Advances in the development of amorphous solid dispersions:The role of polymeric carriers

Amorphous solid dispersion(ASD)is one of the most effective approaches for delivering poorly soluble drugs.In ASDs,polymeric materials serve as the carriers in which the drugs are dispersed at the molecular level.To prepare the solid dispersions,there are many polymers with various physicochemical and thermochemical characteristics available for use in ASD formulations.Polymer selection is of great importance because it influences the stability,solubility and dissolution rates,manufacturing process,and bioavailability of the ASD.This review article provides a comprehensive overview of ASDs from the perspectives of physicochemical characteristics of polymers,formulation designs and preparation methods.Furthermore,considerations of safety and regulatory requirements along with the studies recommended for characterizing and evaluating polymeric carriers are briefly discussed.

Preparation and Characterization of Solid Dispersions of Silymarin with Polyethylene Glycol 6000

Aim To prepare and characterize solid dispersions of silymarin with the intention of improving their dissolution properties. Methods The solid dispersions were prepared by the fusion method with polyethylene glycol 6000(PEG 6000) as the carrier. Evaluation of the properties of the dispersions was performed using dissolution studies, X ray powder diffraction and Fourier transform infrared (FT IR) spectroscopy. Results The rate of dissolution of silymarin was considerably improved as compared with pure silymarin when formulated in solid dispersions with PEG 6000. The data of the X ray diffraction showed some changes in the parameters of lattice spacing [ d ], peak position and relative intensities. FT IR together with those from X ray diffraction showed the absence of well defined drug polymer interactions. Conclusion The dissolution improvement of poorly soluble silymarin could be illuminated by the changes of the lattice parameters of PEG 6000 and the drug.

Dissolution improvement by solid dispersions composed of nifedipine, Eudragit?E and silica from rice husk

Nifedipine is a practically water-insoluble drug used therapeutically as a calcium-channel blocker for systemic and coronary vasodilation.Poorly soluble drugs that undergo dissolution rate-limited gastrointestinal absorption generally show increased bioavailability when dissolution is improved by formulation techniques[1].In solid dispersion system,a drug may exist as an amorphous form in polymeric carriers,and this may result in improved solubility and dissolution rate as compared with crystalline drug.Solid dispersion can be prepared by either fusion or solvent method[2].

Development,characterization and solubility enhancement of comparative dissolution study of second generation of solid dispersions and microspheres for poorly water soluble drug

The poor dissolution characteristics of water-insoluble drugs are a major challenge for pharmaceutical scientists.Reduction of the particle size/increase in the surface area of the drug is a widely used and relatively simple method for increasing dissolution rates.The objective of this study was to improve solubility,release and comparability of dissolution of a poorly soluble drug using two different types of formulations(solid dispersions and microspheres).Hydrochlorothiazide was used as a model drug.The solid dispersions and microspheres were prepared by solvent evaporation method using ethyl cellulose,hydroxypropyl methylcellulose in different drug-to-carrier ratios(1:1,1:2 w:w).The prepared formulations were evaluated for interaction study by Fourier transform infrared spectroscopy,differential scanning calorimetry,percentage of practical yield,drug loading,surface morphology by scanning electron microscopy,optical microscopy and in-vitro release studies.The results showed no interaction between the drug and polymer,amorphous state of solid dispersions and microspheres,percentage yield of 42.53%to 78.10%,drug content of 99.60%to 99.64%,good spherical appearance in formulation VI and significant increase in the dissolution rate.

Physicochemical Characterization and Solubility Enhancement Studies of Mebendazole Solid Dispersions in Solvent Mixtures

Abstract： The objective was to obtain solid dispersion to improve the dissolution rate, solubility and oral absorption of MB （mebendazole）, poor water-soluble drugs. The new formulation was characterized by DSC （differential scanning calorimetry）, PXRD （powder X-ray diffraction）, FT-1R （fourier transform infrared spectroscopy） and STEM （scanning transmission electron microscopy） methods. Solid dispersions of MB with polyvinylpyrrolidone K-30 （PVP K30） were prepared by solvent evaporation method. The solubility of MB （original powder） and that of the solid dispersions was measured at 25℃ in ethanol-water. The aqueous solubility of MB was favoured by the presence of the polymer in solvent mixtures. Combination of solid dispersions with co-solvents increased the water solubility of MB in a larger extent that each method separately. Solubility parameter （o） was used to relate to solubility profiles. MB and the solid dispersions show a solubility curve with a single peak at 51 = 30.78 MPav2. Solid state characterizations indicated that the solid dispersion exist an amorphous material entrapped in polymer matrix getting highest improvement in wettability and solubility.

