Effect of Lipid Additives and Drug on the Rheological Properties of Molten Paraffin Wax, Degree of Surface Drug Coating, and Drug Release in Spray-Congealed Microparticles

The Effect of Compression Pressure on the First Layer Surface Roughness and Delamination of Metformin and Evogliptin Bilayer and Trilayer Tablets

The objectives of this study were to evaluate the delamination of convex-shaped metformin HCl (MF) and evogliptin tartrate (EG) multi-layer tablets depending on the pre-compression and main compression pressures and simultaneously correlate these results with those of a surface roughness analysis. Free-flowing MF and EG (median diameters of 38.3 and 44.7 μm, respectively) granules prepared using the wet granulation method were pre-compressed and subsequently compressed into bilayer and trilayer tablets using a universal testing machine. The compaction force required to break the tablets increased linearly as the main compression pressure increased (30-150 MPa). Conversely, the interfacial strength and compaction breaking force decreased as the pre-compression pressure increased (10-110 MPa). A surface roughness analysis employing a profilometer revealed that the first layer (MF) roughness drastically decreased from 5.89 to 0.51 μm (Ra, arithmetic average of profile height deviations from the mean line) as the pre-compression pressure increased from 10 to 150 MPa in the bilayer tablet. Accordingly, the decrease in the roughness of the first layer reduced the inter-penetration at the interface, as observed via energy dispersive spectrometer (EDS)-equipped scanning electron microscopy, decreasing the interfacial bonding strength and causing delamination of the MF/EG multi-layer tablets. These findings indicate the significance of roughness control in the actual preparation of multi-layer tablets and the usefulness of profilometer- and EDS-based surface analyses for interpreting the delamination of multi-layer tablets.

Effect of drug load and lipid-wax blends on drug release and stability from spray-congealed microparticles

This study was designed to evaluate paraffin wax as a potential controlled release matrix for spray congealing and its impact on drug release and stability of the microparticles. Paraffin wax can form a hydrophobic barrier to moisture and reduce drug degradation besides retarding drug release in the gastrointestinal tract. More hydrophilic lipid-based additives can be incorporated to modulate the drug release through the paraffin wax barrier. This study reports the findings of lipid-wax formulations at preserving the stability of moisture-sensitive drugs in spray-congealed microparticles. Aspirin-loaded microparticles formulated with different drug loads, lipid additives, and lipid:wax ratios were produced by spray congealing. Stearic acid (SA), cetyl alcohol (CA), and cetyl ester (CE) were the lipid additives studied. The microparticles were evaluated for yield, encapsulation efficiency, particle size, drug stability, and release. CE exhibited the greatest effect on increasing drug release, followed by CA and SA. Dissolution profiles showed the best fit to Weibull kinetic model. The degree of drug degradation was low, with CA imparting the least protective effect, followed by SA and CE. Paraffin wax is useful for preserving the stability of moisture-sensitive aspirin and retarding its release from spray-congealed microparticles. The addition of lipid additives modulated drug release without compromising drug stability.

Solvent-Free Fabrication of Biphasic Lipid-Based Microparticles with Tunable Structure

Lipid-based biphasic microparticles are generally produced by long and complex techniques based on double emulsions. In this study, spray congealing was used as a solvent-free fabrication method with improved processability to transform water-in-oil non-aqueous emulsions into spherical solid lipid-based particles with a biphasic structure (b-MPs). Emulsions were prepared by melt emulsification using different compositions of lipids (Dynasan^®118 and Compritol^®888 ATO), surfactants (Cetylstearyl alcohol and Span^®60) and hydrophilic carriers (PEGs, Gelucire^®48/16 and Poloxamer 188). First, pseudo-ternary phase diagrams were constructed to identify the area corresponding to each emulsion type (coarse emulsion or microemulsion). The hydrophobicity of the lipid mostly affected the interfacial tension, and thus the microstructure of the emulsion. Emulsions were then processed by spray congealing and the obtained b-MPs were characterized in terms of thermal and chemical properties (by DSC and FT-IR), external and internal morphology (by SEM, CLSM and Raman mapping). Solid free-flowing spherical particles (main size range 200–355 µm) with different architectures were successfully produced: microemulsions led to the formation of particles with a homogeneous internal structure, while coarse emulsions generated “multicores-shell” particles consisting of variable size hydrophilic cores evenly distributed within the crystalline lipid phase. Depending on their composition and structure, b-MPs could achieve various release profiles, representing a more versatile system than microparticles based on a single lipid phase. The formulation and technological strategy proposed, provides a feasible and cost-effective way of fabricating b-MPs with tunable internal structure and release behavior.

