Solid-state properties of Nifurtimox. Preparation, analytical characterization, and stability of an amorphous phase

The Amorphous State of the Antiepileptic Clobazam: Preparation and Characterization

The aim of this study was to prepare and characterize amorphous clobazam (CLOB) and investigate its devitrification under various stressors (temperature/humidity, compaction and mechanical/thermal stresses). Amorphous CLOB was prepared by melt-quenching in liquid nitrogen. The quench-cooled sample (CLOB-q) was characterized via polarized light and hot-stage microscopies (PLM and HSM), X-ray powder diffraction (XRPD), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), conventional and modulated DSC (DSC-c and MDSC®), thermogravimetry (TG), dynamic mechanical analysis (DMA), X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Stability of CLOB-q toward temperature/humidity, compaction, and combined mechanical and thermal stress were also evaluated. CLOB-q was a truly amorphous form, as revealed by DSC-c, MDSC® and DMA. Its calorimetric glass transition temperature (Tg) was 67.0 °C (20 °C/min) and the ratio Tm/Tg was 1.34, indicating a fragile glass. The water contact angle of CLOB-q (121.8° ± 1.7°) was lower than that of crystalline CLOB (CLOB-c, 131.3° ± 3.6°), likely due to its higher concentration of surface CL, as determined by XPS. Storage of CLOB-q at - 20 °C/0% RH, 25 °C/0% RH and 40 °C/75% RH resulted in its complete devitrification to CLOB-c within 60 days, 4 days, and 42 h respectively. Subjection of CLOB-q to compaction (19.6 kN) and combined mechanical-thermal stresses also resulted in complete crystallization to CLOB-c. In conclusion, amorphous CLOB was successfully prepared in the laboratory for the first time and thoroughly characterized. It easily devitrified to CLOB-c by effect of different stressors, and thus it could not have advantages over CLOB-c in terms of physical stability.

Development and Characterization of Innovative Nifurtimox Formulations as Therapeutic Alternative for Chagas Disease

Chagas disease, caused by Trypanosoma cruzi, remains a neglected tropical disease with limited and often suboptimal chemotherapeutic treatment options. The WHO recommends nifurtimox (NFX) for treating Chagas disease, which, although it is effective in the early stages of infection, has variable efficacy in the chronic phase and induces adverse effects that frequently compromise the continuity of the treatment. This study focused on the development and characterization of innovative lipid-based self-emulsifying drug delivery systems (SEDDSs) and poly(ε-caprolactone) implants containing NFX. The SEDDS formulations modified the NFX release extent and rate. The implant characterization included thermal analysis, X-ray diffraction, thermo-optical analysis, and scanning electron microscopy, confirming the low interaction between NFX and the polymer. In vitro assays demonstrated the enhanced anti-T. cruzi activity of the NFX-SEDDS, with minimal cytotoxicity in mammalian cells. In vivo studies using T. cruzi-infected mice revealed that both formulations effectively suppressed parasitemia, achieving cure rates comparable to those of the standard oral NFX treatment. Additionally, the implants showed improved tolerability and sustained efficacy, delivering a prolonged effect equivalent to 40 oral doses. These findings highlight the potential of these innovative NFX formulations as promising alternatives for treating Chagas disease, particularly in the chronic phase, offering improved adherence and comparable efficacy to the existing therapies.

3D-Printed Tablets of Nifurtimox: In Vitro and In Vivo Anti-Trypanosoma cruzi Studies

Background/Objectives: Chagas disease is a neglected tropical disease caused by infection with the parasite Trypanosoma cruzi. Benznidazole and nifurtimox are the only approved drugs for treating this condition, but their low aqueous solubility may lead to erratic bioavailability. This work aimed for the first time to formulate tablets of nifurtimox by hot melt extrusion coupled with 3D printing as a strategy to increase drug dissolution and the production of tablets with dosage on demand. Methods: Different pharmaceutical-grade polymers were evaluated through film casting, and those with promising nifurtimox amorphization capacity were further used to prepare filaments by hot melt extrusion. The printability of the obtained filaments was tested, and the polyvinyl alcohol filament was further used for printing tablets containing 120 and 60 mg of nifurtimox. Results: Three-dimensional tablets showed a remarkable improvement in the drug dissolution rate compared to commercial tablets and a dissolution efficiency 2.8 times higher. In vivo studies were carried out on Swiss mice. Parasitemia curves of nifurtimox printed tablets were significantly superior to the pure drug. Moreover, NFX 3D tablets provided a similar Trypanosoma cruzi reduction in plasmatic concentration to benznidazole, the gold-standard drug for acute-phase treatment of the Chagas disease. Conclusions: The findings of this work showed that hot melt extrusion coupled with 3D printing is a promising alternative for increasing nifurtimox biopharmaceutical properties and an attractive approach for personalized medicine.

