Pharmaceutical tablet lubrication

Selection of lubricant type and concentration for orodispersible tablets

Lubricants are essential for most tablet formulations as they assist powder flow, prevent adhesion to tableting tools and facilitate tablet ejection. Magnesium stearate (MgSt) is an effective lubricant but may compromise tablet strength and disintegratability. In the design of orodispersible tablets, tablet strength and disintegratability are critical attributes of the dosage form. Hence, this study aimed to conduct an in-depth comparative study of MgSt with alternative lubricants, namely sodium lauryl sulphate (SLS), stearic acid (SA) and hydrogenated castor oil (HCO), for their effects on the tableting process as well as tablet properties. Powder blends were prepared with lactose, sodium starch glycolate or crospovidone as the disintegrant, and a lubricant at different concentrations. Angle of repose was determined for the mixtures. Comparative evaluation was carried out based on the ejection force, tensile strength, liquid penetration and disintegratability of the tablets produced. As the lubricant concentration increased, powder flow and tablet ejection improved. The lubrication efficiency generally decreased as follows: MgSt > HCO > SA > SLS. Despite its superior lubrication efficacy, MgSt is the only lubricant of four evaluated that reduced tablet tensile strength. Tablet disintegration time was strongly determined by tensile strength and liquid penetration, which were in turn affected by the lubricant type and concentration. All the above factors should be taken into consideration when deciding the type and concentration of lubricant for an orodispersible tablet formulation.

Uncovering the mechanism of Tenofovir amibufenamide fumarate punch sticking by combining direct compression experiment and computational simulation

Punch sticking during tablet manufacturing is a prevalent issue for many active pharmaceutical ingredients (APIs) encountered by the pharmaceutical industry. Tenofovir amibufenamide fumarate (TMF), a heavyweight drug for the treatment of hepatitis B, was selected as a model drug due to its tendency to punch sticking during tablet compression. In this study, the cause of sticking was explored by investigating crystal habits, excipients and structure characteristics. The difference in sticking of three crystal habits can be visually represented through direct compression experiments on powdered samples and analysis of crystal surfaces. The excipients play a direct role in decreasing the probability of sticking, and the extent of sticking can be assessed by measuring the tensile strength of the tablet. Additionally, the plasticity index was utilized to theoretically analyze the potential enhancements of four excipients. These experimental results indicate that the block-shaped crystals have superior ability of anti-sticking and that suitable excipients can significantly improve the sticking situation of TMF. Ultimately, the phenomenon of punch sticking was additionally examined through computational calculations, focusing on the mechanical characteristics of TMF molecules and intermolecular interactions. The strategy of combining experiments and simulation calculations has broader significance for the study of drug production.

Successful Formulation Window for the design of pharmaceutical tablets with required mechanical properties

Pharmaceutical tablet formulations combine the active ingredient with processing aids and functional components. This paper evaluates compressibility based predictive models for binary and ternary formulations to establish an acceptable range of tablet compression parameters that satisfy prescribed quality target criteria for tablets including minimum tablet strength and processing constraints such as maximum ejection stress and maximum compaction pressure. The concept of Successful Formulation Window (SFW) is introduced. A methodology is proposed to determine the SFW for a given formulation based on compaction simulator data collected for individual formulation components. The methodology is validated for binary and ternary mixtures and lubricated formulations. The SFW analysis was developed to support tablet formulation design to meet mechanical requirements.

Investigation of Dispersion Kinetics of Particulate Lubricants and their Effect on the Mechanical Strength of MCC Tablets

INTRODUCTION

Tablets are commonly produced by internally adding particulate lubricants, which are known to possibly lower the mechanical strength of tablets. This reduction is caused by the coverage of matrix forming components by lubricant particles, resulting in decreased interparticulate interactions. The known incompatibilities with some active compounds of the predominantly used lubricant, magnesium stearate, call for the in-depth characterization of alternative lubricants.

PURPOSE

Investigation of the dispersion behavior of five commonly applied pharmaceutical lubricants by mathematically modeling the dispersion kinetics for short and extended mixing times.

METHODS

The dispersion behavior of five different pharmaceutical lubricants were examined by systematically varying lubricant concentration and mixing time of binary formulations and evaluating the kinetic of tensile strength reduction by theoretically estimating the surface coverage based on particle sizes.

