Using biorelevant dissolution to obtain IVIVC of solid dosage forms containing a poorly-soluble model compound

A Screen-Printed Potentiometric Sensor for Stability Indicating Assay and Real-Time Monitoring of Trospium Chloride Dissolution Profile in its Pharmaceutical Dosage Form

According to FDA guidance, a biowaiver concept declares that dissolution testing could be approved as a replacement strategy for bioequivalence studies and/or in vivo bioavailability. From the analytical chemistry standpoint, the shift from the classically developed offline methods to the highly integrated miniaturized inline analyzers is one of the pioneering ways that would modernize future of in-vitro - in-vivo correlation (IVIVC). The emergence of screen-printed electrodes (SPE) is now making the move from successive sampling steps and off-line measurements to real-time and in-line monitoring. Recently, “SPE” potentiometric sensor was presented as real-time analyzer that can offer similar analytical results as separation-based chromatographic techniques. Thus, the main objective of this paper is to design a real-time SPE for in situ monitoring of the dissolution of trospium chloride (TRO) in neutral media. Validation of the proposed sensor was performed according to the IUPAC commendations. The measurements performed with this sensor showed an accuracy of average recovery 100.50% and standard deviation of less than 1.0%, also the repeatability and intermediate electrode variabilities were less than 1.0 and 1.3%, respectively. The developed sensor was successfully used for direct observation of the dissolution profile without any need for an extraction step or sample preparation.

Preparation of Hot-Melt Extruded Dosage Form for Enhancing Drugs Absorption Based on Computational Simulation

The aim of this study was to control the dissolution rate and permeability of cilostazol. To enhance the dissolution rate of the active pharmaceutical ingredient (API), hot-melt extrusion (HME) technology was applied to prepare a solid dispersion (SD). To control permeability in the gastrointestinal tract regardless of food intake, the HME process was optimized based on physiologically based pharmacokinetic (PBPK) simulation. The extrudates were produced using a laboratory-scale twin-screw hot-melt extruder with co-rotatory screws and a constant feeding rate. Next, for PBPK simulation, parameter-sensitive analysis (PSA) was conducted to determine the optimization approach direction. As demonstrated by the dissolution test, the solubility of extrudate was enhanced comparing cilostazol alone. Based on the PSA analysis, the surfactant induction was a crucial factor in cilostazol absorption; thus, an extrudate with an even distribution of lipids was produced using hot-melt extrusion technology, for inducing the bile salts in the gastrointestinal tract. In vivo experiments with rats demonstrated that the optimized hot-melt extruded formulation was absorbed more rapidly with lower deviation and regardless of the meal consumed when compared to marketed cilostazol formulations.

In Vitro-In Vivo Correlation for Solid Dispersion of a Poorly Water-Soluble Drug Efonidipine Hydrochloride

The aim of this present study was to investigate the ability of different dissolution methods to predict the in vivo performance of efonidipine hydrochloride (EFH). The solid dispersions of EFH were prepared by solvent evaporation method with HPMC-AS as matrix and urea as a pH adjusting agent. The paddle method, the open-loop, and the closed-loop flow-through cell methods were studied. In the study, Weibull's model was the best fit to explain release profiles. The pharmacokinetics behaviors of two kinds of solid dispersions with different release rate were investigated in comparison to the EFH after oral administration in rats. In vivo absorption was calculated by a numerical deconvolution method. In the study, the level A in vivo and in vitro correlation (IVIVC) was utilized. The correlation coefficient was calculated and interpreted by means of linear regression analysis (Origin.Pro.8.5 software). As a result, excellent IVIVC for solid dispersions and crude drug (r² = 0.9352-0.9916) was obtained for the dissolution rate determined with flow-through cell open-loop system in phosphate buffer solution with 0.1% (w/v) polysorbate 80 at pH 6.5, the flow-rate of 4 mL/min. In addition, the self-assembled flow cell system had good repeatability and accuracy. The dissolution rate of the solid dispersion could be slowed down by the flow-through method, and the difference caused by preparation was significantly distinguished. The study demonstrated that flow-through cell method of the open-loop, compared with paddle method, was suitable for predicting in vivo performance of EFH solid dispersions.

