Influence of Solvent Composition on the Miscibility and Physical Stability of Naproxen/PVP K 25 Solid Dispersions Prepared by Cosolvent Spray-Drying

Revealing facts behind spray dried solid dispersion technology used for solubility enhancement

Poor solubility and bioavailability of an existing or newly synthesized drug always pose challenge in the development of efficient pharmaceutical formulation. Numerous technologies can be used to improve the solubility and among them amorphous solid dispersion based spray drying technology can be successfully useful for development of product from lab scale to commercial scale with a wide range of powder characteristics. Current review deals with the importance of spray drying technology in drug delivery, basically for solubility and bioavailability enhancement. Role of additives, selection of polymer, effect of process and formulation parameters, scale up optimization, and IVIVC have been covered to gain the interest of readers about the technology. Design of experiment (DoE) to optimize the spray drying process has been covered in the review. A lot more research work is required to evaluate spray drying as a technology for screening the right polymer for solid dispersion, especially to overcome the issue related to drug re-crystallization and to achieve a stable product both in vitro and in vivo. Based on the recent FDA recommendation, the need of the hour is also to adopt Quality by Design approach in the manufacturing process to carefully optimize the spray drying technology for its smooth transfer from lab scale to commercial scale.

Enteric protection of naproxen in a fixed-dose combination product produced by hot-melt co-extrusion

In this study hot-melt co-extrusion is used as processing technique to manufacture a fixed-dose combination product providing enteric protection to naproxen incorporated in the core and immediate release to esomeprazole magnesium embedded in the coat. The plasticizing effect of naproxen and triethyl citrate (TEC) was tested on the enteric polymers investigated (Eudragit(®) L100-55, HPMC-AS-LF and HPMCP-HP-50). Core matrix formulations containing HPMC-AS-LF, TEC and a naproxen load of 15, 30 and 50% were processed and characterized. The in vitro naproxen release in 0.1N HCl was prevented for 2h for all formulations. The physicochemical state of the drug in the extrudates was determined and a stability study was performed. Intermolecular interactions between naproxen and polymer were identified using attenuated total reflection Fourier-transform infrared (ATR FT-IR) spectroscopy. When esomeprazole magnesium was formulated in a polyethylene oxide 100K:polyethylene glycol 4K (1:1) matrix, separated from the naproxen-containing layer, the formulation could be easily processed and complete in vitro drug release was observed after 45 min. When co-extruding the core/coat dosage form it was observed that a third layer of polymer, separating the naproxen loaded enteric formulation in the core from the coat, is required to prevent degradation of the acid-labile esomeprazole magnesium at the core/coat interface.

The influence of spray-drying parameters on phase behavior, drug distribution, and in vitro release of injectable microspheres for sustained release

For ternary solid dispersions, it is indispensable to characterize their structure, phase behavior, and the spatial distribution of the dispersed drug as this might influence the release profile and/or stability of these formulations. This study shows how formulation (feed concentration) and process (feed rate, inlet air temperature, and atomizing air pressure) parameters can influence the characteristics of ternary spray-dried solid dispersions. The microspheres considered here consist of a poly(lactic-co-glycolic acid) (PLGA) surface layer and an underlying polyvinylpyrrolidone (PVP) phase. A poorly soluble active pharmaceutical ingredient (API) was molecularly dispersed in this matrix. Differences were observed in component miscibility, phase heterogeneity, particle size, morphology, as well as API surface coverage for selected spray-drying parameters. Observed differences are likely because of changes in the droplet generation, evaporation, and thus particle formation processes. However, varying particle characteristics did not influence the drug release of the formulations studied, indicating the robustness of this approach to produce particles of consistent drug release characteristics. This is likely because of the fact that the release is dominated by diffusion from the PVP layer through pores in the PLGA surface layer and that observed differences in the latter have no influence on the release.

