Effect of Surfactant Chain Length on Emulsification Dynamics of Self Emulsifying Formulation of Poorly Soluble Drug

In this work, the aim was to study the effect of the chain length of surfactant on the self emulsifying system of a poorly soluble drug, aceclofenac. The selection of almond oil as a lipid vehicle was done on the basis of solubility and compatibility of the vehicle with the drug.

The effect of varying chain length of different surfactants of Tween series, namely Tween 20, Tween 40, Tween 60 and Tween 80, was evaluated on self emulsifying efficiency by constructing the pseudoternary diagrams. PEG-400 was used as a co-surfactant in a definite ratio with all the surfactants to minimize their concentration. The best self emulsifying ability was exhibited by Tween 80: PEG-400 combination followed by Tween 60: PEG-400, Tween 40: PEG-400, Tween 20: PEG-400. This observation indicates that as the chain length of Tweens increases, their ability to form a good microemulsion increases if the same co-surfactant is used.

However, it has also been found that the presence of unsaturated bond in Tween 80 provides it an elasticity which supports good intermixing of oil and water, leading to formation of a fine microemulsion. Six different formulations were prepared using a combination of almond oil, Tween 80, PEG-400 and the drug aceclofenac.

The formulations were subjected to various evaluation parameters, such as dispersibility, transmittance, pH, globule size, polydispersibility, zeta potential, viscosity, refractive index and in vitro dissolution. The best formulation was found to have globule size of less than 100 nm and zeta potential of -3.35 ± 0.60 mV, indicating the formation of a microemulsion of aceclofenac with good stability.