Interactions between carbamazepine and polyethylene glycol (PEG) 6000: characterisations of the physical, solid dispersed and eutectic mixtures

Computer numerical control (CNC) carving as an on-demand point-of-care manufacturing of solid dosage form: A digital alternative method for 3D printing

Computer numerical control (CNC) carving is a widely used method of industrial subtractive manufacturing of wood, plastics, and metal products. However, there have been no previous reports of applying this approach to manufacture medicines. In this work, the novel method of tablet production using CNC carving is introduced for the first time. This report provides a proof-of-concept for applying subtractive manufacturing as an alternative to formative (powder compression) and additive (3D printing) manufacturing for the on-demand production of solid dosage forms. This exemplar manufacturing approach was employed to produce patient-specific hydrocortisone (HC) tablets for the treatment of children with congenital adrenal hyperplasia. A specially made drug-polymer cast based on polyethene glycol (PEG 6,000) and hydroxypropyl cellulose was produced using thermal casting. The cast was used as a workpiece and digitally carved using a small-scale 3-dimensional (3D) CNC carving. To establish the ability of this new approach to provide an accurate dose of HC, four different sizes of CNC carved tablet were manufactured to achieve HC doses of 2.5, 5, 7.5 and 10 mg with a relative standard deviation of the tablet weight in the range of 3.69-4.79%. In addition, batches of 2.5 and 5 mg HC tablets met the British Pharmacopeia standards for weight uniformity. Thermal analysis and X-ray powder diffraction indicated that the model drug was in amorphous form. In addition, HPLC analysis indicated a level of purity of 96.5 ± 1.1% of HC. In addition, the process yielded mechanically strong cylindrical tablets with tensile strength ranging from 0.49 to 1.6 MPa and friability values of <1%, whilst maintaining an aesthetic look. In vitro, HC release from the CNC-carved tablets was slower with larger tablet sizes and higher binder contents. This is the first report on applying CNC carving in the pharmaceutical context of producing solid dosage forms. The work showed the potential of this technology as an alternative method for the on-demand manufacturing of patient-specific dosage forms.

The Structure of Liquid and Glassy Carbamazepine

To enhance the solubility of orally administered pharmaceuticals, liquid capsules or amorphous tablets are often preferred over crystalline drug products. However, little is known regarding the variation in bonding mechanisms between pharmaceutical molecules in their different disordered forms. In this study, liquid and melt-quenched glassy carbamazepine have been studied using high energy X-ray diffraction and modeled using Empirical Potential Structure Refinement. The results show significant structural differences between the liquid and glassy states. The liquid shows a wide range of structures; from isolated molecules, to aromatic ring correlations and NH-O hydrogen bonding. Upon quenching from the liquid to the glass the number of hydrogen bonds per molecule increases by ~50% at the expense of a ~30% decrease in the close contact (non-bonded) carbon-carbon interactions between aromatic rings. During the cooling process, there is an increase in both singly and doubly hydrogen-bonded adjacent molecules. Although hydrogen-bonded dimers found in the crystalline states persist in the glassy state, the absence of a crystalline lattice also allows small, hydrogen-bonded NH-O trimers and tetramers to form. This proposed model for the structure of glassy carbamazepine is consistent with the results from vibrational spectroscopy and nuclear magnetic resonance.

The impact of carbamazepine crystallinity on carbamazepine-loaded microparticle formulations

Crystallinity plays a vital role in the pharmaceutical industry. It affects drug manufacturing, development processes, and the stability of pharmaceutical dosage forms. An objective of this study was to measure and analyze the carbamazepine (CBZ) crystallinity before and after formulation. Moreover, it intended to determine the extent to which the crystallinity of CBZ would affect the drug loading, the particle size, and the release of CBZ from the microparticles. The CBZ microparticles were prepared by encapsulating CBZ in ethyl cellulose (EC) polymer using a solvent evaporation method. EC was used here as a release modifier polymer and polyvinyl alcohol (PVA) as an aqueous phase stabilizer. Factorial design was used to prepare the CBZ microparticle formulations, including polymer concentration, solvent (dichloromethane, ethyl acetate), PVA concentrations factor, the homogenization time, and homogenization speed. The crystallinity of CBZ was calculated utilizing differential scanning calorimetry (DSC) thermal analysis. The crystallinity was calculated from the enthalpy of CBZ. Enthalpy was analyzed from the area under the curve peak of CBZ standard and CBZ-loaded microparticles. DSC and ATR-FTIR assessed the possible interaction between CBZ and excipients in the microparticle. The prepared CBZ microparticles showed various changes in the crystallinity rate of CBZ. The changes in the rate of CBZ crystallinity had different effects on the particle size, the drug loading, and the release of CBZ from the polymer. Statistically, all studied factors significantly affected the crystallinity of CBZ after formulation to microparticles.

