In Situ Salt Formation during Melt Extrusion for Improved Chemical Stability and Dissolution Performance of a Meloxicam–Copovidone Amorphous Solid Dispersion

Generality of Enhancing the Dissolution Rates of Free Acid Amorphous Solid Dispersions by the Incorporation of Sodium Hydroxide

The incorporation of a counterion into an amorphous solid dispersion (ASD) has been proven to be an attractive strategy to improve the drug dissolution rate. In this work, the generality of enhancing the dissolution rates of free acid ASDs by incorporating sodium hydroxide (NaOH) was studied by surface-area-normalized dissolution. A set of diverse drug molecules, two common polymer carriers (copovidone or PVPVA and hydroxypropyl methylcellulose acetate succinate or HPMCAS), and two sample preparation methods (rotary evaporation and spray drying) were investigated. When PVPVA was used as the polymer carrier for the drugs in this study, enhancements of dissolution rates from 7 to 78 times were observed by the incorporation of NaOH into the ASDs at a 1:1 molar ratio with respect to the drug. The drugs having lower amorphous solubilities showed greater enhancement ratios, providing a promising path to improve the drug release performance from their ASDs. Samples generated by rotary evaporation and spray drying demonstrated comparable dissolution rates and enhancements when NaOH was added, establishing a theoretical foundation to bridge the ASD dissolution performance for samples prepared by different solvent-removal processes. In the comparison of polymer carriers, when HPMCAS was applied in the selected system (indomethacin ASD), a dissolution rate enhancement of 2.7 times by the incorporated NaOH was observed, significantly lower than the enhancement of 53 times from the PVPVA-based ASD. This was attributed to the combination of a lower dissolution rate of HPMCAS and the competition for NaOH between IMC and HPMCAS. By studying the generality of enhancing ASD dissolution rates by the incorporation of counterions, this study provides valuable insights into further improving drug release from ASD formulations of poorly water-soluble drugs.

Modelling drug degradation of amorphous solid dispersion during twin-screw extrusion

Twin-screw extrusion is one of the major technologies for solid dispersion in the pharmaceutical industry. However, the thermal exposure to the drug during extrusion can easily trigger and exacerbate drug degradation. A conventional method for investigating drug degradation in extrusion is trial-and-error, which can consume much time and material. We propose to model drug degradation kinetics and combine it with thermal history simulation to predict drug degradation. Ritonavir and copovidone were used as a model system of solid dispersion. Hydantoin aminoalchol was the major degradant of RTV in extrudate. In studying the RTV degradation kinetics, only in nitrogen atmosphere, RTV degradation pathway in TGA or DSC was like the degradation pathway in extrusion. The mixing and solubilization of RTV in copovidone also prevented RTV from degrading to oxazolidine derivative. The degradation samples were collected at various temperatures and at different times. The data was fitted into first-order kinetics model to get degradation rates constant at each temperature. The degradation rate constants were fitted into the Arrhenius equation with an activation energy of 159.3 kJ/mol, and a pre-exponential of 1.23 × 1017. An array of extrusion conditions was developed and analyzed via design of experiment (DOE). Relying on the measured melt temperature and residence time after kneading element and die, we simulated the thermal history in the section between kneading element and die. The RTV degradation kinetics in conjunction with simulated thermal history predicted degradation and achieved a 78% regression.

Effects of Additives on the Physical Stability and Dissolution of Polymeric Amorphous Solid Dispersions: a Review

Polymeric amorphous solid dispersion (ASD) is a popular approach for enhancing the solubility of poorly water-soluble drugs. However, achieving both physical stability and dissolution performance in an ASD prepared with a single polymer can be challenging. Therefore, a secondary excipient can be added. In this paper, we review three classes of additives that can be added internally to ASDs: (i) a second polymer, to form a ternary drug-polymer-polymer ASD, (ii) counterions, to facilitate in situ salt formation, and (iii) surfactants. In an ASD prepared with a combination of polymers, each polymer exerts a unique function, such as a stabilizer in the solid state and a crystallization inhibitor during dissolution. In situ salt formation in ASD usually leads to substantial increases in the glass transition temperature, contributing to improved physical stability. Surfactants can enhance the wettability of ASD particles, thereby promoting rapid drug release. However, their potential adverse effects on physical stability and dissolution, resulting from enhanced molecular mobility and competitive molecular interaction with the polymer, respectively, warrant careful consideration. Finally, we discuss the impact of magnesium stearate and inorganic salts, excipients added externally upon downstream processing, on the solid-state stability as well as the dissolution of ASD tablets.

