such as 3D printed matrices and aerogel matrices are discussed. Beside characterization, excipients and matrix forming agents are also enlisted and classified. The incorporated drug could exist in crystalline or in amorphous forms, which makes drug dissolution easily tunable. Main drug release mechanisms are detailed and reviewed to support rational design in pharmaceutical technology and manufacturing considering the fact that R&D members of the industry are forced to obtain knowledge about excipients and methods pros and cons. As innovative and promising research fields of drug delivery, 3D printed products and highly porous, low density aerogels with high specific surface area are spreading, currently limitlessly. These compositions can also be considered as matrix formulations.

Double-Layered Matrix of Shellac Wax-Lutrol in Controlled Dual Drug Release

Double-layered matrix tablets prepared from shellac wax-lutrol were fabricated using a molding technique, and the release of hydrochlorothiazide and propranolol HCl from the inner tablet or outer layer was studied. The simultaneous determination of dual drug release was measured with first derivative UV spectrophotometry. The tablet containing shellac wax as the outer tablet and lutrol as the inner tablet showed more appropriate drug release and the size of the inner layer influenced the rate of drug release. In addition, the aqueous solubility of the drug and the components of the inner tablet or outer layer affected the drug release behavior. Most of the double-layered tablets exhibited the drug-release pattern which fitted well with zero-order kinetic due to the restriction of the release surface. Biphasic drug release pattern was found in the tablet of which the outer layer rapidly eroded. The drug dissolution data from drug-loaded-outer layer could predict the dissolution time for the outer layer of drug-loaded inner part of double-layered matrix tablet. Incorporation of lutrol increased the drug release from shellac wax matrix, and the zero-order release was attained by fabricating it into a double-layered tablet.

K88 Fimbrial Adhesin Targeting of Microspheres Containing Gentamicin Made with Albumin Glycated with Lactose

The formulation and characterization of gentamicin-loaded microspheres as a delivery system targeting enterotoxigenic Escherichia coli K88 (E. coli K88) was investigated. Glycated albumin with lactose (BSA-glucose-β (4-1) galactose) was used as the microsphere matrix (MS-Lac) and gentamicin included as the transported antibiotic. The proposed target strategy was that exposed galactoses of MS-Lac could be specifically recognized by E. coli K88 adhesins, and the delivery of gentamicin would inhibit bacterial growth. Lactosylated microspheres (MS-Lac1, MS-Lac2 and MS-Lac3) were obtained using a water-in-oil emulsion, containing gentamicin, followed by crosslinking with different concentrations of glutaraldehyde. Electron microscopy displayed spherical particles with a mean size of 10–17 µm. In vitro release of gentamicin from MS-Lac was best fitted to a first order model, and the antibacterial activity of encapsulated and free gentamicin was comparable. MS-Lac treatments were recognized by plant galactose-specific lectins from Ricinus communis and Sophora japonica and by E. coli K88 adhesins. Results indicate MS-Lac1, produced with 4.2 mg/mL of crosslinker, as the best treatment and that lactosylated microsphere are promising platforms to obtain an active, targeted system against E. coli K88 infections.

Evaluation of the coat quality of sustained release pellets by individual pellet dissolution methodology

This study explored the application of 400-DS dissolution apparatus 7 for individual pellet dissolution methodology by a design of experiment approach and compared its capability with that of the USP dissolution apparatus 1 and 2 for differentiating the coat quality of sustained release pellets. Drug loaded pellets were prepared by extrusion-spheronization from powder blends comprising 50%, w/w metformin, 25%, w/w microcrystalline cellulose and 25%, w/w lactose, and then coated with ethyl cellulose to produce sustained release pellets with 8% and 10%, w/w coat weight gains. Various pellet properties were investigated, including cumulative drug release behaviours of ensemble and individual pellets. When USP dissolution apparatus 1 and 2 were used for drug release study of the sustained release pellets prepared, floating and clumping of pellets were observed and confounded the release profiles of the ensemble pellets. Hence, the release profiles obtained did not characterize the actual drug release from individual pellet and the applicability of USP dissolution apparatus 1 and 2 to evaluate the coat quality of sustained release pellets was limited. The cumulative release profile of individual pellet using the 400-DS dissolution apparatus 7 was found to be more precise at distinguishing differences in the applied coat quality. The dip speed and dip interval of the reciprocating holder were critical operational parameters of 400-DS dissolution apparatus 7 that affected the drug release rate of a sustained release pellet during the individual dissolution study. The individual dissolution methodology using the 400-DS dissolution apparatus 7 is a promising technique to evaluate the individual pellet coat quality without the influence of confounding factors such as pellet floating and clumping observed during drug release test with dissolution apparatus 1 and 2, as well as to facilitate the elucidation of the actual drug release mechanism conferred by the applied sustained release coat onto the pellets.

