Preparation and characterization of azithromycin – Aerosil 200 solid dispersions with enhanced physical stability

Investigation of the Influence of Copovidone Properties and Hot-Melt Extrusion Process on Level of Impurities, In Vitro Release, and Stability of an Amorphous Solid Dispersion Product

Hot-melt extrusion (HME) is a widely used method for creating amorphous solid dispersions (ASDs) of poorly soluble drug substances, where the drug is molecularly dispersed in a solid polymer matrix. This study examines the impact of three different copovidone excipients, their reactive impurity levels, HME barrel temperature, and the distribution of colloidal silicon dioxide (SiO2) on impurity levels, stability, and drug release of ASDs and their tablets. Initial peroxide levels were higher in Kollidon VA 64 (KVA64) and Plasdone S630 (PS630) compared to Plasdone S630 Ultra (PS630U), leading to greater oxidative degradation of the drug in fresh ASD tablets. However, stability testing (50 °C, closed container, 50 °C/30% RH, open conditions) showed lower oxidative degradation impurities in ASD tablets prepared at higher barrel temperatures, likely due to greater peroxide degradation. Plasdone S630 is suitable for ASDs with drugs prone to oxidative degradation, while standard purity grades may benefit drugs susceptible to free radical degradation, as they generate fewer free radicals post-HME. ASD tablets exhibited greater physical stability than milled extrudate samples, likely due to reduced exposure to stability conditions within the tablet matrix. Including SiO2 in the extrudate composition resulted in greater physical stability of the ASD system in the tablet; however, it negatively affected chemical stability, promoting greater oxidative degradation and hydroxylation of the drug substance. No impact of the distribution of SiO2 on drug release was observed. The study also confirmed the congruent release of copovidone, the drug substance, and Tween 80 using flow NMR coupled with in-line UV/vis. This research highlights the critical roles of peroxide levels and SiO2 in influencing the dissolution and physical and chemical stability of ASDs. The findings provide valuable insights for developing stable and effective pharmaceutical formulations, emphasizing the importance of controlling reactive impurities and excipient characteristics in ASD products prepared by using HME.

Novel Sustained Release Azithromycin Resinate Fabricated by One-Pot Ion-exchange Performed in Hydro-alcoholic Solution

Drug-resin complexes usually form in the aqueous phase. For poorly water-soluble drugs, low drug loading limits the use of resin in drug formulation. In this study, we used a new method to prepare azithromycin resinates, improving the drug loading rate, shortening the preparation time and simplifying the process. We used hydro-alcoholic solution as the drug loading solvent and the ion exchange resin as the carrier, and this method enabled the resin to adsorb both the retardant and the drug. The sustained release effect of retardant Eudragit RL, RS100 was analyzed. Drug loading efficiency, release profiles, morphology, physicochemical characterization and pharmacokinetic study were assessed. Preparation of drug resinate by batch method resulted in 14% higher drug loading of azithromycin and 3.5 h shorter loading time as compared to pure water for hydroalcoholic solution as drug loading solvent. Raman mappings demonstrated that the retardant with higher molecular weight was more likely to adsorb to the outer layer of the resin compared to the drug. The in vitro release and in vivo pharmacokinetic study of azithromycin resinates showed a sustained release profile with few gastrointestinal adverse effects. Therefore, the addition of ethanol not only improved the efficiency of drug loading but also showed sustained-release effect with one-pot preparation of azithromycin resinates.

Strategies to improve the stability of amorphous solid dispersions in view of the hot melt extrusion (HME) method

Oral administration of drugs is preferred over other routes for several reasons: it is non-invasive, easy to administer, and easy to store. However, drug formulation for oral administration is often hindered by the drug's poor solubility, which limits its bioavailability and reduces its commercial value. As a solution, amorphous solid dispersion (ASD) was introduced as a drug formulation method that improves drug solubility by changing the molecular structure of the drugs from crystalline to amorphous. The hot melt extrusion (HME) method is emerging in the pharmaceutical industry as an alternative to manufacture ASD. However, despite solving solubility issues, ASD also exposes the drug to a high risk of crystallisation, either during processing or storage. Formulating a successful oral administration drug using ASD requires optimisation of the formulation, polymers, and HME manufacturing processes applied. This review presents some important considerations in ASD formulation, including strategies to improve the stability of the final product using HME to allow more new drugs to be formulated using this method.

