The pharmacological effects of PDC-748 were tested in numerous in vitro and in vivo studies. The existing pharmacologic findings suggest that PDC-748 possesses certain inhibitory activity to the citric acid- and capsaicin-induced cough reflex in guinea pigs with a dose-dependent manner. Furthermore, a previous Phase I/II uncontrolled, dose-escalating study has shown PDC-748 to be well tolerated and may help to alleviate daytime cough with a dose-responding manner.Hence, PhytoHealth Corporation intends to carry out a Phase II investigation to confirm the preliminary findings using placebo in the comparator group, and to further investigate PDC-748 with a dose escalating manner to establish the dose-response range for its antitussive effect, and if possible, to determine the maximal tolerable dose of PDC-748.