Improvement of tablet coating uniformity using a quality by design approach

A combination of analytical and statistical methods is used to improve a tablet coating process guided by quality by design (QbD) principles. A solid dosage form product was found to intermittently exhibit bad taste. A suspected cause was the variability in coating thickness which could lead to the subject tasting the active ingredient in some tablets. A number of samples were analyzed using a laser-induced breakdown spectroscopy (LIBS)-based analytical method, and it was found that the main variability component was the tablet-to-tablet variability within a lot. Hence, it was inferred that the coating process (performed in a perforated rotating pan) required optimization. A set of designed experiments along with response surface modeling and kriging method were used to arrive at an optimal set of operating conditions. Effects of the amount of coating imparted, spray rate, pan rotation speed, and spray temperature were characterized. The results were quantified in terms of the relative standard deviation of tablet-averaged LIBS score and a coating variability index which was the ratio of the standard deviation of the tablet-averaged LIBS score and the weight gain of the tablets. The data-driven models developed based on the designed experiments predicted that the minimum value of this index would be obtained for a 6% weight gain for a pan operating at the highest speed at the maximum fill level while using the lowest spraying rate and temperature from the chosen parametric space. This systematic application of the QbD-based method resulted in an enhanced process understanding and reducing the coating variability by more than half.     

Dependence of Laser-induced Breakdown Spectroscopy Results on Pulse Energies and Timing Parameters Using Soil Simulants

The dependence of some LIBS detection capabilities on lower pulse energies (<100 mJ) and timing parameters were examined using synthetic silicate samples. These samples were used as simulants for soil and contained minor and trace elements commonly found in soil at a wide range of concentrations. For this study, over 100 calibration curves were prepared using different pulse energies and timing parameters; detection limits and sensitivities were determined from the calibration curves. Plasma temperatures were also measured using Boltzmann plots for the various energies and the timing parameters tested. The electron density of the plasma was calculated using the full-width half maximum (FWHM) of the hydrogen line at 656.5 nm over the energies tested. Overall, the results indicate that the use of lower pulse energies and non-gated detection do not seriously compromise the analytical results. These results are very relevant to the design of field- and person-portable LIBS instruments.     

Nutritional and toxic elemental analysis of dry fruits using laser induced breakdown spectroscopy (LIBS) and inductively coupled plasma atomic emission spectrometry (ICP-AES)

Quantitative investigation of essential and trace heavy elements present in health-beneficial dry fruits (Pistachio, Almonds, Black walnut, White walnut, and Cashew) was investigated using Laser Induced Breakdown Spectroscopy. For an accurate elemental exposure using LIBS technique, the local thermo-dynamical equilibrium of the laser induced plasma was established and verified using McWhirter criterion based on the electron number density in the plasma. Earlier to engage, our LIBS detector was optimized. For quantification of elements, standard calibration curves (CC)-LIBS method was applied. Using our LIBS system, the nutritional elements such as Al, Mg, Ca, Fe, K, Zn, and Na and toxins like Pb, Cr, and Cu were detected in dry fruits. The elemental quantification of dry fruit contents were validated using standard (ICP-AES) method and the relative accuracy of our experimental setup in comparison to ICP approach was in the ranging from 0.1 to 0.3 at 2.5-% error confidence.     

Characterization of tablet film coatings using a laser-induced breakdown spectroscopic technique