Development of in vitro - in vivo correlations for newly optimized Nimesulide formulations

Use of the human volunteers in bioequivalence studies is being discouraged by the Food and drug administration after the introduction of biowaiver approaches. In-vitro in-vivo correlation (IVIVC) with the level A is accepted for the registration of new molecules. In the present study deconvolution technique with numeric approaches was applied after compressing and in vitro validating the 100mg Nimesulide immediate, intermediate and slow release tablets. Single centered, crossover, randomized study was conducted in four phases with a two-week washout period to obtain the plasma drug concentration data after administrating test and reference products in male healthy volunteers. Kinetica^TM 4.4.1 (Thermoelectron corp, USA) was used for the calculation of two ways ANOVA with 90% CI from both log transformed and non- transformed data and Phoenix WinNonlin 7 and it's IVIVC toolkit version 7.0 was used for the application of numeric approaches of IVIVC. Results revealed that the individual internal percentage prediction error for AUC_inf and C_max were found to be < 15% while their average values were < 10% in all medium. Numeric values of % PE at pH 6.8 and pH 7.4 (50 rpm in USP II and 100 rpm in USP I and II apparatus) were found to be (2.5842, 2.9789 and, 7.1732; 7.0944, 2.4721 and 4.350) for AUC_inf and (2.5842, 0.5736 and 4.6928; 5.6214, 3.0551 and -2.4711) values for C_max respectively. The low values of prediction errors demonstrate that the correlation model is projecting the in vivo response of each formulation. Percentage External error (% PE) was not required because individual values of percentage internal error (%PE) of C_max and AUC_last were not >15. In order to predict point to point correlation between fraction drug dissolved and drug absorbed, their mean r² value was found to be > 0.9112 which showed a linear correlation in slightly alkaline pH.

Defining level A IVIVC dissolution specifications based on individual in vitro dissolution profiles of a controlled release formulation

Regulatory guidelines recommend that, when a level A IVIVC is established, dissolution specification should be established using averaged data and the maximum difference between AUC and C_max between the reference and test formulations cannot be greater than 20%. However, averaging data assumes a loss of information and may reflect a bias in the results. The objective of the current work is to present a new approach to establish dissolution specifications using a new methodology (individual approach) instead of average data (classical approach). Different scenarios were established based on the relationship between in vitro-in vivo dissolution rate coefficient using a level A IVIVC of a controlled release formulation. Then, in order to compare this new approach with the classical one, six additional batches were simulated. For each batch, 1000 simulations of a dissolution assay were run. C_max ratios between the reference formulation and each batch were calculated showing that the individual approach was more sensitive and able to detect differences between the reference and the batch formulation compared to the classical approach. Additionally, the new methodology displays wider dissolution specification limits than the classical approach, ensuring that any tablet from the new batch would generate in vivo profiles which its AUC or C_max ratio will be out of the 0.8-1.25 range, taking into account the in vitro and in vivo variability of the new batches developed.

Biomimetic Dissolution: A Tool to Predict Amorphous Solid Dispersion Performance

The presented study describes the development of a membrane permeation non-sink dissolution method that can provide analysis of complete drug speciation and emulate the in vivo performance of poorly water-soluble Biopharmaceutical Classification System class II compounds. The designed membrane permeation methodology permits evaluation of free/dissolved/unbound drug from amorphous solid dispersion formulations with the use of a two-cell apparatus, biorelevant dissolution media, and a biomimetic polymer membrane. It offers insight into oral drug dissolution, permeation, and absorption. Amorphous solid dispersions of felodipine were prepared by hot melt extrusion and spray drying techniques and evaluated for in vitro performance. Prior to ranking performance of extruded and spray-dried felodipine solid dispersions, optimization of the dissolution methodology was performed for parameters such as agitation rate, membrane type, and membrane pore size. The particle size and zeta potential were analyzed during dissolution experiments to understand drug/polymer speciation and supersaturation sustainment of felodipine solid dispersions. Bland-Altman analysis was performed to measure the agreement or equivalence between dissolution profiles acquired using polymer membranes and porcine intestines and to establish the biomimetic nature of the treated polymer membranes. The utility of the membrane permeation dissolution methodology is seen during the evaluation of felodipine solid dispersions produced by spray drying and hot melt extrusion. The membrane permeation dissolution methodology can suggest formulation performance and be employed as a screening tool for selection of candidates to move forward to pharmacokinetic studies. Furthermore, the presented model is a cost-effective technique.