Preparations and characterizations of effervescent granules containing azithromycin solid dispersion for children and elder: Solubility enhancement, taste-masking, and digestive acidic protection

Azithromycin, a macrolide antibiotics, is one of the frequently used drugs in the children and elder. However, due to these population difficulty in swallowing and inefficient absorption, and azithromycin inherent poor solubility, bitter taste, and instability in the stomach acidic condition, it is a challenge to reach high oral bioavailability of this drug. To overcome these issues, we developed and characterized the effervescent granules containing azithromycin solid dispersion. Firstly, the solid dispersion was prepared, employing both wet grinding and solvent evaporation methods, with different types/amounts of polymers. The optimal solid dispersion with β-cyclodextrin at a drug:polymer ratio of 1:2 (w/w), prepared by the solvent evaporation method, significantly enhanced the azithromycin solubility 4-fold compared to the free drug, improved its bitterness from "bitter" to "normal", possessed intermolecular bonding between the drug and polymer, and transformed the azithromycin molecules from crystalline to amorphous state. Secondly, the effervescent granules incorporating the solid dispersion were formulated with varied excipients of sweeteners, gas-generators, pH modulators, and glidants/lubricants. The optimal formula satisfied all the properties stated in the Vietnamese Pharmacopoeia. In summary, the final effervescent granules product could be further investigated in in-vivo and in clinical settings to become a potential azithromycin delivery system with high bioavailability for the children and elder.

Role of Fine Silica as Amorphous Solid Dispersion Carriers for Enhancing Drug Load and Preventing Recrystallization- A Comprehensive Review

Amorphous solid dispersion (ASD) is a popular concept for improving the dissolution and oral bioavailability of poorly water-soluble drugs. ASD faces two primary challenges of low drug loading and recrystallization upon storage. Several polymeric carriers are used to fabricate a stable ASD formulation with a high drug load. The role of silica in this context has been proven significant. Different types of silica, porous and nonporous, have been used to develop ASD. Amorphous drugs get entrapped into silica pores or adsorbed on their surface. Due to high porosity and wide surface area, silica provides better drug dissolution and high drug loading. Recrystallization of amorphous drugs is inhibited by limited molecular ability inside the delicate pores due to hydrogen bonding with the surface silanol groups. A handful of researches have been published on silica-based ASD, where versatile types of silica have been used. However, the effect of different kinds of silica on product stability and drug loading has been rarely addressed. The present study analyzes multiple porous and nonporous silica types and their distinct role in developing a stable ASD. Emphasis has been given to various types of silica which are commonly used in the pharmaceutical industry.

Azithromycin-loaded linolenic acid-modified methoxy poly(ethylene glycol) micelles for bacterial infection treatment

In the study, new polymeric micelles loaded with azithromycin were prepared to enhance azithromycin's solubility and evaluate its in vitro/in vivo antibacterial activity against Staphylococcus aureus. Amphiphilic α-Linolenic acid-methoxy poly (ethylene glycol) polymer (MPEG-LNA) was synthesized through DCC-DMAP esterification procedure. Through thin-film hydration method, optimized azithromycin-loaded micelles (AZI-M) were prepared with 87.15% of encapsulation efficiency and 11.07% of drug loading capacity when the ratio of LNA to MPEG was 4. Azithromycin's water-solubility was obviously enhanced due to its loading into the polymeric micelles. The azithromycin-loaded micelles were characterized in terms of x-ray diffraction, Fourier transform infrared spectroscopy, in vitro release, and in vitro/in vivo antibacterial experiments. Although the drug-loaded micelles provided a slow and continuous azithromycin's release in comparison with free azithromycin, in vitro antibacterial activity results confirmed that its effect on the inhibition of bacterial growth and biofilm formation was similar to free azithromycin. It is more interesting that the azithromycin-loaded micelles achieved good in vivo antibacterial therapeutic effect like QiXian® (azithromycin lactobionate injection) in mouse model of intraperitoneal infection. AZI-M can be considered as a potential candidate for in vivo antibiotic therapy of Staphylococcus aureus infections.