RESULTS

For short mixing times, a unifying relationship between compactibility reduction and theoretical surface coverage was identified. Subsequently, for extended mixing times, distinct differences in the shear strength and dispersion kinetics of the investigated lubricants were found.

CONCLUSIONS

The lubricant particle size controls the tensile strength reduction if short mixing times are applied. For extended mixing times, the investigated lubricants can be divided into two groups in terms of dispersion kinetics. Possible underlying reasons are discussed in detail in order to enhance the general understanding of lubricant dispersions in tablet formulations.

The structure of magnesium stearate trihydrate determined from a micrometre-sized single crystal using a microfocused synchrotron X-ray beam

Crystalline magnesium stearate has been extensively used as an additive in pharmaceutical and other industries for decades. However, the lack of suitably large crystals has hindered the determination of the crystal structure and thereby a more fundamental understanding of the structure-functionality relationship. Presented here is the structure of magnesium stearate trihydrate as determined from X-ray diffraction data of a micrometre-sized single crystal measured at a fourth-generation synchrotron facility. Despite the small size of the single crystals and the weak diffraction, it was possible to determine the positions of the non-hydrogen atoms reliably. Periodic dispersion-corrected density functional theory calculations were used to obtain the positions of the hydrogen atoms playing an important role in the overall organization of the structure via a hydrogen-bond network.

Effects of Granulated Lactose Characteristics and Lubricant Blending Conditions on Tablet Physical Properties in Direct Powder Compression

Lactose is an excipient used extensively for bulking, diluting, and molding active pharmaceutical ingredients in tablet manufacturing. Particularly, granulated lactose (GL) intended for direct powder compression has distinct properties due to differences in manufacturing methods. It contributes to handling blended powders for tableting and tablet quality. In this study, we aimed to compare the functions of different forms of GL added as excipients during direct powder compression on the tablet properties and the effect of magnesium stearate (Mg-S) used as a lubricant on each type of GL. Different GL types obtained using different manufacturing methods (agitated granulation, GL-AG; spray-dried granulation, GL-SD; fluidized bed granulation, GL-FB) were blended with maize starch, low-substituted hydroxypropyl cellulose, and paracetamol in a V-type blender for 10 min. Mg-S was added at varying amounts (0.1, 1.0, and 2.0%) and blending times (5, 10, and 30 min) for the nine types of blended powders for tableting formulation. The powders were tableted, and the tablets were evaluated for weight and drug loading variations, tensile strength, friability, and disintegration time. When tablets with the same blending conditions were compared, the tensile strength and disintegration time were in the order of GL-FB > GL-SD > GL-AG. For each GL, we analyzed the effects of changes in the added amount of Mg-S and blending time using contour plots, evaluated the effects of blending conditions on tablet properties, and determined the target tablet properties. We investigated the optimization of the lubricant blending conditions to obtain suitable tablets.

Magnesium stearate surface coverage on tablets and drug crystals: Insights from SEM-EDS elemental mapping

Scanning electron microscopy-based energy dispersive X-ray spectroscopy (SEM-EDS) is proposed as a versatile tool for quantifying surface area coverage (SAC) by magnesium stearate (MgSt) on pharmaceutical tablets and particles. Our approach involved fast elemental mapping and subsequent SAC quantitation by image analysis. The study was conducted using a multi-component system, but the particle-level mapping was limited to active pharmaceutical ingredient (API) crystals. For both tablets and API particles, the calculated SAC against MgSt loading afforded a positive linear correlation over the range of MgSt levels examined in this work. On the tablet surface, MgSt was found to be preferentially concentrated at or in the close vicinity of grain boundaries, supporting the idea of compression-driven migration and relocation of MgSt within the tablet. On the particle surface, only discrete aggregates of MgSt were observed, as opposed to the widely accepted phenomenon of the formation of a thin lubricant film around host particles. The selection of proper SEM-EDS operating conditions and the challenges confronted in particle surface mapping are discussed in detail.