Pokharkar V. Understanding peroral absorption: regulatory aspects and contemporary approaches to tackling solubility and permeability hurdles

Oral drug absorption is a process influenced by the physicochemical and biopharmaceutical properties of the drug and its inter-relationship with the gastrointestinal tract. Drug solubility, dissolution and permeability across intestinal barrier are the key parameters controlling absorption. This review provides an overview of the factors that affect drug absorption and the classification of a drug on the basis of solubility and permeability. The biopharmaceutical classification system (BCS) was introduced in early 90׳s and is a regulatory tool used to predict bioavailability problems associated with a new entity, thereby helping in the development of a drug product. Strategies to combat solubility and permeability issues are also discussed.

Selection of a discriminant and biorelevant in vitro dissolution test for the development of fenofibrate self-emulsifying lipid-based formulations

Fenofibrate, a BCS class II compound, has a low bioavailability especially when taken orally on an empty stomach. The challenge to find a new formulation for providing bioavailability, independent of food, is still ongoing. If the development of a suitable oral delivery formulation of BCS class II compounds is a frequent and great challenge to formulation scientists, the in vitro evaluation of these new formulations is also a great challenge. The purpose of this study was therefore to select an in vitro dissolution test that would be useful and as biorelevant as possible for the development of fenofibrate self-emulsifying lipid-based formulations. In this context, three different fenofibrate formulations, for which in vivo data are available in the literature, were tested using different dissolution tests until we found the one that was the most suitable. As part of this approach, we started with the simplest in vitro dissolution tests and progressed to tests that were increasingly more complex. The first tests were different single phase dissolution tests: a test under sink conditions based on the USP monograph, and different tests under non-sink conditions in non-biorelevant and biorelevant media. Given the inconclusive results obtained with these tests, biphasic dissolution systems were then tested: one with USP apparatus type II alone and another which combined USP apparatus types II and IV. This last combined test seemed the most suitable in vitro dissolution test for the development of the future fenofibrate lipid-based formulations we intend to develop in our own laboratory.

Virtual population pharmacokinetic using physiologically based pharmacokinetic model for evaluating bioequivalence of oral lacidipine formulations in dogs

The aim of the present study was to investigate virtual population pharmacokinetic using physiologically based pharmacokinetic (PBPK) model for evaluating bioequivalence of oral lacidipine formulations in dogs. The dissolution behaviors of three lacidipine formulations including one commercial product and two self-made amorphous solid dispersions (ASDs) capsules were determined in 0.07% Tween 80 media. A randomized 3-period crossover design in 6 healthy beagle dogs after oral administration of the three formulations at a single dose of 4 mg was conducted. The PBPK modeling was utilized for the virtual bioequivalence study. In vitro dissolution experiment showed that the dissolution behaviors of lacidipine amorphous solid dispersions (ASDs) capsules, which was respectively prepared by HPMC-E5 or Soluplus, as polymer displayed similar curves compared with the reference formulation in 0.07% Tween 80 media. In vivo pharmacokinetics experiments showed that three formulations had comparable maximum plasma drug concentration (C_max), and the time (T_max) to reach C_max of lacidipine tablet, which was prepared by Soluplus, as polymer was slower than other two formulations in consistency with the in vitro dissolution rate. The 90% confidence interval (CI) for the C_max, AUC_0–24 h and AUC_0–∞ of the ratio of the test drug to the referencedrug exceeded the acceptable bioequivalence (BE) limits (0.80–1.25). However, the 90% CI of the AUC_0–24 h, AUC_0–∞ and C_max of the ratio of test to reference drug were within the BE limit, calculated using PBPK modeling when the virtual subjects reached 24 dogs. The results all demonstrated that virtual bioequivalence study can overcome the inequivalence caused by inter-subject variability of the 6 beagle dogs involved in in vivo experiments.

