Potential application of Metolose® in a thermoresponsive transdermal therapeutic system

The purpose of the present study was to formulate a novel thermoresponsive membrane controlled therapeutic system from Metolose® for possible transdermal application. Metolose® gel shows thermal gelation property, which can be characterized by two (T1, T2) temperatures. A sharp decrease of viscosity can be measured at T1, but gelation can be observed at T2. Different types of Metolose® polymers were compared considering their thermoresponsive behaviour. Only thermal gelation was observed in the case of Metolose® SM, while Metolose® SH showed a sudden decrease of viscosity at T1. Since this temperature is above the body temperature, so it should be shifted to the skin temperature in case of possible transdermal application. Modulation of thermoresponsibility was followed by rheological method, and the thermoresponsive drug release from Metolose® gel was studied by static liberation test. Our results demonstrated that the effect of different salts (NaCl, NaHCO3, KCl) of various concentrations in Metolose® SH gel reduced T1 to the skin temperature, which enabled enhanced drug release.