Effects of Coating Materials and Processing Conditions on Flow Enhancement of Cohesive Acetaminophen Powders by High-Shear Processing With Pharmaceutical Lubricants

Potential of Powder Rheology for Detecting Unforeseen Cross-Contamination of Foreign Active Pharmaceutical Ingredients

Unexpected cross-contamination by foreign components during the manufacturing and quality control of pharmaceutical products poses a serious threat to the stable supply of drugs and the safety of customers. In Japan, in 2020, a mix-up containing a sleeping drug went undetected by liquid chromatography during the final quality test because the test focused only on the main active pharmaceutical ingredient (API) and known impurities. In this study, we assessed the ability of a powder rheometer to analyze powder characteristics in detail to determine whether it can detect the influence of foreign APIs on powder flow. Aspirin, which was used as the host API, was combined with the guest APIs (acetaminophen from two manufacturers and albumin tannate) and subsequently subjected to shear and stability tests. The influence of known lubricants (magnesium stearate and leucine) on powder flow was also evaluated for standardized comparison. Using microscopic morphological analysis, the surface of the powder was observed to confirm physical interactions between the host and guest APIs. In most cases, the guest APIs were statistically detected due to characteristics such as their powder diameter, pre-milling, and cohesion properties. Furthermore, we evaluated the flowability of a formulation incorporating guest APIs for direct compression method along with additives such as microcrystalline cellulose, potato starch, and lactose. Even in the presence of several additives, the influence of the added guest APIs was successfully detected. In conclusion, powder rheometry is a promising method for ensuring stable product quality and reducing the risk of unforeseen cross-contamination by foreign APIs.

Taste Masking of Dexketoprofen Trometamol Orally Disintegrating Granules by High-Shear Coating with Glyceryl Distearate

Orally disintegrating granules (ODGs) are a pharmaceutical form commonly used for the administration of NSAIDs because of their easy assumption and fast dispersion. The development of ODGs is not easy for drugs like dexketoprofen trometamol (DXKT), which have a bitter and burning taste. In this work, high-shear coating (HSC) was used as an innovative technique for DKXT taste masking. This study focused on coating DXKT granules using the HSC technique with a low-melting lipid excipient, glyceryl distearate (GDS). The HSC technique allowed for the coating to be developed through the thermal rise resulting from the friction generated by the granules movement inside the equipment, causing the coating excipient to soften. The design of the experiment was used to find the best experimental coating conditions in order to gain effective taste masking by suitably reducing the amount of drug released in the oral cavity. The influence of the granule dimensions was also investigated. Coating effectiveness was evaluated using a simulated saliva dissolution test. It was found that low impeller speed (300 rpm) and a 20% coating excipient were effective in suitably reducing the drug dissolution rate and then in taste masking. The coated granules were characterized for their morphology and solid-state properties by SEM, BET, XRPD, DSC, and NIR analyses. A human taste panel test confirmed the masking of DXKT taste in the selected batch granules.

Improving the Effectiveness of the Conical Screen Mill as a Dry-Coating Process at Lab and Manufacturing Scale

The conical screen mill (comill) is investigated as a dry-coating process for flowability and bulk density enhancement of pharmaceutical powders. In this study, the effectiveness of the comill is improved by using modified screens with reduced open area. In comparison to the screens provided by the comill manufacturer, the modified screens increase mean residence time of the process and improve the extent of flowability and bulk density enhancement. The effectiveness of the comill as a dry-coating process is demonstrated using Avicel PH 105, a fine grade of microcrystalline cellulose, as a model cohesive powder. The process is evaluated thoroughly using a lab scale comill and scalability is demonstrated using a manufacturing scale model. The use of the modified screens is also compared against the so-called "multi-pass" approach in which material is passed through the comill, collected, and passed through once or several times. While the "multi-pass" approach is offered as a simple method to increase mean residence time and to improve process effectiveness, the use of the modified screens is shown to be the superior approach. Due to the ubiquitous use of the comill and the improvement in effectiveness attained in this study, dry-coating is shown to be a practical and readily implemented process for the pharmaceutical industry.

