Multiple emulsions containing rifampicin.

A stable multiple emulsion containing rifampicin in the internal aqueous phase was prepared by the incorporation of additives in both aqueous and oily phases. The formulation and process variables were optimized for primary and secondary emulsification. Drug release studies were performed on selected multiple emulsions to observe the effect of dilution. The release data were fitted to the Higuchi equation for slab and spherical geometry and effective diffusion coefficients were calculated. Stability studies for three months revealed good stability of the multiple emulsions with respect to creaming, phase separation, viscosity change, drug leakage, change in droplet size upon storage and exposure to osmotic and shear stress. The in vivo studies performed with stable multiple emulsions administered orally in human volunteers showed prolonged plasma drug levels. The multiple emulsions were found suitable for an improved tuberculosis therapy.