Laser-induced breakdown spectroscopy (LIBS) was evaluated as an early phase process analytical technology (PAT) tool for the rapid characterization of pharmaceutical tablet coatings. Measurement of coating thickness, uniformity, and photodegradation-predictive potential of the technique were evaluated. Model formulation tablets were coated with varying amounts (2%-4% wt/wt) of red and yellow Opadry II, and a pulsed laser was used to sample at multiple sites across the tablet face. LIBS was able to successfully detect the emissions of Fe and Ti in the coated samples, and a proportional increase in signal with coating thickness was observed. Batch-to-batch variability in the coating procedure was also easily monitored by LIBS. The coating thickness was non-uniform across the tablet surface with higher thickness at the edges, likely due to the concave shape of the tablet. Film coating levels and color of the film had been subjected to photostability studies according to the International Conference on Harmonisation (ICH) guideline to determine effectiveness of the film coats. LIBS measurements of coating thickness provided a good correlation (R (2) > 0.99) to photodegradation as measured by high-performance liquid chromatography (HPLC). Last, the concentration of Fe in the coating was varied and monitored by LIBS. Increasing photostability was observed with increasing levels of ferric oxide, providing a new understanding of the photoprotection mechanism in the coated formulation. Determination of levels of ferric oxide and coating thickness by LIBS demonstrated its utility as a good PAT tool for the determination of photoprotection of the drug, thereby enabling facile optimization of the coating process.     

High-performance liquid chromatographic determination of isoniazid, acetylisoniazid and hydrazine in biological fluids

The basic principle of derivatization of a hydrazide moiety with an aldehyde as applied in the method developed by Lacroix et al. [J. Chromatogr., 307 (1984) 137–144] for the quantitation of isoniazid and acetylisoniazid was imppoved by modification, standardization and extension to allow quantitation of hydrazine in patient samples. It could be shown that 40 μl of 1% methanonic cinnamaldehyde per 200 μl of deproteinized analysate gave maximal chromophoric isoniazid-cinnamaldehyde conjugate, read at 340 nm. The hydrolytic loss of isoniazid, crucial to the quantitation of acetylisoniazid, could be compensated for by introduction of an appropriate set of calibration curves. Although the method described here allows quantitation of monoacetylhydrazie and diacetylhydrazine, in addition to hydrazine, in mono-spiked samples, the method cannot be used for the quantitation of the acetylated metabolites of hydrazine in patient samples because of a lack of specificity. Linear calibration curves in the range 1–25 μg/ml for isoniazid and acetylisoniazid, 10–400 ng/ml for hydrazine and 50–1000 ng/ml for mono-acetylhydrazine and diacetylhydrazine, could be constructed; analyte recoveries approaching 100% could be achieved in all instances.     

Investigation on drug dissolution and particle characteristics of pellets related to manufacturing process variables of high-shear granulation

There is a growing interest for multiparticulate solid dosage forms such as pellets, because of their several advantages over tablets during drug therapy. It is essential to investigate the drug dissolution process which can be influenced by the composition and manufacturing process technology, too. This study was performed applying experimental design in order to evaluate the effects of independent process variables during high-shear pelletisation, taking the impeller speed (x1) and granulation binder flow rate (x2) as factors into consideration. Theophylline containing pellet formulation was prepared using a matrix consisted of ethylcellulose, microcrystalline cellulose and lactose. Dissolution profiles were modeled by the Weibull function to evaluate the power of process variables. Both process variables were powerful to influence the particle agglomeration. A linear regression was found between the particle size and the diffuse reflectance values after the Kubelka-Munk transformation. Differences in the diffuse reflectance spectra of pellet samples related to particle size offer a fast instrumental method for the in-process control.     

Utility of ninhydrin reagent for spectrofluorimetric determination of heptaminol in human plasma

For the determination of heptaminol (HEP) in its authentic and dosage form as well as in human plasma, a new simple, sensitive and cheap fluorimetric method of analysis was developed and validated. The presented method is based on the reaction between aliphatic primary amino moiety present in HEP with ninhydrin and phenylacetaldehyde using Torell and Stenhagen buffer at pH 8.2 that yields a highly fluorescent derivative which after excitation at 390 nm showed a fluorescence emission at 464 nm. The effects of various experimental factors on both the development and stability of the fluorescent product was evaluated and optimized. In the concentration range (0.5–6.0 μg/ml), the constructed calibration curve was linear with a good correlation coefficient (0.9997) and the calculated limit of detection (LOD) and limit of quantitation (LOQ) were 0.14 and 0.43 respectively. The presented method was successfully applied for determination of Corasore® tablets and validated according to ICH guidelines.     

