Evaluation of analytical tools and multivariate methods for quantification of co-former crystals in ibuprofen-nicotinamide co-crystals

Scalability of Pharmaceutical Co-Crystal Formation by Mechanochemistry in Batch

The development of mechanochemistry is considerably growing. Benign by design, this technology complies with several principles of green chemistry, contributing to the achievement of the United Nations Sustainable Development Goals (UN SDGs) and the European Green Deal objectives. Herein, we report the use of mechanochemical processes in batch to prepare kilogram-scale of the Active Pharmaceutical Ingredient (API): Ibuprofen-Nicotinamide (rac-IBP:NCT) co-crystal in an industrial eccentric vibration mill. This scenario shows a sustainable approach to the industrial up-scaling of pharmaceutical co-crystals by a solvent-free mechanochemical process in batch. The quantitative assessment of the greenness of the mechanochemical process against the Twelve Principles of Green Chemistry was performed using the DOZN 2.0 Green Chemistry Evaluator.

Characterization of Co-amorphous Carvedilol-Maleic Acid System Prepared by Solvent Evaporation

The aim of this study was to enhance the solubility and stability of the water-insoluble drug carvedilol (CAR) with maleic acid (MLE) to create a co-amorphous system by a solvent evaporation method. Phase diagrams of co-amorphous CAR-MLE, constructed from peak height in the Fourier-transform infrared (FTIR) spectra and the glass transition temperature (Tg) from differential scanning calorimetry (DSC) measurements, revealed that the optimal molar ratio of CAR to MLE was 2:1. The FTIR spectra indicated that the secondary amine-derived peak of CAR and the carboxy group-derived peak of MLE disappeared in the CAR:MLE (2:1) co-amorphous system. DSC measurements showed that the endothermic peaks associated with the melting of CAR and MLE disappeared and a Tg at 43 °C was apparent. Furthermore, the solubility of CAR tested using the shaking flask method for 24 h at 37 °C was 1.2 μg/mL, whereas that of the co-amorphous system was approximately three times higher, at 3.5 μg/mL. Finally, the stability was evaluated by powder- X-ray diffraction at 40 °C; no clear diffraction peaks originating from crystals were observed in the amorphous state until after approximately 3 months of storage. These results indicate that co-amorphization of CAR with MLE improved the solubility of CAR while maintaining its stability in an amorphous form.

Activation of Ibuprofen via Ultrasonic Complexation with Silver in N-Doped Oxidized Graphene Nanoparticles for Microwave Chemotherapy of Cervix Tumor Tissues

An ultrasonic method (20 kHz) is introduced to activate pristine ibuprofen organic molecular crystals via complexation with silver in nitrogen-doped oxidized graphene nanoplatforms (∼50 nm). Ultrasonic complexation occurs in a single-step procedure through the binding of the carboxylic groups with Ag and H-bond formation, involving noncovalent π_C=C → π_C=C* transitions in the altered phenyl ring and π_PY → π_CO* in ibuprofen occurring between the phenyl ring and C-O bonds as a result of interaction with hydroxyl radicals. The ibuprofen-silver complex in ≪NrGO≫ exhibits a ∼42 times higher acceleration rate than free ibuprofen of the charge transfer between hexacyanoferrate and thiosulfate ions. The increased acceleration rate can be caused by electron injection/ejection at the interface of the ≪Ag-NrGO≫ nanoplatform and formation of intermediate species (Fe(CN)₅(CNSO₃)^x- with x = 4 or 5 and AgHS₂O₃) at the excess of produced H⁺ ions. Important for microwave chemotherapy, ibuprofen-silver complexes in the ≪NrGO≫ nanoplatform can produce H⁺ ions at ∼12.5 times higher rate at the applied voltage range from 0.53 to 0.60 V. ≪Ibu-Ag-NrGO≫ NPs develop ∼10⁵ order higher changes of the electric field strength intensity than free ibuprofen in the microwave absorption range of 100-1000 MHz as revealed from the theoretical modeling of a cervix tumor tissue.