Modeling of Adhesion in Tablet Compression at the Molecular Level Using Thermal Analysis and Molecular Simulations

The molecular basis of adhesion leading to sticking was investigated by exploring the correlation between thermal analysis and molecular simulations. It is hypothesized that intermolecular interactions between a drug molecule and a punch face are the first step in the adhesion process and the rank order of adhesion during tablet compression should correspond to the rank order of the energies of these interactions. In the present study, the sticking propensity was investigated using ibuprofen, flurbiprofen, and ketoprofen as model substances. At the intermolecular level, a thermal analysis model was proposed as an experimental technique to estimate the work of adhesion between ibuprofen, flurbiprofen, and ketoprofen in a DSC aluminum pan. The linear relationship was established between the enthalpy of vaporization and sample mass to demonstrate the accuracy of the instruments used. The threshold mass for ibuprofen, flurbiprofen, and ketoprofen was determined to be 107, 112, and 222 μg, respectively, after three replicate measurements consistent with the experimental results. Ketoprofen showed a 2-fold higher threshold mass compared to ibuprofen and flurbiprofen, which predicts that ketoprofen should have the highest sticking propensity. Computationally, the rank order of the work of adhesion between ibuprofen, flurbiprofen, and ketoprofen with the metal surface was simulated to be -75.91, 44.75, and -96.91 kcal/mol, respectively, using Materials Studio. The rank order of the interaction between the drug molecule and the iron superlattice decreases in the order ketoprofen > ibuprofen > flurbiprofen. The results indicate that the thermal model can be successfully implemented to assess the sticking propensity of a drug at the molecular level. Also, a new molecular simulation script was successfully applied to determine the interaction energy of the drug molecule upon contact with iron.

Starch flow behavior alone and under different glidants action using the shear cell method

The objective of this work was to analyze the flow behavior of a commonly used filler (pregelatinised starch) and the effect of two of the most used lubricants (talc and colloidal silicon dioxide). The studies were carried out according to the conventional methods (Angle of Repose, Bulk and Tapped densities and from these the Compressibility Index) and shear cell methods (Brookfield Powder Flow Tester apparatus) described in European Pharmacopeia (Ph. Eur.). The results showed some surprising and unexpected values for the flow behavior of this filler under influence of the methods and the used glidants. Regarding pure starch and mixtures containing talc, the flow behavior was similar between them and the Flow Index (ff_c) values varied between 1.8 and 4 (very cohesive and cohesive) as consolidation stress (σ₁) increased. In this case, the glidant effect was not observed. However, for the mixtures of starch with colloidal silicon dioxide this effect was observed providing Flow Index (ff_c) values between 2.6 and 8.9 (cohesive and easy-flowing) as consolidation stress (σ₁) increased. Other parameters that are also used to characterize flow properties, more specifically, within silos, chutes and hoppers, such as effective angle of internal friction (φe), effective angle of wall friction (φx), critical arching and critical rathole values, provided similar information. Based in the obtained results from all tests it can be said that the talc did not induce improvement on the starch flow behavior in the used conditions in opposition to the effect produced by colloidal silicon dioxide.HighlightsExample 1. A good flowability of powders is needed in order to be compressed/filled;Example 2. The overcome the poor flow it is usual to use glidants;Example 3. CSD improved the pregelatinised starch (Starch 1500®) flow;Example 4. Talc do not have relevant effect in the pregelatinised starch (Starch 1500®) flow;Example 5. Powder FlowTester method showed more complete and consistent results.

Opposing Effects of Additives in Dry Milling and Tableting of Organic Particles

Applying additives and excipients during the dry processing of fine particles is a common measure to control the particle–particle interactions, to specifically influence the powder properties and to enhance the process efficiency or product quality. In this study, the impacts of a particulate lubricant, a nano-disperse flow additive and liquid grinding aids on the dry fine milling and subsequent tableting of the ground material were investigated for three different organic model compounds. It is presented that the three additive classes cause varying and partly opposing effects during these process steps. Especially the lubricant and the grinding aids were shown to increase the efficiency of the milling process as well as the product fineness of the ground material, and to avoid critical product adhesions on the machine surfaces. Thereby, stable and efficient grinding conditions were partially not possible without the addition of such additives. However, as these positive effects are attributed to a reduction of the adhesive forces between the particles, much lower tablet strengths were achieved for these additives. This propagation of powder, and in turn, final product properties over whole process chains, has not been studied in detail so far. It was further revealed that the material behavior and the microstructure of the product particles is decisive for the processing as well, which is why additive effects may be product-specific and can even be suppressed under certain processing conditions. In comparison to the process performances, the powder properties and surface energies of the product particles were less influenced by the additives. On the contrary, particle-based morphologies or deformation behavior seem to play a major role in comparison to inorganic materials. Thus, it can be stated that global bulk properties and surface energies provide first indications of powder behavior and susceptibility. However, additional specific properties need to be evaluated to more clearly understand the influences of additives.