Effect of food intake and co-administration of placebo self-nanoemulsifying drug delivery systems on the absorption of cinnarizine in healthy human volunteers

Positive food effects may be observed for low aqueous soluble compounds, these effects could potentially be circumvented using lipid based formulations. However, as all compounds are not chemically stable in lipid based systems, alternative dosage regimes could be investigated to evade the stability issue. The two aims for this present study were therefore; i) to investigate if a nutritional drink, Fresubin Energy®, could induce food effect in humans for the poorly soluble compound cinnarizine; and ii) to investigate if co-administration of a self-nano-emulsifying drug delivery systems (SNEDDS) with a conventional cinnarizine tablet could reduce the observed food-effect. A commercial conventional cinnarizine tablet was dosed to 10 healthy volunteers in a cross-over design in both fasted and fed state, with and without co-administration of a SNEDDS, with a one week wash-out period between dosing. The fed state was induced using a nutritional drink (Fresubin Energy®) and gastric emptying was assessed by administration of paracetamol as a marker. The pharmacokinetic analysis showed that the nutritional drink delayed the uptake and increased the fraction of absorbed cinnarizine, indicative of a food effect on the compound. This was in agreement with a previous dog study and indicates that the nutritional drink can be used for inducing the same level of food effect in humans. Though not statistically significant, the co-administration of SNEDDS exhibited a tendency towards a reduction of the observed food effect and an increased absorption of cinnarizine in the fasted state; based upon the individual ratios, which was not reflected in the mean data. However, the co-administration of SNEEDS in the fasted state, also induce a slower gastric emptying rate, which was observed as a delayed tmax for both cinnarizine and paracetamol.

Interspecies prediction of oral pharmacokinetics of different lacidipine formulations from dogs to human: physiologically based pharmacokinetic modelling combined with biorelevant dissolution

PBPK modelling combined with biorelevant dissolution to quantitatively predict dog PK of different lacidipine formulations, and to extrapolate to human.

The biorelevant concentration of Tween 80 solution is a simple alternative medium to simulated fasted state intestinal fluid

The aim of the present study is to investigate whether the use of the biorelevant concentration of conventional surfactants as an alternative medium to simulated fasted state intestinal fluid for drugs with different acid–base properties is feasible.

Dissolution testing of oral modified-release dosage forms

Objectives

The in-vivo performance of oral modified-release dosage forms is determined by the interplay of various physiological- and dosage-form-derived parameters. Thus it is often a challenge to predict the in-vivo drug-release behaviour from modified-release dosage forms based solely on in-vitro release rates.

Key findings

For a long time the most common procedure to obtain in-vitro/in-vivo correlations for modified-release formulations was to apply test conditions typically used for quality control on a retrospective basis. Such so-called ‘compendial approaches’ are typically not biorelevant with respect to volumes, composition and physicochemical properties of the test media and also do not take into consideration the mechanical and hydrodynamic forces that may influence dosage-form behaviour during passage through the gastrointestinal tract.

Summary

This review provides an overview of physiological conditions relevant to in-vivo drug release and of dissolution models which, based on current scientific findings on human gastrointestinal physiology, have been developed to enable a better prediction of the in-vivo performance of oral MR dosage forms.

Discriminatory dissolution method for quality control measurements of carbamazepine immediate release tablets based on in vitro--in vivo investigations

The purpose of this study was to identify a discriminatory dissolution method able to predict the in vivo performance of tablet formulations designed for carbamazepine (CBZ). After evaluation of dissolution medium and rotation speed using a 2⁵ central composite design and investigation of the in vivo release behaviors in beagle dogs, the dissolution method of CBZ 100 mg tablets was validated using a USP apparatus II, at a rotation speed of 75 rpm, and 900 ml deaerated water with 0.5% sodium lauryl sulfate (w/v) as the dissolution medium. Dissolution profiles were evaluated by the Weibull parameters and the modified fit factor, ƒ^(1,area). The in vitro-in vivo relationship of CBZ tablets was examined. Compared with the results from the USP and Chinese Pharmacopoeia monograph, the proposed system provides a superior discriminatory method. Since the dissolution method in pharmacopoeia for CBZ tablets is unable to distinguish between a good and a bad product, the method presented here can be used for the quality control testing of CBZ tablets.