Prediction of Tablet Film-coating Thickness Using a Rotating Plate Coating System and NIR Spectroscopy

The purpose of this research was to create a calibration model based on near-infrared (NIR) spectroscopy data obtained during a small-scale coating process to predict in-line the coating layer thickness of tablets coated in a side-vented drum coater. The developed setup for the small-scale coating process consisted of a rotating plate with 20 tablets molds that pass a spraying unit, a heating unit, and an in-line NIR spectroscopy probe during one rotation. High-density polyethylene (HDPE) was compressed to flat-faced tablets, and these were coated with a sustained release coating suspension containing Kollicoat IR and Kollicoat SR 30D. The film thickness of these tablets was determined for each tablet individually with a digital micrometer. A calibration model of predicted film thickness versus real-film thickness using PLS regression was developed. This model was tested against in-line NIR data obtained from a coating drum process, in which biconvex HDPE tablets were film-coated with the same film-coating suspension. The model predicted a final coating thickness of 240 μm, while the measured average thickness (n = 100 tablets) was 210 μm. Taking into account the use of a different setup and differently shaped tablets, it was possible to predict the coating thickness with accuracy comparable to the one of the digital micrometer. Thus, the small-scale rotating plate system was found to be an efficient means of preparing calibration model for a tablet-coating drum process.     

Glucose concentration determination by means of fluorescence emission spectra of soluble and insoluble glucose oxidase: some useful indications for optical fibre-based sensors

By using soluble and insoluble glucose oxidase, the changes in intrinsic emission fluorescence in the visible spectral region were studied as a function of glucose concentration. Insoluble glucose oxidase (GOD) was obtained by entrapment in a gelatine membrane or by covalent attachment on an agarose membrane grafted with hexamethylendiamine. The intensity of the fluorescence emission peak at 520 nm or the value of the integral fluorescence area from 480 to 580 nm were taken as physical parameters representative of the glucose concentration during the enzyme reaction. By using these parameters, linear calibration curves for glucose concentration were obtained. The extension of the calibration curve and the sensitivity of the adopted systems were found to be dependent on the enzyme state (free or immobilized) and on the immobilization method. In particular, it was found that the extent of the linear range of the calibration curves is increased of one order of magnitude when the glucose oxidase is immobilized, while the sensitivity of the measure is decreased of one order of magnitude by the immobilization process. Measures carried out by using the integral fluorescence area resulted more sensitive than those obtained with the peak size. Useful indications for the construction of optical fibre-based sensors were drawn from the reported results.     

Condensation of heptaminol hydrochloride for its spectrofluorimetric determination in pure form and tablets: application in human plasma

A sensitive, simple, accurate and less expensive fluorimetric method was designed and validated for analysis of heptaminol HCl in both its pure and dosage forms, as well as in human plasma. The main principle used in the proposed approach was the condensation reaction between heptaminol's primary amino moiety and ethyl acetoacetate/formaldehyde reagents, giving a derivative that was highly fluorescent at 416 nm after excitation at 350 nm. Various experimental parameters that affected either the product's development or its stability were evaluated and optimized. The constructed calibration curve was linear over the range 0.2–2 μg/ml, with a good correlation coefficient (0.9996). Both the calculated limit of detection and limit of quantitation were 0.06 and 0.18 μg/ml, respectively. The presented approach was a success when used to determine Corasore® tablets and was validated according to International Council for Harmonisation guidelines.     