Predicting lubricants effect on tablet sticking using ketoprofen as model drug and evaluating sticking propensity using different metals and powder rheology

Tablet sticking occurrence is a persistent, costly, and time-consuming problem that needs to be resolved. Predicting the sticking tendency of a new formulation has been very difficult during the development batches because of short runs and limited data. A model formulation comprising ketoprofen and microcrystalline cellulose was used to predict the effect of magnesium stearate and sodium stearyl fumarate on the occurrence of tablet sticking relative to different punch metals. Lubricant amounts were varied from 0.0% to 2.0 %w/w. Five different metal coupons were used to represent punch metals. The sticking index (SI) of each formulation relative to each metal coupon was determined by measuring angle of internal friction and angle of wall friction by performing shear cell test and wall friction test, respectively. The SI was used to predict each formulation's sticking tendency rank order relative to metal coupon. Both lubricants show a decrease in the powder blend's sticking propensity with increased lubricant concentration. The predicted sticking propensity rank order was then validated by the compression study. The result suggests that the SI can be used to predict tablet sticking, such as by changing the composition of the formulation or changing the punch metal during tablet compression.

Analytical approach for lubricant characterization of excipients using the surface replication method

Lubricants are indispensable pharmaceutical ingredients for preventing tableting failure due to powder adhesion to the die wall. The impact of lubricants was evaluated with use of the Binding Identification for Net Detriment (BIND) surface replication method. Raloxifene hydrochloride (RH) was selected as a model chemical with high adhesion, and four commercially available tablet lubricants - stearic acid, sodium stearyl fumarate, calcium stearate, and magnesium stearate - were used for RH formulation. BIND was applied to the die wall to analyze the effect of various lubricants on binding properties. The preparations without lubricants showed poor tableting properties as evidenced by as much as 61.7% powder adhesion density. Lubricants significantly altered the binding properties, yielding powder adhesion densities of 40.2% (stearic acid), 29.7% (stearyl sodium fumarate), 23.0% (calcium stearate), and 13.6% (magnesium stearate). Evaluation of three grades of magnesium stearate resulted in a two-fold difference between the highest and the lowest powder adhesion density. Throughout the work, conventional methods including visual observations and measurement of ejection force were unable to provide qualitative/quantitative evaluations. The ejection process depends on both axial force and radial force; however, the ejection force show only the axial force. At the same time, visual observation could release significant qualitative results. However, BIND allowed qualitative and quantitative analysis of the binding properties. BIND is a promising assessment method for analyzing the impacts of various lubricants on binding properties and for optimizing RH formulations.

Scaling Tableting Processes from Compaction Simulator to Rotary Presses-Mind the Sub-Processes

Compaction simulators are frequently used in the formulation and process development of tablets, bringing about the advantages of flexibility, low material consumption, and high instrumentation to generate the most possible process understanding. However, their capability of resembling general aspects of rotary press compaction and their precision in simulating or mimicking sub-processes such as feeding and filling need to be systematically studied. The effect of material deformation behavior, blend composition, and feeding on tensile strength and simulation precision as compared with rotary presses of different scales is evaluated in this study. Generally, good simulation performance was found for the studied compaction simulator. Compaction profile-sensitivity was demonstrated for highly visco-plastic materials while shear-sensitivity in feeding was demonstrated for lubricated blends of ductile particles. Strategies for the compensation of both in compaction simulator experiments are presented by careful investigation of the compaction stress over time profiles and introduction of a compaction simulator-adapted shear number approach to account for differences in layout and operation mode between compaction simulator and rotary press, respectively. These approaches support the general aim of this study to provide a more straightforward determination of scaling process parameters between rotary press and compaction simulator and facilitate a quicker and more reliable process transfer.

A systematic evaluation of poloxamers as tablet lubricants

Lubricants are important for both preserving the tooling of high-speed tablet presses and attaining quality tablets. Magnesium stearate (MgSt) is most commonly used due to its superior lubrication efficiency; however, it can lead to negative effects on tabletability and dissolution. In this study, we have systematically evaluated two poloxamers, P188 and P407, for their suitability as alternative tablet lubricants. For two excipients with different mechanical properties, i.e., microcrystalline cellulose and lactose, both poloxamers exhibit acceptable lubrication efficiency without negatively impacting tabletability. Compared to 1% MgSt, the performance of 2% of both poloxamers in an experimental tablet formulation of ritonavir led to better lubrication, higher tabletability, and enhanced in vitro drug release. Thus, the use of P188 and P407 as alternative tablet lubricants deserves further evaluations.

