The only question is how large the market actually is. Not very many people treated with the current options stay in treatment. While there are lots of mechanical good ways to produce an erection, sex is almost 100% psychological. Lack of �psychological attractiveness� is why drugs that require stopping the course of a relationship to do something fail to be used, even if the mechanics of the erection are great. A surprising number of people [to me] will use oral treatments that are not effective, rather than the guaranteed approach that requires intervention. Who wants to stop, say excuse me, and lather up during the course of a romantic encouter? As a sceptic, you may want to check out a recent study [ J Urol 155:1609-1612, 1996]. 79% of 377 patients chose an oral drug (yohimbine) for their first treatment in spite of being informed of the high probability of an unsatisfactory result [less than placebo response rate]. In addition, even when levels of satisfaction are relatively low, many patients continued to use it. Forty-eight percent of this group of 377 patients who initially selected yohimbine were still using the drug 23 months later, but only 28% of those continuing to use yohimbine indicated that they were satisfied with the treatment.
I'll buy Pfizer on drops and bet on Viagra for a clean sweep of the existing market and as a drug that significantly expands the existing market. It'll be like Prozac was for Lilly.
Meanwhile, good luck with the Muse and the other alternatives. Time will tell.