Rapid profiling of enteric coated drug delivery spheres via Broadband Acoustic Resonance Dissolution Spectroscopy (BARDS)

There is an increased trend towards the use of drug and enteric coated sugar spheres for controlled oral delivery of active pharmaceutical ingredients (API).

Development and comparative evaluation of in vitro, in vivo properties of novel controlled release compositions of paroxetine hydrochloride hemihydrate as against Geomatrix™ platform technology

The objective of this study is to develop, in vitro and in vivo evaluation of novel approaches for controlled release of paroxetine hydrochloride hemihydrate (PHH) in comparison to patented formulation PAXIL CR(®) tablets of GlaxoSmithKline (Geomatrix™ technology). In one of the approaches, hydrophilic core matrix tablets containing 85% of the dose were prepared and further coated with methacrylic acid copolymer to delay the release. An immediate release coating of 15% was given as top coat. The tablets were further optionally coated using ethyl cellulose. In the second approach, hydrophobic matrix core tablets containing metharylic acid copolymer were prepared. In the third approach, PHH was granulated with enteric polymer and further hydrophobic matrix core tablets were prepared. The effect of polymer concentration, level of enteric coating on drug release was evaluated by in vitro dissolution study by varying dissolution apparatus and the rotation speeds. It was found that increase in concentration of high viscosity hydroxypropylmethylcellulose (HPMC) resulted in reduction of the release rate. The drug release was observed to be dependent on the level of enteric coating and ethyl cellulose coating, being slower at increased coating. The release mechanism of PHH followed zero-order shifting to dissolution dependent by the increase of HPMC content. The formulation was stable without change in drug release rate. In vivo study in human volunteers confirmed the similarity between test and innovator formulations. In conclusion, HPMC-based matrix tablets, which were further coated using methacrylic acid copolymer, were found to be suitable for the formulation of single layer-controlled release PHH.

The differences between the branded and generic medicines using solid dosage forms: In-vitro dissolution testing

INTRODUCTION

Dissolution is the amount of substance that goes into solution per unit time under standardised conditions of liquid/solid interface, solvent composition and temperature. Dissolution is one of the most important tools to predict the in-vivo bioavailability and in some cases to determine bioequivalence and assure interchangeability.

AIM

To compare the differences in dissolution behaviour of solid dosage forms between innovators (reference products) and their generic counterparts (tested products).

METHODS

Four replicates for each batch of 37 tested medicines was carried out using A PT-DT70 dissolution tester from Pharma Test. A total of 13 branded medicines and 24 generic counterparts were obtained locally and internationally to detect any differences in their dissolution behaviour. They were tested according to the British Pharmacopeia, European Pharmacopeia and the US Pharmacopeia with the rate of dissolution determined by ultra-violet Spectrophotometery.

RESULTS

Most tested medicines complied with the pharmacopoeial specifications and achieved 85% dissolution in 60 min. However, some generic medicines showed significant differences in dissolution rate at 60 and 120 min. Many generic medicines showed a slower dissolution rate than their branded counterparts such as the generic forms of omeprazole 20 mg. Some showed an incomplete dissolution such as the generic form of nifedipine 10 mg. Other generics showed faster dissolution rate than their branded counterpart such as the generic forms of meloxicam 15 mg. Moreover, some generics from different batches of the same manufacturer showed significant differences in their dissolution rate such as the generic forms of meloxicam 7.5 mg. Nevertheless, some generic medicines violated the EMA and the FDA guidelines for industry when they failed to achieve 85% dissolution at 60 min, such as the generic form of diclofenac sodium 50 mg.

