Microemulsion and microemulsion based gel of Zaleplon for transdermal delivery: Preparation, optimization, and evaluation
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In this work solubility and permeability of BCS II drug Zaleplon was increased by loading it into microemulsion which in turns enhance bioavailability. Carbomer 940 was incorporated to fabricate microemulsion based gel (MEBG) which sustained transdermal delivery. Solubility studies screened Castor oil, Tween 80 (surfactant), and Polyethylene glycol 200 (co-surfactant) for preparing Microemulsion. Pseudoternary phase diagrams were used to find out microemulsion region. Box Behnken Design (BBD) was used to optimize microemulsions which were initially investigation for physicochemical characteristics. Oil, Smix and water; Q24, Flux and lag time were selected as independent and dependent variables, respectively. Franz diffusion cell was used to compare in vitro permeability of optimized microemulsions across Rabbit skin. Variables were related using mathematical equations and response surface plots. MEBG was compared for stability, in-vitro drug permeation, skin irritation and anti-inflammatory studies using control gel and in-vivo bioavailability study with oral tablet. Microemulsions showed physiological pH of 5.36 - 5.98, conductivity of 140 - 186 μS/cm, isotropic value of 1.340 - 1.417, average droplet size of 63 - 89 nm, homogeneity, droplet size of 53 - 161 cP and spherical shape. Predicted values of optimized microemulsions were in reasonable agreement with experimental values. Formulations were stable and non-irritating to the skin. Significant difference was investigated when comparing percent inhibition of edema of MEBG (85%) and control gel (42%) with standard. MEBG behavior differed significantly from oral tablet formulation in vivo bioavailability. Such BBD based estimation will reduce time and cost in drug designing, delivery and targeting.
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