Process control and scale-up of pharmaceutical wet granulation processes: a review

Real-time monitoring of granule properties during high shear wet granulation by near-infrared spectroscopy with a chemometrics approach

An in-line near-infrared spectroscopy monitoring method was developed for analyzing granule properties during a high shear wet granulation process.

Enhancing tablet disintegration characteristics of a highly water-soluble high-drug-loading formulation by granulation process

The objective of this study was to improve the disintegration and dissolution characteristics of a highly water-soluble tablet matrix by altering the manufacturing process. A high disintegration time along with high dependence of the disintegration time on tablet hardness was observed for a high drug loading (70% w/w) API when formulated using a high-shear wet granulation (HSWG) process. Keeping the formulation composition mostly constant, a fluid-bed granulation (FBG) process was explored as an alternate granulation method using a 2^(4-1) fractional factorial design with two center points. FBG batches (10 batches) were manufactured using varying disingtegrant amount, spray rate, inlet temperature (T) and atomization air pressure. The resultant final blend particle size was affected significantly by spray rate (p = .0009), inlet T (p = .0062), atomization air pressure (p = .0134) and the interaction effect between inlet T*spray rate (p = .0241). The compactibility of the final blend was affected significantly by disintegrant amount (p < .0001), atomization air pressure (p = .0013) and spray rate (p = .05). It was observed that the fluid-bed batches gave significantly lower disintegration times than the HSWG batches, and mercury intrusion porosimetry data revealed that this was caused by the higher internal pore structure of tablets manufactured using the FBG batches.

A quality by design approach to scale-up of high-shear wet granulation process

High-shear wet granulation is a complex process that in turn makes scale-up a challenging task. Scale-up of high-shear wet granulation process has been studied extensively in the past with various different methodologies being proposed in the literature. This review article discusses existing scale-up principles and categorizes the various approaches into two main scale-up strategies - parameter-based and attribute-based. With the advent of quality by design (QbD) principle in drug product development process, an increased emphasis toward the latter approach may be needed to ensure product robustness. In practice, a combination of both scale-up strategies is often utilized. In a QbD paradigm, there is also a need for an increased fundamental and mechanistic understanding of the process. This can be achieved either by increased experimentation that comes at higher costs, or by using modeling techniques, that are also discussed as part of this review.

Comparative pharmacokinetics of a new oral long-acting formulation of doxycycline hyclate: A canine clinical trial

Doxycicline is used in dogs as treatment of several bacterial infections, mycoplasma, chlamydia and rickettsial diseases. However, it requires long treatments and several doses to be effective. The aim of this study was to determine the pharmacokinetics of four formulations of doxycycline hyclate, administered orally, with different proportions of excipients, acrylic acid-polymethacrylate-based matrices, to obtain longer therapeutic levels than conventional formulation. Forty-eight dogs were randomly assigned in five groups to receive a single oral dose (20mg/kg) of doxycycline hyclate without excipients (control) or a long-acting formulation containing doxycycline, acrylic acid polymer, and polymethacrylate in one of the following four proportions: DOX1(1:0.25:0.0035), DOX2(1:0.5:0.0075), DOX3 (1:1:0.015), or DOX4(1:2:0.0225). Temporal profiles of serum concentrations were obtained at several intervals after each treatment. Therapeutic concentrations were observed for 60h for DOX1 and DOX4, 48h for DOX2 and DOX3 and only 24h for DOX-C. None of the pharmacokinetic parameter differed significantly between DOX1 and DOX2 or between DOX3 and DOX4; however, the findings for the control treatment were significantly different compared to all four long-acting formulations. Results indicated that DOX1 had the most adequate pharmacokinetic-pharmacodynamic relationships for a time-dependent drug and had longer release times than did doxycycline alone. However, all four formulations can be effective depend on the minimum effective serum doxycycline concentration of the microorganism being treated. These results suggest that the use of any of these formulations can reduce the frequency of administration, the patient's stress, occurrence of adverse effects and the cost of treatment.

Pharmacokinetics of an oral extended-release formulation of doxycycline hyclate containing acrylic acid and polymethacrylate in dogs

OBJECTIVE

To determine the pharmacokinetics of doxycycline hyclate administered orally in the form of experimental formulations with different proportions of acrylic acid-polymethacrylate-based matrices.

ANIMALS

30 healthy adult dogs.

PROCEDURES

In a crossover study, dogs were randomly assigned (in groups of 10) to receive a single oral dose (20 mg/kg) of doxycycline hyclate without excipients (control) or extended-release formulations (ERFs) containing doxycycline, acrylic acid polymer, and polymethacrylate in the following proportions: 1:0.5:0.0075 (ERF1) or 1:1:0.015 (ERF2). Serum concentrations of doxycycline were determined for pharmacokinetic analysis before and at several intervals after each treatment.

