Trends in active pharmaceutical ingredient salt selection based on analysis of the Orange Book database

Torsemide Crystalline Salts with a Significant Spring-Parachute Effect

Torsemide is a long acting pyridine sulfonylurea diuretic. Torsemide hydrochloride is widely used now, there are only a few organic acid salts reported. Cocrystallization with organic acids is an effective way to improve its solubility. Here, we reported maleate and phthalate of torsemide, in which the organic acid lost a proton transferring to the pyridine of torsemide, and torsemide interacted with organic acid through N+ - H⋯O- hydrogen bond to form salts crystal. Surprisingly, maleate showed a clear "spring" pattern in apparent solubility, whereas phthalate had a "spring-parachute" effect. Both crystalline salts kept a higher solubility than torsemide without falling. The "spring-parachute" effect of crystalline salts promoted rapid dissolution of torsemide and kept a high concentration, thereby increasing its bioavailability.

Exploring Salts of Memantine with Inorganic Anions: From Polymorphism and Solid-State Transitions to Potential for Drug Formulations

This study examines pharmaceutically acceptable inorganic salts of memantine, specifically focusing on hydrogen sulfate, sulfate, and dihydrogen phosphate salts, with the aim of finding alternatives to the commonly used chloride salt in the treatment of Alzheimer's disease. Through comprehensive solid-state characterization, including powder X-ray diffraction, thermal analysis, and solubility testing, we unveil complex polymorphic behaviors, reversible solid-state transitions, and significant differences in solubility and stability among the salts. Notably, the hydrogen sulfate salt emerges as a promising candidate for drug formulations, offering improved solubility, nonhygroscopic nature, and favorable morphological characteristics compared to the existing chloride salt. This work establishes a foundation for further investigation into memantine salts as potential therapeutics with improved efficacy.

Analysis of the Dissolution Behavior of Theophylline and Its Cocrystal Using ATR-FTIR Spectroscopic Imaging

Attenuated total reflection-Fourier transform infrared (ATR-FTIR) spectroscopic imaging is a powerful tool to visualize the distribution of components, and it has been used to analyze drug release from tablets. In this work, ATR-FTIR spectroscopic imaging was applied for observing the dissolution of molecular crystals from tablet compacts. The IR spectra provided chemically specific information about the transformation of crystal structures during the dissolution experiments. Theophylline (TPL) anhydrate and its cocrystals were used as model systems of molecular crystals. The IR spectra during the dissolution of TPL revealed information about the crystal structure of TPL, which transformed from anhydrate to monohydrate in water. During a dissolution test of a model cocrystal system, it was suggested that an active pharmaceutical ingredient (API) and a coformer were dissolved in water simultaneously. The IR spectra that were acquired during the dissolution of a cocrystal tablet showed new spectral bands attributed to the API after 5 min. This suggested that the precipitation of API was observed during the dissolution experiment. Measurements from ATR-FTIR spectroscopic imaging can visualize the drug release from the tablet and determine the transformation of molecular crystals during their dissolution. These results will have an impact on clarifying the dissolution mechanism of molecular crystals.

Optimizing Drug Development: Harnessing the Sustainability of Pharmaceutical Cocrystals

Environmental impacts of the industrial revolution necessitate adoption of sustainable practices in all areas of development. The pharmaceutical industry faces increasing pressure to minimize its ecological footprint due to its significant contribution to environmental pollution. Over the past two decades, pharmaceutical cocrystals have received immense popularity due to their ability to optimize the critical attributes of active pharmaceutical ingredients and presented an avenue to bring improved drug products to the market. This review explores the potential of pharmaceutical cocrystals as an ecofriendly alternative to traditional solid forms, offering a sustainable approach to drug development. From reducing the number of required doses to improving the stability of actives, from eliminating synthetic operations to using pharmaceutically approved chemicals, from the use of continuous and solvent-free manufacturing methods to leveraging published data on the safety and toxicology, the cocrystallization approach contributes to sustainability of drug development. The latest trends suggest a promising role of pharmaceutical cocrystals in bringing novel and improved medicines to the market, which has been further fuelled by the recent guidance from the major regulatory agencies.

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

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

Norepinephrine Salt Formulations and Risk of Therapeutic Error: Results of a National Survey

OBJECTIVES

Norepinephrine is available commercially in solution containing its salt (eg, tartrate), but only the base form (ie, norepinephrine base) is active pharmacologically. Unfortunately, the outer label of drug packages frequently reports the dosage of norepinephrine as a salt, which can lead potentially to therapeutic errors when prescribing norepinephrine. We performed a survey to assess the level of awareness of this issue.

DESIGN

National survey.

SETTING

Acute care units of Italian hospitals.

PARTICIPANTS

Acute care physicians and nurses.

INTERVENTIONS

A 15-item online survey was emailed to 305 critical care practitioners in Italy. Questions included information on the participants' background, methods of diluting norepinephrine, interpretation of recommended doses from guidelines, and a sample case related to the preparation and administration of the drug.

MEASUREMENTS AND MAIN RESULTS

We collected 106 responses from 54 hospitals. All hospitals used norepinephrine bitartrate salt. Of the participants, 53% responded that the guidelines express norepinephrine dosages as a salt, 23% as the base form, and 24% were unsure or unaware about it. The simulated patient-dose calculation was resolved in 81% of cases with an incorrect calculation referring to the norepinephrine salt and only in 19% referring to the norepinephrine base.

CONCLUSIONS

There is significant variability in dosage management of norepinephrine across different hospital units, as well as a lack of knowledge regarding the salt-to-base ratio. Scientific publications (eg, guidelines) should specify whether they are referring to the base or salt form of norepinephrine. The adoption of different labeling and national standards for dilution may decrease the risk of therapeutic errors.

Position Paper on the Reporting of Norepinephrine Formulations in Critical Care from the Society of Critical Care Medicine and European Society of Intensive Care Medicine Joint Task Force

OBJECTIVES

To provide guidance on the reporting of norepinephrine formulation labeling, reporting in publications, and use in clinical practice.

DESIGN

Review and task force position statements with necessary guidance.

SETTING

A series of group conference calls were conducted from August 2023 to October 2023, along with a review of the available evidence and scope of the problem.

SUBJECTS

A task force of multinational and multidisciplinary critical care experts assembled by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine.

INTERVENTIONS

The implications of a variation in norepinephrine labeled as conjugated salt (i.e., bitartrate or tartrate) or base drug in terms of effective concentration of norepinephrine were examined, and guidance was provided.

MEASUREMENTS AND MAIN RESULTS

There were significant implications for clinical care, dose calculations for enrollment in clinical trials, and results of datasets reporting maximal norepinephrine equivalents. These differences were especially important in the setting of collaborative efforts across countries with reported differences.

CONCLUSIONS

A joint task force position statement was created outlining the scope of norepinephrine-dose formulation variations, and implications for research, patient safety, and clinical care. The task force advocated for a uniform norepinephrine-base formulation for global use, and offered advice aimed at appropriate stakeholders.