Mapping multiple phases in curcumin binary solid dispersions by fluorescence contrasting

The microphases and miscibility in binary curcumin(Cur)solid dispersions(SDs)with amorphous polyvinylpyrrolidone K30(PVP K30)and semi-crystalline poloxamer(P407)and poly(ethylene glycol)6000(PEG6000)as carriers were investigated by fluorescence contrasting utilizing confocal laser scanning microscopy.A super sensitive fluorophore P4 with typical aggregation-caused quenching properties was employed to stain the continuous polymer phases and contrasted with the autofluorescence of the model drug Cur.In addition,differential scanning calorimetry(DSC)and powder X-ray diffraction(PXRD)were utilized to assist in explanation of the fluorescence results.In all three SD systems,there is always a homogenous polymer phase stained by P4 and it is difficult to adulterate Cur crystals by P4.Cur-enriched rather than polymer-enriched domains could be detected.In the Cur-PVP K30 system,Cur exists in an amorphous form at a Cur loading level of 50%and below,while Cur crystallines phase out and continuously grow with the increase of Cur loading from 60%to 90%.The phase behaviors in the Cur-P407 and Cur-PEG 6000 systems are similar but with minor differences.In both systems,Cur phases out as clusters of drug-enriched domains at a loading level of 20%and below,which however cannot be correlated with crystallization,as evidenced by both DSC and PXRD.There is a transition from an amorphous to a crystalline state from 20%to 30%Cur loading,above which Cur crystallines can be detected.It is interesting that a co-mix phase of both Cur-and PEG 6000-enriched domains can be identified at Cur loading levels of 10%and less.Taking together,it is concluded that contrasting Cur autofluorescence with the signals of P4 proves to be a functional strategy to reveal multiple phases in the binary SD systems investigated.

Formulation,characterization and in vivo and in vitro evaluation of aloe-emodin-loaded solid dispersions for dissolution enhancement

OBJECTIVE:To prepare aloe-emodin solid dispersion(AE-SD)and determine the metabolic process of AE and AE-SD in vivo.METHODS:AE-SD was prepared via solvent evaporation or solvent melting using PEG-6000 and PVP-K30 as carriers.Thermogravimetric analysis,X-ray diffraction spectroscopy,differential scanning calorimetry,Fourier transform infrared spectroscopy and scanning electron microscopy were used to identify the physical state of AESD.Optimal prescriptions were screened via the dissolution degree determination method.Using Phoenix software,AE suspension and AE-SD were subjected to a pharmacokinetic comparison study analyzing the alteration of behavior in vivo after AE was prepared as a solid dispersion.Acute toxicity was assessed in mice,and the physiological toxicity was used as the determination criterion for toxicity.RESULTS:AE-SD showed that AE existed in the carrier in an amorphous state.Compared with polyethylene glycol,polyvinylpyrrolidone(PVP)inhibited AE crystallization,causing the drug to transform from a dense crystalline state to an amorphous form and increasing the degree of drug dispersion.Therefore,it was more suitable as a carrier material for AE-SD.The addition of poloxamer(POL)was more beneficial to the stability of solid dispersions and could reduce the amount of PVP.The dissolution test confirmed that the optimal ratio of AE to the composite vector AE-PVP-POL was 1:2:2,and its dissolution effect was also optimal.Based on the pharmacokinetic comparison,the drug absorption was faster and quickly reached the peak of blood drug concentration in AE-SD compared to AE,the Cmax of AE-SD was greater than that of AE,and t1/2 and mean residence time of AE-SD were less than AE.The results showed that the drug metabolism in AE-SD was better,and the residence time was shorter.The toxicology study showed that both AE and AE-SD had no toxicity.CONCLUSION:This paper established that the solubility of the drug could be increased after preparing a solid dispersion,as demonstrated by in vitro dissolution experiments.In vivo pharmacokinetics studies confirmed that AE-SD could improve the bioavailability of AE in vivo,providing a new concept for the research and development of AE preparations.

