The formulations of the patch are shown in Table II. Each formulation consisted of a fixed amount of total polymer at 5.00% w/w. The ratios of chitosan and starch were 5 : 0 or 4.5 : 0.5, according to the previous study . The starch blended with chitosan was corn, tapioca or rice starch. The amount of lactic acid was varied in the formulation to control pH of the polymer solution within the range of 3 to 4.