RESULTS

Following oral administration to the study dogs, each ERF resulted in therapeutic serum doxycycline concentrations for 48 hours, whereas the control treatment resulted in therapeutic serum doxycycline concentrations for only 24 hours. All pharmacokinetic parameters for ERF1 and ERF2 were significantly different; however, findings for ERF1 did not differ significantly from those for the control treatment.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicated that both ERFs containing doxycycline, acrylic acid polymer, and polymethacrylate had an adequate pharmacokinetic-pharmacodynamic relationship for a time-dependent drug and a longer release time than doxycycline alone following oral administration in dogs. Given the minimum effective serum doxycycline concentration of 0.26 μg/mL, a dose interval of 48 hours can be achieved for each tested ERF. This minimum inhibitory concentration has the potential to be effective against several susceptible bacteria involved in important infections in dogs. Treatment of dogs with either ERF may have several benefits over treatment with doxycycline alone.

Gamma scintigraphic evaluation of floating gastroretentive tablets of metformin HCl using a combination of three natural polymers in rabbits

The present research was aimed at formulating a metformin HCl sustained-release formulation from a combination of polymers, using the wet granulation technique. A total of 16 formulations (F1–F16) were produced using different combinations of the gel-forming polymers: tamarind kernel powder, salep (palmate tubers of Orchis morio), and xanthan. Post-compression studies showed that there were no interactions between the active drug and the polymers. Results of in vitro drug-release studies indicated that the F10 formulation which contained 5 mg of tamarind kernel powder, 33.33 mg of xanthan, and 61.67 mg of salep could sustain a 95% release in 12 hours. The results also showed that F2 had a 55% similarity factor with the commercial formulation (C-ER), and the release kinetics were explained with zero order and Higuchi models. The in vivo study was performed in New Zealand White rabbits by gamma scintigraphy; the F10 formulation was radiolabeled using samarium (III) oxide (¹⁵³Sm₂O₃) to trace transit of the tablets in the gastrointestinal tract. The in vivo data supported the retention of F10 formulation in the gastric region for 12 hours. In conclusion, the use of a combination of polymers in this study helped to develop an optimal gastroretentive drug-delivery system with improved bioavailability, swelling, and floating characteristics.

A critical review on tablet disintegration

CONTEXT

Tablet disintegration is an important factor for drug release and can be modified with excipients called tablet disintegrants. Tablet disintegrants act via different mechanisms and the efficacy of these excipients is influenced by various factors.

OBJECTIVE

In this review, the existing literature on tablet disintegration is critically reviewed. Potential disintegration mechanisms, as well as impact factors on the disintegration process will be discussed based on experimental evidence.

METHODS

Search terms for Scopus and Web of Science included "tablet disintegration", "mechanism tablet disintegration", "superdisintegrants", "disintegrants", "swelling force", "disintegration force", "disintegration mechanisms", as well as brand names of commonly applied superdisintegrants. References of identified papers were screened as well.

RESULTS

Experimental data supports swelling and shape recovery as main mechanisms of action of disintegrants. Other tablet excipients and different manufacturing techniques greatly influence the disintegration process.

CONCLUSION

The use of different excipients, experimental setups and manufacturing techniques, as well as the demand for original research led to a distinct patchwork of knowledge. Broader, more systematic approaches are necessary not only to structure the past but also future findings.

Continuous twin screw melt granulation of glyceryl behenate: Development of controlled release tramadol hydrochloride tablets for improved safety

Interest in granulation processes using twin screw extrusion machines is rapidly growing. The primary objectives of this study were to develop a continuous granulation process for direct production of granules using this technique with glyceryl behenate as a binder, evaluate the properties of the resulting granules and develop controlled release tablets containing tramadol HCl. In addition, the granulation mechanism was probed and the polymorphic form of the lipid and drug release rate were evaluated on stability. Granules were prepared using a Leistritz NANO16 twin screw extruder operated without a constricting die. The solid state of the granules were characterized by differential scanning calorimetry and X-ray diffraction. Formulated tablets were studied in 0.1N HCl containing 0-40% ethanol to investigate propensity for alcohol induced dose dumping. The extrusion barrel temperature profile and feed rate were determined to be the primary factors influencing the particle size distribution. Granules were formed by a combination immersion/distribution mechanism, did not require subsequent milling, and were observed to contain desirable polymorphic forms of glyceryl behenate. Drug release from tablets was complete and controlled over 16 h and the tablets were determined to be resistant to alcohol induced dose dumping. The drug release rate from the tablets was found to be stable at 40°C and 75% relative humidity for the duration of a 3 month study.

