The primary outcome measures will include the Erectile Function (EF) domain of the International Index of Erectile Function (IIEF), Sexual Encounter Profile (SEP), Questions 2 and 3 from SEP. The IIEF EF domain has a 30-point total score, where higher scores reflect better erectile function. SEP is a diary in which participants record each sexual attempt made throughout the study. The two questions from the Sexual Encounter Profile (SEP) deal with the ability to achieve vaginal penetration (SEP2), and the ability to maintain an erection long enough for successful intercourse (SEP3). The erectile function domain category of the IIEF will be used to evaluate the change in erectile status from baseline following administration of hMaxi-K. Change from baseline on the six questions of the IIEF's Erectile function domain category at every visit after administration of study drug will be calculated and compared among the two dose and one placebo groups.