A molecularly enhanced proof of concept for targeting cocrystals at molecular scale in continuous pharmaceuticals cocrystallization

It is impossible to optimize a process for a target drug product with the desired profile without a proper understanding of the interplay among the material attributes, the process parameters, and the attributes of the drug product. There is a particular need to bridge the micro- and mesoscale events that occur during this process. Here, we propose а molecular engineering methodology for the continuous cocrystallization process, based on Raman spectra measured experimentally with a probe and from quantum mechanical calculations. Using molecular dynamics simulations, the theoretical Raman spectra were calculated from first principles for local mixture structures under an external shear force at various temperatures. A proof of concept is developed to build the process design space from the computed data. We show that the determined process design space provides valuable insight for optimizing the cocrystallization process at the nanoscale, where experimental measurements are difficult and/or inapplicable. The results suggest that our method may be used to target cocrystallization processes at the molecular scale for improved pharmaceutical synthesis.

Quantification of Losartan Potassium Polymorphs Using Powder X-Ray Diffraction

BACKGROUND

Losartan potassium, a common antihypertensive drug on the market, has multiple polymorphs, of which form I is used as a pharmaceutical crystal form. Form I can be partially converted to form III under some circumstances. The quantification of losartan potassium polymorphs is important to control the quality of pharmaceuticals.

OBJECTIVE

To establish a method to determine the contents of losartan potassium polymorphs.

METHODS

Pure form I and form III of losartan potassium were obtained by recrystallization, and characterized by powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy, Raman spectroscopy, and thermal analysis. A powder X-ray diffraction method was developed to characterize form I and form III of losartan potassium. Peak area and weight percentage were used to establish calibration curve.

RESULTS

The calibration curve was linear over the range of 1-50% (w/w), using the characteristic peak area ratio of form I at 11.13° 2θ and form III at 5.64° 2θ as the quantitative parameter. The precisions were excellent between 0.6-4.9%, and the limit of quantification was 2.02% (w/w).

CONCLUSIONS

This PXRD method can be used to analyze mixtures of losartan potassium polymorphs (forms I and III) quantitatively and control the quality of bulk drug.

HIGHLIGHTS

This is a new method of quantifying the amount of form III in polymorphic forms of losartan potassium using data obtained by PXRD. It is consistent, sensitive, and accurate.

In-line Raman spectroscopy and chemometrics for monitoring cocrystallisation using hot melt extrusion

The application of in-line Raman spectroscopy to monitor the formation of a 1:1 cocrystal of ibuprofen (IBU) as a BCS class II drug and nicotinamide as coformer using hot-melt extrusion (HME) was investigated. The process was monitored over different experimental conditions inserting the Raman probe before the extruder die. Partial least square (PLS) was applied as a robust chemometric technique to build predictive models at different levels of chemometric by dividing the experimental data set into calibration and validation subsets. Powder X-Ray diffraction (PXRD) spectra of a set of standard samples were used as calibration to calculate the cocrystal yield from HME experiments regressed by the PLS models. Examination of the full spectra with standard normal variate (SNV) scatter correction with first derivative provided the best fitting goodness and reliability for prediction. Differential scanning calorimetry (DSC) was used as a complementary technique to confirm the composition of the extrudates. Tracking the cocrystal formation throughout the barrel by inserting two Raman probes simultaneously in two different heating zones revealed highly valuable information for understanding the mechanism of cocrystal formation during the HME process.