Validation and implementation of a liquid chromatography/tandem mass spectrometry assay to quantitate ON 01910.Na, a mitotic progression modulator, in human plasma

A reverse-phase high performance liquid chromatographic method with tandem mass spectrometry (LC-MS/MS) was developed and validated for the quantitation of ON 01910.Na, a novel synthetic benzyl styryl sulfone, in human plasma. The assay involved a simple sample preparation with acetonitrile protein precipitation. ON 01910.Na and the internal standard temazepam were separated on a Waters X-Terra MS C(18) column with mobile phase of acetonitrile containing 0.1% formic acid /10mM ammonium acetate (55:45, v/v) using isocratic flow at 0.2 mL/min for 5 min. The analytes were monitored by tandem-mass spectrometry with electrospray positive ionization. Two calibration curves were generated over the range of 10-2000 ng/mL and 100-20000 ng/mL. The lower limit of quantitation (LLOQ) was 10 ng/mL for ON 01910.Na in human plasma. The accuracy and within- and between-day precisions were within the acceptance criteria for bioanalytical assays. ON 01910.Na was found stable in plasma at -70 degrees C for at least 1 year. The method was successfully applied to characterize the plasma concentration-time profiles of ON 01910.Na in the cancer patients in the Phase I study.     

Development and validation of a new gas flame ionization detector method for the determination of finasteride in tablets

A simple, rapid, and sensitive method based on gas chromatography with flame ionization detection is described for the determination of finasteride in tablets. The method is based on the derivatization of finasteride with N,O-bis(trimethylsilyl)trifluoroacetamide-1% trimethylchlorosilane at 60 degrees C for 30 min. The method was validated for specificity, linearity, precision, accuracy, robustness, and limit of quantification. The degree of linearity of the calibration curves, the percentage recoveries of finasteride, and the limit of detection (LOD) and limit of quantification (LOQ) for the gas chromatographic method were determined. The assay was linear over the concentration range of 10 to 50 microg ml(-1) (R approximately 0.999). LOQ and LOD (signal/noise ratio = 10) were found to be 10 and 2 microg ml(-1), respectively. The method was found to be simple, specific, precise, accurate, and reproducible. All of the validation parameters were within the acceptance range. The developed method was applied successfully to estimate the amount of finasteride in tablets. The results were compared statistically with those obtained by the official method using t and F tests. There was no significant difference between the two methods with respect to mean values and standard deviations at the 95% confidence level.     

Investigation of Critical Core Formulation and Process Parameters for Osmotic Pump Oral Drug Delivery

Push–pull osmotic pump (PPOP) tablets of a practically insoluble model drug were developed and the effect of various formulation and process parameters on tablet performance was evaluated in order to identify critical factors. The formulation factors such as the viscosity grade of polyethylene oxide as the primary polymer as well as the level and location of osmogen within the bilayer tablets led to a difference in performance of osmotic tablets and hence should be critically evaluated in the design of such dosage forms. Modification of granulation process, i.e., the granulating liquid composition or drying method of granules, did not impact the drug release from the osmotic tablets at the evaluated scale of this study. The influence of varying dose and aqueous solubility of other model drugs (i.e., theophylline, acetaminophen, and verapamil HCl) on the developed PPOP template was also investigated. Results showed that irrespective of the perceived complexity of development and manufacturing of osmotic pumps, the osmotic tablets in this study demonstrated a robust and yet flexible platform in accommodating different types of drug candidates, regardless of solubility, for the dose levels below 25% w/w of the pull layer formulation.     

Quantitation of malondialdehyde in gingival crevicular fluid by a high-performance liquid chromatography-based method