Emerging Multi-Drug Eutectics: Opportunities and Challenges

Complexity and heterogeneous nature of most diseases have posed greater challenges in the modern healthcare system. Fixed-dose combination can offer an ideal way to improve patient compliance and higher therapeutic efficacy. However, biopharmaceutical issues associated with the drug combinations remain unaddressed. Multidrug eutectics (MDE) have demonstrated significant promise in improving the biopharmaceutical attributes with synergistic therapeutic action. Eutectic mixtures are the multicomponent solid forms that possess lesser melting point than the individual components at a fixed composition. Non-covalent linking of drug combinations as MDE is an innovative strategy with enhanced solubility, dissolution, and mechanical and potential therapeutic efficacy. This review provides a comprehensive overview of the design of MDE, rational selection of drugs, characterization tools, and their therapeutic potential. Besides, the futuristic perspective where MDE could make a significant impact on combination therapy is briefly outlined. Graphical Abstract.

Diacerein solid dispersion loaded tablets for minimization of drug adverse effects: statistical design, formulation, in vitro, and in vivo evaluation

Diacerein is a BCS class II drug employed in osteoarthritis management. The acid/base hydrolysis of the unabsorbed diacerein in the colon is responsible for its laxative effect. Therefore, this work aimed to enhance the solubility, dissolution, and oral bioavailability of diacerein. Such enhancement means lower doses and fewer gastrointestinal adverse effects. A 4¹.3¹.2¹ full factorial design was adopted to prepare 24 solid dispersion formulae. Solid-state characterization showed the dissolution of diacerein crystals as metastable amorphous or microcrystalline forms in a matrix system that enhanced the drug dissolution. Desirability factor suggested compounding an optimized formula (F1) of Pluronic^®F68 with 1:3 drug:carrier ratio using rotavap that showed higher drug solubility (187.61 µg/mL) than drug powder (22.5 µg/mL). It achieved higher dissolution efficiency (4.04-fold) and rate (6.6-fold) as well as 100% release in 2 min. F1 was compressed into tablets recording greater dissolution efficiency (1.24-fold) and rate (12.5-fold) than the marketed product. The prepared tablet accomplished a 2.66-fold enhancement in diacerein bioavailability compared to the marketed product. In conclusion, the formulation of diacerein as solid dispersion loaded tablets could be of added value for the treatment of osteoarthritis in terms of enhanced patient compliance. Solid dispersion is an easy and scalable technique.

Investigating Cocrystallization of Carbamazepine with Structurally Compatible Coformers: New Cocrystal and Eutectic Phases with Enhanced Dissolution

In this work, carbamazepine (CBZ), an anticonvulsant drug was cocrystallized with several structurally complement coformers (coformers with amide, acid and hydrazide functional groups) to enhance its dissolution. CBZ formed a cocrystal phase with acetamide (ACE) when mixtures of CBZ and ACE (containing CBZ mole fractions, X_CBZ of 0.25, 0.33, 0.5, and 0.67) were subjected to solid-state grinding (SSG), evaporative crystallization (EC), slurry conversion (SC), and slow cooling crystallization (SLC). Upon heating, the CBZ-ACE cocrystal phase formed from CBZ-ACE mixtures containing X_CBZ of 0.25, 0.33 and 0.67 underwent solid-state phase transition to CBZ form I and CBZ cocrytsal phase obtained from the CBZ-ACE mixture containing X_CBZ of 0.5 converted to CBZ form III. Interestingly, slow cooling cocrystallization experiments resulted in crystallization of a cocrystal as well as the CBZ dihydrate forms. The powder dissolution studies demonstrated that among the different CBZ-ACE-SSG cocrystal phases, CBZ-ACE-SSG-X_CBZ-0.33 cocrystal exhibited 7.47 times improved dissolution whereas the CBZ eutectic phase with nicotinic acid hydrazide (NAH) exhibited 4.93 times increased dissolution when compared to raw CBZ.

Different BCS Class II Drug-Gelucire Solid Dispersions Prepared by Spray Congealing: Evaluation of Solid State Properties and In Vitro Performances

Delivery of poorly water soluble active pharmaceutical ingredients (APIs) by semi-crystalline solid dispersions prepared by spray congealing in form of microparticles (MPs) is an emerging method to increase their oral bioavailability. In this study, solid dispersions based on hydrophilic Gelucires^® (Gelucire^® 50/13 and Gelucire^® 48/16 in different ratio) of three BCS class II model compounds (carbamazepine, CBZ, tolbutamide, TBM, and cinnarizine, CIN) having different physicochemical properties (logP, pKa, Tm) were produced by spray congealing process. The obtained MPs were investigated in terms of morphology, particles size, drug content, solid state properties, drug-carrier interactions, solubility, and dissolution performances. The solid-state characterization showed that the properties of the incorporated drug had a profound influence on the structure of the obtained solid dispersion: CBZ recrystallized in a different polymorphic form, TBM crystallinity was significantly reduced as a result of specific interactions with the carrier, while smaller crystals were observed in case of CIN. The in vitro tests suggested that the drug solubility was mainly influenced by carrier composition, while the drug dissolution behavior was affected by the API solid state in the MPs after the spray congealing process. Among the tested APIs, TBM-Gelucire dispersions showed the highest enhancement in drug dissolution as a result of the reduced drug crystallinity.