Molecular engineering of cocrystallization process in holt melt extrusion based on kinetics of elementary molecular processes

Continuous co-crystallization in a twin-screw granulator is a promising technology. In order to fundamentally optimize the process flow, it is necessary to investigate the kinetics of molecular interactions within the mixture and the effect of these interactions on co-crystal formation. In this study, the processes governing the co-crystallization of ibuprofen and nicotinamide were considered. Density functional theory calculations employing the Hirshfeld partitioning scheme were used to identify donor-acceptor sites on each molecule. A total of twenty-one different molecular interactions was identified (nine of ibuprofen and nicotinamide (resembling co-crystals), three of ibuprofen and itself (resembling the ibuprofen dimer), and nine of nicotinamide and itself (resembling the nicotinamide dimer)). Each interaction was defined as an artificial reversible reaction and the kinetics were calculated using the transition state theory of chemical reactions, where linear and quadratic synchronous transition methods were utilized to identify transition-state structures; the minimum energy path was determined using the nudged elastic band method. A kinetic Monte Carlo framework was used to study the collective/coupled effect of reactions on the progress of the co-crystallization process. it was found that operating at low temperatures (especially lower or very close to the melting temperature of ibuprofen) for longer residency times creates a safe route for maximizing the presence of ibuprofen and nicotinamide co-crystals. If the proposed route is applied, the purity and properties of the produced co-crystal would be significant, especially its desirable availability within the body.

Recent Progress of Oridonin and Its Derivatives for the Treatment of Acute Myelogenous Leukemia

First stage human clinical trial (CTR20150246) for HAO472, the L-alanine-(14-oridonin) ester trifluoroacetate, was conducted by a Chinese company, Hengrui Medicine Co. Ltd, to develop a new treatment for acute myelogenous leukemia. Two patents, WO2015180549A1 and CN201410047904.X, covered the development of the I-type crystal, stability experiment, conversion rate research, bioavailability experiment, safety assessment, and solubility study. HAO472 hewed out new avenues to explore the therapeutic properties of oridonin derivatives and develop promising treatment of cancer originated from naturally derived drug candidates. Herein, we sought to overview recent progress of the synthetic, physiological, and pharmacological investigations of oridonin and its derivatives, aiming to disclose the therapeutic potentials and broaden the platform for the discovery of new anticancer drugs.

Salt Cocrystal of Diclofenac Sodium-L-Proline: Structural, Pseudopolymorphism, and Pharmaceutics Performance Study

Previously, we have reported on a zwitterionic cocrystal of diclofenac acid and L-proline. However, the solubility of this multicomponent crystal was still lower than that of diclofenac sodium salt. Therefore, this study aimed to observe whether a multicomponent crystal could be produced from diclofenac sodium hydrate with the same coformer, L-proline, which was expected to improve the pharmaceutics performance. Methods involved screening, solid phase characterization, structure determination, stability, and in vitro pharmaceutical performance tests. First, a phase diagram screen was carried out to identify the molar ratio of the multicomponent crystal formation. Next, the single crystals were prepared by slow evaporation under two conditions, which yielded two forms: one was a rod-shape and the second was a flat-square form. The characterization by infrared spectroscopy, thermal analysis, and diffractometry confirmed the formation of the new phases. Finally, structural determination using single crystal X-ray diffraction analysis solved the new salt cocrystals as a stable diclofenac-sodium-proline-water (1:1:1:4) named NDPT (natrium diclofenac proline tetrahydrate), and unstable diclofenac-sodium-proline-water (1:1:1:1), named NDPM (natrium diclofenac proline monohydrate). The solubility and dissolution rate of these multicomponent crystals were superior to those of diclofenac sodium alone. The experimental results that this salt cocrystal is suitable for further development.

Solid-State Quantification of Cocrystals in Pharmaceutical Tablets Using Transmission Low-Frequency Raman Spectroscopy

To enable the continuous production of cocrystal-containing pharmaceutical tablets, guaranteeing the cocrystal content of the final pharmaceutical tablets in the solid state is critical. This study demonstrates the quantification of caffeine-glutaric acid cocrystals in model tablets using transmission low-frequency Raman spectroscopy. Although distinguishing between cocrystals and raw materials using conventional Raman spectroscopy is difficult, the use of low-frequency Raman spectroscopy enables the discrimination of cocrystals and raw materials. Low-frequency Raman spectra were analyzed by the partial least-squares method (PLS) to obtain the predicted contents in the model tablets. To evaluate the quantitative ability of this method, the root means square error of cross-validation (RMSECV) was determined by comparing the actual concentration and predicted content with a calibration curve. For cocrystal-containing tablets, the quantitative ability of the transmission mode (RMSECV = 2.06- 3.17) was 13.4-31.4% higher than that of the backscattering mode (RMSECV= 2.37- 3.91). The coexistence of raw crystalline materials did not affect the quantitative ability for cocrystals.