Formulation and evaluation of controlled-release tablet of zolpidem tartrate by melt granulation technique

The present investigation describes the influence of the concentration of PEG 6000 as a melt binder and ratio of HPMC K4M : PVP on Zolpidem tartrate controlled-release tablet formulations using 3(2) full factorial design. The ratio of HPMC K4M and PVP K30 (X(1)) and the concentration of melt binder (X(2)) were selected as independent variables, and drug release at 1 hr (Q(1)), 4 hr (Q(4)), 8 hr (Q(8)), diffusion coefficient (n), and release rate constant (K) were selected as a dependent variable. Tablets were prepared by melt granulation technique and evaluated for various evaluation parameters. It was observed that concentration of melt binder had significant effect on Q(1), Q(4), n, and K Binder concentration 25% w/w was found optimum. Optimized formulation (F(7)) showed good similarity with theoretical profile of drug. The X(2) variable had a significant effect on dependent variables, and the X(1) variable had no significant effect on dependent variables.

Characterising the behaviour of poorly water soluble drugs in the intestine: application of biorelevant media for solubility, dissolution and transport studies

OBJECTIVES

Based on the knowledge of human intestinal fluids, compositions of biorelevant media and their impact on solubility, dissolution and permeability studies of poorly soluble drug compounds are discussed.

KEY FINDINGS

Human intestinal fluids show large variations with regard to composition and pH, which complicate the selection of biorelevant media. The influence of concentration and ratio of bile salts, phospholipids and hydrolysis products, such as monoglycerides and free fatty acids, in well characterised media, on the solubility, dissolution and permeability of a given drug provides valuable information on the behaviour of the drug in the intestine, thus enabling the prediction of the in-vivo absorption.

SUMMARY

This review discusses the implications of biorelevant media composition on the solubility, dissolution and permeability of poorly soluble drug compounds. Biorelevant media contain bile salts and phospholipids and when simulating the fed state also monoglycerides and free fatty acids. Solubility of some poorly soluble drugs increase independently of the type of surfactants included in the biorelevant media, while others have a higher solubility in monoglyceride- and fatty acid-containing media. This is independent of the log P (the octanol-water partition coefficient) of the drug. The use of biorelevant dissolution media improves the correlation to in-vivo data, compared with compendial media, and although the field of permeability studies is complex the use of biorelevant media in this setting shows promise with respect to a better prediction of absorption.

Comparison of dissolution profiles and serum concentrations of two lamotrigine tablet formulations

Objective: The aim of this study was to investigate the extent of variations in lamotrigine serum concentrations between two immediate-release tablet formulations. Data were compared with in vitro difference and similarity tests on dissolution profiles of the two formulations.

Methods: Dissolution characteristics of formulations A (reference) and B (test) were evaluated at three points spanning the physiologic pH range (pH 1.2, pH 4.5, pH 6.8). A model-independent approach of difference (f1) and similarity (f2) tests were applied to dissolution data. A clinical study was performed with 16 patients who were divided into two groups — one group received formulation A (n=9) and the other received formulation B (n=7). Lamotrigine steady-state concentrations were determined by high-performance liquid chromatography on a reverse-phase column.

Results: There were no statistically significant differences in lamotrigine serum concentrations between the two groups, although formulation B had slightly higher mean concentration values (formulation A: 3.97±4.1 μg/mL; formulation B: 5.78±2.7 μg/mL). Dissolution profiles of the two formulations were similar in the pH 1.2 dissolution medium; however, the dissolution profiles of formulation B were outside the dissolution limit (≥85% at 15 minutes) in the pH 4.5 and 6.8 dissolution media.

Conclusions: No significant changes in the serum concentrations of lamotrigine were seen between the two investigated formulations. There is no evidence to suggest that the differences in dissolution profiles at pH 4.5 and pH 6.8 affect the therapeutic efficacy of the formulations. It is evident that the doses of test formulation given to the patients were higher as a consequence of common assumption that generic products have a lower absorption rate, which is proven unnecessary in this study. This investigation was a pilot study and thus further investigations with a larger sample size are necessary to determine if there is a connection between dissolution profiles and the therapeutic effect of investigated formulations.