A Continuous Conical-Mill Operation for Dry Coating of Pharmaceutical Powders: The Role of Processing Time

Over the last decade, the conical mill has emerged as a potential piece of equipment to use for continuous dry coating pharmaceutical powders. In this work, silicon dioxide was used as a guest particle on two excipients, fast flow lactose (FFL) and grade PH200 microcrystalline cellulose (MCC), for dry coating by a conical mill with a modified screen that permitted batch and continuous mode operation. Samples were pre-processed in a V-blender. SEM images, particle size distribution, and EDS mapping were used to characterise the treated powders. Pre-processed samples showed some discrete coating of the host particle. After batch processing, the samples were covered with a complete coating. When processed at high impeller speed, coating of FFL was a mix of A200P and FFL fines generated by attrition. Continuous mode processed samples, which had a lower processing time, were coated discretely and showed a better coating than the pre-processed samples. Increasing guest/host mass ratio with FFL host particle had a positive impact on the quality of the coating. These results help to build the case that the processing time of the conical mill is a key parameter to the success of the conical mill as dry coating equipment in the pharmaceutical industry.

Efficient development of sorafenib tablets with improved oral bioavailability enabled by coprecipitated amorphous solid dispersion

An amorphous solid dispersion (ASD) of sorafenib (SOR) in hydroxypropyl methylcellulose acetate succinate (HPMC-AS), prepared by coprecipitation, was used to develop an immediate release tablet with improved oral bioavailability. An ASD of 40% drug loading with HPMC-AS (M grade), which exhibited superior physical stability and enhanced dissolution, was selected for tablet development. Systematic characterization of powder properties of the ASD led to the choice of the dry granulation process to overcome poor flowability of the ASD. The designed tablet formulation was evaluated using a material-sparing and expedited approach to optimize compaction conditions for manufacturing ASD tablets with low friability and rapid disintegration. The resulting SOR ASD tablets exhibited approximately 50% higher relative bioavailability in dogs than the marketed SOR tablet product, Nexavar®.

Correlations between surface composition and aerosolization of jet-milled dry powder inhaler formulations with pharmaceutical lubricants

Co-jet-milling drugs and lubricants may enable simultaneous particle size reduction and surface coating to achieve satisfactory aerosolization performance. This study aims to establish the relationship between surface lubricant coverage and aerosolization behavior of a model drug (ciprofloxacin HCl) co-jet-milled with lubricants [magnesium stearate (MgSt) or l-leucine]. The co-jet-milled formulations were characterized for particle size, morphology, cohesion, Carr's index, and aerosolization performance. The surface lubricant coating was assessed by probing surface chemical composition using X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary-ion mass spectrometry (ToF-SIMS). The effects of co-jet-milling on the surface energy and in vitro dissolution of ciprofloxacin were also evaluated. Our results indicated that, in general, the ciprofloxacin co-jet-milled with l-leucine at >0.5% w/w showed a significant higher fine particle fraction (FPF) compared with the ciprofloxacin jet-milled alone. The FPF values plateau at or above 5% w/w for both MgSt and l-leucine. We have established the quantitative correlations between surface lubricant coverage and aerosolization in the tested range for each of the lubricants. More importantly, our results suggest different mechanisms to improve aerosolization for MgSt-coating and l-leucine-coating, respectively: MgSt-coating reduces inter-particulate interactions through the formation of low surface energy coating films, while l-leucine-coating not only reduces the surface energy but also creates rough particle surfaces that reduce inter-particulate contact area. Furthermore, surface coatings with 5% w/w MgSt (which is hydrophobic) did not lead to substantial changes in in vitro dissolution. Our findings have shown that the coating structure/quality and their effects could be highly dependent on the process and the coating material. The findings from this mechanistic study provide fundamental understanding of the critical effects of MgSt and l-leucine surface coverages on aerosolization and powder flow properties of inhalation particles.