Co-Amorphization, Dissolution, and Stability of Quench-Cooled Drug-Drug Coamorphous Supersaturating Delivery Systems with RT-Unstable Amorphous Components

Background: Supersaturating drug delivery systems (SDDSs) have gained significant attention as a promising strategy to enhance the solubility and bioabsorption of Biopharmaceutics Classification System (BCS) II drugs. To overcome challenges associated with polymer-based amorphous SDDS (aSDDS), coamorphous (CAM) systems have emerged as a viable alternative. Among them, "drug-drug" CAM (ddCAM) systems show considerable potential for combination drug therapy. However, many drugs in their pure amorphous forms are unstable at room temperature (RT), complicating their formation and long-term stability profiles. Consequently, limited knowledge exists regarding the behavior of ddCAMs containing RT-unstable components formed via quench cooling. Methods: In this study, we used naproxen (NAP), a RT-unstable amorphous drug, in combination with felodipine (FEL) or nitrendipine (NTP), two RT-stable amorphous drugs, to create "FEL-NAP" and "NTP-NAP" ddCAM pairs via quench cooling. Our work used a series of methods to perform a detailed analysis on the co-amorphization, dissolution, solubility, and stability profiles of ddCAMs containing RT-unstable drugs, contributing to advancements in co-amorphization techniques for generating SDDS. Results: This study revealed that the co-amorphization and stability profiles of ddCAMs containing RT-unstable components produced via a quench-cooling method were closely related to drug-drug pairing types and ratios. Both quench-cooling and incorporation into coamorphous systems improved the dissolution, solubility, and physical stability of individual APIs. Conclusions: Our findings provide deeper insight into the co-amorphization, dissolution, and stability characteristics of specific drug-drug coamorphous systems FEL-NAP and NTP-NAP, offering valuable guidance for developing new ddCAM coamorphous formulations containing some RT-unstable drugs.

Conformational analysis and spectroscopic properties of antichagasic nifurtimox

Considering the health relevance of Chagas' disease, recent research efforts have focused on developing more efficient drug delivery systems containing nifurtimox (NFX). This paper comprehensively investigates NFX through conformational analysis and spectroscopic characterization. Using a conformer-rotamer ensemble sampling tool (CREST-xtb), five distinct conformers of NFX were sampled within a 3.0 kcal mol-1 relative energy window. Subsequently, such structures were used as inputs for geometry optimization by density functional theory (DFT) at B3LYP-def2-TZVP level of theory. Notably, harmonic vibrational frequencies were calculated to establish an in-depth comparison with experimental results and existing literature for the NFX or similar molecules and functional groups, thereby achieving a widely reasoned assignment of the mid-infrared band absorptions for the first time. Moreover, UV-VIS spectra of NFX were obtained in several solvents, enabling the determination of the molar absorptivity coefficient for the two electronic transitions observed for NFX. Among the aprotic solvents, a bathochromic effect was observed in the function of the dielectric constants. Furthermore, a hypochromic effect was observed when the drug was dissolved in protic solvents. These findings offer crucial support for new drug delivery systems containing NFX while demonstrating the potential of spectrophotometric studies in establishing quality control assays for NFX drug products.

Preparation and characterization of new salts of tioconazole. Comparison of their dissolution performance

Tioconazole is an effective antifungal agent with very low solubility in aqueous media, which limits its bioavailability and efficacy. Aiming to overcome the drug limitations by improving the solubility of this active pharmaceutical ingredient, solution precipitation techniques were employed to prepare four new crystalline salts, namely the mesylate, tosylate, maleate (1:1), and fumarate (1:1) hemihydrate. The thermal stabilities, dissolution properties, and structural characteristics of the solids were determined, and the study was extended to compare their properties with the already-known oxalate salt. The structural characterization of the new phases was carried out using a multi-method approach, which included thermal (differential scanning calorimetry and thermogravimetry), diffractometric (powder X-ray diffraction), and spectroscopic (near-infrared and mid-infrared) methodologies. The determination of the melting point of the salts confirmed the findings made by thermal methods. Functional characteristics of the salts, involving their intrinsic dissolution rates were also determined. It was found that the salts exhibited improved thermal stability and that the nature of the counterion modulated their dissolution characteristics. The salts displayed better intrinsic dissolution rates than the free base, to the point of being "highly soluble" according to the Biopharmaceutical Classification System. At pH 4.3, the sulfonic acid derivatives exhibited better dissolution rates than their carboxylic acid-derived counterparts, greatly improved regarding bare tioconazole. The results suggest that the salts have great potential to be used as replacements for the free base; in principle, careful salt selection may help to fulfill each solubility need for the different scenarios where the drug may be used.

Selected Aspects of the Analytical and Pharmaceutical Profiles of Nifurtimox

Nifurtimox is a nitroheterocyclic drug employed for treatment of trypanosomiases (Chagas disease and West African sleeping sickness); its use for certain cancers has also been assessed. Despite having been in the market for over 50 years, knowledge of nifurtimox is still fragmentary and incomplete. Relevant aspects of the chemistry and biology of nifurtimox are reviewed to summarize the current knowledge of this drug. These comprise its chemical synthesis and the preparation of some analogues, as well as its chemical degradation. Selected physical data and physicochemical properties are also listed, along with different approaches toward the analytical characterization of the drug, including electrochemical (polarography, cyclic voltammetry), spectroscopic (ultraviolet-visible, nuclear magnetic resonance, electron spin resonance), and single crystal X-ray diffractometry. The array of polarographic, ultraviolet-visible spectroscopic, and chromatographic methods available for the analytical determination of nifurtimox (in bulk drug, pharmaceutical formulations, and biological samples), are also presented and discussed, along with chiral chromatographic and electrophoretic alternatives for the separation of the enantiomers of the drug. Aspects of the drug likeliness of nifurtimox, its classification in the Biopharmaceutical Classification System, and available pharmaceutical formulations are detailed, whereas pharmacological, chemical, and biological aspects of its metabolism and disposition are discussed.