Liquid Lipids Act as Polymorphic Modifiers of Tristearin-Based Formulations Produced by Melting Technologies

Despite the growing interest in lipid-based formulations, their polymorphism is still a challenge in the pharmaceutical industry. Understanding and controlling the polymorphic behavior of lipids is a key element for achieving the quality and preventing stability issues. This study aims to evaluate the impact of different oral-approved liquid lipids (LL) on the polymorphism, phase transitions and structure of solid lipid-based formulations and explore their influence on drug release. The LL investigated were isopropyl myristate, ethyl oleate, oleic acid, medium chain trigycerides, vitamin E acetate, glyceryl monooleate, lecithin and sorbitane monooleate. Spray-congealing was selected as an example of a melting-based solvent-free manufacturing method to produce microparticles (MPs) of tristearin (Dynasan^®118). During the production process, tristearin MPs crystallized in the metastable α-form. Stability studied evidenced a slow phase transition to the stable β-polymorph overtime, with the presence of the α-form still detected after 60 days of storage at 25 °C. The addition of 10% w/w of LL promoted the transition of tristearin from the α-form to the stable β-form with a kinetic varying from few minutes to days, depending on the specific LL. The combination of various techniques (DSC, X-ray diffraction analysis, Hot-stage polarized light microscopy, SEM) showed that the addition of LL significantly modified the crystal structure of tristearin-based formulations at different length scales. Both the polymorphic form and the LL addition had a strong influence on the release behavior of a model hydrophilic drug (caffeine). Overall, the addition of LL can be considered an interesting approach to control triglyceride crystallization in the β-form. From the industrial viewpoint, this approach might be advantageous as any polymorphic change will be complete before storage, hence enabling the production of stable lipid formulations.

Lipids for Taste masking and Taste assessment in pharmaceutical formulations

Pharmaceutical products often have drawbacks of unacceptable taste and palatability which makes it quite difficult for oral administration to some special populations like pediatrics and geriatrics. To curb this issue different approaches like coating, granulation, extrusion, inclusion complexation, ion-exchange resins, etc for taste masking are employed and among them use of lipids have drawn special attention of researchers. Lipids have a lower melting point which is ideal for incorporating drugs in some of these methods like hot-melt extrusion, melt granulation, spray drying/congealing and emulsification. Lipids play a significant role as a barrier to sustain the release of drugs and biocompatible nature of lipids increases their acceptability by the human body. Further, lipids provide vast opportunities of altering pharmacokinetics of the active ingredients by modulating release profiles. In taste sensors, also known as electronic tongue or e-tongue, lipids are used in preparing taste sensing membranes which are subsequently used in preparing taste sensors. Lipid membrane taste sensors have been widely used in assessing taste and palatability of pharmaceutical and food formulations. This review explores applications of lipids in masking the bitter taste in pharmaceutical formulations and significant role of lipids in evaluation of taste and palatability.

Pharmaceutical Application of Tablet Film Coating

Tablet film coating is a common but critical process providing various functionalities to tablets, thereby meeting diverse clinical needs and increasing the value of oral solid dosage forms. Tablet film coating is a technology-driven process and the evolution of coated dosage forms relies on advancements in coating technology, equipment, analytical techniques, and coating materials. Although multiple coating techniques are developed for solvent-based or solvent-free coating processes, each method has advantages and disadvantages that may require continuous technical refinement. In the film coating process, intra- and inter-batch coating uniformity of tablets is critical to ensure the quality of the final product, especially for active film coating containing active pharmaceutical ingredients in the coating layer. In addition to experimental evaluation, computational modeling is also actively pursued to predict the influence of operation parameters on the quality of the final product and optimize process variables of tablet film coating. The concerted efforts of experiments and computational modeling can save time and cost in optimizing the tablet coating process. This review provides a brief overview of tablet film coating technology and modeling approaches with a focus on recent advancements in pharmaceutical applications.