CONCLUSION

Most medicines in this study complied with the pharmacopeial limits. However, some generics dissolved differently than their branded counterparts. This can clearly question the interchangeability between the branded and its generic counterpart or even among generics.

Advanced technologies for oral controlled release: cyclodextrins for oral controlled release

Cyclodextrins (CDs) are used in oral pharmaceutical formulations, by means of inclusion complexes formation, with the following advantages for the drugs: (1) solubility, dissolution rate, stability, and bioavailability enhancement; (2) to modify the drug release site and/or time profile; and (3) to reduce or prevent gastrointestinal side effects and unpleasant smell or taste, to prevent drug-drug or drug-additive interactions, or even to convert oil and liquid drugs into microcrystalline or amorphous powders. A more recent trend focuses on the use of CDs as nanocarriers, a strategy that aims to design versatile delivery systems that can encapsulate drugs with better physicochemical properties for oral delivery. Thus, the aim of this work was to review the applications of the CDs and their hydrophilic derivatives on the solubility enhancement of poorly water-soluble drugs in order to increase their dissolution rate and get immediate release, as well as their ability to control (to prolong or to delay) the release of drugs from solid dosage forms, either as complexes with the hydrophilic (e.g., as osmotic pumps) and/or hydrophobic CDs. New controlled delivery systems based on nanotechnology carriers (nanoparticles and conjugates) have also been reviewed.

Formulation and in vitro-in vivo evaluation of ketoprofen-loaded albumin microspheres for intramuscular administration

The objective of this work was to prepare and evaluate ketoprofen-loaded albumin microspheres for intramuscular administration. Microspheres were prepared by emulsion cross-linking method using a 2(3) factorial design and the effect of different factors on entrapment efficiency was determined. Microspheres were evaluated for entrapment efficiency, percentage yield, particle size and release behaviour. Selected formulations were then tested by differential scanning calorimetry, X-ray diffraction and scanning electron microscopy. Further they were analysed for residual solvents, syringeability and stability. Microspheres were then sterilized and bioavailability studies were carried out in New Zealand white rabbits. The physical characteristics of microspheres showed that they were suitable for IM administration. The sterilization technique adopted was adequate to maintain sterility. In vivo studies showed increase in C(max), AUC, t(1/2) and MRT (p < 0.05) administered in the form of microspheres. MRT of ketoprofen was almost 3.2-times in the form of microspheres. From these results it was concluded that the developed albumin microspheres of ketoprofen is a potential delivery system for once-a-day intramuscular administration.

AC biosusceptometry technique to evaluate the gastrointestinal transit of pellets under influence of prandial state

Multiparticulate dosage forms have been proposed when distal regions of gastrointestinal tract are desirable as target of drugs. It is known that physiological parameters might interfere with the processes related to the drug delivery and absorption and therefore, it is essential to evaluate the behavior of such delivery systems in vivo. The aim of this study was to propose the AC Biosusceptometry technique as a noninvasive and radiation free device to evaluate the gastrointestinal transit of a magnetic multiparticulate dosage form in healthy volunteers under fasting and fed conditions. Magnetic pellets were prepared by the powder layering method of ferrite on nonpareils sugar beads and coated by using Eudragit. Our data showed that the AC Biosusceptometry technique was able to monitoring the gastrointestinal transit of pellets presenting similar profiles as demonstrated by standard techniques. Food intake has markedly influenced the gastric emptying as well as the colon arrival and the small intestine transit of magnetic pellets.

Development and validation of a discriminating in vitro 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 H(2)O + 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.