Lipid peroxidation (LPO) has been associated with periodontal disease, and the evaluation of malondialdehyde (MDA) in the gingival crevicular fluid (GCF), an inflammatory exudate from the surrounding tissue of the periodontium, may be useful to clarify the role of LPO in the pathogenesis of periodontal disease. We describe the validation of a method to measure MDA in the GCF using high-performance liquid chromatography. MDA calibration curves were prepared with phosphate-buffered solution spiked with increasing known concentrations of MDA. Healthy and diseased GCF samples were collected from the same patient to avoid interindividual variability. MDA response was linear in the range measured, and excellent agreement was observed between added and detected concentrations of MDA. Samples' intra- and interday coefficients of variation were below 6.3% and 12.4%, respectively. The limit of quantitation (signal/noise=5) was 0.03 μM. When the validated method was applied to the GCF, excellent agreement was observed in the MDA quantitation from healthy and diseased sites, and diseased sites presented more MDA than healthy sites (P<0.05). In this study, a validated method for MDA quantitation in GCF was established with satisfactory sensitivity, precision, and accuracy.     

Automated calibration and in-line measurement of product quality during therapeutic monoclonal antibody purification using Raman spectroscopy

Current manufacturing and development processes for therapeutic monoclonal antibodies demand increasing volumes of analytical testing for both real-time process controls and high-throughput process development. The feasibility of using Raman spectroscopy as an in-line product quality measuring tool has been recently demonstrated and promises to relieve this analytical bottleneck. Here, we resolve time-consuming calibration process that requires fractionation and preparative experiments covering variations of product quality attributes (PQAs) by engineering an automation system capable of collecting Raman spectra on the order of hundreds of calibration points from two to three stock seed solutions differing in protein concentration and aggregate level using controlled mixing. We used this automated system to calibrate multi-PQA models that accurately measured product concentration and aggregation every 9.3 s using an in-line flow-cell. We demonstrate the application of a nonlinear calibration model for monitoring product quality in real-time during a biopharmaceutical purification process intended for clinical and commercial manufacturing. These results demonstrate potential feasibility to implement quality monitoring during GGMP manufacturing as well as to increase chemistry, manufacturing, and controls understanding during process development, ultimately leading to more robust and controlled manufacturing processes.     

Determination of figures of merit for near-infrared and raman spectrometry by net analyte signal analysis for a 4-component solid dosage system

Process analytical technology has elevated the role of sensors in pharmaceutical manufacturing. Often the ideal technology must be selected from many suitable candidates based on limited data. Net analyte signal (NAS) theory provides an effective platform for method characterization based on multivariate figures of merit (FOM). The objective of this work was to demonstrate that these tools can be used to characterize the performance of 2 dissimilar analyzers based on different underlying spectroscopic principles for the analysis of pharmaceutical compacts. A fully balanced, 4-constituent mixture design composed of anhydrous theophylline, lactose monohydrate, microcrystalline cellulose, and starch was generated; it consisted of 29 design points. Six 13-mm tablets were produced from each mixture at 5 compaction levels and were analyzed by near-infrared and Raman spectroscopy. Partial least squares regression and NAS analyses were performed for each component, which allowed for the computation of FOM. Based on the calibration error statistics, both instruments were capable of accurately modeling all constituents. The results of this work indicate that these statistical tools are a suitable platform for comparing dissimilar analyzers and illustrate the complexity of technology selection.     

Micelle-enhanced spectrofluorimetric method for the rapid determination of bronchodilator terbutaline and its prodrug bambuterol: application for content uniformity test

A novel, simple and sensitive spectrofluorimetric approach for determination of terbutaline sulphate (TER) and its prodrug bambuterol (BAM) in their pure and pharmaceutical dosage forms was developed. The suggested approach depends on enhancing the native fluorescence of either TER or BAM at 315 and 297.2 nm after excitation at 277 and 259 nm, respectively, using sodium dodecyl sulphate (SDS) as a micellar medium. In the presence of 0.7% w/v SDS, ~1.38-fold and 1.18-fold enhancement is achieved in the relative fluorescence intensity (RFI) of TER and BAM, respectively. The fluorescence–concentration curves were rectilinear over the concentration range 0.8–16 μg ml⁻¹, with detection limits (LOD) of 0.252 and 0.26 (μg ml⁻¹), quantitation limits (LOQ) of 0.76 and 0.79 (μg ml⁻¹), determination coefficients (r2) of 0.9981, and slopes of 45.92 and 10.44 for TER and BAM, respectively. The suggested approach was validated in accordance with International Council for Harmonisation criteria and was effectively applied in the analysis of the studied drugs in their commercial tablets. The high sensitivity of the proposed approach allows its application in evaluating the content uniformity testing of the studied drugs in their tablets through using the official United States Pharmacopeia criteria. Statistical analogies of the findings with that of the reported methods showed really good harmony and indicated no major differences in precision and accuracy.     

