Impact of Alternative Solid State Forms and Specific Surface Area of High-Dose, Hydrophilic Active Pharmaceutical Ingredients on Tabletability

Spray Drying for Direct Compression of Pharmaceuticals

Tableting by direct compression (DC) is one of the simplest and most cost-effective drug manufacturing approaches. However, most active pharmaceutical ingredients (APIs) and excipients lack the compression and flow properties required to meet the needs of high-speed industrial tablet presses. Therefore, the majority of DC APIs and excipients are modified via processing/co-processing particle engineering techniques to boost their properties. Spray drying is one of the most commonly employed techniques to prepare DC grades of APIs and excipients with prominent advantages. This review aims to present an overview of the commercially marketed and investigationally-prepared DC APIs and excipients produced by spray drying.

Spray drying of naproxen and naproxen sodium for improved tableting and dissolution - physicochemical characterization and compression performance

In this work, the tabletability and dissolution of spray-dried forms of naproxen and its sodium salt were compared with those of unprocessed drugs. Solutions of naproxen or naproxen sodium alone or with HPMC (5% w/w of drug content) were spray dried. Scanning electron micrographs showed that naproxen sodium spray-dried particles were spherical, whereas those of naproxen were non-spherical but isodiametric. Powder x-ray diffraction and thermal analysis indicated that co-spray drying with HPMC resulted in reduced crystallinity of naproxen and higher naproxen sodium dihydrate content. FTIR and Raman analysis showed shifting, merging or elimination of bands in the spectra of the co-spray dried products signifying solid-state alterations. When mixed with suitable processing aids (7% w/w), all co-spray dried powders produced satisfactory tablets in the pressure range 73-295 MPa. Conversely, physical mixtures of naproxen compressed with the same aids failed tableting, whereas naproxen sodium produced weak tablets. Dissolution tests showed significant improvement for co-spray dried drugs tablets. Therefore, since the large therapeutic doses of naproxen and sodium naproxen limit the use of tableting aids, the improved compaction and dissolution performance of the spray-dried forms may be a formulation alternative.

Isolation of Itraconazole Nanostructured Microparticles via Spray Drying with Rational Selection of Optimum Base for Successful Reconstitution and Compaction

The addition of matrix formers within a formulation provides a means for enhancing the redispersibility of nanoparticles (NPs) enabling them to retain their advantageous properties imparted onto them by their sub-micron size. In this work, NPs were isolated in the solid state via spray drying with a range of sugars. The processed powders were characterized, establishing that itraconazole (ITR) nanostructured microparticles (NMPs) spray dried in the presence of mannitol and trehalose had favorable redispersibility confirmed by dynamic light scattering and nanoparticle tracking analysis. Solid-state analysis confirmed the crystalline nature of NMPs based on mannitol and the amorphous character of trehalose-based NMPs. The NMPs powders were compacted at a range of pressures, producing tablets with high tensile strength without compromising their disintegration time. A greater amount of ITR was solubilized from trehalose NMPs compared to the mannitol-based compacts in 0.1 M HCl, showing a promise for enhanced in vivo activity. Overall, as trehalose exhibited superior carrier properties for ITR NMPs, this type of excipient included in the formulation warrants careful consideration. The structured approach to matrix former selection and tabletting studies can reduce the amount of material and time required for testing in the initial stages of product development.

Overcoming Poor Tabletability of Bulky Absorption Enhancers by Spray Drying Technology

Absorption enhancers are often a major component of solid oral peptide formulations as compared to the active pharmaceutical ingredient and excipients. This commonly results in poor tabletability that is hard to mitigate in direct compaction by addition of small amounts of excipients. To improve the tabletability of bulky absorption enhancers, the model absorption enhancers, sodium cholate and deoxycholic acid, were co-spray-dried with hydroxypropyl methylcellulose E5, where the percentage of absorption enhancers was not lower than 90% (w/w). The physicochemical properties of the resulting powders were assessed by laser diffraction, scanning electron microscopy, X-ray powder diffraction, thermogravimetric analysis, and differential scanning calorimetry. The powders were compressed into tablets, and the tabletability was evaluated. Co-spray drying with 10% of hydroxypropyl methylcellulose significantly improved the tabletability of the both absorption enhancers. Moreover, it was demonstrated that small particle size and amorphous state rather than high moisture content contributed to the improved tabletability of the spray-dried powders. The study suggests that spray drying technology can be promising to overcome the poor tabletability of oral peptide formulation consisting of large amounts of absorption enhancers.