How rotational speed of planetary ball mill and polymer load influence the performance and water vapor sorption in solid dispersions composed of tadalafil and soluplus

The presence of residual water may deteriorate the performance of amorphous solid dispersions prepared by ball milling,affecting molecular mobility,crystallinity,particle size and finally,the drug dissolution rate.As the stability of these metastable systems depend on both formulation and process variables,the aim of this study was to assess for the first time,the impact that the polymer load and the rotational speed applied upon high energy ball milling could have on the performance of binary co-milled solid dispersions composed of tadalafil(a hydrophobic crystalline drug)and Soluplus(an amphiphilic,hygroscopic amorphous polymer).Each of these variables was tested at three levels.Scanning electron microscopy,laser diffraction and X-ray powder diffraction were used to analyze morphology,particle size distribution and crystallinity of ball milled formulations respectively.Dissolution studies were also carried out.Advanced tools of applied physics,namely solid state 1H NMR and relaxometry were used to assess the structure and water mobility upon gaseous phase hydration on storage.It was shown that both tested variables determined the particle size of the formulation.When the rotational speed of 400 rpm was used,all solid dispersion were XRD-amorphous,but to ensure the immediate release of tadalafil its micellar solubilization in Soluplus was necessary.While the formulation was exposed to water vapor,the hydration level increased with an increasing polymer load as well.Hence,the rotational speed governed the space available for the adsorption of water molecules and their organization in a monolayer or multilayers.Such behavior may have impact on the kinetics of the amorphous drug recrystallization,and finally deteriorate its dissolution.

Preparation and evaluation of the solid dispersions of poorly soluble silybin

To improve its solubility and dissolution,solid dispersions of silybin in PVP K30 were prepared by the conventional solvent evaporation method and characterized by equilibrium solubility and dissolution studies,differential scanning calorimetry （DSC） and Fourier transform infrared spectroscopy（FTIR）.Silybin solid dispersions showed increased solubility and rates of dissolution compared with pure drug and corresponding physical mixtures of silybin and PVP K30.Thermograms of various solid dispersions did not show the melting peak of pure silybin,indicating that silybin was in amorphous form inside the polymer carrier.FTIR studies demonstrated the presence of interactions between hydroxyl groups of silybin and carbonyl groups of PVP K30 in solid dispersions.Solid dispersion techniques can be used to formulate water insoluble drugs to improve their dissolution in vitro and absorption in vivo.

The preparation and characteristics of febuxostat SiO2 solid dispersions

In the present research, we selected Sylysia as a porous material and febuxostat（FBT） as model drug to prepare the FBT SiO2 solid dispersions using a solvent evaporation method. We firstly established an HPLC method for determining FBT in our prepared FBT SiO2 solid dispersions. And then, the characteristics of FBT SiO2 solid dispersions were investigated, including differential scanning calorimetry（DSC）, powder X-ray diffraction（PXRD）, scanning electron microscope（SEM）, particle size and distribution. The solubility and dissolution of FBT SiO2 solid dispersion were also evaluated. The results of DSC and PXRD showed that the FBT existed in an amorphous state in FBT SiO2 solid dispersions. The SEM and particle size results indicated that the shape and average particle size of FBT SiO2 solid dispersions was similar to the Sylysia. The solubility and dissolution of FBT in FBT SiO2 solid dispersions were significantly enhanced compared with the pure FBT. In conclusion, we successfully prepared FBT SiO2 solid dispersions to increase the solubility and dissolution rate of the poorly water-soluble FBT.