Moisture-Resistant Co-Spray-Dried Netilmicin with l-Leucine as Dry Powder Inhalation for the Treatment of Respiratory Infections

Netilmicin (NTM) is one of the first-line drugs for lower respiratory tract infections (LRTI) therapy, but its nephrotoxicity and ototoxicity caused by intravenous injection restrict its clinical application. Dry powder inhalation (DPI) is a popular local drug delivery system that is introduced as a solution. Due to the nature of NTM hygroscopicity that hinders its direct use through DPI, in this study, L-leucine (LL) was added into NTM dry powder to reduce its moisture absorption rate and improve its aerosolization performance. NTM DPIs were prepared using spray-drying with different LL proportions. The particle size, density, morphology, crystallinity, water content, hygroscopicity, antibacterial activity, in vitro aerosolization performance, and stability of each formulation were characterized. NTM DPIs were suitable for inhalation and amorphous with a corrugated surface. The analysis indicated that the water content and hygroscopicity were decreased with the addition of LL, whilst the antibacterial activity of NTM was maintained. The optimal formulation ND₂ (NTM:LL = 30:1) showed high fine particle fraction values (85.14 ± 8.97%), which was 2.78-fold those of ND₀ (100% NTM). It was stable after storage at 40 ± 2 °C, 75 ± 5% relative humidity (RH). The additional LL in NTM DPI successfully reduced the hygroscopicity and improved the aerosolization performance. NTM DPIs were proved to be a feasible and desirable approach for the treatment of LRTI.

Qualitative and Quantitative Characterization of Composition Heterogeneity on the Surface of Spray Dried Amorphous Solid Dispersion Particles by an Advanced Surface Analysis Platform with High Surface Sensitivity and Superior Spatial Resolution

Surface composition critically impacts stability (e.g., crystallization) and performance (e.g., dissolution) of spray dried amorphous solid dispersion (ASD) formulations; however, traditional characterization techniques such as Raman and infrared spectroscopies may not provide useful information on surface composition on the spray dried ASD particles due to low spatial resolution, high probing depth, and lack of quantitative information. This study presents an advanced surface characterization platform consisting of two complementary techniques: X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF-SIMS). Such a platform enables qualitative and quantitative measurements of surface composition for the fine spray dried ASD particles with ultrasurface-sensitivity (less than 10 nm from the surface) and superior spatial resolution (approximately 250 nm for ToF-SIMS). Both XPS and ToF-SIMS demonstrated that the polymer (PVPVA) was dominantly enriched on the surface of our spray dried naproxen-PVPVA ASD particles. Of a particular note was that XPS could differentiate two batches of spray dried ASD particles with a subtle difference in surface composition produced by varying feed solution solvents. This advanced surface characterization platform will provide essential surface information to understand the mechanisms underlying the impact of surface composition on stability (e.g., crystallization) and functionality (e.g., dissolution) in future studies.

Physico-Chemical Properties, Aerosolization and Dissolution of Co-Spray Dried Azithromycin Particles with L-Leucine for Inhalation

PURPOSE

Inhalation therapy is popular to treat lower respiratory tract infections. Azithromycin is effective against some bacteria that cause respiratory tract infections; but it has poor water solubility that may limit its efficacy when administrated as inhalation therapy. In this study, dry powder inhaler formulations were developed by co-spray drying azithromycin with L-leucine with a purpose to improve dissolution.

METHODS

The produced powder formulations were characterized regarding particle size, morphology, surface composition and in-vitro aerosolization performance. Effects of L-leucine on the solubility and in-vitro dissolution of azithromycin were also evaluated.

RESULTS

The spray dried azithromycin alone formulation exhibited a satisfactory aerosol performance with a fine particle fraction (FPF) of 62.5 ± 4.1%. Addition of L-leucine in the formulation resulted in no significant change in particle morphology and FPF, which can be attributed to enrichment of azithromycin on the surfaces of composite particles. Importantly, compared with the spray-dried amorphous azithromycin alone powder, the co-spray dried powder formulations of azithromycin and L-leucine demonstrated a substantially enhanced in-vitro dissolution rate. Such enhanced dissolution of azithromycin could be attributed to the formation of composite system and the acidic microenvironment around azithromycin molecules created by the dissolution of acidic L-leucine in the co-spray dried powder. Fourier transform infrared spectroscopic data showed intermolecular interactions between azithromycin and L-leucine in the co-spray dried formulations.

CONCLUSIONS

We developed the dry powder formulations with satisfactory aerosol performance and enhanced dissolution for a poorly water soluble weak base, azithromycin, by co-spray drying with an amino acid, L-leucine.