Felodipine-loaded Spanlastics: superior nanocarriers for transdermal delivery

Abstract Felodipine is a dihydropyridine calcium channel blocker commonly used for the treatment of mild to moderate hypertension and angina pectoris. Felodipine undergoes extensive hepatic first pass metabolism resulting in low oral bioavailability of 15 %. The aim of this study is to develop a formulation of nanovesicular Spanlastics to improve the transdermal delivery of felodipine and solve the problem of low bioavailability. The felodipine-loaded Spanlastics were prepared using the ethanol injection method with Span 60 as surfactant and Tween 80, which provides elasticity to the vesicles, according to the 23 factorial design using Design Expert® Software version 13. The solution that had the highest desirability was optimized. The final five runs were incorporated into a gel base and evaluated for in vitro drug release, spreadability and viscosity. Stability studies were conducted over a period of 3 months. The formulated Spanlastics had a particle size in the range of (132–155) nm and an entrapment efficiency in the range of (80–94) %. The final five runs were found to have optimum characteristics. Differential scanning calorimetry, X-ray diffraction studies and Fourier transform infrared studies were performed to ensure the encapsulation of the drug in the nanovesicles. The developed hydrogel showed in vitro drug release in the range of (80–94) % and the formulation was found to be stable after a period of 3 months. The optimized formula comprised of Span 60 and Tween 80 in ratio of 8:2. Overall, the results confirmed that Spanlastics loaded with felodipine proved to be superior nanocarriers for transdermal delivery of felodipine.