New approach to evaluate the lubrication process in various granule filling levels and rotating mixer sizes using a thermal effusivity sensor

The principles of thermal effusivity are applied to an understanding of the detailed mechanisms of the lubrication process in a rotating mixer. The relationships and impact of the lubrication process by the pattern of powder flow, the filling level, and the rotating mixer size were investigated. Thermal effusivity profiles of the lubrication process, as obtained, indicate that lubrication is a two-phase process. The intersection point of the first and second phases (IPFS) is influenced by changing the filling level, thus changing the resulting number of avalanche flows created. The slope of the second phase (SSP) is influenced by the relationship between the number and the length of avalanche flows. Understanding this difference between the first and second phases is important to successfully evaluate the impact of proposed changes in the lubrication process. From this knowledge, a predictive model of the lubrication profile can be generated to allow an evaluation of proposed changes to the lubrication process. This model allows estimation of the lubrication profile at different filling levels and in different rotating mixer sizes. In this study, the actual lubrication profile almost coincides with the model predicted lubrication profile. Based on these findings, it is assumed that lubrication profiles at a commercial scale can be predicted from data generated at the laboratory scale. Further, it is assumed that changes in the filling level can also be estimated from the laboratory or current data.

Solid formulations by a nanocrystal approach: critical process parameters regarding scale-ability of nanocrystals for tableting applications

Nanocrystallization is among the foremost drug delivery platform approaches for the commercial development of poorly soluble drugs. There exists an urge to enable a universal shift of the production of the solid nanocrystal formulations from laboratory scale to industrially feasible scale. The success of any formulation development depends on its transferability to large scale manufacture. The objectives of the study were to increase the nanocrystallization batch size and to screen and optimize parameters for industrially feasible itraconazole (ITC) and indomethacin (IND) nanocrystal composition for tablet formulation. Thus, ITC and IND were transformed into nanocrystal suspensions, using an increased batch size of a wet milling process, freeze-dried, and further developed into both direct compression (DC) and granulated (G) tableting masses. According to the investigated powder and tablet properties (true density, flowability, dose uniformity, maximum upper punch force, crushing strength, dissolution and disintegration) and stability testings, it was clear that the amount of the nanocrystals in the solid tablet formulation is critical in order to fully utilize the benefits of the nanocrystals, i.e., fast dissolution, and to produce high-quality tablets. The DC designs of both the model drugs with compositions including 40% of freeze-dried nanocrystalline drug powder outperformed the corresponding granulated tablets in all parameters after the stability surveillance.

A comparison of granules produced by high-shear and fluidized-bed granulation methods

Placebo granules were manufactured by both wet high-shear and fluidized-bed techniques. The granules were compared based on size, shape, surface morphology, and a variety of different flowability measurements. This comparison showed that granule formation and growth were different, with induction growth for high-shear granulation and steady growth for fluidized-bed granulation. Final granules from high-shear granulation were more spherical and dense compared with the irregular granules from fluidized-bed granulation. The high-shear granules demonstrated better overall flow properties.

Drug nanocrystals: A way toward scale-up

Drug nanocrystals comprise unique drug delivery platforms playing a significantly important and distinctive role in drug delivery and as such, the industry and academia are spending a lot of their time and money in developing the nanocrystal products. The current research works in this field depict a vivid shift from lab scale optimization studies to scale up focused studies. In this emerging scenario of nanocrystal technology, a review on some exemplary and progressing research studies with either scalability as their objective or upscaling as their future scope may smoothen the future upscaling attempts in this field. Hence, this paper reviews the efforts of such research works as case studies since an analysis of such research studies may input certain beneficial knowledge to carry out more scale up based research works on nanocrystals.

In silico modeling of in situ fluidized bed melt granulation

Fluidized bed melt granulation has recently been recognized as a promising technique with numerous advantages over conventional granulation techniques. The aim of this study was to evaluate the possibility of using response surface methodology and artificial neural networks for optimizing in situ fluidized bed melt granulation and to compare them with regard to modeling ability and predictability. The experiments were organized in line with the Box-Behnken design. The influence of binder content, binder particle size, and granulation time on granule properties was evaluated. In addition to the response surface analysis, a multilayer perceptron neural network was applied for data modeling. It was found that in situ fluidized bed melt granulation can be used for production of spherical granules with good flowability. Binder particle size had the most pronounced influence on granule size and shape, suggesting the importance of this parameter in achieving desired granule properties. It was found that binder content can be a critical factor for the width of granule size distribution and yield when immersion and layering is the dominant agglomeration mechanism. The results obtained indicate that both in silico techniques can be useful tools in defining the design space and optimization of in situ fluidized bed melt granulation.