An unusual ionic cocrystal of ponatinib hydrochloride: characterization by single-crystal X-ray diffraction and ultra-high field NMR spectroscopy

This study describes the discovery of a unique ionic cocrystal of the active pharmaceutical ingredient (API) ponatinib hydrochloride (pon·HCl), and characterization using single-crystal X-ray diffraction (SCXRD) and solid-state NMR (SSNMR) spectroscopy. Pon·HCl is a multicomponent crystal that features an unusual stoichiometry, with an asymmetric unit containing both monocations and dications of the ponatinib molecule, three water molecules, and three chloride ions. Structural features include (i) a charged imidazopyridazine moiety that forms a hydrogen bond between the ponatinib monocations and dications and (ii) a chloride ion that does not feature hydrogen bonds involving any organic moiety, instead being situated in a "square" arrangement with three water molecules. Multinuclear SSNMR, featuring high and ultra-high fields up to 35.2 T, provides the groundwork for structural interpretation of complex multicomponent crystals in the absence of diffraction data. A 13C CP/MAS spectrum confirms the presence of two crystallographically distinct ponatinib molecules, whereas 1D 1H and 2D 1H-1H DQ-SQ spectra identify and assign the unusually deshielded imidazopyridazine proton. 1D 35Cl spectra obtained at multiple fields confirm the presence of three distinct chloride ions, with density functional theory calculations providing key relationships between the SSNMR spectra and H⋯Cl- hydrogen bonding arrangements. A 2D 35Cl → 1H D-RINEPT spectrum confirms the spatial proximities between the chloride ions, water molecules, and amine moieties. This all suggests future application of multinuclear SSNMR at high and ultra-high fields to the study of complex API solid forms for which SCXRD data are unavailable, with potential application to heterogeneous mixtures or amorphous solid dispersions.

Effect of Buffer pH and Concentration on the Dissolution Rates of Sodium Indomethacin-Copovidone and Indomethacin-Copovidone Amorphous Solid Dispersions

The incorporation of counterions into amorphous solid dispersions (ASDs) has been proven to be effective for improving the dissolution rates of ionizable drugs in ASDs. In this work, the effect of dissolution buffer pH and concentration on the dissolution rate of indomethacin-copovidone 40:60 (IMC-PVPVA, w/w) ASD with or without incorporated sodium hydroxide (NaOH) was studied by surface area-normalized dissolution to provide further mechanistic understanding of this phenomenon. Buffer pH from 4.7 to 7.2 and concentration from 20 to 100 mM at pH 5.5 were investigated. As the buffer pH decreased, the IMC dissolution rate from both ASDs decreased. Compared to IMC-PVPVA ASD, the dissolution rate decrease from IMCNa-PVPVA ASD was more resistant to the decrease of buffer pH. In contrast, while buffer concentration had a negligible impact on the IMC dissolution rate from IMC-PVPVA ASD, the increase of buffer concentration significantly reduced the IMC dissolution rate from IMCNa-PVPVA ASD. Surrogate evaluation of microenvironment pH modification by the dissolution of IMCNa-PVPVA ASD demonstrated the successful elevation of buffer microenvironment pH and the suppression of such pH elevation by the increase of buffer concentration. These results are consistent with the hypothesis that the dissolution rate enhancement by the incorporation of counterions originates from the enhanced drug solubility by ionization and the modification of diffusion layer pH in favor of drug dissolution. At the studied drug loading (∼40%), relatively congruent release between IMC and PVPVA was observed when IMC was ionized in ASD or in solution, highlighting the importance of studying the ionization effect on the congruent release of ASDs, especially when drug ionization is expected in vivo. Overall, this work further supports the application of incorporating counterions into ASDs for improving the dissolution rates of ionizable drugs when enabling formulation development is needed.

Crystal Modifications of a Cyclic Guanosine Phosphorothioate Analogue, a Drug Candidate for Retinal Neurodegenerations

In contribution to the pharmaceutical development of cyclic guanosine monophosphorothioate analogue cGMPSA as a potential active pharmaceutical ingredient (API) for the treatment of inherited retinal degenerations (IRDs), its neutral form (cGMPSA-H) and salts of sodium (-Na), calcium (-Ca), ammonium (-NH4 ), triethylammonium (-TEA), tris(hydroxymethyl)aminomethane (-Tris), benethamine (-Bnet), and benzathine (-BZ) were prepared. Their solid-state properties were studied with differential scanning calorimetry, thermogravimetric analysis, hot-stage microscopy, and dynamic vapor sorption, and their solubilities were measured in deionized H2 O as well as aqueous HCl and NaOH buffers. A total of 21 crystal modifications of cGMPSA were found and characterized by X-ray powder diffraction. Despite their crystalline character, no API forms featured any observable melting points during thermal analyses and instead underwent exothermic decomposition at ≥163 °C. Both the vapor sorption behavior and solubility were found to differ significantly across the API forms. cGMPSA-BZ featured the lowest aqueous solubility and hygroscopicity, with 50 μg/mL and 5 % mass gain at maximum relative humidity. The synthesis and crystallization of some crystal modifications were upscaled to >10 g. Single crystal X-ray diffraction was performed which resulted in the first crystal structure determination and absolute configuration of a cyclic guanosine monophosphorothioate, confirming the RP - conformation at the phosphorus atom.

Computational and Experimental Screening Approaches to Aripiprazole Salt Crystallization

INTRODUCTION

The screening of multicomponent crystal system (MCC) is a key method for improving physicochemical properties of active pharmaceutical ingredients (APIs). The challenges associated with experimental salt screening include a large number of potential counterions and solvent systems and tendency to undergo disproportionation to produce free form during crystallization. These challenges may be mitigated by a combination of experimental and computational approaches to salt screening. The goal of this study is to evaluate performance of the counterion screening methods and propose and validate novel approaches to virtual solvent screening for MCC crystallization.

METHODS

The actual performance of the ΔpKa > 3 rule for counterion selection was validated using multiple screenings reports. Novel computational models for virtual solvent screening to avoid MCC incongruent crystallization were proposed. Using the ΔpKa rule, 10 acid counterions were selected for experimental aripiprazole (APZ) salt screening using 10 organic solvents. The experimental results were used to validate the proposed novel virtual solvent screen models.

RESULTS

Experimental APZ salt screening resulted in a total of eight MCCs which included glucuronate, mesylate, oxalate, tartrate, salicylate and mandelate. The new model to virtually screen solvents provided a general agreement with APZ experimental findings in terms of selecting the optimal solvent for MCC crystallization.

CONCLUSION

The rational selection of counterions and organic solvents for MCC crystallization was presented using combined novel computational model as well as experimental studies. The current virtual solvent screen model was successfully implemented and validated which can be easily applied to newly discovered APIs.