Templated Reactive Crystallization of Active Pharmaceutical Ingredient in Hydrogel Microparticles Enabling Robust Drug Product Processing

Commercialization of most promising active pharmaceutical ingredients (APIs) is impeded either by poor bioavailability or challenging physical properties leading to costly manufacture. Bioavailability of ionizable hydrophobic APIs can be enhanced by its conversion to salt form. While salt form of the API presents higher solution concentration than the non-ionized form, poor physical properties resulting from particle anisotropy or non-ideal morphology (needles) and particle size distribution not meeting dissolution rate targets can still inhibit its commercial translation. In this regard, API physical properties can be improved through addition of non-active components (excipients or carriers) during API manufacture. In this work, a facile method to perform reactive crystallization of an API salt in presence of the microporous environment of a hydrogel microparticle is presented. Specifically, the reaction between acidic antiretroviral API, raltegravir and base potassium hydroxide is performed in the presence of polyethylene glycol diacrylamide hydrogel microparticles. In this bottom-up approach, the spherical template hydrogel microparticles for the reaction lead to monodisperse composites loaded with inherently micronized raltegravir-potassium crystals, thus improving API physical properties without hampering bioavailability. Overall, this technique provides a novel approach to reactive crystallization while maintaining the API polymorph and crystallinity.

A comparative study of femtosecond pulsed laser ablation of meloxicam in distilled water and in air

The increasing prevalence of water insoluble or poorly soluble drugs calls for the development of new formulation methods. Common approaches include the reduction of particle size and degree of crystallinity. Pulsed laser ablation is a clean technique for producing sub-micrometre sized drug particles and has the potential to induce amorphization. We studied the effect of femtosecond pulsed laser ablation (ELI ALPS THz pump laser system: λ_c = 781 nm, τ = 135 fs) on meloxicam in distilled water and in air. The ablated particles were characterized chemically, morphologically and in terms of crystallinity. We demonstrated that femtosecond laser ablation can induce partial amorphization of the particles in addition to a reduction in particle size. In the case of femtosecond pulsed laser ablation in air, the formation of pure meloxicam spheres showed that this technique can produce amorphous meloxicam without the use of excipients, which is a unique result. We also aimed to describe the ablation processes in both investigated media.

Intra-articular treatment of temporomandibular joint osteoarthritis by injecting actively-loaded meloxicam liposomes with dual-functions of anti-inflammation and lubrication

Temporomandibular joint (TMJ) osteoarthritis is a common osteochondral degenerative disease which can severely affect patient's mouth opening and mastication. Meloxicam (MLX), one of the most widely used non-steroidal anti-inflammatory drugs, is the main clinical therapy for the treatment of TMJ osteoarthritis. However, the clinical effect is greatly compromised because of its poor water solubility and high lipophilicity. In the present study, we developed an actively-loaded liposomal formulation, namely MLX-Ca(AC)₂Lipo, using meglumine to enhance aqueous solubility and divalent metal (Ca²⁺) solution to improve encapsulation efficiency. By the formation of the nano-bowl shaped MLX-Ca precipitates inside the liposomes, MLX-Ca(AC)₂Lipo successfully achieved an optimal encapsulation efficiency as high as 98.4% compared with previous passive loading method (60.6%). Additionally, MLX-Ca(AC)₂Lipo maintained stable, and the slow drug release not only prolonged the duration of drug efficacy but also improved bioavailability. It was shown in the in vitro and in vivo tests that MLX-Ca(AC)₂Lipo downregulated the synthesis of the inflammatory factors (such as prostaglandin-E2) and as a consequence reduced chondrocytes apoptosis and extracellular matrix degeneration. Furthermore, the intra-articular injection of MLX-Ca(AC)₂Lipo enhanced bioinspired lubrication of TMJ, protecting the cartilage from progressive wear. In summary, MLX-Ca(AC)₂Lipo with dual-functions of anti-inflammation and lubrication is a promising nanomedicine for the treatment of TMJ osteoarthritis by intra-articular injection.