Influence of dissolution media composition on drug release and in-vitro/in-vivo correlation for paracetamol matrix tablets prepared with novel carbomer polymers

The influence of dissolution media composition on drug release kinetics and in-vitro/in-vivo correlation (IVIVC) for hydrophilic matrix tablets based on Carbopol 971P and Carbopol 71G was investigated. A number of buffered and unbuffered media differing with respect to their pH value, ionic strength and ionic species was evaluated. The observed in-vitro drug release profiles were compared with the hypothetical drug release profiles in-vivo calculated by numerical deconvolution from the results of an in-vivo study. The obtained IVIVC plots were examined using linear and non-linear (proportional odds, proportional hazards and proportional reversed hazards) mathematical models. Although the studied sustained release agents were chemically identical, they exhibited pronounced differences in drug product behaviour both in-vitro and in-vivo. The use of non-linear modelling resulted in an improved level of correlation, especially in the case of Carbopol 71G matrices. The obtained results indicated the susceptibility of drug release kinetics and hence IVIVC in the case of anionic polymer matrices to media composition, and emphasized the need for thorough evaluation of applied media during the development of biorelevant dissolution methodology. Although the use of non-linear modelling could be advantageous, the need for a simple and meaningful nonlinear relationship is pointed out.

Preparation and characterization of quercetin-loaded polymethyl methacrylate microcapsules using a polyol-in-oil-in-polyol emulsion solvent evaporation method

Flavonoids and related compounds exhibit a wide range of useful pharmacological properties but present challenges related to their stability and solubility in commonly available solvents. In this study, polymethyl methacrylate (PMMA) microcapsules were prepared using a novel polyol-in-oil-in-polyol (P/O/P) emulsion solvent evaporation method as a means of stabilizing the flavonoids, using quercetin as a model flavonoid drug. The morphology of the microcapsules was evaluated using a scanning electron microscope, revealing a spherical shape with a smooth surface. The cross-section image of the PMMA microcapsules prepared with an amphiphilic polymer in the inner polyol phase showed that the microcapsule was filled with several submicron microspheres. The mean diameter varied from 1.03 ± 0.12 μm to 2.39 ± 0.42 μm, and the encapsulation efficiency ranged from 12.7% to 26.9%. When free quercetin was stored at 42°C, the residual quercetin content gradually decreased to 18% over 28 days as a result of oxidation. However, when encapsulated in PMMA microcapsules with an amphiphilic polymer in the inner polyol phase, the residual quercetin content decreased to just 82%. In-vitro release studies indicated a sustained release pattern throughout the 36-h study. The release kinetics of the microcapsules with an amphiphilic polymer followed a diffusion-controlled mechanism and the microcapsule without amphiphilic polymer followed an anomalous diffusion behaviour. This study suggests that the novel P/O/P emulsion solvent evaporation method can be applied to the encapsulation of flavonoids.

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.

Investigation of the Biopharmaceutical Behavior of Theophylline Hydrophilic Matrix Tablets Using USP Methods and an Artificial Digestive System

This work aimed to investigate the biopharmaceutical behavior of hydrophilic matrix tablets of theophylline using different in vitro methods: USP II, USP IV, and a novel in vitro system simulating the gastrointestinal tract in man called the artificial digestive system (ADS). The potentiality of each method was evaluated by establishing in vitro/in vivo correlation. Using USP methods, the drug release was pH-independent and dependent on agitation intensity. Level A IVIVCs could be established using the different in vitro methods but one to one correlation was established only when the ADS method was used. For the prediction of in vivo drug dosage form behavior based on in vitro methods, the ADS showed a high predictability when compared to USP in vitro methods.

In-vitro/in-vivo correlation of pulsatile drug release from press-coated tablet formulations: A pharmacoscintigraphic study in the beagle dog

