Application of advanced thermal analysis for characterization of crystalline and amorphous phases of carvedilol

The Impact of Various Poly(vinylpyrrolidone) Polymers on the Crystallization Process of Metronidazole

In this paper, we propose one-step synthetic strategies for obtaining well-defined linear and star-shaped polyvinylpyrrolidone (linPVP and starPVP). The produced macromolecules and a commercial PVP K30 with linear topology were investigated as potential matrices for suppressing metronidazole (MTZ) crystallization. Interestingly, during the formation of binary mixtures (BMs) containing different polymers and MTZ, we found that linear PVPs exhibit maximum miscibility with the drug at a 50:50 weight ratio (w/w), while the star-shaped polymer mixes with MTZ even at a 30:70 w/w. To explain these observations, comprehensive studies of MTZ-PVP formulations with various contents of both components were performed using Fourier-transform infrared spectroscopy, differential scanning calorimetry, and X-ray diffraction. The obtained results clearly showed that the polymer's topology plays a significant role in the type of interactions occurring between the matrix and MTZ. Additionally, we established that for MTZ-PVP 50:50 and 75:25 w/w BMs, linear polymers have the most substantial impact on inhibiting the crystallization of API. The star-shaped macromolecule turned out to be the least effective in stabilizing amorphous MTZ at these polymer concentrations. Nevertheless, long-term structural investigations of the MTZ-starPVP 30:70 w/w system (which is not achievable for linear PVPs) demonstrated its complete amorphousness for over one month.

Tip loaded cyclodextrin-carvedilol complexes microarray patches

Carvedilol, a β-blocker prescribed for chronic heart failure, suffers from poor bioavailability and rapid first pass metabolism when administered orally. Herein, we present the development of tip microarray patches (MAPs) composed of ternary cyclodextrin (CD) complexes of carvedilol for transdermal delivery. The ternary complex with hydroxypropyl γ-cyclodextrin (HPγCD) and poly(vinyl pyrrolidone) (PVP) reduced the crystallinity of carvedilol, as evidenced by DSC, XRD, NMR, and SEM analysis. MAPs were fabricated using a two-step process with the ternary complex as the needle layer. The resulting MAPs were capable of breaching ex vivo neonatal porcine skin to a depth ≈600 μm with minimal impact to needle height. Upon insertion, the needle dissolved within 2 h, leading to the transdermal delivery of carvedilol. The MAPs displayed minimal toxicity and acceptable biocompatibility in cell assays. In rats, MAPs achieved significantly higher AUC levels of carvedilol than oral administration, with a delayed Tmax and sustained plasma levels over several days. These findings suggest that the carvedilol-loaded dissolving MAPs have the potential to revolutionise the treatment of chronic heart failure.

Ultrasound-assisted continuous crystallization of metastable polymorphic pharmaceutical in a slug-flow tubular crystallizer

Metastable polymorphic pharmaceuticals have garnered significant attention in recent years due to their enhanced physicochemical properties, including solubility, bioavailability, and intellectual property considerations. However, the manufacturing of metastable form pharmaceuticals remains a formidable challenge. The stable preparation of metastable carvedilol (CVD) form Ⅱ crystals during CVD production is elusive, leading to substantial inconsistencies in product quality and regulatory compliance. In this study, we successfully prepared metastable CVD Form Ⅱ crystals using a continuous tubular crystallizer. Our findings demonstrate that the tubular crystallizer exhibits high efficiency and robustness for generating metastable crystal Form Ⅱ. We optimized the crystallization process by incorporating air bubble segments and employing ultrasonic irradiation strategies to overcome blockages and wall sticking issues encountered during operation. Ultimately, we developed an ultrasound-assisted continuous slug-flow tubular crystallization method and evaluated its performance. The results indicate that the CVD crystals produced through this process are resilient, sustainable, and uninterrupted products with promising potential for producing metastable polymorphic pharmaceuticals while effectively addressing encrustation problems associated with continuous tubular crystallization.

Heat capacity of cytisine - the drug for smoking cessation

The characterization of cytisine (CYT) and its blends with poly(lactic acid) was performed using thermal analysis, elemental analysis, infrared spectroscopy, and powder X-ray diffractometry. The heat capacities, total enthalpy, and phase transitions of CYT were established from 1.8 to 448.15 K (-271.35 - 175 °C) by advanced thermal analysis. Data were obtained using a Quantum Design Physical Property Measurement System (PPMS) and a differential scanning calorimetry (DSC). The low-temperature heat capacity of the crystalline CYT in the range of 1.8 to 300 K (-271.35 - 26.86 °C) was measured by PPMS and fitted to a theoretical model in the low temperature region below 11 K (-262.15 °C), to orthogonal polynomials in the middle range 5 K < T < 60 K (-268.15 °C < t < -213.15 °C) and to the Debye and Einstein functions in the high range of temperature above 60 K (-213.15 °C). The liquid heat capacity was calculated based on the approximated linear regression data above the molten state of the experimental heat capacity of CYT obtained by the standard DSC measurements, and it was expressed as C_p^liquid = 0.0838T + 346.78 J·K^-1·mol^-1. The calculated heat capacity in the solid state was extended to a higher temperature and was used, together with liquid heat capacity, as the reference baselines for the advanced thermal analysis of CYT. The PPMS and DSC/TMDSC methods are complementary methods for thermal analysis of cytisine. The PPMS method allowed determination of the equilibrium heat capacity in the solid state, which together with the equilibrium heat capacity in the liquid state allowed to analyze of the experimental apparent heat capacity of cytisine obtained based on DSC. The melting temperature and the total heat of fusion of crystalline material were established as 431.8 K (158.65 °C) and 26.5 kJ·mol^-1, respectively. The solid and liquid heat capacities and transition parameters of CYT were applied to calculate total enthalpies for fully amorphous and crystalline states. Analyses of DSC and X-ray confirmed the presence of the solid-solid transition linking with not so far described a polymorphism phenomenon of CYT. Based on the thermogravimetric analysis the temperature of degradation of CYT was determined as 460.5 K (187.35 °C). Also, a preliminary thermal analysis of the blends of cytisine and poly(lactic acid) as a new candidate for drug delivery system was presented.