Use of polymer combinations in the preparation of solid dispersions of a thermally unstable drug by hot-melt extrusion

The objective of the study was to prepare solid dispersions containing a thermally unstable drug by hot-melt extrusion(HME).Carbamazepine(CBZ)was selected as model drug and combinations of Kollidon VA64(VA64),Soluplus(SOL)and Eudragit EPO(EPO)were utilized as carriers.Preformulation was conducted to identify the suitability of polymer combinations based on solubility parameters,differential scanning calorimetry(DSC),hot stage microscopy and thermogravimetric analysis.Physicochemical properties of solid dispersions were determined by DSC,X-ray diffraction,fourier transform infrared spectroscopy,dissolution and accelerated stability testing.The results show that drug-polymer miscibility at temperatures below the melting point(Tm)of CBZ was improved by combining EPO with VA64 or SOL.With 30%drug loading in a solid dispersion in SOL:EPO(1:1,w/w),CBZ was mainly present in an amorphous form accompanied by a small amount of a microcrystalline form.The dissolution rate of the solid dispersion was significantly increased(approximately 90%within 5 min)compared to either the pure drug(approximately 85%within 60 min)or the corresponding physical mixture(approximately 80%within 60 min)before and after storage.The solid dispersion in SOL:EPO(1:1,w/w)was relatively stable at 401C/75%RH under CBZ tablet packaging conditions for at least 3 months.In conclusion,polymer combinations that improve drug-polymer miscibility at an HME processing temperature below the Tm of a drug appear to be beneficial in the preparation of solid dispersions containing thermally unstable drugs.

Development and Evaluation of Stable Paracetamol Loaded Solid Dispersion with Enhanced Analgesic and Hepatoprotective Property

Paracetamol (PCM) is enlisted in the WHO model list as an essential medicine for pain and palliative care, but at overdose, it causes hepatic damage. This study was designed to assess the analgesic efficacy and hepatoprotective property of a solid dispersion (SD) loaded with PCM. A number of PCM loaded formulations (PSDs) were fabricated using silica alone or in combination with polyethylene glycol and/or Na-citrate followed by in-vitro dissolution profiling. Selected PSDs with improved dissolution profile were subjected to solid-state characterization (DSC, PXRD, FTIR, and SEM), stability study along with investigation of in-vivo analgesic efficacy and effect on hepatocytes. Among these, PSD10 showed a rapid and significantly higher in-vitro drug release than pure PCM. This improvement was distinct to other PSDs also. Solid-state characterization of PSD10 authenticated the conversion of crystalline PCM to amorphous form upon formulation. Subsequent oral administration of PSD10 in Swiss albino mice showed 1.44-fold greater analgesic efficacy than pure PCM at dose 30 mg/kg. Besides, at acute toxic dose, liver histology of PSD10 mice was comparable with NC mice indicating hepatic protection upon formulation, whereas the PCM mice showed extensive hepatic necrosis which was also endorsed by significantly higher values of SGPT, SGOT, and ALP than PSD10 mice. Finally, an accelerated stability study of PSD10 performed according to the guideline of ICH noticed no remarkable deviation in its dissolution performance as well as crystalline nature. Thus, this newly developed PSD10 may be a safe and promising alternative for pain management and palliative care.

Preparation,physicochemical characterization and cyctotoxicity of solid dispersion of paclitaxel and polyvinylpyrrolidone

The objective of this study was to prepare and characterize paclitaxel-polyvinylpyrrolidone （PTX-PVP） solid dispersions with the intention of improving its solubility and dissolution properties. The PTX-PVP solid dispersion systems were prepared by solvent method. The release rate ofpaclitaxel was determined from dissolution studies and the physicochemical properties of solid dispersion were investigated by differential scanning calorimetry （DSC）, powder X-ray diffraction （PXRD） and scanning electron microscopy （SEM）. The cytotoxicities ofpaclitaxel in solid dispersion to the SKOV-3 cells were assayed by a SRB staining method. The results showed that the solubility and dissolution rate of paclitaxel were significantly improved in solid dispersion system compared with that of the pure drug and physical mixture. The results of DSC and PXRD showed that the paclitaxel in solid dispersion was amorphous form. No paclitaxel crystals in the solid dispersions was found during SEM analysis. Cytotoxicity study suggested that the inhibitory rates of PTX-PVP solid dispersion to SKOV-3 cells were higher than that of pure paclitaxel. The solubility and dissolution of paclitaxel were improved by solid dispersion technique. In vitro cytotoxicity of paclitaxel in solid dispersion was higher than that of pure drug.