Synthesis, Functionalization, and Bioapplications of Two-Dimensional Boron Nitride Nanomaterials

Two-dimensional boron nitride nanostructures (2D-BNNs) have been increasingly investigated for their applications in several scientific and technological areas. This considerable interest is due to their unique physicochemical properties, which include high hydrophobicity, heat and electrical insulation, resistance to oxidation, antioxidation capacity, thermal conductivity, high chemical stability, mechanical strength, and hydrogen storage capacity. They are also used as fillers, antibacterial agents, protective coating agents, lubricants, boron neutron capture therapy agents, nanocarriers for drug delivery, and for the receptor phase in chemosensors. The investigations for their use in medicine and biomedicine are very promising, including cancer therapy and wound healing. In this review, 2D-BNNs synthesis and their surface modification strategies, biocompatibility, and bioapplication studies are discussed. Finally, a perspective for the future use of these novel nanomaterials in the biomedical field is provided.

Mixing Cell: a Device to Mimic Extent of Lubrication and Shear in Continuous Tubular Blenders

Continuous manufacturing (CM) has clear potential for manufacturing solid oral dosages. It provides several advantages that may aid the manufacturing and quality of drug products. However, one of the main challenges of this technology is the relatively large amount of knowledge required and the amounts of material needed to develop the process during the early stages of development. Early process development evaluations of continuous manufacturing equipment often require larger amounts of material compared with batch, which hinder CM prospect for drugs during the early stages of process development. In this work, a small-scale evaluation of the mixing process occurring in a continuous mixing system was performed. The evaluation involved the use of a small-scale "mixing cell" which was able to replicate the lubrication process of a continuous mixer. It is worth mentioning that we designed the mixing cell by reconfiguration of an existing continuous tubular blender. The extent of lubrication evaluation was performed for three example formulations and was done by mimicking the amount of shear provided to a formulation by means of matching the number of paddle-passes that a formulation experiences within a continuous blending process in the batch mixing cell. The evaluation showed that the small-scale mixing cell was able to replicate the extent of lubrication-evaluated by measuring the tensile strength of compacts being made with both the continuous and mixing cell experiments-occurring in the continuous mixer using a fraction of the amount of materials needed to perform the same evaluation in the continuous blending process.

A drop penetration method to measure powder blend wettability

Water wettability of pharmaceutical blends affects important quality attributes of final products. We investigate the wetting properties of a pharmaceutical blend lubricated with Magnesium Stearate (MgSt) as a function of the mechanical shear strain applied to the blend. We measure the penetration dynamics of sessile drops deposited on slightly compressed powder beds. We consider a blend composed of 9% Acetaminophen 90% Lactose and 1% MgSt by weight. Comparing the penetration time of water and a reference liquid Polydimethylsiloxane (silicon oil) we obtain an effective cosine of the contact angle with water, based on a recently developed drop penetration method. We repeat the experiments for blends exposed to increasing levels of shear strain and demonstrate a significant decrease in water wettability (decrease in the cosine of the contact angle). The results are consistent with the development of a hydrophobic film coating the powder particles as a result of the increased shear strain. Finally, we show that, as expected dissolution times increase with the level of shear strain. Therefore, the proposed drop penetration method could be used to directly assess the state of lubrication of a pharmaceutical blend and act as a quality control on powder blend attributes before the blend is tableted.

Excipient Stability in Oral Solid Dosage Forms: A Review

The choice of excipients constitutes a major part of preformulation and formulation studies during the preparation of pharmaceutical dosage forms. The physical, mechanical, and chemical properties of excipients affect various formulation parameters, such as disintegration, dissolution, and shelf life, and significantly influence the final product. Therefore, several studies have been performed to evaluate the effect of drug-excipient interactions on the overall formulation. This article reviews the information available on the physical and chemical instabilities of excipients and their incompatibilities with the active pharmaceutical ingredient in solid oral dosage forms, during various drug-manufacturing processes. The impact of these interactions on the drug formulation process has been discussed in detail. Examples of various excipients used in solid oral dosage forms have been included to elaborate on different drug-excipient interactions.