Selection of the most suitable dissolution method for an extended release formulation based on IVIVC level A obtained on cynomolgus monkey

OBJECTIVE

The purpose of this study is primarily to identify the most suitable in vitro dissolution method(s) for their ability to predict the in vivo performance of extended release prototype tablet formulations designed for a new chemical entity, Biopharmaceutic Classification System class II drug, weak base, based on the data collected in cynomolgus monkey.

MATERIALS AND METHODS

Different types of buffer at different pH were selected as dissolution medium resulting in a broad variety of release patterns (slow to fast). The in vivo and in vitro data were put in relation.

RESULTS

As a consequence of the discrimination between both tested formulations, the in vitro-in vivo correlation (IVIVC) qualities and shapes changed significantly. The obtained level A showed that the simple HCl medium was superior to biorelevant media and media containing surfactant when investigating IVIVCs in cynomolgus monkey. In addition, the results of dissolution in HCl suggested rather a diffusion mechanism of the extended release matrix formulation as the main factor of the release.

CONCLUSION

Adjusting dissolution testing conditions to match the behavior of the formulations in vitro with that in vivo by taking into account the properties of the drug and the formulation is a straightforward and useful approach in identifying a predictive method in the development of the IVIVC. These investigations will definitely help by derisking of new formulations as well as by rating changes in existing formulations with regard to their impact on bioavailability before entry into human.

A modified physiological BCS for prediction of intestinal absorption in drug discovery

In this study, the influence of physiologically relevant media on the compound position in a biopharmaceutical classification system (BCS) which resembled the intestinal absorption was investigated. Both solubility and permeability limited compounds (n = 22) were included to analyze the importance of each of these on the final absorption. Solubility was determined in three different dissolution media, phosphate buffer pH 6.5 (PhB 6.5), fasted state simulated intestinal fluid (FaSSIF), and fed state simulated intestinal fluid (FeSSIF) at 37 °C, and permeability values were determined using the 2/4/A1 cell line. The solubility data and membrane permeability values were used for sorting the compounds into a BCS modified to reflect the fasted and fed state. Three of the seven compounds sorted as BCS II in PhB 6.5 (high permeability, low solubility) changed their position to BCS I when dissolved in FaSSIF and/or FeSSIF (high permeability, high solubility). These were low dosed (20 mg or less) lipophilic molecules displaying solvation limited solubility. In contrast, compounds having solid-state limited solubility had a minor increase in solubility when dissolved in FaSSIF and/or FeSSIF. Although further studies are needed to enable general cutoff values, our study indicates that low dosed BCS Class II compounds which have solubility normally restricted by poor solvation may behave as BCS Class I compounds in vivo. The large series of compounds investigated herein reveals the importance of investigating solubility and dissolution under physiologically relevant conditions in all stages of the drug discovery process to push suitable compounds forward, to select proper formulations, and to reduce the risk of food effects.

Silica nanoparticles to control the lipase-mediated digestion of lipid-based oral delivery systems

We investigate the role of hydrophilic fumed silica in controlling the digestion kinetics of lipid emulsions, hence further exploring the mechanisms behind the improved oral absorption of poorly soluble drugs promoted by silica-lipid hybrid (SLH) microcapsules. An in vitro lipolysis model was used to quantify the lipase-mediated digestion kinetics of a series of lipid vehicles formulated with caprylic/capric triglycerides: lipid solution, submicrometer lipid emulsions (in the presence and absence of silica), and SLH microcapsules. The importance of emulsification on lipid digestibility is evidenced by the significantly higher initial digestion rate constants for SLH microcapsules and lipid emulsions (>15-fold) in comparison with that of the lipid solution. Silica particles exerted an inhibitory effect on the digestion of submicrometer lipid emulsions regardless of their initial location, i.e., aqueous or lipid phases. This inhibitory effect, however, was not observed for SLH microcapsules. This highlights the importance of the matrix structure and porosity of the hybrid microcapsule system in enhancing lipid digestibility as compared to submicrometer lipid emulsions stabilized by silica. For each studied formulation, the digestion kinetics is well correlated to the corresponding in vivo plasma concentrations of a model drug, celecoxib, via multiple-point correlations (R(2) > 0.97). This supports the use of the lipid digestion model for predicting the in vivo outcome of an orally dosed lipid formulation. SLH microcapsules offer the potential to enhance the oral absorption of poorly soluble drugs via increased lipid digestibility in conjunction with improved drug dissolution/dispersion.

