Comparison of the physical and thermodynamic stability of amorphous azelnidipine and its coamorphous phase with piperazine

Abstract

A major challenge in drug development is that the majority of drugs are water insoluble, and a powerful method to conquer this obstacle is to transfer a crystalline drug into its amorphous phase (AP) or coamorphous phase (CAP) with a coformer. In the present study, the physical and chemical stabilities of an AP and a CAP based on the dihydropyridine calcium ion antagonist azelnidipine (AZE) were investigated using thermal analysis and a solution chemistry method. The identification of two APs (named a-AP and b-AP, from crystalline a-AZE and b-AZE, respectively) and one AZE-piperazine CAP was attempted using powder X-ray diffraction, temperature modulated differential scanning calorimetry and Fourier-transform infrared spectroscopy. The transition thermodynamics from the two APs and the CAP to stable crystalline b-AZE (b-Cry) were investigated using a solubility method. The solubility of the two APs, the CAP and b-Cry in 0.01 M HCl medium at 298, 304, 310, 316 and 322 K was investigated; the values obtained were used to calculate the thermodynamic parameters of the transition reaction.The transition temperatures of a-AP, b-AP and the CAP to form b-Cry in 0.01 M HCl were 237.7, 400.3, and 231.4 K, respectively. The glass transition temperature (T g ) values of a-AP, b-AP and the CAP were 365.5, 358.9 and 347.6 K, respectively, indicating a high physical stability for a-AP. However, b-AP proved to be the most thermodynamically stable form at room temperature compared with a-AP and CAP in the 0.01 M HCl medium. As evidenced by those observations, no general relationship occurred between the solid physical stability and the solution chemical stability for AP and CAP. The kinetics of the solidstate decomposition, studied using DSC analysis, showed that the activation energies for decomposition of a-AP, b-AP and CAP at high temperatures were 133.0, 114.2 and 131.6 kJ mol À1 , respectively.

Effect of Crystallinity on the Properties of Polycaprolactone Nanoparticles Containing the Dual FLAP/mPEGS-1 Inhibitor BRP-187

“…Furthermore, it was observed that the residual amount of PVA in the drug-loaded NPs was higher compared to the empty NPs for all PCL copolymers ( Table 1 and SI, Table S3 ). As mentioned before, such differences are typically a result of strong drug–polymer interactions [ 31 ], and in this case, the interactions of the BRP-187 with the chains of PVA polymer. Moreover, the residual PVA content was noticeably higher for less crystalline copolymers with a higher δCL fraction and highest for the particles consisting of the PδCL homopolymer ( Figure 2 B).…”