Abiraterone Acetate Complexes with Biometals: Synthesis, Characterization in Solid and Solution, and the Nature of Chemical Bonding

Abiraterone acetate (AbirAc) is the most used steroidal therapeutic agent for treatment of prostate cancer. The mainly hydrophobic molecular surface of AbirAc results in its poor solubility and plays an important role for retention of abiraterone in the cavity of the receptor formed by peptide chains and heme fragments. In order to evaluate the hydrolytic stability of AbirAc, to modify its solubility by formation of new solid forms and to model bonding of this medication with the heme, a series of d-metal complexes with AbirAc was obtained. AbirAc remains stable in water, acetonitrile, tetrahydrofuran, and ethanol, and readily interacts with dications as a terminal ligand to create discrete complexes, including [FePC(AbirAc)2] and [ZnTPP(AbirAc)] (H2PC = phthalocyanine and H2TPP = 5,10,15,20-tetraphenylporphyrine) models for ligand-receptor bonding. In reactions with silver(I) nitrate, AbirAc acts as a bridge ligand. Energies of chemical bonding between AbirAc and these cations vary from 97 to 235 kJ mol-1 and exceed those between metal atoms and water molecules. This can be indicative of the ability of abiraterone to replace solvent molecules in the coordination sphere of biometals in living cells, although the model [ZnTPP] complex remains stable in CDCl3, CD2Cl2, and 1,1,2,2-tetrachloroethane-d2 solvents and decomposes in polar dimethylsulfoxide-d6 and methanol-d4 solvents, as follows from the 1H DOSY spectra. Dynamics of its behavior in 1,1,2,2-tetrachloroethane-d2 were studied by ROESY and NMR spectra.

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

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

Exploiting common ion addition to accelerate zolpidem hemitartrate release from Eudragit EPO extrudates

The current study aimed at optimizing a previously developed non-clinical formulation for use in zolpidem deprescribing. The formulation under investigation consists of extruded zolpidem hemitartrate (30% w/w) and Eudragit EPO (70% w/w) mixtures which display unsatisfactory dissolution behavior. Both milled extrudates and physical mixtures were compressed to produce tablets with identical target weight and solid fraction. First, the susceptibility of zolpidem hemitartrate towards heat and shear degradation was identified utilizing thermal and HPLC-DAD analysis. The drug salt proved prone to thermally induced disproportionation. Moreover, the impurity content increased after applying hot melt extrusion although ICH guidelines were still attained. Secondly, extrudates and physical mixtures were subjected to FTIR analysis. As a result, interaction and protonation of the dimethyl aminoethyl group from Eudragit EPO resulting from zolpidem disproportionation was elucidated. As such, the formulations' slow dissolution kinetics in comparison to formulations containing non-ionizable polymers (e.g. Kollidon 12PF and Kollidon VA64) is explained. Finally, addition of tartaric acid, a microenvironmental pH modulator and common ion, proved a successful method to increase dissolution kinetics. The amount of drug released after 15 min increased drastically from 10 to 40% upon the addition of 5% tartaric acid. Immediate release behavior (80% within 15 min) was however not yet attained.

Bioactive Phenolate Salts: Thymol Salts

Phenolate salts of bioactive agents have been reported only scarcely. This is the first report on the formation and characterization of thymol phenolate salts as representatives of phenol-containing bioactive molecules. Thymol has been used in medicine and agriculture for decades owing to its excellent therapeutic properties. However, in light of its poor aqueous solubility, thermal instability, and especially its high chemical volatility, the utility of thymol is hampered. The present work focuses on tuning the physicochemical properties of thymol by modifying its chemical structure through salt formation. In this context, a series of metal (Na, K, Li, Cu, and Zn) and ammonium (tetrabutylammonium and choline) salts of thymol were synthesized and characterized using IR, NMR, CHN elemental analysis, and DSC analyses. The molecular formulae of thymol salts were determined based on CHN analysis and thymol quantification studies from UV-Vis spectrometric analysis. In most cases, the thymol phenolate was prepared as a 1 : 1 molar ratio with metal/ammonium ion. Only the Cu salt of thymol was isolated at a ratio of two phenolate units per copper ion. Most of the synthesized thymol salts were found to have increased thermal stability relative to thymol. The physicochemical properties such as solubility, thermal stability, and evaporation rate of thymol salts were thoroughly studied in comparison with thymol. The in vitro release studies of Cu from the copper salt of thymol is pH-dependent: rapid release of copper was observed in the lower pH release medium (100 % release at pH 1 for 12 days) and the rates of release were slower at higher pH values (5 % release at pH 2, and <1 % release at pH 4, 6, 8, and 10) over a period of about three weeks.

Site Identification by Ligand Competitive Saturation-Biologics Approach for Structure-Based Protein Charge Prediction

Protein-based therapeutics typically require high concentrations of the active protein, which can lead to protein aggregation and high solution viscosity. Such solution behaviors can limit the stability, bioavailability, and manufacturability of protein-based therapeutics and are directly influenced by the charge of a protein. Protein charge is a system property affected by its environment, including the buffer composition, pH, and temperature. Thus, the charge calculated by summing the charges of each residue in a protein, as is commonly done in computational methods, may significantly differ from the effective charge of the protein as these calculations do not account for contributions from bound ions. Here, we present an extension of the structure-based approach termed site identification by ligand competitive saturation-biologics (SILCS-Biologics) to predict the effective charge of proteins. The SILCS-Biologics approach was applied on a range of protein targets in different salt environments for which membrane-confined electrophoresis-determined charges were previously reported. SILCS-Biologics maps the 3D distribution and predicted occupancy of ions, buffer molecules, and excipient molecules bound to the protein surface in a given salt environment. Using this information, the effective charge of the protein is predicted such that the concentrations of the ions and the presence of excipients or buffers are accounted for. Additionally, SILCS-Biologics also produces 3D structures of the binding sites of ions on the proteins, which enable further analyses such as the characterization of protein surface charge distribution and dipole moments in different environments. Notable is the capability of the method to account for competition between salts, excipients, and buffers on the calculated electrostatic properties in different protein formulations. Our study demonstrates the ability of the SILCS-Biologics approach to predict the effective charge of proteins and its applicability in uncovering protein-ion interactions and their contributions to protein solubility and function.

Strategies for Managing Solid Form Transformation Risk in Drug Product

The International Conference of Harmonization (ICH) Q6A document provides guidance on setting specifications for new drug substances and drug products.¹ In this paper we focus on decision trees 4 (#1) to (#3) in the guidance related to solid-state form transformation. Form transformation could occur from use of high energy forms to overcome solubility challenges or stresses from manufacturing processes. The decision trees provide guidance on when and how polymorphic form changes should be monitored and controlled. However, guidance is high level and does not capture aspects related to assessments needed to understand if there is a risk of transformation or tools that can be integrated to understand the severity of bioavailability impact at different stages of development. The objective of this paper is therefore to provide comprehensive chemistry manufacturing and controls (CMC) and regulatory strategies to manage the risk of form transformation. This includes practical workflows for form transformation risk assessment, analytical tools to detect and quantify the transformation including their shortcomings, biopharmaceutical tools to understand the severity of transformation risk and if needed justify the limits based on clinical relevance. Finally, a few case studies are discussed that capture how the workflow can be used to manage transformation risk.