Preparation of Azithromycin Amorphous Solid Dispersion by Hot-Melt Extrusion: An Advantageous Technology with Taste Masking and Solubilization Effects

Azithromycin (AZI) is one of the most commonly used macrolide antibiotics in children, but has the disadvantages of a heavy bitter taste and poor solubility. In order to solve these problems, hot-melt extrusion (HME) was used to prepare azithromycin amorphous solid dispersion. Preliminary selection of a polymer for HME was conducted by calculating Hansen solubility parameter to predict the miscibility of the drug and polymer. Eudragit^® RL PO was chosen as the polymer due to its combination of taste-masking effect and dissolution. Moreover, the solubility was improved with this polymer. Design of experiments (DoE) was used to optimize the formulation and process, with screw speed, extrusion temperature, and drug percentage as independent variables, and content, dissolution, and extrudates diameter as dependent variables. The optimal extrusion parameters were obtained as follows: temperature-150 °C; screw speed-75 rpm; and drug percentage-25%. Differential scanning calorimetry (DSC) and Powder X-ray Diffraction (PXRD) studies of the powdered solid dispersions showed that the crystalline AZI transformed into the amorphous form. Fourier transform infrared spectroscopy (FTIR) results indicated that the formation of a hydrogen bond between AZI and the polymer led to the stabilization of AZI in its amorphous form. In conclusion, this work illustrated the importance of HME for the preparation of amorphous solid dispersion of AZI, which can solve the problems of bitterness and low solubility. It is also of great significance for the development of compliant pediatric AZI preparation.

Famotidine-loaded solid self-nanoemulsifying drug delivery system demonstrates exceptional efficiency in amelioration of peptic ulcer

Famotidine (FMD) is a highly potent H₂-receptor antagonist used in peptic ulcer treatment. However, the drug possesses poor aqueous solubility and permeability. FMD-loaded solid self-nanoemulsifying drug delivery system (FMD-S-SNEDDS) comprised of Labrafil® M 1944 CS, Tween® 20 and PEG 400, adsorbed on Aerosil® 200, has been developed. FMD-S-SNEDDS has demonstrated acceptable micromeritic properties, and upon reconstitution in water, spherical nanosized particles were released, as demonstrated by dynamic light scattering studies and transmission electron microscopy imaging. High encapsulation efficiency of FMD in the developed SNEDDS has been attained, and the saturated solubility of the drug has increased by 20-fold when it was incorporated in the SNEDDS. Several in vitro characterizations have been carried out, including, Fourier transform-infrared spectroscopy, differential scanning calorimetry, scanning electron microscopy, and drug dissolution studies. In vivo, upon administration of the free drug suspension, marketed product (FAMOTIN®) and FMD-S-SNEDDS (40 mg/kg) in peptic ulcer rat models, FMD-S-SNEDDS and the marketed FMD demonstrated 12.5- and 4.7-fold reduction in ulcers number, and 28.7- and 7.2-fold reduction in ulcer severity, respectively, compared to the control untreated animals. FMD-S-SNEDDS showed a significant (p < 0.05) increase in the levels of depleted glutathione and endothelial nitric oxide synthase, and significantly (p < 0.05) reduced the elevated level of malondialdehyde, as compared to the free and marketed FMD. Only FMD-S-SNEDDS could restore the elevated proton pump activity and cyclic adenosine monophosphate RNA expression to their normal levels. Hence, FMD-S-SNEDDS provides a great potential as a nanotherapeutic system for treatment of peptic ulcer.