Dissolution Improvement of Cisapride by Solid Dispersion with HPMC

To prepare a solid dispersion of cisapride with hydroxypropylmethyl cellulose(HPMC E5 LV) as carrier for the purpose of accelerating the in vitro drug release by means ofimproving the solubility of the model drug. Methods Alcohol and simulated gastric fluid (SGF) wereused to dissolve cisapride and HPMC in order to make the model drug dispersed homogeneously in thecarrier. The HPMC-cisapride solid dispersion was then obtained by conventional solvent evaporationmethod. Powder X-ray diffraction (XRD) was used to measure the diffraction peaks of pure carrier,pure cisapride, physical mixture of HPMC with cisapride (4:1), and HPMC-cisapride solid dispersion(4:1) to confirm the crystal existence. The solubility of pure drug and HPMC-cisapride soliddispersion was measured with water, SGF and simulated intestinal fluid (SIF) . The in vitro drugreleases of the sustained release tablet prepared with pure cisapride or HPMC-cisapride soliddispersion were investigated with water and SGF as media, respectively. Results No diffraction peakswere found by X-ray diffraction in the HPMC-cisapride solid dispersion (4:1), indicating that thedrug existed in an amorphous form at that drug-carrier ratio. Compared with the pure drug, thesolubilities of HPMC-cisapride solid dispersion are increased by 239.4% in SGF, 132.6% in water, and117.9% in SIF. According to the in vitro drug release, the sustained release tablet prepared withHPMC-cisapride solid dispersion had a faster drug release than did that prepared with pure drug. Thein vitro drug release profiles were found to comply with Higuchi's rule. Conclusion The in vitrodrug release of the sustained release tablet made by HPMC-cisapride solid dispersion is improvedowing to the increased drug solubility.

Preparation and physicochemical characterization of solid dispersion of quercetin and polyvinylpyrrolidone

Aim The objective of this study was to prepare and characterize quercetin-polyvinylpyrrolidone （Qurc-PVP） solid dispersion with the intention of improving its dissolution properties, Methods Qurc-PVP sclid dispersion was prepared by solvent method. The release rate of quercetin was determined from dissolution studies and the physicochemical properties of solid dispersion were investigated by differential scanning calorimetry （DSC）, infrared spectroscopy （IR）, powder X-ray diffraction （PXRD） and scanning electron microscopy （SEM）. Results The results showed that the dissolution rate of quercetin was significantly improved by solid dispersion compared to that of the pure drug and physical mixture, Solubility studies revealed a markedly increase in the solubility of quercetin. The results of DSC and PXRD showed that the quercetin in solid dispersion was amorphous form. From SEM analysis, there was no quercetin crystal observed in the solid dispersions. Conclusion The solubility and dissolution of quercetin were improved by solid dispersion technique.

A RP-HPLC method for determination of paclitaxel in its solid dispersion

Aim To develop and validate a RP-HPLC method for the analysis of paclitaxel in a solid dispersion. Methods Paclitaxel and the internal standard norethisterone were separated using a Phenomenex ODS 3 column and monitored at a wavelength at 227 nm. The isocratic mobile phase consisting of methanol-acetonitrile-water （40：30：30, V/V） was pumped at a flow-rate of 1.0 mL·min^-1. The dissolution studies were performed according to published studies. Results Under these chromatographic conditions, the calibration curve was linear in the range of 4-40 μg·mL ^-1 with the correlation coefficient of 0.9999. The mean recovery was 98.42 % （RSD = 1.19 %）. At the 60 min time point, the dissolution of paclitaxel from the solid dispersion was nearly 100 %, however, the original form of paclitaxel was about 30 %. Conclusion The method was proven to be specific, accurate and precise for determining the dissolution of paclitaxel from solid dispersion.

Improved dissolution and bioavailability of silymarin delivered by a solid dispersion prepared using supercritical fluids

The objective of this study was to improve the dissolution and bioavailability of silymarin(SM).Solid dispersions(SDs)were prepared using solution-enhanced dispersion by supercritical fluids(SEDS)and evaluated in vitro and in vivo,compared with pure SM powder.The particle sizes,stability,and contents of residual solvent of the prepared SM-SDs with SEDS and solvent evaporation(SE)were investigated.Four polymer matrix materials were evaluated for the preparation of SM-SD-SEDS,and the hydrophilic polymer,polyvinyl pyrrolidone K17,was selected with a ratio of 1:5 between SM and the polymer.Physicochemical analyses using X-ray diffraction and differential scanning calorimetry indicated that SM was dispersed in SD in an amorphous state.The optimized SM-SD-SEDS showed no loss of SM after storage for 6 months and negligible residual solvent(ethanol)was detected using gas chromatography.In vitro drug release was increased from the SM-SDSEDS,as compared with pure SM powder or SM-SD-SE.In vivo,the area under the rat plasma SM concentration-time curve and the maximum plasma SM concentration were 2.4-fold and 1.9-fold higher,respectively,after oral administration of SM-SD-SEDS as compared with an aqueous SM suspension.These results illustrated the potential of using SEDS to prepare SM-SD,further improving the biopharmaceutical properties of this compound.