Advanced crystallisation methods for small organic molecules

Molecular materials based on small organic molecules often require advanced structural analysis, beyond the capability of spectroscopic techniques, to fully characterise them. In such cases, diffraction methods such as single crystal X-ray diffraction (SCXRD), are one of the most powerful tools available to researchers, providing molecular and structural elucidation at atomic level resolution, including absolute stereochemistry. However SCXRD, and related diffraction methods, are heavily dependent on the availability of suitable, high-quality crystals, thus crystallisation often becomes the major bottleneck in preparing samples. Following a summary of classical methods for the crystallisation of small organic molecules, this review will focus on a number of recently developed advanced methods for crystalline material sample preparation for SCXRD. This review will cover two main areas of modern small organic molecule crystallisation, namely the inclusion of molecules within host complexes (e.g., "crystalline sponge" and tetraaryladamantane based inclusion chaperones) and the use of high-throughput crystallisation, employing "under-oil" approaches (e.g., microbatch under-oil and ENaCt). Representative examples have been included for each technique, together with a discussion of their relative advantages and limitations to aid the reader in selecting the most appropriate technique to overcome a specific analytical challenge.

Usefulness of the BioGIT system in screening for differences in early exposure in the fasted state on an a priori basis

The objective of the present study was to confirm the usefulness of BioGIT data in the evaluation of the impact of dose and/or formulation on early exposure after oral administration of immediate release or enabling products of low solubility active pharmaceutical ingredients (APIs) with a glass of water in the fasted state. BioGIT experiments were performed with four APIs: Compound Α (tablet, three dose levels), Compound E (capsule PiC1, capsule PiC2 and tablet), fenofibrate (Lipidil® capsule and Lipidil 145 ONE® tablet) and Compound F (HP-β-CD aqueous solution and tablet). Based on mean plasma AUC_0-60min values which became available after completion of the BioGIT experiments, mean BioGIT AUC_0-50min values were useful for the evaluation of the impact of dose and/or formulation on early exposure. The log-transformed ratios of mean BioGIT AUC_0-50min values for two doses and/or two formulations estimated in this study and in a recent study for two diclofenac potassium products (Cataflam® tablet and Voltfast® sachet, same dose) vs. the corresponding log-transformed ratios of mean plasma AUC_0-60min values (n = 7 pairs of ratios), were included in a previously established correlation between log-transformed ratios of mean BioGIT AUC_0-50min values and log-transformed ratios of plasma AUC_0-60min values (n = 9 pairs of ratios). The correlation between log-transformed plasma AUC_0-60min ratios vs. log-transformed BioGIT AUC_0-50min ratios was confirmed (n = 16 pairs of ratios, R = 0.90). Compared with the previously established correlation the statistical characteristics were improved. Based on this study, the BioGIT system could be useful as a screening tool for assessing the impact of dose and/or formulation differences on early exposure, after administration of immediate release or enabling drug products of low solubility APIs with a glass of water in the fasted state, on an a priori basis.

Synthesis, Structural Elucidation, and Anti-Inflammatory Activity of a Water-Soluble Derivative of Arctiin

The poor oral bioavailability of arctiin caused by its low water solubility is the biggest obstacle in developing it as a drug. In this work, a new water-soluble glucuronide derivative of arctiin (arctigenin-4'-O-glucuronide) was synthesized through 2,2,6,6-tetramethylpiperidine 1-oxyl mediated oxidation reaction. Subsequently, its anti-inflammatory effect was evaluated by mice acute lung injury model in vivo. The results showed that the glucuronide derivative of arctiin not only had better water solubility but also displayed improved anti-inflammatory activity in vivo, thus serving as an innovative compound in the drug development of arctiin.

Exploring the Potential of Multinuclear Solid-State 1 H, 13 C, and 35 Cl Magnetic Resonance To Characterize Static and Dynamic Disorder in Pharmaceutical Hydrochlorides

Crystallographic disorder, whether static or dynamic, can be detrimental to the physical and chemical stability, ease of crystallization and dissolution rate of an active pharmaceutical ingredient. Disorder can result in a loss of manufacturing control leading to batch-to-batch variability and can lengthen the process of structural characterization. The range of NMR active nuclei makes solid-state NMR a unique technique for gaining nucleus-specific information about crystallographic disorder. Here, we explore the use of high-field ³⁵ Cl solid-state NMR at 23.5 T to characterize both static and dynamic crystallographic disorder: specifically, dynamic disorder occurring in duloxetine hydrochloride (1), static disorder in promethazine hydrochloride (2), and trifluoperazine dihydrochloride (3). In all structures, the presence of crystallographic disorder was confirmed by ¹³ C cross-polarization magic-angle spinning (CPMAS) NMR and supported by GIPAW-DFT calculations, and in the case of 3, ¹ H solid-state NMR provided additional confirmation. Applying ³⁵ Cl solid-state NMR to these compounds, we show that higher magnetic fields are beneficial for resolving the crystallographic disorder in 1 and 3, while broad spectral features were observed in 2 even at higher fields. Combining the data obtained from ¹ H, ¹³ C, and ³⁵ Cl NMR, we show that 3 exhibits a unique case of disorder involving the ⁺ N-H hydrogen positions of the piperazinium ring, driving the chloride anions to occupy three distinct sites.

Preparation and Physiochemical Analysis of Novel Ciprofloxacin / Dicarboxylic Acid Salts

The crystal structures of four novel dicarboxylic acid salts of ciprofloxacin (CFX) with modified physicochemical properties, prepared by mechanochemical synthesis and solvent crystallization, are reported. A series of dicarboxylic acids of increasing molecular weight was chosen, predicted to interact via a carboxylic acid:secondary amine synthon. These were succinic (SA), glutaric (GA), adipic (AA) and pimelic (PA) acids (4, 5, 6, 7 carbon atoms respectively). Characterized by single crystal and powder X-ray diffraction, Fourier-Transform Infrared Spectroscopy, thermogravimetric analysis, differential scanning calorimetry, scanning electron microscopy and aqueous solubility measurements, these salts showed distinct physicochemical properties relative to ciprofloxacin base. Searches of the Cambridge Structural Database (CSD) confirmed CFX-SA, CFX-GA, CFX-AA and CFX-PA to be novel crystal structures. Furthermore, the GA salt has substantially higher solubility than the widely available hydrochloride monohydrate salt (CFX-HCl·H₂O). CFX-SA, CFX-GA and CFX-AA showed minimum inhibitory concentration (MIC) of 0.008 g/L and CFX-PA showed MIC of 0.004 g/L. The prepared CFX salts retained antibacterial activity exhibiting equivalent antimicrobial activity to CFX-HCl·H₂O. These salts have positive implications for increasing the application of CFX beyond conventional oral formulations and highlight mechanochemical activation as suitable production method.