Enhanced oral bioavailability of Tanshinone IIA using lipid nanocapsules: Formulation, in-vitro appraisal and pharmacokinetics

Tanshinone IIA (TSIIA) is a promising phytomedicine that has been extensively studied due to its numerous biological activities, especially as an anticancer drug. However, it suffers from poor oral bioavailability owing to low aqueous solubility, poor permeability and exposure to first-pass metabolism. This study endeavored to improve TSIIA oral bioavailability by encapsulation into lipid nanocapsules (LNCs) for the first time. A previously reported phase-inversion method was used to prepare Tanshinone II A loaded LNCs (TSIIA-LNCs) with slight modifications based on a constructed phase diagram. They were then in-vitro characterized and their oral pharmacokinetics were studied in rats. TSIIA-LNCs showed excellent colloidal properties (size; 70 nm, PDI < 0.2 and zeta-potential; -13.5 mV), a high percent entrapment efficiency (98%) and a good drug payload (2.6 mg/g). Furthermore, the in-vivo pharmacokinetic study revealed a significant enhancement in both the rate and extent of absorption of TSIIA-LNCs compared with TSIIA suspension with about 3.6-fold increase in AUC _0-inf value (p ≤ 0.01). Additionally, a significant increase in both half-life and mean residence time was exhibited by TSIIA-LNCs (p ≤ 0.01), confirming their long circulating properties. Therefore, the elaborated LNCs could be addressed as a promising nanoplatform permitting higher TSIIA oral bioavailability.

Evaluation of Mogroside V as a Promising Carrier in Drug Delivery: Improving the Bioavailability and Liver Distribution of Silybin

The objective of this work was to investigate the capacity of mogroside V (MOG-V), a food additive, as a novel carrier to improve the bioavailability and liver distribution of silybin (SLY). Solid dispersion particles (SDPs) of SLY/MOG-V were prepared utilizing the solvent evaporation method. The physicochemical characterizations of SDPs were evaluated by using dynamic light scattering (DLS), differential scanning calorimetry (DSC), and powder X-ray diffraction (PXRD) measurements. DLS results demonstrated the formation of nanoparticles (206 nm) of SDPs in water. DSC and PXRD analysis revealed that SLY was in amorphous form or molecularly dispersed in SDPs. SDPs also exhibited a major increase in both dissolution rate and saturation solubility, as evidenced by a 1931-fold improvement (2201 μg/mL) in solubility compared with pure SLY (1.14 μg/mL). The pharmacokinetic study in rats showed that oral absorption of SLY/MOG-V SDPs was dramatically increased. The mean value of AUC until 12 h for SLY/MOG-V SDPs (27,481 ng·min/mL) was 24.5-fold higher than that of pure SLY (1122 ng·min/mL). In vivo tissue distribution experiment in mice confirmed that the major distribution tissue was changed from lungs to liver after SLY was loaded into MOG-V. In addition, even orally administrated to mice at a high dose (4.2 g/kg), MOG-V exhibited no undesirable effect on the plasma glucose concentrations. Thus, MOG-V may have the applicability to serve as an ideal excipient for solubilization or as a novel liver targeting carrier for the delivery of SLY.