Contribution of Crystal Lattice Energy on the Dissolution Behavior of Eutectic Solid Dispersions

In the literature, it is reported that eutectics lead to the enhanced dissolution of a poorly soluble compound. However, the solubility theory suggests that since crystal structures of two components are unchanged that all else being equal, the dissolution rates of a fused mixture (FM) should be the same as a physical mixture (PM). The influence of crystal lattice energy on dissolution profiles was investigated using the PM and FM. Experimental phase diagrams constructed using differential scanning calorimetry data were compared with those theoretically derived. Deviation of the experimental phase diagram curves from the theoretical model indicates the nonideal behavior of both systems (ibuprofen/poly(ethylene glycol)-6000 and acetaminophen/caffeine). Both the binary systems showed an increase in the dissolution rate of the PM and FM. However, the dissolution from the PM was comparable with the FM's dissolution profile. The theoretical solubility calculations using the modified solubility equation showed that the use of the eutectic temperature instead of the drug's melting point should give a 3-4-fold increase in drug solubility. However, the correlation between dissolution and solubility calculation showed that the FM did not improve the dissolution when compared with the respective PM's dissolution profile. The proposed explanation is that the unchanged crystal lattice energy in eutectics still limits the solubility and therefore the dissolution rate.

Vibrational Dynamics of Carbamazepine: Studies Based on Two-Dimensional Correlation Spectroscopy and X-ray Diffraction

Fourier transform infrared spectroscopy as well as X-ray diffraction (XRD) were employed to thoroughly study phase transitions taking place during heating-cooling-heating cycle of carbamazepine (CBZ), a well known and commonly used antiepileptic drug. Both techniques revealed cold crystallization taking place during second heating. Moreover, XRD studies for the first time proved the coexistence of CBZ (form I) and iminostilbene (product of the degradation of CBZ) after a heating-cooling cycle. Moving window two-dimensional correlation (MW 2D-COS) spectroscopy and two-dimensional correlation spectroscopy were shown to be effective tools to reveal phase sequences and to provide information about the order of sequential changes of bands' intensities during each phase transition, respectively.

Dissolution enhancement of carbamazepine using twin-screw melt granulation

The current study explored the twin-screw melt granulation (TSMG) as a potential technology for the water solubility enhancement of biopharmaceutical classification system (BCS) class II drugs. As a model drug, carbamazepine (CBZ) was formulated with three different polymers as melt granules produced in a co-rotating twin-screw granulator. Polyethylene glycol 6000 (PEG 6000) and Kolliphor® (poloxamer) P407 were used as binding materials at two different granulation temperatures (T_max: 70 °C; 100 °C). Additionally, Soluplus® (polyvinyl caprolactam-polyvinyl acetate-polyethylene glycol graft copolymer) was chosen as binder of higher melting/ granulation temperature (T_max: 140 °C). Temperature dependent polymorphic transition of CBZ during melt granulation was observed and identified using XRPD- (X-ray powder diffraction) and FTIR- (Fourier transform infrared spectroscopy) analysis. The effects of polymer type, polymer content (10, 15, 20% (w/w)) and granulation temperature on polymorphic transition, their impact on wettability (contact angle via drop shape-analysis), and the resulting dissolution performance at non-sink conditions in phosphate buffer (pH 6.8), were studied. This study showed that TSMG led to a crystalline system facilitating supersaturation when brought in solution, even when high drug loads (up to 90% (w/w)) were used. In general, for all granules produced, the supersaturation level and its duration varied with the extent of polymorphic transition and binder concentration. The results of this study indicated the importance of temperature control and polymer selection for tailoring desired dissolution profiles.

Stabilisation and Growth of Metastable Form II of Fluconazole in Amorphous Solid Dispersions

The crystallisation of metastable drug polymorphs in polymer matrices has been reported as a successful approach to enhance the solubility of poorly water-soluble drug molecules. This can be achieved using different polymers, drug to polymer ratios and formulation techniques enabling the formation of stable nuclei and subsequent growth of new or metastable drug polymorphs. In this work we elucidated the polymorphism behaviour of a model compound fluconazole (FLU) embedded in solid dispersions with amorphous Soluplus^® (SOL) obtained using spray drying and fusion methods. The effect of humidity on the stability of FLU in the obtained dispersions was also evaluated. FLU at a drug content below 40 wt. % stayed amorphous in the dispersions prepared using the fusion method and crystallised exclusively into metastable form II at a drug content above 40 wt. % and 70% relative humidity (RH) conditions. In contrast, a mixture of forms I, II and hydrate of FLU was detected in the spray dried formulations after 14 days of storage at 40 °C/40% RH, with preferential growth of thermodynamically stable form I of FLU. This study highlights the importance of preparation techniques and the drug:polymer ratio in the formulation of amorphous solid dispersions and provides further understanding of the complex crystallisation behaviour of amorphous pharmaceuticals encapsulated in the polymer matrixes.

