Oral nanoemulsions of candesartan cilexetil: formulation, characterization and in vitro drug release studies

Nanoemulsion is considered to be a new and exciting field of research that seeks to exploit the attractive properties of components to improve oral delivery of drugs like candesartan cilexetil used in the management of chronic diseases. Candesartan cilexetil is a lipophilic acidic drug with a half-life of about (5–10) hour and absolute bioavailability of (14–40%). For this reason, the study target was to formulate and characterize candesartan cilexetil nanoemulsions that could improve solubility, dissolution and stability of the lipophilic drug candesartan cilexetil. The solubility of candesartan cilexetil was checked in various vehicles in order to choose the best solubilizing components for building up an efficient nanoemulsion based on regulating hydrophilic/lipophilic balance (HLB) value above 10, and then pseudo-ternary phase diagram was used as a useful tool to evaluate the nanoemulsion domain. The nanoemulsion formulations were prepared using various concentrations of cinnamon oil, tween 80 with poloxamer mixture and transcutol HP as oil, surfactant mixture and co-surfactant respectively by aqueous titration method at surfactant/co-surfactant ratios of 3:1 and 4:1 and varying the type of poloxamer in each ratio. The prepared nanoemulsions were tested for nanodispersion stability studies, droplet size distribution, polydispersity index, zeta potential, viscosity, filter paper spreadability, dye miscibility, electroconductivity, pH, percent transmittance, surface tension, refractive index, morphology and drug dissolution. It was found that release rate and extent for all prepared nanoformulations were significantly higher (p < 0.05) than marketed tablet formulation as well as plain drug powder.