Intravesical delivery of 5‐aminolevulinic acid from water‐in‐oil nano/submicron‐emulsion systems

The present work reports on the development of water‐in‐oil (w/o) emulsions for the intravesical administration of 5‐aminolevulinic acid (ALA). The physicochemical properties of droplet size, zeta potential, and viscosity of the emulsions are characterized and the ability of the emulsions to release ALA following in vitro application is tested. The delivery systems are administered intravesically for 1 and 3 h in rats to examine the drug accumulation in bladder tissue. The mean size and zeta potential of the emulsions are 50-200 nm and −3 to −14 mV, respectively. The loading of ALA into the emulsions resulted in a slower and sustained release. The release extent was found to be inversely related to the droplet size of the emulsions. The emulsions did not increase the drug permeation into tissues during short exposure duration (1 h). When the dwell time was extended to 3 h, the systems showed a 2.7‐fold increase in the ALA concentration in the bladder wall. Images of confocal laser scanning microscopy demonstrated a higher and deeper fluorescence signal, with emulsion administration, as compared to the aqueous control. Intravesical emulsion delivery provides a significant advantage for drugs targeting bladder tissues. © 2009 Wiley‐Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2375-2385, 2010