New Insight Into Thermodynamical Stability of Carbamazepine

Carbamazepine (CBZ)-an antiepileptic drug-belongs to Biopharmaceutics Classification System II Class. It has low solubility and consequently limited bioavailability. One of the ways to improve drugs solubility is amorphization of their structure. Herein, cooling CBZ-at different cooling rates-was investigated as a way to obtain glassy, better soluble form. During preliminary differential scanning calorimetry experiments, some peculiar behavior of the examined material, different from those stated in the literature, was observed. Further investigations using differential scanning calorimetry, thermogravimetric analysis, and polarizing optical microscope revealed that decomposition temperature of CBZ is about 30°C lower than previously assumed. Moreover, high-resolution thermogravimetric measurements indicate that some decomposition processes could start even below the temperature reported as the melting point of the form I of CBZ.

Fabrication of Hierarchical Polymeric Thin Films by Spin Coating Toward Production of Amorphous Solid Dispersion for Buccal Drug Delivery System: Preparation, Characterization, and In Vitro Release Investigations

The landscape of thin films is continuously evolving as an attractive self-administration mean to drive patient compliance. This work reports incorporation of drugs into various polymeric compositions using spin coating technology to screen amorphous solid dispersion film formation for buccal applications. Polarized light microscopy and differential scanning calorimetry were used for characterization. Physical stability was assessed after films storage at 0% RH/25°C for 6 months. Chlorpheniramine maleate, theophylline, and famotidine were used as model drugs and mixed with Opadry amb II^® or Kollicoat IR^®. Acryl-EZE II^® or Zein was also used as surface (design I) or surface and base polymers (design II). Of all the drug-Opadry combinations, only chlorpheniramine was amorphously dispersed up to 25% (w/w). In contrast, Kollicoat IR^® resulted in amorphous dispersions of all the tested drugs, suggesting that it has a better solubilization capacity. Drugs prepared in design II achieved higher in vitro release compared to respective design I, indicating that lower content of Acryl-EZE II^® or Zein can decrease drug release over 3 h. It has been also revealed that Zein could improve physical stability of the aged theophylline solid-dispersed films. Release kinetics of model drugs were satisfactory when described by first-order kinetics, facilitated through anomalous transport of both diffusion and polymer swelling.

Effect of Sulindac Binary System on In Vitro and In Vivo Release Profiles: An Assessment of Polymer Type and Its Ratio

The bioavailability of sulindac (SDC), a nonsteroidal anti-inflammatory drug, is low due to poor aqueous solubility and poor dissolution rate. For this reason it is necessary to enhance the solubility and enhance dissolution of the drug by dispersing SDC in polyethylene glycols 6000 (PEG 6000) and polyvinyl pyrrolidone 40000 (PVP 40000) matrices using the coevaporation technique. Studying the influence of SDC to polymer ratio on drug content, percent yield, particle size, and in vitro release was performed. Differential scanning calorimetry, X-ray diffraction, and scanning electron microscopy were used to characterize any change in crystal habit of SDC in the prepared formulae. The anti-inflammatory effect of SDC was studied using the hind paw edema model. It was found that incorporation of SDC in PEG 6000 and PVP 40000 matrices resulted in improving the dissolution rate, which was found to depend on the polymer and its weight ratio of the drug. It is clearly obvious that the dissolution rate was remarkably improved in drug PVP 40000 molecular dispersions when compared to drug PEG 6000 systems. Solid dispersion of SDC in PEG and PVP improved the anti-inflammatory effect of SDC and it was found that formula SDV5 exhibited a more pronounced inhibition of swelling than other formulae.

Characterization of Heterogeneity and Spatial Distribution of Phases in Complex Solid Dispersions by Thermal Analysis by Structural Characterization and X-ray Micro Computed Tomography

PURPOSE

This study investigated the effect of drug-excipient miscibility on the heterogeneity and spatial distribution of phase separation in pharmaceutical solid dispersions at a micron-scale using two novel and complementary characterization techniques, thermal analysis by structural characterization (TASC) and X-ray micro-computed tomography (XμCT) in conjunction with conventional characterization methods.

METHOD

Complex dispersions containing felodipine, TPGS, PEG and PEO were prepared using hot melt extrusion-injection moulding. The phase separation behavior of the samples was characterized using TASC and XμCT in conjunction with conventional thermal, microscopic and spectroscopic techniques. The in vitro drug release study was performed to demonstrate the impact of phase separation on dissolution of the dispersions.

RESULTS

The conventional characterization results indicated the phase separating nature of the carrier materials in the patches and the presence of crystalline drug in the patches with the highest drug loading (30% w/w). TASC and XμCT where used to provide insight into the spatial configuration of the separate phases. TASC enabled assessment of the increased heterogeneity of the dispersions with increasing the drug loading. XμCT allowed the visualization of the accumulation of phase separated (crystalline) drug clusters at the interface of air pockets in the patches with highest drug loading which led to poor dissolution performance. Semi-quantitative assessment of the phase separated drug clusters in the patches were attempted using XμCT.