Development and evaluation of lafutidine solid dispersion via hot melt extrusion:Investigating drug-polymer miscibility with advanced characterisation

In current study,immediate release solid dispersion(SD)formulation of antiulcer drug lafutidine(LAFT)was developed using hot melt extrusion(HME)technique.Amphiphilic Soluplus
used as a primary solubilizing agent,with different concentrations of selected surfactants like PEG 400,Lutrol F127(LF127),Lutrol F68(LF68)were used to investigate their influence on formulations processing via HME.Prepared amorphous glassy solid dispersion was found to be thermodynamically and physicochemically stable.On the contrary,traces of crystalline LAFT not observed in the extrudates according to differential scanning calorimetry(DSC),X-ray diffraction(XRD),scanning electron microscopy(SEM)and Raman spectroscopy.Raman micro spectrometry had the lowest detection limit of LAFT crystals compared with XRD and DSC.Atomic Force microscopy(AFM)studies revealed drugpolymer molecular miscibility and surface interaction at micro level.1HeCOSY NMR spectroscopy confirmed miscibility and interaction between LAFT and Soluplus
,with chemical shift drifting and line broadening.MD simulation studies using computational modelling showed intermolecular interaction between molecules.Dissolution rate and solubility of LAFT was enhanced remarkably in developed SD systems.Optimized ratio of polymer and surfactants played crucial role in dissolution rate enhancement of LAFT SD.The obtained results suggested that developed LAFT has promising potential for oral delivery and might be an efficacious approach for enhancing the therapeutic potential of LAFT.

Solid lipid dispersion of calcitriol with enhanced dissolution and stability

Solid dispersion of calcitriol with lipophilic surfactants and triglycerides was developed by melt-mixing method to modify the release and enhance stability of the drug.The solid dispersions were characterized by differential scanning calorimetry(DSC),hot stage polarized optical microscopy(HSPM),infrared spectroscopy(FTIR)and stability studies.The solid dispersion significantly enhanced the stability of calcitriol,which could be attributed to the high antioxidant activity of the solid lipid dispersion.The rapid dissolution rate from the solid dispersion was attributed to the amorphous or solid solution state of drug with improved specific surface area and wettability than the drug crystals.Therefore,solid dispersion of calcitriol with D-a-tocopheryl polyethylene glycol 1000 succinate(TPGS)offers a good approach to modify the release and enhance stability of calcitriol.The influence of lipophilic solid dispersion on drug bioavailability needs further investigation.

The characterization and dissolution performances of spray dried solid dispersion of ketoprofen in hydrophilic carriers

Solid dispersion is one of the most promising strategies to improve oral bioavailability of poorly soluble API.However,there are inconsistent dissolution performances of solid dispersion reported which entails further investigation.In this study,solid dispersions of ketoprofen in three hydrophilic carriers,i.e.PVP K30,PVPVA 6:4 and PVA were prepared and characterized.Physical characterization of the physical mixture of ketoprofen and carriers shows certain extent of amorphization of the API.This result is coinciding to evaluation of drug-polymer interaction using ATR-FTIR whereby higher amorphization was seen in samples with higher drug-polymer interaction.XRPD scanning confirms that fully amorphous solid dispersion was obtained for SD KTP PVP K30 and PVPVA system whereas partially crystalline system was obtained for SD KTP PVA.Interestingly,dissolution profiles of the solid dispersion had shown that degree of amorphization of KTP was not directly proportional to the dissolution rate enhancement of the solid dispersion system.Thus,it is concluded that complete amorphization does not guarantee dissolution enhancement of an amorphous solid dispersion system.