New Solid Forms of Nitrofurantoin and 4-Aminopyridine Salt: Influence of Salt Hydration Level on Crystal Packing and Physicochemical Properties

The crystallization of the poorly soluble drug nitrofurantoin (NFT) with 4-aminopyridine (4AmPy) resulted in three multicomponent solid forms with different hydration levels: anhydrous salt [NFT+4AmPy] (1:1), salt monohydrate [NFT+4AmPy+H₂O] (1:1:1), and salt tetrahydrate [NFT+4AmPy+H₂O] (1:1:4). Each salt was selectively prepared by liquid-assisted grinding in the presence of acetonitrile or ethanol/water mixture at a specific composition. The NFT hydrated salts were characterized using single crystal X-ray diffraction. The [NFT+4AmPy+H₂O] salt (1:1:1) crystallized as an isolated site hydrate, while the [NFT+4AmPy+H₂O] salt (1:1:4) crystallized as a channel hydrate. The dehydration processes of the NFT salt hydrates were investigated using differential scanning calorimetry and thermogravimetric analysis. A powder dissolution experiment was carried out for all NFT multicomponent solid forms in pH 7.4 phosphate buffer solution at 37 °C.

Hydrates of active pharmaceutical ingredients: A 35Cl and 2H solid-state NMR and DFT study

This study uses ³⁵Cl and ²H solid-state NMR (SSNMR) spectroscopy and dispersion-corrected plane-wave density functional theory (DFT) calculations to characterize the molecular-level structures and dynamics of hydrates of active pharmaceutical ingredients (APIs). We use ³⁵Cl SSNMR to measure the EFG tensors of the chloride ions to characterize hydrated forms of hydrochloride salts of APIs, along with two corresponding anhydrous forms. DFT calculations are used to refine the crystal structures of the APIs and determine relationships between the ³⁵Cl EFG tensors and the spatial arrangements of proximate hydrogen bonds, which are particularly influenced by interactions with water molecules. We find that the relationship between ³⁵Cl EFG tensors and local hydrogen bonding geometries is complex, but meaningful structure/property relationships can be garnered through use of DFT calculations. Specifically, for every case in which such a comparison could be made, we find that the hydrate has a smaller magnitude of C_Q than the corresponding anhydrous form, indicating a chloride ion environment with a ground-state electron density of higher spherical symmetry in the former. Finally, variable-temperature ³⁵Cl and ²H SSNMR experiments on a deuterium-exchanged sample of the API cimetidine hydrochloride monohydrate are used to monitor temperature-dependent influences on the spectra that may arise from motional influences on the ³⁵Cl and ²H EFG tensors. From the ²H SSNMR spectra, we determine that the motions of water molecules are characterized by jump-like motions about their C₂ rotational axes that occur on timescales that are unlikely to influence the ³⁵Cl central-transition (+1/2 ↔︎ -1/2) powder patterns (this is confirmed by ³⁵Cl SSNMR). Together, these methods show great promise for the future study of APIs in their bulk and dosage forms, especially variable hydrates in which crystallographic water content varies with external conditions such as humidity.

Anti-malarial activity of HCl salt of SKM13 (SKM13-2HCl)

Malaria is among the most devastating and widespread tropical parasitic diseases in developing countries. To prevent a potential public health emergency, there is an urgent need for new antimalarial drugs, with single-dose cures, broad therapeutic potential, and novel mechanism of action. We synthesized HCl salt of SKM13 (SKM13-2HCl) based on the modification of SKM13 to improve solubility in water. The anti-malarial activity of the synthesized drug was evaluated in both in vitro and in vivo models. The selective index indicated that SKM13-2HCl showed the same effectiveness with SKM13 in Plasmodium falciparum in in-vitro. Even though, in vivo mouse study demonstrated that SKM13 (20 mg/kg) at single dose could not completely inhibit P. berghei growth in blood. The survival rate increased from 33 to 90% at 15 days after infection. However, SKM13-2HCl (20 mg/kg) at a single dose increased the survival rate up to 100% at the same duration. Ultra-High-Performance Liquid Chromatography (UHPLC) showed that solubility in water of SKM13 and SKM13-2HCL was 0.389 mg/mL and 417 mg/mL, respectively. Pharmacokinetics (PK) analysis corresponded to the increased solubility of SKM13-2HCl over SKM13. Haematological parameters [red blood cell (RBC) count, haemoglobin level, and haematocrit level] supported the comparable efficacy of SKM13 and SKM13-2HCl in a 4-day suppression test. One mode of these drugs was found to be activating phosphorylation of eIF2α, hallmark of ER-stress, to kill parasite. Novel salt derivative of SKM13 (SKM13-2HCl) have enhanced anti-malarial activity against P. falciparum with endoplasmic reticulum (ER)-stress and salt form of SKM13 is an excellent direction to develop anti-malarial drug candidate in mice model.

Oral drug delivery strategies for development of poorly water soluble drugs in paediatric patient population

Selecting the appropriate formulation and solubility-enabling technology for poorly water soluble drugs is an essential element in the development of formulations for paediatric patients. Different methodologies and structured strategies are available to select a suitable approach and guide formulation scientists for development of adult formulations. However, there is paucity of available literature for selection of technology and overcoming the challenges in paediatric formulation development. The need for flexible dosing, and the limited knowledge of the safety of many formulation excipients in paediatric subjects, impose significant constraints and in some instances require adaptation of the approaches taken to formulating these drugs for the adult population. Selection of the best drug delivery system for paediatrics requires an efficient, systematic approach that considers a drug's physical and chemical properties and the targeted patient population's requirements. This review is a step towards development of a strategy for the design of solubility enhancing paediatric formulations of highly insoluble drugs. The aim of this review is to provide an overview of different approaches and strategies to consider in order to assist development of paediatric formulation for poorly water-soluble drugs with the provision of examples of some marketed products. In addition, it provides recommendations to overcome the range of challenges posed by these strategies and adaptations of the adult approach/product presentation required to enable paediatric drug development and administration.

Pharmaceutical pollution: Prediction of environmental concentrations from national wholesales data

The regulation and monitoring of pharmaceutical pollution in Europe lag behind that of more prominent groups. However, the repurposing of sales data to predict surface water environmental concentrations is a promising supplement to more commonly used market-based risk assessment and measurement approaches. The Norwegian Institute of Public Health (NIPH) has since the 1980s compiled the Drug Wholesale Statistics database - covering all sales of both human and veterinary pharmaceuticals to retailers, pharmacies, and healthcare providers. To date, most similar works have focused either on a small subset of Active Pharmaceutical Ingredients (APIs) or used only prescription data, often more readily available than wholesale data, but necessarily more limited. By using the NIPH's product wholesale records, with additional information on API concentrations per product from, we have been able to calculate sales weights per year for almost 900 human and veterinary APIs for the period 2016-2019. In this paper, we present our methodology for converting the provided NIPH data from a public health to an ecotoxicological resource. From our derived dataset, we have used an equation to calculate Predicted Environmental Concentration per API for inland surface waters, a key component of environmental risk assessment. We further describe our filtering to remove ecotoxicological-exempt and data deficient APIs. Lastly, we provide a limited comparison between our dataset and similar publicly available datasets for a subset of APIs, as a validation of our approach and a demonstration of the added value of wholesale data. This dataset will provide the best coverage yet of pharmaceutical sales weights for an entire nation. Moreover, our developed routines for processing 2016-2019 data can be expanded to older Norwegian wholesales data (1974-present). Consequently, our work with this dataset can contribute to narrowing the gap between desk-based predictions of exposure from consumption, and empirical but expensive environmental measurement.