MCR-ALS analysis of IR spectroscopy and XRD for the investigation of ibuprofen - nicotinamide cocrystal formation

To improve aqueous solubility, a poorly water-soluble active ingredient is classically combined with a conformer to form cocrystals. Hot melt extrusion is one preparation method for the formation of cocrystal solids. The aim of our study was to determine the optimal temperature conditions for the formation of ibuprofen and nicotinamide cocrystals using real-time infrared (IR) and X-ray diffraction (XRD) measurements. IR spectra and XRD patterns were subjected to multivariate curve resolution alternating least squares (MCR-ALS) analysis and decomposed into several components. Each component was descriptive of a specific step in the formation of the cocrystal. Cocrystal formation was followed by a separation phase between amorphous ibuprofen and crystalline nicotinamide. Our results suggest that, when using the hot melt exclusion method, careful consideration should be made towards optimizing processing temperatures in order to prevent amorphization and promote control over the process of cocrystal formation.

Quantifying API polymorphs in formulations using X-ray powder diffraction and multivariate standard addition method combined with net analyte signal analysis

The direct quantification of Active Pharmaceutical Ingredients in solid formulations is a challenging open issue. A consolidated analytical technique based on X-ray Powder Diffraction is available, being the definitive test for the identification of polymorphs and crystal phases. However, its application for quantitative analysis is hindered by matrix effects: refinement methods (e.g. Rietveld method) require a complete knowledge of samples' composition, while univariate calibration methods require the matrix effect to be studied and severely suffer from the co-presence of crystalline and amorphous phases in the sample. Multivariate analysis is the only way to bypass problems affecting refinements procedures and univariate calibration. In particular, the multivariate standard addition method (SAM) is promising; however, it is straightforward only when the analytical blank (matrix devoid of analyte) is available: in that case SAM is applied by simply extrapolating the SAM model to the matrix experimental signal. In this work, the quantitative analysis of polymorphic forms of Active Pharmaceutical Ingredients based on X-ray Powder Diffraction is performed for the first time by a method based on multivariate standard addition method combined with net analyte signal procedure; it allows for reliable quantification of polymorphs of active principles in solid formulations, which are rapidly analyzed without any sample pre-treatment. Two test cases are presented: quantification of two polymorphs of piracetam in binary mixtures (forms II and III), and quantification of paracetamol (form I) in Tachifludec®.

Preparation of pharmaceutical cocrystal formulations via melt mixing technique: A thermodynamic perspective

The aim of the present study was to evaluate the thermodynamic properties of in-situ formation of cocrystal formulations by the melt-mixing method. Specifically, the thermodynamic mixing behaviour of carbamazepine-nicotinamide and ibuprofen-nicotinamide cocrystals prepared with the aid of Soluplus^® (SOL) were evaluated using thermodynamic lattice-based solution theories. Thermodynamic miscibility of both cocrystals with SOL was predicted by calculating Gibb's free energy based on the Flory-Huggins (FH) interaction parameter (χ), while the activity coefficient of cocrystals estimated with the aid of solid-liquid equilibrium equation and FH lattice theory, showed good thermodynamic miscibility of the components at elevated temperatures used normally during melt-mixing based processes. Complete phase transition diagrams constructed with the aid of DSC measurements and FH solution theory, suggested the existence of two transition zones: (1) a stable cocrystal zone, located at the right-hand-side of the spinodal phase separation curve, where stable cocrystals are prepared and (2) an unstable cocrystal zone, located at the left-hand-side of the spinodal curve up to liquidus, where the matrixforming polymer sets a kinetic barrier to recrystallization and hence, a barrier to the formation of cocrystals. The validity of the suggested thermodynamic phase transition zones was experimentally verified by ATR-FTIR and hot-stage polarized light microscopy.