Case study: The characterization and implementation of dielectric spectroscopy (biocapacitance) for process control in a commercial GMP CHO manufacturing process

Dielectric spectroscopy (biocapacitance) is an up-and-coming technology for real time monitoring of biomass in cell culture processes and has opened the door for next-generation cell culture process control techniques such as automated on-demand nutrient feeding. In this case study we empirically demonstrate the lower limit of quantitation (LOQ), probe-to-probe consistency, and scalability of in situ biocapacitance probes using data generated from small- and large-scale Chinese hamster ovary (CHO) bioreactor cultures. The process understanding experiments culminated in the use of biocapacitance for process control in the current good manufacturing practices (GMP) manufacturing environment, first to automate the dilution of seed train cultures during scale-up stages and later as a method of predicting future glucose demand. The automated biomass-probe-based inoculation strategy yielded consistent results in six consecutive seed trains in the GMP manufacturing suite. In the process of improving our understanding of the technology we determined that biocapacitance could additionally be used as an indicator of a shift in the salt balance of a cell culture, and that collecting real time biomass data via biocapacitance has the potential to reduce the total timeline for feed strategy development by providing additional insights into culture performance which are not otherwise apparent using conventional optical cell counting methods.     

Influence of Geometry on the Drug Release Profiles of Stereolithographic (SLA) 3D-Printed Tablets

Additive manufacturing (3D printing) permits the fabrication of tablets in shapes unattainable by powder compaction, and so the effects of geometry on drug release behavior is easily assessed. Here, tablets (printlets) comprising of paracetamol dispersed in polyethylene glycol were printed using stereolithographic 3D printing. A number of geometric shapes were produced (cube, disc, pyramid, sphere and torus) with either constant surface area (SA) or constant surface area/volume ratio (SA/V). Dissolution testing showed that printlets with constant SA/V ratio released drug at the same rate, while those with constant SA released drug at different rates. A series of tori with increasing SA/V ratio (from 0.5 to 2.4) were printed, and it was found that dissolution rate increased as the SA/V ratio increased. The data show that printlets can be fabricated in multiple shapes and that dissolution performance can be maintained if the SA/V ratio is constant or that dissolution performance of printlets can be fine-tuned by varying SA/V ratio. The results suggest that 3D printing is therefore a suitable manufacturing method for personalized dosage forms.     

Validity of a Power Law Approach to Model Tablet Strength as a Function of Compaction Pressure

Designing quality into dosage forms should not be only based on qualitative or purely heuristic relations. A knowledge space must be generated, in which at least some mechanistic understanding is included. This is of particular interest for critical dosage form parameters like the strength of tablets. In line with this consideration, the scope of the work is to explore the validity range of a theoretically derived power law for the tensile strength of tablets. Different grades of microcrystalline cellulose and lactose, as well as mixtures thereof, were used to compress model tablets. The power law was found to hold true in a low pressure range, which agreed with theoretical expectation. This low pressure range depended on the individual material characteristics, but as a rule of thumb, the tablets having a porosity of more than about 30% or being compressed below 100 MPa were generally well explained by the tensile strength relationship. Tablets at higher densities were less adequately described by the theory that is based on large-scale heterogeneity of the relevant contact points in the compact. Tablets close to the unity density therefore require other theoretical approaches. More research is needed to understand tablet strength in a wider range of compaction pressures.