CONCLUSION

TASC and XμCT can provide unique information regarding the phase separation behavior of solid dispersions which can be closely associated with important product quality indicators such as heterogeneity and microstructure.

A New Extrudable Form of Hypromellose: AFFINISOL™ HPMC HME

Hypromellose is a hydrophilic polymer widely used in immediate- and modified-release oral pharmaceutical dosage forms. However, currently available grades of hypromellose are difficult, if not impossible, to process by hot melt extrusion (HME) because of their high glass transition temperature, high melt viscosity, and low degradation temperature. To overcome these challenges, a modified grade of hypromellose, AFFINISOL™ HPMC HME, was recently introduced. It has a significantly lower glass transition temperature and melt viscosity as compared to other available grades of hypromellose. The objective of this paper is to assess the extrudability and performance of AFFINISOL™ HPMC HME (100LV and 4M) as compared to other widely used polymers in HME, including HPMC 2910 100cP (the currently available hypromellose), Soluplus®, Kollidon® VA 64, and EUDRAGIT® E PO. Formulations containing polymer and carbamazepine (CBZ) were extruded on a co-rotating 16-mm twin-screw extruder, and the effect of temperature, screw speed, and feed rate was investigated. The performance of the solid dispersions was evaluated based on Flory-Huggins modeling and characterized by differential scanning calorimetry (DSC), X-ray powder diffraction (XRD), Raman spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and dissolution. All formulations extruded well except for HPMC 2910 100cP, which resulted in over-torqueing the extruder (machine overloading because the motor cannot provide efficient energy to rotate the shaft). Among the HME extrudates, only the EUDRAGIT® E PO formulation was crystalline as confirmed by DSC, XRD, and Raman, which agreed with predictions from Flory-Huggins modeling. Dissolution testing was conducted under both sink and non-sink conditions. Sink dissolution testing in neutral media revealed that amorphous CBZ in the HME extrudates completely dissolved within 15 min, which was much more rapid than the time for complete dissolution of bulk CBZ (60 min) and EUDRAGIT® E PO solid dispersion (more than 6 h). Non-sink dissolution in acidic media testing revealed that only CBZ contained in the AFFINISOL™ HPMC HME, and EUDRAGIT® E PO solid dispersions rapidly supersaturated after 15 min, reaching a twofold drug concentration compared to the CBZ equilibrium solubility. In summary, AFFINISOL™ HPMC HME 100LV and AFFINISOL™ HPMC HME 4M are useful in the pharmaceutical HME process to increase wetting and dissolution properties of poorly water-soluble drugs like CBZ.

Preclinical formulations: insight, strategies, and practical considerations

A lot of resources and efforts have been directed to synthesizing potentially useful new chemical entities (NCEs) by pharmaceutical scientists globally. Detailed physicochemical characterization of NCEs in an industrial setup begins almost simultaneously with preclinical testing. Most NCEs possess poor water solubility posing bioavailability issues during initial preclinical screening, sometimes resulting in dropping out of an NCE with promising therapeutic activity. Selection of right formulation approach for an NCE, based on its physicochemical properties, can aid in improving its solubility-related absorption and bioavailability issues. The review focuses on preclinical formulations stressing upon different preclinical formulation strategies and deciphers the understanding of formulation approaches that could be employed. It also provides detailed information related to a vast pool of excipients available today, which is of immense help in designing preclinical formulations. Few examples mentioned, throw light on key aspects of preclinical formulation development. The review will serve as an important guide for selecting the right strategy to improve bioavailability of NCEs for academic as well as industrial formulation scientists.

Determination of the solubility of crystalline low molar mass compounds in polymers by differential scanning calorimetry

A mathematical equation has been derived to calculate the liquidus for a binary system consisting of an amorphous polymer and a crystalline low molar mass compound. The experimental input to this equation is an interaction enthalpy, which is derived from the variation of the melting enthalpy with composition in differential scanning calorimetry (DSC) experiments. The predictive power of the equation has been tested with mixtures of acetylsalicylic acid, carbamazepine, or intraconazole with poly(ethylene glycol) as well as mixtures of carbamazepine with poly(acrylic acid), poly(hydroxystyrene), or poly(vinylpyrrolidone). It has been confirmed that the evaluation of the melting enthalpy in DSC is a suitable method to identify the preferred solute-polymer combinations for thermodynamically stable molecular dispersions.