Glasdegib Dimaleate: Synthesis, Characterization and Comparison of Its Properties with Monomaleate Analogue

Glasdegib is a recently approved drug for the treatment of acute myeloid leukemia. It is formulated and marketed in monomaleate salt form. In our investigation, we were able to prepare a glasdegib dimaleate form, which could, in theory, exist in double-salt form or as a mixture of salt and co-crystal species. Therefore, the obtained crystals of glasdegib dimaleate were characterized via 15N ssNMR and single-crystal X-ray diffraction, which revealed that the obtained glasdegib dimaleate exists in double-salt form. This is a surprising finding based on the pKa values for glasdegib and maleic acid. Furthermore, we fully characterized the new dimaleate form using thermal analyses (DSC and TGA) and spectroscopy (IR and Raman). Finally, the physicochemical properties, such as solubility and chemical stability, of both forms were determined and compared.

Solubility of Organic Salts in Solvent-Antisolvent Mixtures: A Combined Experimental and Molecular Dynamics Simulations Approach

We combine molecular dynamics simulations with experiments to estimate solubilities of an organic salt in complex growth environments. We predict the solubility by simulations of the growth and dissolution of ions at the crystal surface kink sites at different solution concentrations. Thereby, the solubility is identified as the solution's salt concentration, where the energy of the ion pair dissolved in solution equals the energy of the ion pair crystallized at the kink sites. The simulation methodology is demonstrated for the case of anhydrous sodium acetate crystallized from various solvent-antisolvent mixtures. To validate the predicted solubilities, we have measured the solubilities of sodium acetate in-house, using an experimental setup and measurement protocol that guarantees moisture-free conditions, which is key for a hygroscopic compound like sodium acetate. We observe excellent agreement between the experimental and the computationally evaluated solubilities for sodium acetate in different solvent-antisolvent mixtures. Given the agreement and the rich data the simulations produce, we can use them to complement experimental tasks, which in turn will reduce time and capital in the design of complicated industrial crystallization processes of organic salts.

Molecular Dynamics Simulation of Association Processes in Aqueous Solutions of Maleate Salts of Drug-like Compounds: The Role of Counterion

The study of the formation of microstructures during the interaction of a protonated drug-like compound (API) with a maleic acid monoanion sheds light on the assembly processes in an aqueous solution at the molecular level. Molecular dynamics (MD) simulations coupled with density functional theory (DFT) calculations made it possible to find initial hydrogen bonding motifs during the assembly process, leading to the formation of heterodimers and trimers. The process of trimer formation [protonated API—maleic acid monoanion—protonated API] proceeds through the formation of three intermolecular H-bonds by the CO₂⁻ group of the maleic acid monoanion in both systems. The total enthalpy/energy of these H-bonds is more than 70 kJ/mol. Thus, the maleic acid monoanion plays a key role in the processes of association in aqueous solution, and the interaction of the maleic acid monoanion with API is more preferable than the interaction of API molecules with each other. DFT computations in the discrete continuum approximation reveal the spectral features of heterodimers and trimers, and the ATR-IR spectra confirmed these findings. MD simulations followed by DFT calculations made it possible to describe the initial stages of the formation of pharmaceutical cocrystals in an aqueous solution.

Phosphate moiety in FDA-approved pharmaceutical salts and prodrugs

The salification and prodrug approaches modulate the physicochemical properties and absorption, distribution, metabolism, excretion, and toxicity parameters of drugs and lead candidates. The "phosphate" is one of the key counterions/promoiety used in the salt formation and prodrug synthesis. Salification with phosphoric acid enhances the aqueous solubility and thereby facilitates the administration of a drug by the parenteral route. Phosphate moiety in prodrug synthesis mainly improves permeability by lipophilic substitution. Histamine phosphate is the first phosphate salt, and hydrocortisone phosphate was the first prodrug approved by FDA in 1939 and 1952, respectively. The orange book enlists 12 phosphate salts and 17 phosphate prodrugs. Phosphate prodrugs, namely combretastatin A-4 diphosphate, combretastatin A-4 phosphate, lufotrelvir, TP-1287, pyridoxal phosphate, riboflavin phosphate, and psilocybin are clinical candidates. This review focuses on the FDA-approved phosphate salts and prodrugs from 1939 to 2021. The biopharmaceutical advantage of phosphate salts and prodrugs over the parent molecule is also deliberated.

Crystal Engineering of Pharmaceutical Cocrystals in the Discovery and Development of Improved Drugs

The subject of crystal engineering started in the 1970s with the study of topochemical reactions in the solid state. A broad chemical definition of crystal engineering was published in 1989, and the supramolecular synthon concept was proposed in 1995 followed by heterosynthons and their potential applications for the design of pharmaceutical cocrystals in 2004. This review traces the development of supramolecular synthons as robust and recurring hydrogen bond patterns for the design and construction of supramolecular architectures, notably, pharmaceutical cocrystals beginning in the early 2000s to the present time. The ability of a cocrystal between an active pharmaceutical ingredient (API) and a pharmaceutically acceptable coformer to systematically tune the physicochemical properties of a drug (i.e., solubility, permeability, hydration, color, compaction, tableting, bioavailability) without changing its molecular structure is the hallmark of the pharmaceutical cocrystals platform, as a bridge between drug discovery and pharmaceutical development. With the design of cocrystals via heterosynthons and prototype case studies to improve drug solubility in place (2000-2015), the period between 2015 to the present time has witnessed the launch of several salt-cocrystal drugs with improved efficacy and high bioavailability. This review on the design, synthesis, and applications of pharmaceutical cocrystals to afford improved drug products and drug substances will interest researchers in crystal engineering, supramolecular chemistry, medicinal chemistry, process development, and pharmaceutical and materials sciences. The scale-up of drug cocrystals and salts using continuous manufacturing technologies provides high-value pharmaceuticals with economic and environmental benefits.

Overcoming Bioavailability Challenges of Dasabuvir and Enabling a Triple-Combination Direct-Acting Antiviral HCV Regimen through a Salt of Very Weak Acid for Oral Delivery

Dasabuvir is a non-nucleoside polymerase inhibitor for the treatment of hepatitis C virus (HCV) infection. It is an extremely weak diacidic drug (pK_a = 8.2 and 9.2) and a prolific solvate former. Due to its exceedingly low aqueous solubility (≤0.127 μg/mL at pH 1-6.8, dose number of 1.31 × 10⁴), crystalline dasabuvir free acid exhibited poor oral bioavailability in initial animal pharmacokinetic (PK) assessment. This necessitated the development of enabling formulation for human clinical studies to achieve the required therapeutic in vivo concentration of dasabuvir. While salt formation has been widely used to enhance the solubility and dissolution rate of solids, this approach has rarely been applied to develop oral solid dosage forms for acidic drugs as weak as dasabuvir due to concerns of rapid disproportionation and crystallization of its free acid. In this contribution, we detail our efforts in identifying dasabuvir monosodium monohydrate as a drug substance that is stable, manufacturable, and, most importantly, significantly enhances the dissolution and oral absorption of this poorly soluble drug. The oral delivery of dasabuvir through the salt approach has enabled the commercialization of the triple-combination direct-acting antiviral HCV regimen, Viekira Pak. The methodologies and solutions identified in targeted studies to overcome technical challenges encountered along the way (i.e., incorporation of polymers to inhibit crystallization and disproportionation and species mapping to enable salt manufacturing process, etc.) can be applied to other insoluble compounds.