Customized Novel Design of 3D Printed Pregabalin Tablets for Intra-Gastric Floating and Controlled Release Using Fused Deposition Modeling

Three-dimensional (3D) printing has been recently employed in the design and formulation of various dosage forms with the aim of on-demand manufacturing and personalized medicine. In this study, we formulated a floating sustained release system using fused deposition modeling (FDM). Filaments were prepared using hypromellose acetate succinate (HPMCAS), polyethylene glycol (PEG 400) and pregabalin as the active ingredient. Cylindrical tablets with infill percentages of 25%, 50% and 75% were designed and printed with the FDM printer. An optimized formulation (F6) was designed with a closed bottom layer and a partially opened top layer. Filaments and tablets were characterized by means of fourier-transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), X-ray powder diffraction (XRPD), and thermogravimetric analysis (TGA). The results show that the processing condition did not have a significant effect on the stability of the drug and the crystallinity of the drug remained even after printing. A dissolution study revealed that drug release is faster in an open system with low infill percentage compared to closed systems and open systems with a high infill ratio. The optimized formulation (F6) with partially opened top layer showed zero-order drug release. The results show that FDM printing is suitable for the formulation of floating dosage form with the desired drug release profile.

Exploring the Potential of Mesoporous Silica as a Carrier for Puerarin: Characterization, Physical Stability, and In Vivo Pharmacokinetics

The aim of this study was to evaluate the use of a novel porous silica carrier, AEROPERL^® 300 Pharma (AP), to improve the in vitro release and oral bioavailability of puerarin (PUE) in solid dispersions (SDs). PUE-AP SD formulations with different ratios of drug to silica (RDS) were prepared by the solvent method. The scanning electron microscopy (SEM) results indicated that the dispersion of PUE improved as the concentration of AP was increased. The differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results revealed that PUE mostly existed in an amorphous state in the SDs. The rate of drug dissolution from the SDs was significantly higher than that from the PUE powder (p < 0.05). The in vitro drug release percentage from the PUE-AP SDs increased as the RDS was reduced. The oral bioavailability of PUE from the SDs improved when using AP, as indicated by AUC_(0-∞), which was 2.05 and 2.01 times greater than that of the PUE (API) and PVP K30 SDs, respectively (p < 0.05). The drug content, in vitro release profiles, and the amorphous state of PUE in the PUE-AP SDs showed no significant changes after being stored at room temperature for 6 months or under accelerated conditions (40 ± 2°C, 75 ± 5% relative humidity) for 3 months. AP has a high pore volume, large specific surface area, excellent flowability, and hydrophilic properties, making it capable of improving the dissolution and bioavailability of poorly water-soluble drugs.

Production of a new platform based on fumed and mesoporous silica nanoparticles for enhanced solubility and oral bioavailability of raloxifene HCl

The purpose of the present study was to compare mesoporous and fumed silica nanoparticles (NPs) to enhance the aqueous solubility and oral bioavailability of raloxifene hydrochloride (RH). Mesoporous silica NPs (MSNs) and fumed silica NPs were used by freeze-drying or spray-drying methods. MSNs were obtained with different ratios of cetyltrimethylammonium bromide. Saturation solubility of the NPs was compared with the pure drug. The optimised formulation was characterised by scanning electron microscopy (SEM), X-ray diffraction (XRD) and differential scanning calorimetry. The pharmacokinetic studies were done by oral administration of a single dose of 15 mg/kg of pure drug or fumed silica NPs of RH in Wistar rats. MSNs enhanced the solubility of RH from 19.88 ± 0.12 to 76.5 μg/ml. Freeze-dried fumed silica increased the solubility of the drug more than MSNs (140.17 ± 0.45 μg/ml). However, the spray-dried fumed silica caused about 26-fold enhancement in its solubility (525.7 ± 93.5 μg/ml). Increasing the ratio of silica NPs enhanced the drug solubility. The results of XRD and SEM analyses displayed RH were in the amorphous state in the NPs. Oral bioavailability of NPs showed 3.5-fold increase compared to the pure drug. The RH loaded fumed silica NPs prepared by spray-drying technique could more enhance the solubility and oral bioavailability of RH.