Pharmaceutical Salts of Piroxicam and Meloxicam with Organic Counterions

Piroxicam (PRM) and meloxicam (MEL) are two nonsteroidal anti-inflammatory drugs, belonging to the Biopharmaceutics Classification System Class II drugs. In this study, six novel pharmaceutical salts of PRM and MEL with three basic organic counterions, that is, 4-aminopyridine (4AP), 4-dimethylaminopyridine (4DMP), and piperazine (PPZ), were prepared by both slurrying and slow evaporation. These salts were characterized by single-crystal and powder X-ray diffraction, thermal analysis, and Fourier transform infrared spectroscopy. All six salts, especially MEL-4DMP and MEL-4AP, showed a significantly improved apparent solubility and dissolution rate in sodium phosphate solution compared with the pure APIs. Notably, PRM-4AP and PRM-4DMP salts exhibited enhanced fluorescence, and the PRM-PPZ salt showed weaker fluorescence compared with that of pure PRM due to different luminescence mechanisms.

Optimization of Meloxicam Solid Dispersion Formulations for Dissolution Enhancement and Storage Stability Using 33 Full Factorial Design Based on Response Surface Methodology

This study aimed to formulate and optimize solid-dispersion of meloxicam (MX) employing response-surface-methodology (RSM). RSM allowed identification of the main effects and interactions between studied factors on MX dissolution and acceleration of the optimization process. 3³ full factorial design with 27 different formulations was proposed. Effects of drug loading percentage (A), carriers' ratio (B), method of preparation (C), and their interactions on percent MX dissolved after 10 and 30 min (Q_10min & Q_30min) from fresh and stored samples were studied in distilled water. The considered levels were 2.5%, 5.0%, and 7.5% (factor A), three ratios of Soluplus®/Poloxamer-407 (factor B). Physical mixture (PM), fusion method (FM), and hot-melt-extrusion (HME) were considered factor (C). Stability studies were carried out for 3 months under stress conditions. The proposed optimization design was validated by 3-extra checkpoints formulations. The optimized formulation was selected via numerical optimization and investigated by DSC, XRD, PLM, and in vitro dissolution study. Results showed that HME technique gave the highest MX dissolution rate compared to other techniques (FM & PM). At constant level of factor (C), the amount of MX dissolved increased by decreasing MX loading and increasing Soluplus in carriers' ratio. Actual responses of the optimized formulation were in close consistency with predicted data. Amorphous form of MX in the optimized formulation was proved by DSC, XRD, and PLM. Selected factors and their levels of the optimization design were significantly valuable for demonstrating and adapting the expected formulation characteristics for rapid dissolution of MX (Q_10min= 89.09%) from fresh and stored samples.

Role of polymers in the physical and chemical stability of amorphous solid dispersion: A case study of carbamazepine

Incorporating the amorphous drug in polymeric components has been demonstrated as a feasible approach to enhance the bioavailability of poorly water-soluble drugs. The objective of this study was to investigate the role of polymers in the stability of amorphous solid dispersion (ASD) by evaluating the drug-polymer interaction, microenvironmental pH, and stability of ASD. Carbamazepine (CBZ), a Biopharmaceutics Classification System Class II compound, was utilized as a model drug. Polyvinylpyrrolidone (PVP), poly(1-vinylpyrrolidone-co-vinyl acetate) (PVPVA), polyacrylic acid (PAA), and hydroxypropyl methylcellulose (HPMCAS) were selected as model polymers. CBZ ASDs were characterized by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), Fourier transform infrared (FTIR) spectroscopy, and dissolution studies. Molecular modeling was conducted to understand the strength of interaction between CBZ and each polymer. FTIR spectroscopy and molecular modeling results show that the interaction between CBZ and PAA is the strongest among all the ASDs, as PAA is an acidic polymer with the potential to form strong hydrogen bonding with CBZ. Besides, hydrophobic interaction is detected between CBZ and HPMCAS. CBZ-PAA and CBZ-HPMCAS ASDs reveal better physical stability than CBZ-PVP and CBZ-PVPVA ASDs under 40 °C/75% RH for 8 weeks. However, CBZ-PAA ASD shows chemical degradation after stability testing due to its acidic microenvironmental pH. This paper shows that strong intermolecular interactions between CBZ and polymers contribute to the physical stability of the ASDs. Additionally, acidic polymers yield an acidic microenvironment pH of the ASDs that causes chemical degradation during storage. Hence, a balance between the ability of a given polymer to promote physical stability and chemical stability may need to be considered.

