8. Patients must be in a stable, monogamous, heterosexual relationship that is secure and communicative, for at least 1 year prior to the Screen Visit. The relationship is to be with the same partner who is sexually functional, both psychologically and physically, and the partner is expected to be physically present (i.e., available for sexual activity at some time during a 24 hour day) at least 50% of each month during the 4-week Screen period and 24-week efficacy period of the trial.