Enhanced absorption and drug targeting by positively charged submicron emulsions

This overview presents the state of the art of positively charged submicron emulsions, their physicochemical properties, biofate, and therapeutic applications, especially for intravenous, ocular, and oral administration. The positive charge of submicron emulsions results from cationic excipients such as lipids, polymers, and surfactants in formulations. It was observed that positively charged submicron emulsions are stable in the presence of physiological cations and can interact in vivo with negatively charged biological membranes, resulting in an enhanced drug uptake and site-specific targeting. Numerous authors have shown that cationic emulsions can improve the oral bioavailability of lipophilic drugs and enhance drug permeation through cornea, leading to increased drug concentration in ocular tissues as compared to negatively charged submicron emulsions. In addition, positively charged oil droplets can accumulate markedly in the lung following i.v. injection, opening new therapeutic possibilities for lung cancer chemotherapy. (C) 2000 Wiley-Liss, Inc.