Solid dispersion of ursolic acid in Gelucire 50/13: a strategy to enhance drug release and trypanocidal activity

Solid dispersions (SDs) are an approach to increasing the water solubility and bioavailability of lipophilic drugs such as ursolic acid (UA), a triterpenoid with trypanocidal activity. In this work, Gelucire 50/13, a surfactant compound with permeability-enhancing properties, and silicon dioxide, a drying adjuvant, were employed to produce SDs with UA. SDs and physical mixtures (PMs) in different drug/carrier ratios were characterized and compared using differential scanning calorimetry, hot stage microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), particle size, water solubility values, and dissolution profiles. Moreover, LLC-MK2 fibroblast cytotoxicity and trypanocidal activity evaluation were performed to determine the potential of SD as a strategy to improve UA efficacy against Chagas disease. The results demonstrated the conversion of UA from the crystalline to the amorphous state through XRD. FTIR experiments provided evidence of intermolecular interactions among the drug and carriers through carbonyl peak broadening in the SDs. These findings helped explain the enhancement of water solubility from 75.98 μg/mL in PMs to 293.43 μg/mL in SDs and the faster drug release into aqueous media compared with pure UA or PMs, which was maintained after 6 months at room temperature. Importantly, improved SD dissolution was accompanied by higher UA activity against trypomastigote forms of Trypanosoma cruzi, but not against mammalian fibroblasts, enhancing the potential of UA for Chagas disease treatment.

Micromechanical and physical stability analysis of an irradiated poly (lactic-co-glycolic acid) donut-shaped minitablet device for intraocular implantation

This study pragmatically characterized the micromechanical and physical stability of a poly(lactic-co-glycolic acid) (PLGA)-based ganciclovir (GCV)-loaded donut-shaped minitablet (DSMT) device for intraocular implantation. Thermal and spectroscopic analysis was performed on various drug-polymer permutations. Porositometric profiles were quantitatively analyzed coupled with qualitatively SEM imaging. The tensile strength (TS) and fracture energy (FE) of the device was also determined pre- and post-γ-sterilization. Inimitably, chemometric and molecular modeling provided a supportive confirmatory tool for establishing fundamental correlative suppositions between the transitioned surface morphology and the micromechanical stability after γ-irradiation. Isotherm plot volumes ranged between -0.028 ± 0.022 and 0.110 ± 0.005 m(2)/g for pre- and post-sterilized devices, respectively, revealing a microporous alteration in porosity. Pre-sterilized devices had larger pores (BJHa=286.22 vs. 192.49 Å) and lower FE (151.301 ± 6.089 N/m) and TS (26.396 ± 1.062 N) values while sterilized devices had crystalline matrices that facilitated the superiorly controlled drug release kinetcs obtained. DSC thermograms displayed the characteristic disordered crystallization of GCV and hydration exotherms resulting from ionization during γ-irradiation. FTIR spectrograms showed fingerprint molecular imprints of GCV and axial stretching of hybridized carbons of PLGA with no subversive drug-polymer interactions after γ-irradiation. Integration of the results inveterately revealed that compression and subsequent γ-irradiation of the device affected desirable micromechanical and solid-state stability behavior.

Sulfobutyl ether(7) β-cyclodextrin (SBE(7) β-CD) carbamazepine complex: preparation, characterization, molecular modeling, and evaluation of in vivo anti-epileptic activity

The objective of the present investigation was to study the ability of sulfobutyl ether(7)-β-cyclodextrin to form an inclusion complex with carbamazepine, an anti-epileptic drug with poor water solubility. The formation of the complex was carried out using the industrially feasible spray-drying method. The inclusion complex and physical mixtures were characterized by various techniques such as differential scanning calorimetry (DSC), infrared (IR), nuclear magnetic resonance (NMR), X-ray diffraction (XRD), and molecular modeling. The DSC, IR, and NMR studies confirmed the formation of an inclusion complex between carbamazepine and sulfobutyl ether(7) β-cyclodextrin whereas XRD studies indicated an amorphous nature of the inclusion complex. Molecular modeling studies disclosed different modes of interaction between carbamazepine and sulfobutyl ether(7) β-cyclodextrin with good correlation with experimental observations. The inclusion complex exhibited significantly higher in vitro dissolution profile as compared with pure carbamazepine powder. The in vivo anti-epileptic activity of carbamazepine/sulfobutyl ether(7) β-cyclodextrin complex was evaluated in pentylenetetrazole-induced convulsions model. The carbamazepine/sulfobutyl ether(7) β-cyclodextrin complex showed significantly higher anti-epileptic activity (p <0.01) as compared with that of carbamazepine suspension on oral administration.

Solid dispersions of imidazolidinedione by PEG and PVP polymers with potential antischistosomal activities

Solid dispersions have been used as a strategy to improve the solubility, dissolution rate, and bioavailability of poor water-soluble drugs. The increase of the dissolution rate presented by (5Z)-3-(4-chloro-benzyl)-5-(4-nitro-benzylidene)-imidazolidine-2,4-dione (LPSF/FZ4) from the solid dispersions is related to the existence of intermolecular interactions of hydrogen bond type (>N-H···O<) between the amide group (>N-H) of the LPSF/FZ4 and the ether group (-O-) of the polyethyleneglycol polymer, or the carbonyl (C=O) of the polyvinylpyrrolidone polymer (PVP). The intensity of these interactions is directly reflected in the morphology acquired by LPSF/FZ4 in these systems, where a new solid phase, in the form of amorphous aggregates of irregular size, was identified through scanning electron microscopy and confirmed in the characterizations achieved using X-ray diffraction and thermal analysis of DSC. The solid dispersions with the polymer PVP, in higher concentrations, were revealed to be the best option to be used in the formulations of LPSF/FZ4 in both theoretical and experimental studies.

