RESUMEN
Simple and multiple emulsions have a wide range of pharmaceutical applications. Therefore, the stabilization of such emulsions is a challenge to ensure a stable formulation along the period of storage, usage and at the same time to conserve the efficacy of the incorporated medicament. Simple o/w and multiple w/o/w emulsions were prepared using castor and paraffin oils as oil phases and stabilized solely by silica nanoparticles of well-controlled surface properties. Two non-steroidal ant-inflammatory drugs, namely flurbiprofen and diclofenac sodium were incorporated in the stabilized simple and multiple emulsions, respectively. The stability of emulsions and the in vitro release of the drugs from the prepared emulsions were studied. In addition, the anti-inflammatory activity of the drugs from these liquid formulations was assessed using carageenan-induced hindpaw edema in rats. The results indicated that the prepared liquid emulsions, which stabilized with silica nanoparticles, were highly stable. The in vitro release of flurbiprofen and diclofenac sodium from these simple and multiple emulsions showed higher rates compared with those preapred from paraffin oil due to their lower viscosities. The results revealed also that the percentage of oil has a pronounced effect on the in vitro release rates of the drugs from the emulsions. Furthermore, topical flurbiprofen and diclofenac sodium emulsions exhibited a potent local anti-inflammatory activity compared with the orally adminstered drugs in the suspension form and this activity reached its peak [57-84%] 3 hrs after carrageenan injection and persisted for 5 hrs, the period of study