Solvent-Assisted Hot Melt Extrusion of a Thermally Labile, High Melting Point Compound

Molecular dispersions are a highly effective method of increasing bioavailability for a poorly soluble active pharmaceutical ingredient (API) and can be prepared on a large scale by hot melt extrusion (HME). Processing thermally labile active pharmaceutical ingredients (APIs) via HME is generally more difficult, with operating temperatures limited to below that of the API melting point. API melting is considered essential to facilitate the formation of a fully homogeneous amorphous system. Processing below the melting point renders the system much more susceptible to residual crystalline content; hence, HME is not suitable for APIs which degrade upon melting. In the following work, meloxicam (MEL) was used as a model API, possessing properties of high melting temperature and thermal lability. In this proof of concept work, a modified HME method, termed solvent-assisted HME, was used to overcome this issue and prepare an amorphous solid dispersion using HME, wherein a solvent was incorporated in the formulation blend during extrusion and removed post-processing. Formulations containing 10%wt meloxicam (MEL) and 90%wt polyvinylpyrrolidone vinyl acetate (PVPVA) copolymer were extruded using a twin-screw extruder at temperatures below the melting point of MEL. Dimethylformamide (DMF) solvent was added directly into the extruder barrel through a liquid addition port, resulting in extrudate products having a higher conversion of API to the amorphous form. The incorporation of solvent allowed a significant reduction in processing temperatures due to its increased mobility, while also driving the conversion of the API to its amorphous form. The solvent was successfully reduced through a secondary drying step using a vacuum oven. This advancement has demonstrated the potential for thermally labile APIs to be processed via HME expanding the applications of this technology.

Eudragit®: A Versatile Family of Polymers for Hot Melt Extrusion and 3D Printing Processes in Pharmaceutics

Eudragit® polymers are polymethacrylates highly used in pharmaceutics for the development of modified drug delivery systems. They are widely known due to their versatility with regards to chemical composition, solubility, and swelling properties. Moreover, Eudragit polymers are thermoplastic, and their use has been boosted in some production processes, such as hot melt extrusion (HME) and fused deposition modelling 3D printing, among other 3D printing techniques. Therefore, this review covers the studies using Eudragit polymers in the development of drug delivery systems produced by HME and 3D printing techniques over the last 10 years. Eudragit E has been the most used among them, mostly to formulate immediate release systems or as a taste-masker agent. On the other hand, Eudragit RS and Eudragit L100-55 have mainly been used to produce controlled and delayed release systems, respectively. The use of Eudragit polymers in these processes has frequently been devoted to producing solid dispersions and/or to prepare filaments to be 3D printed in different dosage forms. In this review, we highlight the countless possibilities offered by Eudragit polymers in HME and 3D printing, whether alone or in blends, discussing their prominence in the development of innovative modified drug release systems.

Amorphous Salts Solid Dispersions of Celecoxib: Enhanced Biopharmaceutical Performance and Physical Stability

Numerous amorphous solid dispersion (ASD) formulations of celecoxib (CEL) have been attempted for enhancing the solubility, dissolution rate, and in vivo pharmacokinetics via high drug loading, polymer combination, or by surfactant addition. However, physical stability for long-term shelf life and desired in vivo pharmacokinetics remains elusive. Therefore, newer formulation strategies are always warranted to address poor aqueous solubility and oral bioavailability with extended shelf life. The present investigation elaborates a combined strategy of amorphization and salt formation for CEL, providing the benefits of enhanced solubility, dissolution rate, in vivo pharmacokinetics, and physical stability. We generated amorphous salts solid dispersion (ASSD) formulations of CEL via an in situ acid-base reaction involving counterions (Na⁺ and K⁺) and a polymer (Soluplus) using the spray-drying technique. The generated CEL-Na and CEL-K salts were homogeneously and molecularly dispersed in the matrix of Soluplus polymer. The characterization of generated ASSDs by differential scanning calorimetry revealed a much higher glass-transition temperature (T_g) than the pure amorphous CEL, confirming the salt formation of CEL in solid dispersions. The micro-Raman and proton nuclear magnetic resonance spectroscopy further confirmed the formation of salt at the -S═O position in the CEL molecules. CEL-Na-Soluplus ASSD exhibited a synergistic enhancement in the aqueous solubility (332.82-fold) and in vivo pharmacokinetics (9.83-fold enhancement in the blood plasma concentration) than the crystalline CEL. Furthermore, ASSD formulations were physically stable for nearly 1 year (352 days) in long-term stability studies at ambient conditions. Hence, we concluded that the ASSD is a promising strategy for CEL in improving the physicochemical properties and biopharmaceutical performance.