Redox-Active Magnetic Composites for Anionic Contaminant Removal from Water

Global water security is jeopardized by the presence of anthropogenic contaminants, which can persist resiliently in the environment and adversely affect human health. Surface adsorption of polluting species is an effective technique for water purification. In this work, redox-active magnetic compounds were designed for the targeted removal of inorganic and organic anions in water via polymeric redox-active vinylferrocene (VFc) and pyrrole (Py) moieties. An Fe₃O₄@SiO₂@PPy@P(VFc-co-HEMA) composite was prepared in a four-step process, with the outermost layer possessing heightened hydrophilicity as a result of the optimized incorporation of 2-hydroxyethylmethacrylate (HEMA) monomers into the backbone of the ferrocene macromolecule. The synthesized materials are able to separate carcinogenic hexavalent chromium oxyanions and other charged micropollutants, and exhibit a 2-fold or greater enhancement in adsorption uptake once the redox-active ferrocene groups are oxidized to ferrocenium cations, with capacities of 23, 49, 66, and 95 mg/g VFc for maleic acid, 2-(6-methoxy-2-naphthyl)propionic acid (Naproxen), (2,4-dichlorophenoxy)acetic acid (2,4-D), and (2-dodecylbenzene)sulfonic acid (DBS), respectively, and a > 99% extractability of chromium in the 1 ppm range. The application of redox-active components to a magnetic particulate scaffold improves maneuverability and phase contact, giving rise to new potential aqueous separation process frameworks for water or product purification.

A simple quinoline salt derivative is active in vitro against plasmodium Faciparum asexual blood stages and inhibits the development of cerebral malaria in murine model

Chloroquine (CQ) was the most effective and widely used drug for the prophylaxis and treatment of severe and non-severe malaria. Although its prophylactic use has led to resistance to P. falciparum in all endemic countries, CQ still remains the drug of choice for the treatment of vivax malaria. Otherwise, the speed in which parasite resistance to available antimalarials rises and spreads in endemic regions points to the urgent need for the development of new antimalarials. Quinoline derivatives have been used as a tool in the search for new drugs and were investigated in the present study in an attempt to produce a HIT compound to avoid the cerebral malarial (CM). Seven compounds were synthesized, including three quinoline derivate salts. The cytotoxicity and antiplasmodial activity were assayed in vitro, highlighting compound 3 as a HIT, which also showed interaction with ferriprotoporphyrin IX similarly to CQ. Physicochemical and pharmacokinetic properties of absorption were found to be favorable when analyzed in silico. The in vivo assays, using the experimental cerebral malaria (ECM) model, showed important values of parasite growth inhibition on the 7th day-post infection (Q15 15 mg/kg: 76.9%, Q30 30 mg/kg: 90,1% and Q50 50 mg/kg: 92,9%). Compound 3 also showed significant protection against the development of CM, besides hepatic and renal parameters better than CQ. In conclusion, this quinoline derivative demonstrated promising activity for the treatment of malaria and was able to avoid the development of severe malaria in mice.

Oxalic Acid, a Versatile Coformer for Multicomponent Forms with 9-Ethyladenine

Six new multicomponent solids of 9-ethyladenine and oxalic acid have been detected and characterized. The salt screening has been performed by mechanochemical and solvent crystallization processes. Single crystals of the anhydrous salts in 1:1 and 2:1 nucleobase:coformer molar ratio were obtained by solution crystallization and elucidated by single-crystal X-ray analysis. The supramolecular interactions observed in these solids have been studied using density functional theory (DFT) calculations and characterized by the quantum theory of “atoms in molecules” (QTAIM) and the noncovalent interaction plot (NCIPlot) index methods. The energies of the H-bonding networks observed in the solid state of the anhydrous salts in 1:1 and 2:1 nucleobase:coformer are reported, disclosing the strong nature of the charge assisted NH···O hydrogen bonds and also the relative importance of ancillary C–H··O H-bonds.

Integration of advanced methods and models to study drug absorption and related processes: An UNGAP perspective

This collection of contributions from the European Network on Understanding Gastrointestinal Absorption-related Processes (UNGAP) community assembly aims to provide information on some of the current and newer methods employed to study the behaviour of medicines. It is the product of interactions in the immediate pre-Covid period when UNGAP members were able to meet and set up workshops and to discuss progress across the disciplines. UNGAP activities are divided into work packages that cover special treatment populations, absorption processes in different regions of the gut, the development of advanced formulations and the integration of food and pharmaceutical scientists in the food-drug interface. This involves both new and established technical approaches in which we have attempted to define best practice and highlight areas where further research is needed. Over the last months we have been able to reflect on some of the key innovative approaches which we were tasked with mapping, including theoretical, in silico, in vitro, in vivo and ex vivo, preclinical and clinical approaches. This is the product of some of us in a snapshot of where UNGAP has travelled and what aspects of innovative technologies are important. It is not a comprehensive review of all methods used in research to study drug dissolution and absorption, but provides an ample panorama of current and advanced methods generally and potentially useful in this area. This collection starts from a consideration of advances in a priori approaches: an understanding of the molecular properties of the compound to predict biological characteristics relevant to absorption. The next four sections discuss a major activity in the UNGAP initiative, the pursuit of more representative conditions to study lumenal dissolution of drug formulations developed independently by academic teams. They are important because they illustrate examples of in vitro simulation systems that have begun to provide a useful understanding of formulation behaviour in the upper GI tract for industry. The Leuven team highlights the importance of the physiology of the digestive tract, as they describe the relevance of gastric and intestinal fluids on the behaviour of drugs along the tract. This provides the introduction to microdosing as an early tool to study drug disposition. Microdosing in oncology is starting to use gamma-emitting tracers, which provides a link through SPECT to the next section on nuclear medicine. The last two papers link the modelling approaches used by the pharmaceutical industry, in silico to Pop-PK linking to Darwich and Aarons, who provide discussion on pharmacometric modelling, completing the loop of molecule to man.