Application of biorelevant dissolution tests to the prediction of in vivo performance of diclofenac sodium from an oral modified-release pellet dosage form

In vitro biorelevant dissolution tests enabling the prediction of in vivo performance of an oral modified-release (MR) dosage form were developed in this study. In vitro dissolution of MR diclofenac sodium pellets containing 100mg active ingredient was evaluated under simulated pre- and postprandial conditions using USP Apparatus 3 (reciprocating cylinder, Bio-Dis) and 4 (flow-through cell) and results compared with compendial methods using USP Apparatus 1 (basket) and 2 (paddle). In vivo, the effects of food on the absorption of diclofenac sodium from the pellet dosage form were investigated by administering the product to 16 healthy volunteers pre- and postprandially in a crossover-design study. The in vitro results were compared with the in vivo data by means of Level A in vitro-in vivo correlation (IVIVC) and Weibull distribution analysis. The compendial dissolution tests were not able to predict food effects. The biorelevant dissolution tests predicted correctly that the release (and hence absorption) of diclofenac sodium would be slower in the fed state than in the fasted state. No significant differences in extent of absorption due to changes in extent of release were predicted or observed. The results demonstrate good correlations between in vitro drug release and in vivo drug absorption in both pre- and postprandial states using the biorelevant dissolution test methods.

The science of USP 1 and 2 dissolution: present challenges and future relevance

Since its inception, the dissolution test has come under increasing levels of scrutiny regarding its relevance, especially to the correlation of results to levels of drug in blood. The technique is discussed, limited to solid oral dosage forms, beginning with the scientific origins of the dissolution test, followed by a discussion of the roles of dissolution in product development, consistent batch manufacture (QC release), and stability testing. The ultimate role of dissolution testing, "to have the results correlated to in vivo results or in vivo in vitro correlation," is reviewed. The recent debate on mechanical calibration versus performance testing using USP calibrator tablets is presented, followed by a discussion of variability and hydrodynamics of USP Apparatus 1 and Apparatus 2. Finally, the future of dissolution testing is discussed in terms of new initiatives in the industry such as quality by design (QbD), process analytical technology (PAT), and design of experiments (DOE).

Silica-lipid hybrid (SLH) microcapsules: a novel oral delivery system for poorly soluble drugs

A silica-lipid hybrid (SLH) microcapsule system for oral delivery of poorly water-soluble drugs is reported for the first time. For the model drug celecoxib (CEL), SLH microcapsules composed of medium-chain triglycerides, lecithin and silica nanoparticles; with an internal porous matrix structure, were shown to offer several physicochemical and biopharmaceutical advantages in comparison with unmodified drug, lipid emulsion, dry emulsion and the commercial product, Celebrex. DSC and XRD analyses confirmed non-crystalline CEL in SLH microcapsules and verified medium term physical stability. Dissolution under sink conditions revealed a 2- to 5-fold increase in dissolution efficiencies (%DE) and significantly reduced t(50%) (> or =50-fold) for CEL formulated as SLH microcapsules. Orally dosed in vivo studies in rats demonstrated superior pharmacokinetics for SLH microcapsules. Specifically, the fasted-state bioavailability (F) was statistically higher (p<0.05) than for aqueous suspension, lipid solution, o/w emulsion and a maltodextrin-stabilised dry emulsion, and was greater than for Celebrex. SLHs showed the highest maximum plasma concentration (C(max)) among all tested formulations (p<0.05). Linear correlations were observed between %DE and the pharmacokinetic parameters (F and C(max)). It is postulated that SLH microcapsules improve CEL oral absorption via dissolution enhancement, potentially in conjunction with other unexplored mechanisms, hence offering the possibility of dose reduction for improved therapeutic efficacy and cost-effectiveness of poorly soluble drugs.