Preparation, characterization and in-Vitro/in-Vivo evaluation of meloxicam extruded pellets with enhanced bioavailability and stability

OBJECTIVE

The present study involved enhancement of Meloxicam (MX) oral absorption for rapid onset of therapeutic action. A challenging approach using hot-melt-extrusion technique (HME) for production of stable novel preparation of MX pellets was successfully proposed.

METHODS

Manipulating HME processing parameters (barrel-temperatures and screw-speed) and proper polymer(s) selection (Soluplus, a combination of Soluplus/Poloxamar and Polyethylene Glycol 6000) were the main strategies involved for productive extrusion of MX. Evaluation of MX solid-state (TGA, DSC and PLM), absolute percent crystallinity, in-vitro dissolution (in acidic/aqueous pHs), and stability testing in accelerated conditions up to 6-months as well as a long-term shelf for 36-months were performed. A comparative bioavailability study of selected MX-Pellets was carried-out against the innovator product (Mobic^®) in 6 healthy volunteers under fed-conditions.

RESULTS

TGA, DSC and PLM analyses proved the dispersion of MX in amorphous-state within polymeric matrix by HME. MX/Soluplus pellets exhibited the lowest crystallinity % and best dissolution performance among other polymers in both pHs. In addition, presence of Soluplus safeguards final pellets stability under different storage conditions. MX rate of absorption (T_max) from Soluplus-based pellets attained a value of 45 min, which was 6-times faster than Mobic^® (4.5 hr).

CONCLUSION

A promising oral MX formula prepared by HME was successfully developed with a rapid onset of analgesic action (T_max of 45 mins; almost 2-times faster than reported intramuscular injection), hence appropriate in the early relief of pain associated with rheumatoid arthritis and osteoarthritis. Moreover, the proposed formula was physico-chemically stable up to 36 months of shelf-life storage.

Innovations in Thermal Processing: Hot-Melt Extrusion and KinetiSol® Dispersing

Thermal processing has gained much interest in the pharmaceutical industry, particularly for the enhancement of solubility, bioavailability, and dissolution of active pharmaceutical ingredients (APIs) with poor aqueous solubility. Formulation scientists have developed various techniques which may include physical and chemical modifications to achieve solubility enhancement. One of the most commonly used methods for solubility enhancement is through the use of amorphous solid dispersions (ASDs). Examples of commercialized ASDs include Kaletra®, Kalydeco®, and Onmel®. Various technologies produce ASDs; some of the approaches, such as spray-drying, solvent evaporation, and lyophilization, involve the use of solvents, whereas thermal approaches often do not require solvents. Processes that do not require solvents are usually preferred, as some solvents may induce toxicity due to residual solvents and are often considered to be damaging to the environment. The purpose of this review is to provide an update on recent innovations reported for using hot-melt extrusion and KinetiSol® Dispersing technologies to formulate poorly water-soluble APIs in amorphous solid dispersions. We will address development challenges for poorly water-soluble APIs and how these two processes meet these challenges.

Scale-Up and In-line Monitoring During Continuous Melt Extrusion of an Amorphous Solid Dispersion

Chemical degradation of drug substances remains a major drawback of extrusion. Larger-scale extrusion equipment has advantages over smaller equipment due to deeper flight elements and added flexibility in terms of screw design, unit operations, and residence time. In a previous study, we extruded a meloxicam-copovidone amorphous solid dispersion (ASD) on a Nano-16 extruder and achieved 96.7% purity. The purpose of this study is to introduce a strategy for scaling the process to an extruder with dissimilar geometry and to investigate the impact on the purity of the ASD. The formulation previously optimized on the Nano-16, 10:90 meloxicam and copovidone, was used for scale-up. Our approach to scale-up to the ZSE-18, utilized specific mechanical energy input and degree of fill from the Nano-16. Vacuum was added to prevent hydrolysis of meloxicam. Downstream feeding and micronization of meloxicam were introduced to reduce the residence time. In-line monitoring of the solubilization of meloxicam was monitored with a UV probe positioned at the die. We were able to achieve the same purity of meloxicam with the Micro-18 as we achieved with Nano-16. When process conditions alone were not sufficient, meglumine was added to further stabilize meloxicam. In addition to the chemical stability advantage that meglumine provided, we also observed solubility enhancement which allowed for an increase in drug loading to 20% while maintaining 100% purity.