The aim of the current study was to investigate the in-vitro and in-vivo performance of a press-coated tablet (PCT) intended for time delayed drug release, consisting of a rapidly disintegrating theophylline core tablet, press-coated with barrier granules containing glyceryl behenate (GB) and low-substituted hydroxypropylcellulose (L-HPC). The PCTs showed pulsatile release with a lag time dependent upon the GB and L-HPC composition of the barrier layer. In-vivo gamma-scintigraphic studies were carried out for PCTs containing GB:L-HPC at 65:35 w/w and 75:25 w/w in the barrier layer in four beagle dogs, in either the fed or fasted state. The in-vivo lag time in both the fed and fasted states did not differ significantly (p>0.05) from the in-vitro lag time. Additionally, no significant difference (p<0.05) between in-vivo fed and fasted disintegration times was observed, demonstrating that in-vivo performance of the PCT was not influenced by the presence or absence of food in the gastrointestinal tract. A distinct lag time was obtained prior to the appearance of drug in plasma and correlated (R2=0.98) with disintegration time observed from scintigraphic images. However, following disintegration, no difference in pharmacokinetic parameters (AUC(0-6 dis), K(el), Cmax) was observed. The current study highlighted the potential use of these formulations for chronopharmaceutical drug delivery.

Formulation and evaluation of ketorolac tromethamine-loaded albumin microspheres for potential intramuscular administration

The objective of this work was to prepare and evaluate ketorolac tromethamine-loaded albumin microspheres using a factorial design. Albumin microspheres were prepared by emulsion cross-linking method. Selected formulations were characterized for their entrapment efficiency, particle size, surface morphology, and release behavior. Analysis of variance (ANOVA) for entrapment efficiency indicated that entrapment efficiency is best fitted to a response surface linear model. From the statistical analysis it was observed that as the drug:polymer (D:P) ratio and volume of glutaraldehyde increased, there was a significant increase in the encapsulation efficiency. Scanning electron microscopy of the microspheres revealed a spherical, nonporous and uniform appearance, with a smooth surface. Based on the entrapment efficiency and physical appearance, 9 formulations were selected for release study. The maximum particle size observed was below 40 microm. The release pattern was biphasic, characterized by an initial burst effect followed by a slow release. All selected microspheres, except those having less polymer proportion (D:P ratio is 1:1), exhibited a prolonged release for almost 24 hours. On comparing r (2) values for Higuchi and Peppas kinetic models, different batches of microspheres showed Fickian, non-Fickian, and diffusion kinetics. The release mechanism was regulated by D:P ratio and amount of cross-linking agent. From the experimental data obtained with respect to particle size and extent of drug release, it could be concluded that the prepared microspheres are useful for once-a-day intramuscular administration of ketorolac tromethamine.

Enteric Coated Magnetic HPMC Capsules Evaluated in Human Gastrointestinal Tract by AC Biosusceptometry

PURPOSE

To employ the AC Biosusceptometry (ACB) technique to evaluate in vitro and in vivo characteristics of enteric coated magnetic hydroxypropyl methylcellulose (HPMC) capsules and to image the disintegration process.

MATERIALS AND METHODS

HPMC capsules filled with ferrite (MnFe2O4) and coated with Eudragit were evaluated using USP XXII method and administered to fasted volunteers. Single and multisensor ACB systems were used to characterize the gastrointestinal (GI) motility and to determine gastric residence time (GRT), small intestinal transit time (SITT) and orocaecal transit time (OCTT). Mean disintegration time (t50) was quantified from 50% increase of pixels in the imaging area.

RESULTS

In vitro and in vivo performance of the magnetic HPMC capsules as well as the disintegration process were monitored using ACB systems. The mean disintegration time (t50) calculated for in vitro was 25+/-5 min and for in vivo was 13+/-5 min. In vivo also were determined mean values for GRT (55+/-19 min), SITT (185+/-82 min) and OCTT (240+/-88 min).

CONCLUSIONS

AC Biosusceptometry is a non-invasive technique originally proposed to monitoring pharmaceutical dosage forms orally administered and to image the disintegration process.