Understanding the compaction behaviour of low-substituted HPC: macro, micro, and nano-metric evaluations

The fast development in materials science has resulted in the emergence of new pharmaceutical materials with superior physical and mechanical properties. Low-substituted hydroxypropyl cellulose is an ether derivative of cellulose and is praised for its multi-functionality as a binder, disintegrant, film coating agent and as a suitable material for medical dressings. Nevertheless, very little is known about the compaction behaviour of this polymer. The aim of the current study was to evaluate the compaction and disintegration behaviour of four grades of L-HPC namely; LH32, LH21, LH11, and LHB1. The macrometric properties of the four powders were studied and the compaction behaviour was evaluated using the out-of-die method. LH11 and LH22 showed poor flow properties as the powders were dominated by fibrous particles with high aspect ratios, which reduced the powder flow. LH32 showed a weak compressibility profile and demonstrated a large elastic region, making it harder for this polymer to deform plastically. These findings are supported by AFM which revealed the high roughness of LH32 powder (100.09 ± 18.84 nm), resulting in small area of contact, but promoting mechanical interlocking. On the contrary, LH21 and LH11 powders had smooth surfaces which enabled larger contact area and higher adhesion forces of 21.01 ± 11.35 nN and 9.50 ± 5.78 nN, respectively. This promoted bond formation during compression as LH21 and LH11 powders had low strength yield.

Cocrystal habit engineering to improve drug dissolution and alter derived powder properties

Objectives

Cocrystallization of sulfadimidine (SDM) with suitable coformers, such as 4-aminosalicylic acid (4-ASA), combined with changes in the crystal habit can favourably alter its physicochemical properties. The aim of this work was to engineer SDM : 4-ASA cocrystals with different habits to investigate the effect on dissolution, and the derived powder properties of flow and compaction.

Methods

Cocrystals were prepared in a 1 : 1 molar ratio by solvent evaporation using ethanol (habit I) or acetone (habit II), solvent evaporation followed by grinding (habit III) and spray drying (habit IV).

Key findings

Powder X-ray diffraction showed Bragg peak position was the same in all the solid products. The peak intensity varied, indicating different preferred crystal orientation confirmed by SEM micrographs: large prismatic crystals (habit I), large plate-like crystals (habit II), small cube-like crystals (habit III) and microspheres (habit IV). The habit III exhibited the fasted dissolution rate; however, it underwent a polymorphic transition during dissolution. Habits I and IV exhibited the highest Carr's compressibility index, indicating poor flowability. However, habits II and III demonstrated improved flow. Spray drying resulted in cocrystals with improved compaction properties.

Conclusions

Even for cocrystals with poor pharmaceutical characteristics, a habit can be engineered to alter the dissolution, flowability and compaction behaviour.

Scalable surface area characterization by electrokinetic analysis of complex anion adsorption

By means of the in situ electrokinetic assessment of aqueous particles in conjunction with the addition of anionic adsorbates, we develop and examine a new approach to the scalable characterization of the specific accessible surface area of particles in water. For alumina powders of differing morphology in mildly acidic aqueous suspensions, the effective surface charge was modified by carboxylate anion adsorption through the incremental addition of oxalic and citric acids. The observed zeta potential variation as a function of the proportional reagent additive was found to exhibit inverse hyperbolic sine-type behavior predicted to arise from monolayer adsorption following the Grahame-Langmuir model. Through parameter optimization by inverse problem solving, the zeta potential shift with relative adsorbate addition revealed a nearly linear correlation of a defined surface-area-dependent parameter with the conventionally measured surface area values of the powders, demonstrating that the proposed analytical framework is applicable for the in situ surface area characterization of aqueous particulate matter. The investigated methods have advantages over some conventional surface analysis techniques owing to their direct applicability in aqueous environments at ambient temperature and the ability to modify analysis scales by variation of the adsorption cross section.