Setting Ideal Lubricant Mixing Time for Manufacturing Tablets by Evaluating Powder Flowability

We investigated the effectiveness of using Carr's flowability index (FI) and practical angle of internal friction (Φ) as indexes for setting the target Mg-St mixing time needed for preparing tablets with the target physical properties. We used FI as a measure of flowability under non-loaded conditions, and Φ as a measure of flowability under loaded conditions for pharmaceutical powders undergoing direct compression with varying concentrations of Mg-St and mixing times. We evaluated the relationship between Mg-St mixing conditions and pharmaceutical powder flowability, analyzed the correlation between the physical properties of the tablets (i.e., tablet weight variation, drug content uniformity, hardness, friability, and disintegration time of tablets prepared using the pharmaceutical powder), and studied the effect of Mg-St mixing conditions and pharmaceutical powder flowability on tablet properties. Mg-St mixing time highly correlated with pharmaceutical powder FI (R ² = 0.883) while Mg-St concentration has low correlation with FI, and FI highly correlated with the physical properties of the tablet (R ² values: weight variation 0.509, drug content variation 0.314, hardness 0.525, friability 0.477, and disintegration time 0.346). Therefore, using pharmaceutical powder FI as an index could enable prediction of the physical properties of a tablet without the need for tableting, and setting the Mg-St mixing time by using pharmaceutical powder FI could enable preparation of tablets with the target physical properties. Thus, the FI of the intermediate product (i.e., pharmaceutical powder) is an effective index for controlling the physical properties of the finished tablet.

Evaluation of Sucrose Fatty Acid Esters as Lubricants in Tablet Manufacturing

Lubricants are essential additives in tablet formulations. Magnesium stearate (Mg-St) is the most commonly used lubricant in tableting. Here, we used sucrose fatty acid ester (SE) as an additive to manufacture tablets by direct compression. We evaluated the effects of hydrophile-lipophile balance (HLB) and the amount of SE on the flowability of a pharmaceutical powder using angle of repose and practical angle of internal friction measurements. In addition, we investigated the effects of SE on tablet properties. When SEs with an HLB ≥3 were added, the angle of repose was approximately the same as that of a pharmaceutical powder containing Mg-St, with no major differences in flowability. However, the practical angle of internal friction became closer to pharmaceutical powder containing Mg-St as HLB decreased. As HLB increased, the practical angle of internal friction approached the value of additive-free pharmaceutical powder. Tablets containing 2.0% Mg-St had a mean hardness of 40 N and disintegrated in approximately 6 min, whereas tablets containing 2.0% SE (low HLB) had a mean hardness of approximately ≥80 N and disintegrated within 3 min. The results indicate that SEs can be used as lubricants in tablet production by direct compression and to reduce problems associated with the use of Mg-St. In particular, we suggest that SEs with low HLB values can be used as excipients to achieve high tablet hardness and short disintegration time.

Quality-by-Design II: Application of Quantitative Risk Analysis to the Formulation of Ciprofloxacin Tablets

Qualitative risk assessment methods are often used as the first step to determining design space boundaries; however, quantitative assessments of risk with respect to the design space, i.e., calculating the probability of failure for a given severity, are needed to fully characterize design space boundaries. Quantitative risk assessment methods in design and operational spaces are a significant aid to evaluating proposed design space boundaries. The goal of this paper is to demonstrate a relatively simple strategy for design space definition using a simplified Bayesian Monte Carlo simulation. This paper builds on a previous paper that used failure mode and effects analysis (FMEA) qualitative risk assessment and Plackett-Burman design of experiments to identity the critical quality attributes. The results show that the sequential use of qualitative and quantitative risk assessments can focus the design of experiments on a reduced set of critical material and process parameters that determine a robust design space under conditions of limited laboratory experimentation. This approach provides a strategy by which the degree of risk associated with each known parameter can be calculated and allocates resources in a manner that manages risk to an acceptable level.