Pharmaceutical microparticle engineering with electrospraying: the role of mixed solvent systems in particle formation and characteristics

Microparticles of Celecoxib, dispersed in a matrix of poly(lactic-co-glycolic acid) (PLGA), were prepared by electrospraying using different solvent mixtures to investigate the influence upon particle formation and the resulting particle characteristics. Mixtures consisting of a good solvent, acetone, and an anti-solvent, methanol, for PLGA were studied in different ratios. Properties of the spraying solutions were examined and the resulting microparticles were characterized with regard to size, morphology, porosity, solid state form, surface chemistry and drug release. Particle formation was strongly influenced by the polymer molecular conformation during droplet formation and by the anti-solvent concentration during droplet drying. A strong correlation was found between particle morphology and the solubility of the polymer in the solvent mixtures. The lack of chain entanglements in droplets containing anti-solvent resulted in compact polymer conformation and grain-like particle morphology. Further, the early precipitation of polymer and low chain interaction with increasing content of anti-solvent resulted in surface enrichment of drug (from 10 and 20% up to 41 and 57% respectively), also demonstrated by the increasingly higher drug release rates. The results demonstrate the importance of solvent composition in particle preparation and indicate potential for exploiting this dependence to improve pharmaceutical particle design and performance.

Preparation of naproxen-ethyl cellulose microparticles by spray-drying technique and their application to textile materials

The objective of this study is to develop a new textile-based drug delivery system containing naproxen (NAP) microparticles and to evaluate the potential of the system as the carrier of NAP for topical delivery. Microparticles were prepared by spray-drying using an aqueous ethyl cellulose dispersion. The drug content and entrapment efficiency, particle size and distribution, particle morphology and in vitro drug release characteristics of microparticles were optimized for the application of microparticles onto the textile fabrics. Microparticles had spherical shape in the range of 10-15 μm and a narrow particle size distribution. NAP encapsulated in microparticles was in the amorphous or partially crystalline nature. Microparticles were tightly fixed onto the textile fabrics. In vitro drug release exhibited biphasic release profile with an initial burst followed by a very slow release. Skin permeation profiles were observed to follow near zero-order release kinetics.

Condensation dynamics of the L-Pro-L-Phe and L-Hyp-L-Phe binary mixtures in solution

We employ the achiral liquid chromatography with diode array, evaporative light scattering and mass spectrometric detection (HPLC-DAD, HPLC-ELSD and LC-MS) to assess structural instability (understood as spontaneous oscillatory chiral conversion and spontaneous oscillatory condensation) of the two pairs of amino acids, L-proline-L-phenylalanine (L-Pro-L-Phe) and L-hydroxyproline-L-phenylalanine (L-Hyp-L-Phe), in aqueous acetonitrile. In our earlier studies, we managed to demonstrate that single amino acids in aqueous and non-aqueous solutions undergo spontaneous oscillatory chiral conversion and oscillatory condensation. We also investigated condensation in the binary L-Pro-L-Hyp mixture in aqueous solution, and proposed a theoretical model to explain the specific dynamics of this process, which involves mutual catalytic effects of the two amino acids. In this study, we demonstrate oscillatory instability with the other two amino acid pairs in the organic-aqueous solution and reflect on the dynamics of condensation in the investigated cases. The choice of L-Pro and L-Hyp is due to their important role as building blocks of collagen, which is omnipresent in the connective tissues of mammals, and largely responsible for tissue architecture and strength. L-Phe is one of the 20 exogenous amino acids and is a building block of the majority of naturally occurring proteins.

