Female sexual arousal disorder (FSAD) is a frequent finding in women in middle age and more prevalent in post-menopausal women. Topical alprostadil is currently under development for the treatment of FSAD. The purpose of this research is to determine if this formula of alprostadil is safe and effective in women with FSAD. We will be comparing alprostadil to placebo. Each participant will be treated for 1 month with active alprostadil and 1 month with placebo without knowing which they are using. This way, the investigators can compare the effects of alprostadil to the effects of an inactive topical gel.