Investigating molecular interactions of high-loaded glipizide-HPMCAS microparticles by integrated experimental and modeling techniques

Molecular interactions between drug and polymeric carriers are believed to be the key for high drug loading and better physical stability of micro-particles. However, molecular interactions between drug and polymer are still difficult to investigate using only experimental tools. In this study, high-loaded glipizide (GLP)/hydroxypropyl methylcellulose acetate succinate (HPMCAS) (1/1 w/w) micro-particles were prepared using an in situ pH-dependent solubility method. Molecular interactions within the micro-particles were investigated by integrated experimental and modeling techniques. The dissolution rate of GLP/HPMCAS micro-particles was significantly better than those of solid dispersions and physical mixtures. Scanning electron microscopy images showed that the polymer inhibited GLP recrystallization. Experimental (FTIR spectroscopy, differential scanning calorimetry, powder X-ray diffraction and nuclear magnetic resonance spectroscopy) and molecular dynamics simulation revealed that hydrogen-bonding was the key to the properties of the micro-particles. Our research developed high drug-loading GLP/HPMCAS micro-particles and investigated the interactions between drug and polymer at the molecular level. This integrated approach could be practical methodology for future formulation design.

The inhibiting role of hydroxypropylmethylcellulose acetate succinate on piperine crystallization to enhance its dissolution from its amorphous solid dispersion and permeability

The purpose of this study was to demonstrate that inhibiting crystallization by HPMCAS played a key role in enhancing dissolution and absorption of piperine (Pip) from its amorphous solid dispersion (ASD). Nucleation induction time and supersaturation tests were used to evaluate the ability of the polymers to inhibit crystallization of Pip. The prepared solid dispersions were characterized by DSC and FTIR. The dissolution rate of Pip from its ASDs was assayed by a dissolution test. Pip permeability was investigated by single-pass intestinal perfusion studies. The order of the ability of polymers to inhibit Pip crystallization was HF > MF > LF > L100-55. The best inhibition effect of HF can be attributed to its hydrophobicity and steric hindrance. Pip is amorphous in polymer matrices when the ratio of Pip/HPMCAS is lower than 1 : 1 and Pip/L100-55 is lower than 3 : 1. IR spectra show that there are hydrogen bonds between the amide groups of Pip and the carboxyl groups of polymer. The order of the ability of polymers to enhance Pip dissolution is HF > MF > LF > L100-55, which coincided with the ability of polymers to inhibit Pip crystallization. Increased apparent permeability via HF-induced supersaturation and decreased apparent permeability via solubilization with L100-55 are demonstrated. Nucleation induction time and supersaturation tests may be used to screen appropriate polymers for preparing ASDs.

HPMCAS enhances piperine dissolution and permeability in amorphous solid dispersion by inhibiting crystallization.

A novel composition of ticagrelor by solid dispersion technique for increasing solubility and intestinal permeability

The aim of this study is to improve the bioavailability of ticagrelor, BCS class 4 drug, using solid dispersion technique, and to evaluate the potential of ticagrelor loaded-solid dispersion, as a new formulation. The solid dispersion formulation was prepared via solvent evaporation method using ethanol. TPGS and Neusilin® US2 selected via screening studies were used for preparing formulation. The results of scanning electron microscopy, differential scanning calorimetry and powder X-ray diffraction showed that the crystallinity of the ticagrelor was completely transformed to an amorphous form and maintained in the solid dispersion formulation. The released amount of the optimized solid dispersion significantly increased by 2.2- and 34-fold in comparison with physical mixture (Ticagrelor:TPGS:Neusilin® US2 = 1:2:2, w/w/w) and commercial product (Brilinta®) in distilled water at 90 min, respectively. The absorptive permeability was improved (1.4-fold) and the efflux ratio was decreased (0.45-fold) by formulation containing TPGS acting as a P-gp inhibitor compared to pure drug. The solid dispersion formulation improved the peak plasma concentration (C_max) and relative bioavailability compared to that of pure drug as 238.09 ± 25.96% and 219.78 ± 36.33%, respectively, after oral administration in rats. Thus, we successfully prepared the solid dispersion formulation for enhancing oral bioavailability of ticagrelor, and then this formulation would be recommended as a practical oral pharmaceutical product.