In-line monitoring of particle size in a fluid bed granulator: investigations concerning positioning and configuration of the sensor

According to the ICH Q8 guideline, analytic technologies (PAT) are important tools for characterization and optimization of pharmaceutical manufacturing processes. Particle size as a critical quality attribute for granules is therefore an important parameter that should be monitored during the fluid bed granulation process. This work focusses on optimizing position and configuration of an SFT-sensor for the in-line measurement of particle size distribution in a Glatt GPCG 3 fluid bed granulator. As model-substances, different grades of microcrystalline cellulose were used. The in-line measured particle size and particle rate in the sensor were evaluated. A sensor position in the deceleration zone of the granulator was found to be promising for in-line particle size measurement. Most reliable data were generated in this position when the probe was placed in a distance of 11cm from the chamber wall to avoid bias by the inlet air stream. No major influence of rotation angle of the probe was found in this position. Furthermore, an entire fluid bed granulation process was successfully monitored with the sensor installed in the optimized setting.

Towards better process understanding: chemometrics and multivariate measurements in manufacturing of solid dosage forms

The manufacturing of tablets involves many unit operations that possess multivariate and complex characteristics. The interactions between the material characteristics and process related variation are presently not comprehensively analyzed due to univariate detection methods. As a consequence, current best practice to control a typical process is to not allow process-related factors to vary i.e. lock the production parameters. The problem related to the lack of sufficient process understanding is still there: the variation within process and material properties is an intrinsic feature and cannot be compensated for with constant process parameters. Instead, a more comprehensive approach based on the use of multivariate tools for investigating processes should be applied. In the pharmaceutical field these methods are referred to as Process Analytical Technology (PAT) tools that aim to achieve a thorough understanding and control over the production process. PAT includes the frames for measurement as well as data analyzes and controlling for in-depth understanding, leading to more consistent and safer drug products with less batch rejections. In the optimal situation, by applying these techniques, destructive end-product testing could be avoided. In this paper the most prominent multivariate data analysis measuring tools within tablet manufacturing and basic research on operations are reviewed.

In-line monitoring of the drug content of powder mixtures and tablets by near-infrared spectroscopy during the continuous direct compression tableting process

Continuous manufacturing methods offer economic and quality advantages when compared with batch manufacturing methods. In continuous manufacturing, one requires real time assurance of quality of product via the implementation of PAT tools. This study focuses on an in-line near-infrared (NIR) spectroscopic method for determining the drug content of powder mixtures and tablets during a continuous tableting process. Tablets consisting of acetaminophen (20-30%), lactose (69.07-78.93%) and magnesium stearate (0.93-1.07%) were prepared in a continuous direct compression line that consisted of two loss-in-weight feeders, one for acetaminophen and one for premixed lactose and magnesium stearate, and a continuous mixer followed by a rotary tablet press. NIR spectroscopy was applied to the continuous mixer and tablet press to perform a 100% product check at full tableting speed. The UV-spectrophotometric method was used as an off-line reference method to determine the acetaminophen content in the samples. The powder mixture and tablet samples were taken during the process for the calibration of continuous mixer and tablet press, respectively. For the continuous mixer, model creation with the PLS method yielded R-Square and RMSEC (root mean square error of calibration) values of 0.975% and 0.56%, respectively. For the tablet press, the corresponding R-Square and RMSEC values were 0.943% and 0.75%, respectively. A test run demonstrated good predictability in the estimation of the API content in the powder mixtures and tablets during the continuous tableting process. For the continuous mixer and tablet press, the RMSEP (root mean square error of prediction) values were 0.96% and 1.37%, respectively. This study demonstrates that an NIR instrument capable of fast spectra acquisition can be a valuable tool for the in-line monitoring of the continuous mixing and tableting processes.

Design space approach in optimization of fluid bed granulation and tablets compression process

The aim of this study was to optimize fluid bed granulation and tablets compression processes using design space approach. Type of diluent, binder concentration, temperature during mixing, granulation and drying, spray rate, and atomization pressure were recognized as critical formulation and process parameters. They were varied in the first set of experiments in order to estimate their influences on critical quality attributes, that is, granules characteristics (size distribution, flowability, bulk density, tapped density, Carr's index, Hausner's ratio, and moisture content) using Plackett-Burman experimental design. Type of diluent and atomization pressure were selected as the most important parameters. In the second set of experiments, design space for process parameters (atomization pressure and compression force) and its influence on tablets characteristics was developed. Percent of paracetamol released and tablets hardness were determined as critical quality attributes. Artificial neural networks (ANNs) were applied in order to determine design space. ANNs models showed that atomization pressure influences mostly on the dissolution profile, whereas compression force affects mainly the tablets hardness. Based on the obtained ANNs models, it is possible to predict tablet hardness and paracetamol release profile for any combination of analyzed factors.