Soluplus-Stabilized Nimodipine-Entrapped Spanlastic Formulations Prepared with Edge Activator (Tween20): Comparative Physicochemical Evaluation.

Background: Nimodipine (ND) is a vasodilator drug that is used for acute subarachnoid hemorrhage. It has a predominant hydrophobic property, causing low solubility and low bioavailability. Spanlastics are elastic nanovesicular systems based on non-ionic surfactants and edge activators as major components. The goal of this work is to formulate ND as spanlastic nanovesicles to improve the drug's bioavailability.

Methods: Spanlastic formulations containing ND were prepared by using the ethanol injection method. The composition of the ND formulation includes Span60 as a nonionic surfactant and Tween 20 as edge activators in different ratios. Stabilizers like Soluplus are used in some formulations and then compared with other formulations without that stabilizer. The evaluation study involved Vesicle Size (VS), PolyDispersity Index (PDI), and Entrapment Efficiency (%EE). Then, the optimized formula was subjected to an in vitro release study and zeta potential, additionally comparing the optimized formula with the formula without soluplus in the same concentration in Scanning Electron Microscopy (SEM), solubility study, Deformability Index (DI), and stability study.

Results: The results indicated a significant shift in some evaluation criteria and a non-significant change in other characterizations, including the difference in polymer ratio, sonication time, and the existence of a stabilizer. The best formula, F27, was found to have VS, PDI, %EE, and zeta potential of 125.7±0.29 nm, 0.4744±0.002, and 85.43±0.17% and -20.01 ± 0.89 mV, respectively. The photomicrographs of the prepared spanlastic revealed a more uniform and spherical spanlastic, indicating a greater capacity for continuous release. With the addition of Soluplus, the formula became more stable in one month and had a higher deformability index.

Discussion: A significant shift was observed in both VS and PDI. As the stabilizer concentration increases, VS and PDI will decrease. The non-significant shift was noted in the %EE with the presence of a stabilizer. Soluplus has the ability to spontaneously self-assemble into spherical particles. Additionally, PEG 6000, as a component of Soluplus's structure, has a tendency to form strong or tightly bound bilayers and prevent aggregation and formulation of large vesicles.

Conclusion: This study explains the accessibility of the formulation of ND as spanlastic nanovesicles by using the ethanol injection method. This spanlastic formulation contains non-ionic surfactants and edge activators (Span 40 and Tween 20) in varying ratios. To get a stable formula, Soluplus is added to prevent the development of crystals and agglomeration.