Fused Deposition Modeling (FDM) 3D Printed Tablets for Intragastric Floating Delivery of Domperidone

The aim of this study was to explore the feasibility of fused deposition modeling (FDM) 3D printing to prepare intragastric floating sustained release (FSR) tablets. Domperidone (DOM), an insoluble weak base, was chosen as a model drug to investigate the potential of FSR in increasing its oral bioavailability and reducing its administration frequency. DOM was successfully loaded into hydroxypropyl cellulose (HPC) filaments using hot melt extrusion (HME). The filaments were then printed into hollow structured tablets through changing the shell numbers and the infill percentages. Physical characterization results indicated that the majority of DOM gradually turned into the amorphous form during the fabrication process. The optimized formulation (contain 10% DOM, with 2 shells and 0% infill) exhibited the sustained release characteristic and was able to float for about 10 h in vitro. Radiographic images showed that the BaSO₄-labeled tablets were retained in the stomach of rabbits for more than 8 h. Furthermore, pharmacokinetic studies showed the relative bioavailability of the FSR tablets compared with reference commercial tablets was 222.49 ± 62.85%. All the results showed that FDM based 3D printing might be a promising way to fabricate hollow tablets for the purpose of intragastric floating drug delivery.

In vitro characterization of pH-sensitive azithromycin-loaded methoxy poly (ethylene glycol)-block-poly (aspartic acid-graft-imidazole) micelles

In order to improve azithromycin's antibacterial activity in acidic medium, monomethoxy poly (ethylene glycol)-block-poly (aspartic acid-graft-imidazole) copolymer was synthesized through allylation, free radical addition, ring-opening polymerization and amidation reactions with methoxy poly (ethylene glycol) as raw material. Drug loading capacity and encapsulation efficiency of azithromycin-loaded micelles prepared via thin film hydration method were 11.58±0.86% and 96.06±1.93%, respectively. The drug-loaded micelles showed pH-dependent property in the respects of particle size, zeta potential at the range of pH 5.5-7.8. It could control drug in vitro release and demonstrate higher release rate at pH 6.0 than that at pH 7.4. In vitro antibacterial experiment indicated that the activity of azithromycin-loaded micelles against S. aureus was superior to free azithromycin in medium at both pH 6.0 and pH 7.4. Using fluorescein as substitute with pH-dependent fluorescence decrease property, laser confocal fluorescence microscopy analysis confirmed that cellular uptake of micelles was improved due to protonation of copolymer's imidazole groups at pH 6.0. The enhanced cellular uptake and release of drug caused its activity enhancement in acidic medium when compared with free drug. The micellar drug delivery system should be potential application in the field of bacterial infection treatment.

Isolation and Physical Property Optimization of an Amorphous Drug Substance Utilizing a High Surface Area Magnesium Aluminometasilicate (Neusilin(®) US2)

Control and optimization of the physical properties of a drug substance (DS) are critical to the development of robust drug product manufacturing processes and performance. A lack of isolatable, for example, crystalline, DS solid forms can present challenges to achieving this control. In this study, an isolation scheme for an amorphous DS was developed and integrated into the synthetic route producing DS with optimized properties. An inert absorbent excipient (Neusilin® US2) was used to isolate the DS via a novel antisolvent scheme as the final step of the route. Isolation was executed at kilogram scale utilizing conventional equipment. The resulting 50 wt% DS:Neusilin complex had improved physical stability and exceptional micromeritic and tableting properties. Improved dissolution was observed and attributed to enhanced dispersion and increased surface area. Characterization data suggest a high degree of penetration of the DS into the Neusilin, with DS occupying 70% of mesopore and 12% of macropore volume. This approach has application in the isolation and particle engineering of difficult to isolate DS without additional unit operation, such as spray drying, and has the potential for a high degree of optimization and control of physical properties over the course of DS development.