Effect of surface coating with magnesium stearate via mechanical dry powder coating approach on the aerosol performance of micronized drug powders from dry powder inhalers

The objective of this study was to investigate the effect of particle surface coating with magnesium stearate on the aerosolization of dry powder inhaler formulations. Micronized salbutamol sulphate as a model drug was dry coated with magnesium stearate using a mechanofusion technique. The coating quality was characterized by X-ray photoelectron spectroscopy. Powder bulk and flow properties were assessed by bulk densities and shear cell measurements. The aerosol performance was studied by laser diffraction and supported by a twin-stage impinger. High degrees of coating coverage were achieved after mechanofusion, as measured by X-ray photoelectron spectroscopy. Concomitant significant increases occurred in powder bulk densities and in aerosol performance after coating. The apparent optimum performance corresponded with using 2% w/w magnesium stearate. In contrast, traditional blending resulted in no significant changes in either bulk or aerosolization behaviour compared to the untreated sample. It is believed that conventional low-shear blending provides insufficient energy levels to expose host micronized particle surfaces from agglomerates and to distribute guest coating material effectively for coating. A simple ultra-high-shear mechanical dry powder coating step was shown as highly effective in producing ultra-thin coatings on micronized powders and to substantially improve the powder aerosolization efficiency.

Evaluation of the performance characteristics of bilayer tablets: Part I. Impact of material properties and process parameters on the strength of bilayer tablets

Bilayer tableting technology has gained popularity in recent times, as bilayer tablets offer several advantages over conventional tablets. There is a dearth of knowledge on the impact of material properties and process conditions on the performance of bilayer tablets. This paper takes a statistical approach to develop a model that will determine the effect of the material properties and bilayer compression process parameters on the bonding strength and mode of breakage of bilayer tablets. Experiments were carried out at pilot scale to simulate the commercial manufacturing conditions. As part of this endeavor, a seven-factor half-fraction factorial (2(7-1)) design was executed to study the effect of bilayer tablet compression process factors on the bonding strength of bilayer tablets. Factors studied in this work include: material properties (plastic and brittle), layer ratio, dwell time, layer sequence, first- and second-layer forces, and lubricant concentration. Bilayer tablets manufactured in this study were tested using the axial tester, as it considers both the interfacial and individual layer bonding strengths. Responses of the experiments were analyzed using PROC GLM of SAS (SAS Institute Inc, Cary, North Carolina). A model was fit using all the responses to determine the significant interactions (p < 0.05). The results of this study indicated that nature of materials played a critical role on the strength of bilayer compacts and also on mode of fracture. Bilayer tablets made with brittle materials in both the layers are strongest, and fracture occurred in the first layer indicating that interface is stronger than layers. Significant interactions were observed between the selected factors and these results will provide an insight into the interplay of material properties, process parameters, and lubricant concentration on the bonding strength and mode of breakage of bilayer tablets.

Drug-lactose binding aspects in adhesive mixtures: controlling performance in dry powder inhaler formulations by altering lactose carrier surfaces

For dry powder inhaler formulations, micronized drug powders are commonly mixed with coarse lactose carriers to facilitate powder handling during the manufacturing and powder aerosol delivery during patient use. The performance of such dry powder inhaler formulations strongly depends on the balance of cohesive and adhesive forces experienced by the drug particles under stresses induced in the flow environment during aerosolization. Surface modification with appropriate additives has been proposed as a practical and efficient way to alter the inter-particulate forces, thus potentially controlling the formulation performance, and this strategy has been employed in a number of different ways with varying degrees of success. This paper reviews the main strategies and methodologies published on surface coating of lactose carriers, and considers their effectiveness and impact on the performance of dry powder inhaler formulations.

Investigation of the heating rate dependency associated with the loss of crystalline structure in sucrose, glucose, and fructose using a thermal analysis approach (part I)

Thermodynamic melting occurs at a single, time-independent temperature with a constant enthalpy value. However, substantial variation in the melting parameters (T(m onset), T(m peak), and ΔH) for sucrose, glucose, and fructose has been reported in the literature. Although a number of explanations have been put forth, they do not completely account for the observed variation. Thus, this research was performed to elucidate the fundamental mechanism underlying the loss of crystalline structure in the sugars using both thermal (Part I) and chemical (Part II) analysis approaches. A strong heating rate dependency observed in the melting parameters for the sugars implies the occurrence of a kinetic process during the loss of crystalline structure. The difference in heat capacity and modulated heat flow amplitude in the stepwise quasi-isothermal modulated differential scanning calorimetry experiments for the sugars compared to indium and mannitol (thermodynamic melting comparison materials) strongly suggests thermal decomposition as the kinetic process responsible for the loss of crystalline structure, which is the critical difference between our conclusion and others. We propose the term "apparent melting" to distinguish the loss of crystalline structure due to a kinetic process, such as thermal decomposition, from thermodynamic melting.