Gastrointestinal transit and disintegration of enteric coated magnetic tablets assessed by ac biosusceptometry

The oral administration is a common route in the drug therapy and the solid pharmaceutical forms are widely used. Although much about the performance of these formulations can be learned from in vitro studies using conventional methods, evaluation in vivo is essential in product development. The knowledge of the gastrointestinal transit and how the physiological variables can interfere with the disintegration and drug absorption is a prerequisite for development of dosage forms. The aim of this work was to employing the ac biosusceptometry (ACB) to monitoring magnetic tablets in the human gastrointestinal tract and to obtain the magnetic images of the disintegration process in the colonic region. The ac biosusceptometry showed accuracy in the quantification of the gastric residence time, the intestinal transit time and the disintegration time (DT) of the magnetic formulations in the human gastrointestinal tract. Moreover, ac biosusceptometry is a non-invasive technique, radiation-free and harmless to the volunteers, as well as an important research tool in the pharmaceutical, pharmacological and physiological investigations.

Once-a-Day Extended-Release Dosage form of Divalproex Sodium III: Development and Validation of a Level A in Vitro–in Vivo Correlation (IVIVC)

Defining a quantitative and reliable relationship between in vitro drug release and in vivo absorption is highly desired for rational development, optimization, and evaluation of controlled-release dosage forms and manufacturing process. During the development of a once-daily extended-release (ER) tablet of divalproex sodium, a predictive in vitro drug release method was designed and statistically evaluated using three formulations with varying release rates. In order to establish an internally and externally validated Level A IVIVC, a total of five different ER formulations of divalproex sodium were used to evaluate a linear IVIVC model based on the in vitro test method. For internal validation, a single-dose four-way crossover study (N = 16) was performed using fast-, medium-, and slow-releasing ER formulations and a 12-h IV infusion of valproic acid as reference. To validate the IVIVC externally, a second three-way crossover study (N = 36) was performed using slightly-fast-, medium-, and slightly-slow-releasing ER formulations. The in vivo absorption-time profile was inferred by deconvolution of the observed plasma concentration-time profiles against the unit disposition function (UDF). A linear IVIVC model was established in which the in vivo absorption was expressed as a function of in vitro drug release. Plasma profiles of ER formulations were estimated via convolution of in vitro release profiles with the UDF. Successful internal and external validations of the model were demonstrated by individual and average absolute percent prediction errors of </=9% for both C(max) and AUC(infinity). In conclusion, a Level A IVIVC describing the entire time-course of plasma concentrations was developed and validated, both internally and externally, for ER formulations of divalproex sodium.

Nimesulide PLA microspheres as a potential sustained release system for the treatment of inflammatory diseases

Polylactic acid (PLA-L) microspheres were prepared as a biodegradable polymeric carrier for a non-steroidal anti-inflammatory drug, nimesulide. The preparation of this system was performed by the classical emulsion solvent-evaporation method. Size analysis of the microparticulate system showed that unloaded and loaded nimesulide-PLA microspheres had average diameters of about 42.9 nm and 2.1 microm, respectively. Scanning electron microscopy (SEM) of loaded and unloaded microsphere samples showed that the particles shape were perfectly spherical, the loading efficiency of nimesulide in PLA microspheres was 70%; Thus, the microparticle system evaluated in this work showed the potential to act as a sustained release system for nimesulide: in vitro dissolution profiles showed the PLA-L microparticles were able to sustain the release of the drug for a considerable period of time (28.7% within 108 h).

Development and evaluation of bio-dissolution systems capable of detecting the food effect on a polysaccharide-based matrix system

Methods are proposed and tested for mimicking the in vitro food effect on controlled release dosage forms, using USP dissolution apparatus 3. Using in vivo data a pH and time profile was constructed, and the methods utilized either presoaking in peanut oil or continuous oil contact to mimic the presence of a high fat meal. A water soluble drug (propranolol hydrochloride, class 1 by BCS) was used as a model material. Both methods were able to confirm that a labile multiparticulate system (Inderal LA) was susceptible to such in vitro effects. A hydrocolloid matrix tablet showed low susceptibility to either technique. There was a good correlation between methods, which may indicate that the oil presoaking method, which is less time consuming to carry out and leads to more simple subsequent analysis, may be sufficient to identify dosage forms susceptible to physical food effects.