Pharmacokinetics of multiple doses of co-crystal of tramadol-celecoxib: findings from a four-way randomized open-label phase I clinical trial

Aim

We compared the pharmacokinetic (PK) profiles of co‐crystal of tramadol–celecoxib (CTC) vs. each reference product (alone and in open combination) after single (first dose) and multiple dosing.

Methods

Healthy adults aged 18–50 years received, under fasted conditions, 15 twice‐daily doses of the following treatments (separated by ≥14‐day washout): 200 mg immediate‐release (IR) CTC (equivalent to 88 mg tramadol and 112 mg celecoxib; treatment 1); 100 mg IR tramadol (treatment 2), 100 mg celecoxib (treatment 3); and 100 mg IR tramadol and 100 mg celecoxib (treatment 4). The treatment sequence was assigned by computer‐generated randomization. PK parameters were calculated using non‐compartmental analysis. Parameters for CTC were adjusted according to reference product dose.

Results

A total of 30 subjects (20 males, mean age 35 years) were included. Multiple‐dose tramadol PK parameters for treatments 1, 2 and 4, respectively, were 551, 632 and 661 ng ml⁻¹ [mean maximum plasma concentration (C_max)]; 4796, 4990 and 5284 ng h ml⁻¹ (area under the plasma concentration–time curve over the dosing interval at steady state); and 3.0, 2.0 and 2.0 h (median time to C_max at steady state). For treatments 1, 3 and 4, multiple‐dose celecoxib PK parameters were 445, 536 and 396 ng ml⁻¹; 2803, 3366 and 2897 ng h ml⁻¹; and 2.0, 2.0 and 3.0 h. Single‐dose findings were consistent with multiple‐dose data. Types of adverse events were consistent with known reference product safety profiles.

Conclusion

After single (first dose) and multiple dosing, PK parameters for each active pharmaceutical ingredient in CTC were modified by co‐crystallization compared with reference products alone or in open combination.

Preparation and characterization of adefovir dipivoxil-stearic acid cocrystal with enhanced physicochemical properties

The objectives of this study were to prepare cocrystal composed of adefovir dipivoxil (AD) and stearic acid (SA) and to investigate the enhanced properties of the cocrystal. The cocrystal was prepared by antisolvent precipitation and characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), X-ray powder diffraction (XRPD), and differential scanning calorimetry (DSC). The enhanced properties were evaluated by dissolution testing, permeability studies, and powder rheology analysis. The AD raw material has a cuboid-like crystal and the cocrystal has a needle shape. In the FT-IR study, there were bathochromic shifts caused by the hydrogen bonding. The melting point of the cocrystal was 52.9 °C, which was lower than that of AD. The XRPD pattern also had distinct differences, supporting the formation of a new crystalline form. The cocrystal showed changes in the lattice energy and the solvation strength, which caused an enhanced dissolution. The permeability was increased due to the SA, which acts as a P-gp inhibitor. The tabletability was enhanced due to the altered crystal habit. In conclusion, cocrystal containing AD and SA was successfully prepared, presenting advantages such as enhanced solubility, tabletability, and permeability. The use of the cocrystal is a desirable approach for the improved physicochemical properties.