The influence of various excipients on the conversion kinetics of carbamazepine polymorphs in aqueous suspension

The influence of various excipients on the conversion of carbamazepine polymorphs to the dihydrate in aqueous suspension has been investigated. Ten excipients having functional groups which were potentially able to form hydrogen bonds with carbamazepine (group 1: methylcellulose, hypromellose (hydroxypropyl methylcellulose), hydroxypropylcellulose (HPC), 2-hydroxyethylcellulose (HEC), carmellose sodium (sodium carboxymethylcellulose), cellobiose; group 2: povidone (polyvinylpyrrolidone), povidone-vinyl acetate copolymer (povidone/VA) and N-methyl-2-pyrrolidone; group 3: macrogol (polyethylene glycol) and polyethylene oxide-polypropylene oxide copolymer (PEO/PPO)) were selected. Carbamazepine polymorphic forms III and I were dispersed separately into each aqueous excipient solution (0.1%, w/v) for 30 min at room temperature. The inhibition effect of each excipient was quantified using Raman spectroscopy combined with multivariate analyses. The solubility parameter of each excipient was calculated and used for categorizing excipients. Excipients in groups 1 and 2, which had both low solubility parameters (&lt; 27.0 MPa½) and strong hydrogen bonding groups, inhibited the conversion completely. With increasing solubility parameter, the inhibition effect decreased for group 1 excipients, especially for carbamazepine form I, which had a higher specific surface area. Also, the excipients of group 3, lacking strong hydrogen bonding groups, showed poor inhibition although they had low solubility parameters (&lt; 21.0 MPa½). This study indicated the importance of both hydrogen bonding interaction and a suitable hydrophobicity (expressed by the solubility parameter) in the inhibition of the conversion of carbamazepine to the dihydrate.

In Vitro Characterization of Carbamazepine-Loaded Precifac Lipospheres

Lipospheres of carbamazepine were prepared by melt dispersion technique using Precifac ATO 5 in the various drug-lipid ratios. The resulting free-flowing lipospheres were evaluated with respect to surface morphology, particle size distribution, encapsulation efficiency, and in vitro release behavior. The effect of druglipid ratio, the surfactant added, emulsion stabilizer, and stirring speed also were identified as the key variables affecting the formation of discrete spherical lipospheres and drug release rate. The preparation conditions were optimized by using 0.4% w/v span 20 (Hydrophilic-Lipophilic Balance, HLB = 8.6) as a surfactant and 1% w/v gelatin solution as a stabilizer in presence of a high level of water. We found that the ratio of drug to lipid affects the size of the spheres. The incorporation efficiency was found to be high at all loadings. Increasing the lipid:drug ratio produced more spherical, smooth, and round lipospheres. All the prepared lipospheres exhibited slow release profiles dictating the Higuchi mode of release. We saw that the higher the sphere size and the ratio of Precifac, the slower is in vitro drug release.

In Vitro Performance of Carbamazepine Loaded to Various Molecular Weights of Poly (D, L-Lactide-Co-Glycolide)

The purpose of this study was to develop and assess the in vitro characteristics of carbamazepine-loaded microspheres. A solvent evaporation method was used to incorporate carbamazepine (CBZ) into poly (D,L-lactide-co-glycolide) (PLGA) with different molecular weights. The optimum conditions for CBZ-PLGA microspheres preparation were considered and the in vitro release of CBZ of PLGA microspheres were followed up to 24 hr in USP dissolution medium. The effect of using different ratios of PLGA microspheres, prepared with different molecular weights, for optimizing CBZ release also was investigated. CBZ encapsulation efficiency was 68 to 82% for all prepared formulations. Thermograms of CBZ-PLGA microspheres suggest that CBZ was totally entrapped with the PLGA polymer. The presence of Pluronic F-68 has improved the encapsulation of CBZ, resulted in better and smoother microspheres surfaces and enhanced its release pattern. CBZ release profiles were biphasic patterns; after an initial burst, a constant CBZ release rate was observed up to 24 hr. The release from these PLGA-based spherical matrices was consistent with the diffusion mechanism. CBZ dissolution T(50%) was significantly affected (> 3-fold) by increasing the lactide percent from 33.3 to 66.6% from different microspheres mixtures. The present study provides evidence that the encapsulation of CBZ to PLGA microspheres, either as a single polymer or mixture of two, was a successful attempt to control the release of CBZ.