Once‐a‐Day Controlled‐Release Dosage Form of Divalproex Sodium II: Development of a Predictive In Vitro Drug Release Method

During formulation design of a once-daily controlled release matrix system of divalproex sodium, the in vitro dissolution test (USP II, 100 rpm, pH 6.8 buffer) was found to result in release rates that were slower than in vivo absorption. The test method also did not sufficiently discriminate formulations with different in vivo absorption rates. To develop an in vitro method that is directly correlated with in vivo absorption, statistically designed studies were carried out to investigate the effects of various in vitro testing variables on drug release using USP dissolution apparatuses. The variables studied included agitation intensity, apparatus, pH, surfactant and ionic strength of the dissolution medium. Experimental data were analyzed using ANOVA. In vitro/in vivo correlation was tested based on the hypothesis that the same linear regression equation holds for three formulations with different release rates. A mixed effects model was used in which the dependence among observations from the same subject was taken into account. Factorial studies indicated that higher pH, addition of sodium lauryl sulphate (SLS) to the dissolution medium, and higher agitation intensity increased the release rate from the matrix tablet. Use of SLS not only lead to increased release rates that are more comparable to in vivo absorption rates, but also improved differentiation among formulations with varying release rates. Furthermore, drug release was also affected by interactions among the variables studied. Statistical analysis indicated that a combination of higher SLS concentration and lower pH provided enhanced differentiation between release profiles of the fast and slow releasing formulations. Based on the above findings, a new set of testing conditions was identified and demonstrated to be predictive of in vivo drug absorption for various controlled release formulations of divalproex sodium. The new method uses USP Apparatus II operating at 100 rpm in 500 mL of 0.1 N HCl for 45 min followed by 900 mL of 0.05 M phosphate buffer containing 75 mM SLS, pH 5.5, 37 +/- 0.5 degrees C. In conclusion, adjusting dissolution testing conditions to match the behavior of the formulations in vitro with that in vivo is a useful approach in identifying a predictive method in development of in vitro-in vivo correlation.

Disintegration of magnetic tablets in human stomach evaluated by alternate current Biosusceptometry

Oral administration is the most convenient route for drug therapy. The knowledge of the gastrointestinal transit and specific site for drug delivery is a prerequisite for development of dosage forms. The aim of this work was to demonstrate that is possible to monitor the disintegration process of film-coated magnetic tablets by multi-sensor alternate current Biosusceptometry (ACB) in vivo and in vitro. This method is based on the recording of signals produced by the magnetic tablet using a seven sensors array and signal-processing techniques. The disintegration was confirmed by signals analysis in healthy human volunteers' measurements and in vitro experiments. Results showed that ACB is efficient to characterize the disintegration of dosage forms in the stomach, being a research tool for the development of new pharmaceutical dosage forms.

Development and evaluation of sustained release mini-matrices prepared via hot melt extrusion

Sustained release mini-matrices (multiple unit dosage form) were developed by means of hot-melt extrusion using ibuprofen as the model drug and ethyl cellulose as sustained release agent. Ibuprofen release from the ibuprofen-ethyl cellulose matrices (60:40 w/w) was too slow (20% in 24 h). Other excipientia (hydroxypropyl methylcellulose and xanthan gum) were added to the formulation to increase the drug release. Changing the viscosity and substitution type of HPMC, the amount of HPMC, the drug load and the HPMC:EC ratio modified the in vitro drug release. Burst release was noticed for the formulations containing HPMC and a nearly time independent drug release was seen for the xanthan gum based mini-matrices. Drug release from the mini-matrices was mainly diffusion controlled and swelling played an important role to obtain complete drug release. The formulations were at least 12 months stable during storage at 60% RH and room temperature. At a higher relative humidity and temperature the drug release increased.

Optimization of dissolution test precision for a ketoprofen oral extended-release product

An example of application of experimental design methodologies to the set up of dissolution test conditions for a new ketoprofen oral extended-release dosage form is presented. The aim of the work was to find the best experimental conditions, using a USP apparatus 2 (paddle), for maximizing the method precision as degree of repeatability. The considered factors mainly influencing the dissolution test results were pH and volume of dissolution medium, and paddle stirring speed. Two distinct 4-run Plackett-Burman designs were carried out: one at gastric and the other at intestinal pH values. Each run was performed in triplicate in order to calculate the standard deviations of the drug dissolution efficiency at 60 and 120 min, selected as responses to be minimized. Optimum conditions to carry out the dissolution test were: 900 ml volume of dissolution medium and 70 rpm paddle stirring speed for both environments and pH 1 and 5.5, for the gastric and intestinal environment, respectively.