Solution-state polymer assemblies influence BCS class II drug dissolution and supersaturation maintenance

Spray dried dispersions (SDDs), solid dispersions of polymer excipients and active pharmaceuticals, are important to the field of oral drug delivery for improving active stability, bioavailability, and efficacy. Herein, we examine the influence of solution-state polymer assemblies on amorphous spray-dried dispersion (SDD) performance with two BCS II model drugs, phenytoin and probucol. These drugs were spray dried with 4 model polymer excipients consisting of poly(ethylene-alt-propylene) (PEP), N,N,-dimethylacrylamide (DMA), or 2-methacrylamido glucopyranose (MAG): amphiphilic diblock ter- and copolymers, PEP-P(DMA-grad-MAG) and PEP-PDMA, and their respective hydrophilic analogues, P(DMA-grad-MAG) and PDMA. Selective and nonselective solvents for the hydrophilic block of the diblock ter- and copolymers were used to induce or repress solution-state assemblies prior to spray drying. Prespray dried solution-state assemblies of these four polymers were probed with dynamic light scattering (DLS) and showed differences in solution assembly size and structure (free polymer versus aggregates versus micelles). Solid-state structures of spray dried dispersions (SDDs) showed a single glass transition event implying a homogeneous mixture of drug/polymer. Crystallization temperatures and enthalpies indicated that the drugs interact mostly with the DMA-containing portions of the polymers. Scanning electron microscopy was used to determine SDD particle size and morphology for the various polymer-drug pairings. In vitro dissolution tests showed excellent performance for one system, spray-dried PEP-PDMA micelles with probucol. Dissolution structures were investigated through DLS to determine drug-polymer aggregates that lead to enhanced SDD performance. Forced aggregation of the polymer into regular micelle structures was found to be a critical factor to increase the dissolution rate and supersaturation maintenance of SDDs, and may be an attractive platform to exploit in excipient design for oral drug delivery.

Interactions between drugs and polymers influencing hot melt extrusion

Objectives

Hot melt extrusion (HME) as a technique for producing amorphous solid dispersion (ASD) has been widely used in pharmaceutical research. The biggest challenge for the application of HME is the thermal degradation of drug, poor physical stability of ASD and precipitation of drug during dissolution. Interactions between drugs and polymers may play an important role in overcoming these barriers. In this review, influence of drug–polymer interactions on HME and the methods for characterizing the drug–polymer interactions were reviewed.

Key findings

Strong drug–polymer interactions, especially ionic interactions and hydrogen bonds, are helpful to improving the thermal stability of drug during HME, enhancing the physical stability of ASD during storage and maintaining supersaturated solution after dissolution in gastrointestinal tract. The interactions can be quantitatively and qualitatively characterized by many analysing methods.

Conclusions

As many factors collectively determine the properties of HME products, drug–polymer interactions play an extremely important role. However, the action mechanisms of drug–polymer interactions need intensive investigation to provide more useful information for optimizing the formulation and the process parameters of HME.

Rapid assessment of homogeneity and stability of amorphous solid dispersions by atomic force microscopy--from bench to batch

Purpose

To verify the robustness and fundamental value of Atomic Force Microscopy (AFM) and AFM-based assays to rapidly examine the molecular homogeneity and physical stability of amorphous solid dispersions on Hot-Melt-Extrudates.

Methods

Amorphous solid dispersions were prepared with a Hot-Melt Extruder (HME) and profiled by Raman Microscopy and AFM following a sequential analytical routine (Multi-Scale-Imaging-of-Miscibiliy (MIMix)). Extrudates were analyzed before and after incubation at elevated temperature and humidity. The data were compared with published results as collected on miniaturized melt models. The value of molecular phase separation rates for long term stability prediction was assessed.

Results

Data recorded on the extrudates are consistent with those published, and they can be compared side by side. Such direct data comparisons allow the identification of possible sources of extrudate heterogeneities. The surface roughness analysis of fracture-exposed interfaces is a novel quantitative way to trace on the nanometer scale the efficiencies of differently conducted HME-processes. Molecular phase separation rates are shown to be relevant for long term stability predictions.

Conclusions

The AFM-based assessment of API:excipient combinations is a robust method to rapidly identify miscible and stable solid dispersions in a routine manner. It provides a novel analytical tool for the optimization of HME processes.

Electronic supplementary material

The online version of this article (doi:10.1007/s11095-013-1045-0) contains supplementary material, which is available to authorized users.