Nutraceuticals in Bulk and Dosage Forms: Analysis by 35Cl and 14N Solid-State NMR and DFT Calculations

This study uses ³⁵Cl and ¹⁴N solid-state NMR (SSNMR) spectroscopy and dispersion-corrected plane-wave density functional theory (DFT) calculations for the structural characterization of chloride salts of nutraceuticals in their bulk and dosage forms. For eight nutraceuticals, we measure the ³⁵Cl EFG tensor parameters of the chloride ions and use plane-wave DFT calculations to elucidate relationships between NMR parameters and molecular-level structure, which provide rapid NMR crystallographic assessments of structural features. We employ both ³⁵Cl direct excitation and ¹H→³⁵Cl cross-polarization methods to characterize a dosage form containing α-d-glucosamine HCl, observe possible impurity and/or adulterant phases, and quantify the weight percent of the active ingredient. To complement this, we also investigate ¹⁴N SSNMR spectroscopy and DFT calculations to characterize nitrogen atoms in the nutraceuticals. This includes a discussion of targeted acquisition experimental protocols (i.e., acquiring a select region of the overall pattern that features key discontinuities) that allow ultrawideline spectra to be acquired rapidly, even for unreceptive samples (i.e., those with long values of T₁(¹⁴N), short values of T₂^eff(¹⁴N), or very broad patterns). It is hoped that these experimental and computational protocols will be useful for the characterization of various solid forms of nutraceuticals (i.e., salts, polymorphs, hydrates, solvates, cocrystals, amorphous solid dispersions, etc.), help detect impurity and counterfeit solid phases in dosage forms, and serve as a foundation for future NMR crystallographic studies of nutraceutical solid forms, including studies using ab initio crystal structure prediction algorithms.

35 Cl-1 H Heteronuclear correlation magic-angle spinning nuclear magnetic resonance experiments for probing pharmaceutical salts

Heteronuclear multiple-quantum coherence (HMQC) pulse sequences for establishing heteronuclear correlation in solid-state nuclear magnetic resonance (NMR) between ³⁵ Cl and ¹ H nuclei in chloride salts under fast (60 kHz) magic-angle spinning (MAS) and at high magnetic field (a ¹ H Larmor frequency of 850 MHz) are investigated. Specifically, recoupling of the ³⁵ Cl-¹ H dipolar interaction using rotary resonance recoupling with phase inversion every rotor period or the symmetry-based SR4² ₁ pulse sequences are compared. In our implementation of the population transfer (PT) dipolar (D) HMQC experiment, the satellite transitions of the ³⁵ Cl nuclei are saturated with an off-resonance WURST sweep, at a low nutation frequency, over the second spinning sideband, whereby the WURST pulse must be of the same duration as the recoupling time. Numerical simulations of the ³⁵ Cl-¹ H MAS D-HMQC experiment performed separately for each crystallite orientation in a powder provide insight into the orientation dependence of changes in the second-order quadrupolar-broadened ³⁵ Cl MAS NMR lineshape under the application of dipolar recoupling. Two-dimensional ³⁵ Cl-¹ H PT-D-HMQC MAS NMR spectra are presented for the amino acids glycine·HCl and l-tyrosine·HCl and the pharmaceuticals cimetidine·HCl, amitriptyline·HCl and lidocaine·HCl·H₂ O. Experimentally observed ³⁵ Cl lineshapes are compared with those simulated for ³⁵ Cl chemical shift and quadrupolar parameters as calculated using the gauge-including projector-augmented wave (GIPAW) method: the calculated quadrupolar product (P_Q ) values exceed those measured experimentally by a factor of between 1.3 and 1.9.

Carboxylic Acid Counterions in FDA-Approved Pharmaceutical Salts

Salification is one of the powerful and widely employed approaches to improve the biopharmaceutical properties of drugs. The FDA's eighty-year trajectory of new drug approvals depicts around one-third of the drugs clinically used as their pharmaceutical salts. Among various cationic and anionic counterions used in FDA-approved pharmaceutical salts, the carboxylic acids have significantly contributed. A total of 94 pharmaceutical salts discovered during 1943-2020 comprises carboxylic acids as counterions with a major contribution of acetate, maleate, tartrate, fumarate, and succinate. Hydrocodone tartrate is the first FDA-approved carboxylate salt approved in 1943. Overall, the analysis shows that fifteen carboxylic acid counterions are present in FDA-approved pharmaceutical salts with a major share of acetate (18 drugs). This review provides an account of FDA-approved carboxylate salts from 1939 to 2020. The decade-wise analysis indicates that 1991-2000 contributed a maximum number of carboxylate salts (24) and least (3) in 1939-1950. The technical advantage of carboxylate salts over free-base or other counterions is also discussed. Graphical Abstract.

Characterisation and fundamental insight into the formation of new solid state, multicomponent systems of propranolol

The physiochemical properties of acidic or basic active pharmaceutical ingredients (APIs) can be optimised by forming salts with different counterions. The aim of this work was to synthesise a novel salt of propranolol (PRO) using sebacic acid (SEBA) as the counterion and to gain mechanistic understanding of not only the salt formation, but also its eutectic phase formation with SEBA. Thermal analysis showed a solid-state reaction occurring between PRO and SEBA leading to the formation of dipropranolol sebacate (DPS) melting at app. 170 °C and the eutectic composed of DPS and SEBA melting at app. 103 °C, comprising 0.33 mol fraction of PRO as determined by the Tammann plot. X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR) confirmed the identity of the new multicomponent phases of PRO. DPS can be conveniently obtained by heat-induced crystallisation, grinding and conventional solvent crystallisation. Detailed analysis by FTIR revealed H-bond interactions between DPS and SEBA at the inter-phase in the eutectic. Bravais, Friedel, Donnay and Harker crystal morphology coupled with full interaction maps analysis allowed to understand further the nature of interactions which led to formation of the eutectic phase. This work contributes to furthering research on multicomponent pharmaceutical systems to harness their full potential.

Asymmetric copper-catalyzed propargylic amination with amine hydrochloride salts

The highly enantioselective copper-catalyzed propargylic amination of propargylic esters with amine hydrochloride salts has been realized for the first time using copper salts with chiral N,N,P-ligands. This method features a broad substrate scope and wide functional group tolerance, generating propargylic amines in good to excellent yields with high enantioselectivities (up to 99% ee). The utility of the approach was demonstrated by late-stage functionalization of marketed pharmaceuticals.

Formulation of ionic liquid APIs via spray drying processes to enable conversion into single and two-phase solid forms

Ionic liquid (IL) forms of drugs are increasingly being explored to address problems presented by poorly water-soluble drugs and solid-state stability. However, before ILs of active pharmaceutical ingredients (APIs) can be routinely incorporated into oral solid dosage forms (OSDs), challenges surrounding their ease of handling and manufacture must be addressed. To this end a framework for transforming API-ILs into solid forms at high loadings based on spray encapsulation using an immiscible polymer has recently been demonstrated. The current work demonstrates that this framework can be applied to a broad range of newly synthesized low glass transition temperature (T_g) API-ILs. Furthermore, the work explores a second novel approach to solidification of API-ILs based on polymer-API-IL miscibility that, to the best of our knowledge, has not been previously demonstrated. Modulated differential scanning calorimetry (mDSC) and attenuated total reflectance Fourier transform infrared spectroscopy showed that it was possible to produce spray dried solid materials, at acceptable loadings and yields for OSD applications in the form of both two-phase phase encapsulated systems and single phase amorphous solid dispersions (ASDs). This was achieved by the appropriate selection of an API-IL insoluble polymer (ethyl cellulose) for phase separated systems, or a miscible polymer with an exceptionally high T_g (the polysaccharide, maltodextrin) for the ASDs. Both approaches successfully overcame the T_g suppression associated with room temperature ILs. This work represents the first step to understanding the fundamental critical physical attributes of these systems to facilitate a more mechanistic methodology for their design.