A dissolution test for a pressure-controlled colon delivery capsule: rotating beads method

The rotating beads method is a new in-vitro dissolution test proposed for drugs formulated as pressure-controlled colon delivery capsules (PCDCs). The apparatus consisted of a glass vessel (500 mL) containing 4-mm (i.d.) glass beads (5000, 10000 or 15000) and dissolution medium (0-067 M phosphate buffer, pH 7; 25, 50 or 100 mL) containing polyvinyl alcohol (PVA; 5, 10 or 20 w/v%) to simulate the viscosity of the colon. The vessel was rotated at 5, 10 or 25 rev min(-1) and the temperature was maintained at 37 degrees C. Fluorescein was used as a model drug to explore the optimized conditions under which differences in the drug dissolution rate are detected between colon delivery systems. Fluorescein was formulated in four types of colon delivery systems. One was a tablet coated with an enteric polymer, Eudragit S-100, and the other three were PCDCs prepared with different thicknesses of ethylcellulose coating membrane (type I, II, III). The dissolution behaviour of fluorescein from the PCDC formulation was significantly different from that of the Eudragit S-100-coated tablets, when the dissolution conditions were as follows: rotation speed, 10 rev min(-1); bead number, 10000; dissolution medium, 50mL with 10% PVA. This dissolution method was applied to acetaminophen sustained-release tablets and two other drugs having low solubility in the colon, tegafur and 5-aminosalicylic acid. Similarly, significant differences in the dissolution rates of drugs from the PCDC formulation and the enteric tablet were detected. There was good correlation between the in-vitro dissolution rates and in-vivo absorption rates using T50 (the time for half of the amount of drug to be released from the preparation) and Cmax/Tmax (enteric tablet) or Cmax/(Tmax-Ti) (PCDC), where Ti is the first appearance time in the systemic circulation. The rotating beads method is a valuable technique for evaluating the dissolution rate of drugs formulated in PCDC.

A pH-dependent colon targeted oral drug delivery system using methacrylic acid copolymers. I. Manipulation Of drug release using Eudragit L100-55 and Eudragit S100 combinations

Lactose-based placebo tablets were coated using various combinations of two methacrylic acid copolymers, Eudragit L100-55 and Eudragit S100, by spraying from aqueous systems. The Eudragit L100-55-Eudragit S100 combinations (w/w) studied were 1:0, 4:1, 3:2, 1:1, 2:3, 1:4, 1:5 and 0:1. The coated tablets were tested in vitro for their suitability for pH dependent colon targeted oral drug delivery. The same coating formulations were then applied on tablets containing mesalazine as a model drug and evaluated for in vitro dissolution rates under various conditions. The disintegration data obtained from the placebo tablets demonstrate that disintegration rate of the studied tablets is dependent on: (i) the polymer combination used to coat the tablets, (ii) pH of the disintegration media, and (iii) the coating level of the tablets. Dissolution studies performed on the mesalazine tablets further confirmed that the release profiles of the drug could be manipulated by changing the Eudragit L100-55 and Eudragit S100 ratios within the pH range of 5.5 to 7.0 in which the individual polymers are soluble respectively, and a coating formulation consisting of a combination of the two copolymers can overcome the issue of high gastrointestinal (GI) pH variability among individuals. The results also demonstrated that a combination of Eudragit L100-55 and Eudragit S100 can be successfully used from aqueous system to coat tablets for colon targeted delivery of drugs and the formulation can be adjusted to deliver drug at any other desirable site of the intestinal region of the GI tract on the basis of pH-variability. For colon targeted delivery of drugs the proposed combination system is superior to tablets coated with either Eudragit L100-55 or Eudragit S100 alone.