In-line monitoring of cocrystallization process and quantification of carbamazepine-nicotinamide cocrystal using Raman spectroscopy and chemometric tools

A cocrystallization process may involve several molecular species, which are generally solid under ambient conditions. Thus, accurate monitoring of different components that might appear during the reaction is necessary, as well as quantification of the final product. This work reports for the first time the synthesis of carbamazepine-nicotinamide cocrystal in aqueous media with a full conversion. The reactions were monitored by Raman spectroscopy coupled with Multivariate Curve Resolution - Alternating Least Squares, and the quantification of the final product among its coformers was performed using Raman spectroscopy and Partial Least Squares regression. The slurry reaction was made in four different conditions: room temperature, 40°C, 60°C and 80°C. The slurry reaction at 80°C enabled a full conversion of initial substrates into the cocrystal form, using water as solvent for a greener method. The employment of MCR-ALS coupled with Raman spectroscopy enabled to observe the main steps of the reactions, such as drug dissolution, nucleation and crystallization of the cocrystal. The PLS models gave mean errors of cross validation around 2.0 (% wt/wt), and errors of validation between 2.5 and 8.2 (% wt/wt) for all components. These were good results since the spectra of cocrystals and the physical mixture of the coformers present some similar peaks.

Pokharkar V. Understanding peroral absorption: regulatory aspects and contemporary approaches to tackling solubility and permeability hurdles

Oral drug absorption is a process influenced by the physicochemical and biopharmaceutical properties of the drug and its inter-relationship with the gastrointestinal tract. Drug solubility, dissolution and permeability across intestinal barrier are the key parameters controlling absorption. This review provides an overview of the factors that affect drug absorption and the classification of a drug on the basis of solubility and permeability. The biopharmaceutical classification system (BCS) was introduced in early 90׳s and is a regulatory tool used to predict bioavailability problems associated with a new entity, thereby helping in the development of a drug product. Strategies to combat solubility and permeability issues are also discussed.

Quantification of febuxostat polymorphs using powder X-ray diffraction technique

Febuxostat is a pharmaceutical compound with more than 20 polymorphs of which form A is most widely used and usually exists in a mixed polymorphic form with form G. In the present study, a quantification method for polymorphic form A and form G of febuxostat (FEB) has been developed using powder X-ray diffraction (PXRD). Prior to development of a quantification method, pure polymorphic form A and form G are characterized. A continuous scan with a scan rate of 3° min(-1) over an angular range of 3-40° 2θ is applied for the construction of the calibration curve using the characteristic peaks of form A at 12.78° 2θ (I/I0100%) and form G at 11.72° 2θ (I/I0100%). The linear regression analysis data for the calibration plots shows good linear relationship with R(2)=0.9985 with respect to peak area in the concentration range 10-60 wt.%. The method is validated for precision, recovery and ruggedness. The limits of detection and quantitation are 1.5% and 4.6%, respectively. The obtained results prove that the method is repeatable, sensitive and accurate. The proposed developed PXRD method can be applied for the quantitative analysis of mixtures of febuxostat polymorphs (forms A and G).

Simultaneous quantification of three polymorphic forms of carbamazepine in the presence of excipients using Raman spectroscopy

The occurrence of polymorphic transitions is a serious problem for pharmaceutical companies, because it can affect the bioavailability of the final product. With several known polymorphic forms carbamazepine is one of the most problematic drugs in this respect. Raman spectroscopy is a vibrational technique that is becoming very important in the pharmaceutical field, mainly due to its highly specific molecular fingerprint capabilities and easy use as a process analytical tool. However, multivariate methods are necessary both for identification and quantification. In this work an analytical methodology using Raman spectroscopy and interval Partial Least Squares Regression (iPLS), was developed in order to quantify mixtures of carbamazepine polymorphs in the presence of the most common excipients. The three polymorphs CBZ I, CBZ III and CBZ DH (which is a dihydrate) were synthesized and characterized by PXRD and DSC. Subsequently, tablets were manufactured using excipients and 15 different mixtures of carbamazepine polymorphs. The iPLS model presented average prediction validation errors of 1.58%, 1.04% and 0.22% wt/wt, for CBZ I, CBZ III and CBZ DH, respectively, considering the whole mass of the tablet. The model presents a good prediction capacity and the proposed methodology could be used to perform quality control in final products.