Influence of Polymorphic Form, Morphology, and Excipient Interactions on the Dissolution of Carbamazepine Compacts

To gain a deeper understanding of the behavior of carbamazepine (CBZ) and CBZ dihydrate (DH) compacts during in vitro dissolution tests various factors were investigated: hydrate formation of CBZ, crystal morphology, surface area, and excipient influence. Dissolution tests were performed in three different dissolution media: distilled water, hydroxypropyl methylcellulose (HPMC), and polyethylene glycol (PEG) solutions. For the CBZ compacts, the dissolution rate of CBZ in water was fastest (0.338 mg L(-1) min(-1)). With increasing ability of the excipients to inhibit the hydration of CBZ (PEG < HPMC), surprisingly the dissolution rate of CBZ compacts decreased: PEG solution (0.314 mg L(-1) min(-1)) > HPMC solution (0.257 mg L(-1) min(-1)). This implies that DH formation resulted in an apparent increase in the dissolution rate rather than slowing it down. For the DH compacts, the dissolution rate in water (0.055 mg L(-1) min(-1)) was slower than that of PEG and HPMC solutions (0.174 and 0.178 mg L(-1) min(-1), respectively). The contact angle measurements showed a significantly higher value in water (61.0 degrees) than in PEG and HPMC solutions (44.8 degrees and 43.1 degrees, respectively). Although the dissolution of CBZ and DH compacts in various dissolution media are complex processes, the influence and relative importance of these factors were clearly detected providing better understanding of the dissolution behavior of the drug.

Factors Affecting the Formation of Eutectic Solid Dispersions and Their Dissolution Behavior

The objective of this work was to obtain a fundamental understanding of the factors, specifically the properties of poorly water-soluble drugs and water-soluble carriers, which influence predominantly, the formation of eutectic or monotectic crystalline solid dispersion and their dissolution behavior. A theoretical model was applied on five poorly water-soluble drugs (fenofibrate, flurbiprofen, griseofulvin, naproxen, and ibuprofen) having diverse physicochemical properties and water-soluble carrier (polyethylene glycol (PEG) 8000) for the evaluation of these factors. Of these, two drugs, fenofibrate and flurbiprofen, and PEG of different molecular weights (3350, 8000, and 20000), were chosen as model drugs and carriers for further investigation. Experimental phase diagrams were constructed and dissolution testing was performed to assess the performance of the systems. The theoretical model predicted the formation of eutectic or monotectic solid dispersions of fenofibrate, griseofulvin, ibuprofen, and naproxen with PEG, holding the contribution of specific intermolecular interactions between compound and carrier to zero. In the case of the flurbiprofen-PEG eutectic system, intermolecular interactions between drug and polymer needed to be taken into consideration to predict the experimental phase diagram. The results of the current work suggest that the thermodynamic function of melting point and heat of fusion (as a measure of crystal energy of drug) plays a significant role in the formation of a eutectic system. Lipophilicity of the compound (as represented by cLog P) was also demonstrated to have an effect. Specific interactions between drug and carrier play a significant role in influencing the eutectic composition. Molar volume of the drug did not seem to have an impact on eutectic formation. The polymer molecular weight appeared to have an impact on the eutectic composition for flurbiprofen, which exhibits specific interactions with PEG, whereas no such impact of polymer molecular weight on eutectic composition was observed for fenofibrate, which does not exhibit specific interactions with PEG. The impact of polymer molecular weight on dissolution of systems where specific drug-polymer interactions are exhibited was also observed. The current work provides valuable insight into factors affecting formation and dissolution of eutectic systems, which can facilitate the rational selection of suitable water-soluble carriers.

Eudragit E accelerated the diketopiperazine formation of enalapril maleate determined by thermal FTIR microspectroscopic technique

PURPOSE

Enalapril may undergo the thermal-induced intramolecular interaction to cause an enalapril diketopiperazine (DKP) formation. It is interesting to study the influence of Eudragit E, as a coating polymer, on the stability of enalapril maleate. The reaction kinetics of the solid-state degradation process of pure enalapril maleate and Eudragit E/enalapril maleate mixture with different weight ratios were examined. The mechanism of solid-state interaction between Eudragit E and enalapril maleate was also discussed.

METHODS

The cast samples of pure enalapril maleate or Eudragit E/enalapril maleate mixture after evaporating the solvent were prepared on an aluminum foil and also determined by reflectance Fourier transform infrared (FTIR) microspectroscopy equipped with thermal analyzer.

RESULTS

The result indicates that the interaction might occur between enalapril maleate and Eudragit E in the solid state after evaporating the solvent. The thermal-dependent FTIR spectra show that not only the formation of DKP but also the six-membered cyclic anhydride occurred in the enalapril maleate/Eudragit E mixture in the heating process. Two pathways for solid-sate interaction were proposed. The stability of enalapril maleate was dependent on the weight ratio of enalapril maleate and Eudragit E. The activation energy (n = 3) of DKP formation for pure enalapril maleate was about 141.2+/-0.7 kJ/mol, but it was reduced significantly to 86.7+/-0.8 kJ/mol after interaction with Eudragit E (weight ratio: 1:1), suggesting Eudragit E might exacerbate the degradation of enalapril maleate. However, the degradation accelerated by Eudragit E was reduced in high content of Eudragit E.

CONCLUSIONS

When the weight ratio of both components was 1:1, Eudragit E might interact with the carboxyl group of maleic acid to exacerbate the degradation of enalapril maleate. However, the excess amount of Eudragit E might somewhat reduce the degradation of enalapril, due to the interaction that occurred between Eudragit E and carboxyl group of enalapril.