Effects of Drug Particle Size and Lipid Additives on Drug Release from Paraffin Wax Formulations Prepared by Spray Congealing Technique

Paraffin wax is a hydrophobic meltable material that can be suitably used in spray congealing to develop drug-loaded microparticles for sustained release, taste-masking or stability enhancement of drugs. However, these functional properties may be impaired if the drug particles are not completely embedded. Moreover, highly viscous melts are unsuitable for spray dispersion. In this study, the effects of drug particle size and lipid additives, namely stearic acid (SA), cetyl alcohol (CA) and cetyl esters (CE), on melt viscosity and extent of drug particles embedment were investigated. Spray congealing was conducted on the formulations, and the resultant microparticles were analysed for their size, drug content, extent of drug particles embedment and drug release. The melt viscosity increased with smaller solid inclusions while lipid additives decreased the viscosity to varying extents. The spray-congealed microparticle size was largely dependent on the viscosity. The addition of lipid additives to paraffin wax enabled more complete embedment of the drug particles. CA produced microparticles with the lowest drug release, followed by SA and CE. The addition of CA and CE enhanced the drug release and showed potential for taste-masking. Judicious choice of drug particle size and matrix materials is important for successful spray congealing to produce microparticles with the desired characteristics.

Design and In Vivo Pharmacokinetic Evaluation of Triamcinolone Acetonide Microcrystals-Loaded PLGA Microsphere for Increased Drug Retention in Knees after Intra-Articular Injection

A novel polymeric microsphere (MS) containing micronized triamcinolone acetonide (TA) in a crystalline state was structured to provide extended drug retention in joints after intra-articular (IA) injection. Microcrystals with a median diameter of 1.7 μm were prepared by ultra-sonication method, and incorporated into poly(lactic-co-glycolic acid)/poly(lactic acid) (PLGA/PLA) MSs using spray-drying technique. Cross-sectional observation and X-ray diffraction analysis showed that drug microcrystals were evenly embedded in the MSs, with a distinctive crystalline nature of TA. In vitro drug release from the novel MSs was markedly decelerated compared to those from the marketed crystalline suspension (Triam inj.^®), or even 7.2 μm-sized TA crystals-loaded MSs. The novel system offered prolonged drug retention in rat joints, providing quantifiable TA remains over 28 days. Whereas, over 95% of IA TA was removed from joints within seven days, after injection of the marketed product. Systemic exposure of the steroidal compound was drastically decreased with the MSs, with <50% systemic exposure compared to that with the marketed product. The novel MS was physicochemically stable, with no changes in drug crystallinity and release profile over 12 months. Therefore, the TA microcrystals-loaded MS is expected to be beneficial in patients especially with osteoarthritis, with reduced IA dosing frequency.

Rapid Preparation of Spherical Granules via the Melt Centrifugal Atomization Technique

Granules with superior fluidity and low moisture absorption are ideal for tableting and capsule filling. Melt granulation as a solvent-free technology has attracted increasing interest for the granulation of moisture-sensitive drugs. The objective of the present study was to develop a solvent-less and high throughput melt granulation method via the melt centrifugal atomization (MCA) technique. The granule formability of various drugs and excipients via MCA and their dissolution properties were studied. It was found that the yield, fluidity, and moisture resistance of the granules were affected by the drug and excipient types, operation temperature, and collector diameter. The drugs were in an amorphous state in pure drug granules, or were highly dispersed in excipients as solid dispersions. The granules produced via MCA showed an improved drug dissolution. The present study demonstrated that the solvent-free, one-step, and high-throughput MCA approach can be used to produce spherical granules with superior fluidity and immediate drug release characteristics for poorly water-soluble and moisture-sensitive therapeutics.