This trial examines the way flibanserin is metabolized in postmenopausal women with Hypoactive Sexual Desire Disorder.

Inclusion criteria:

1. Patients must be in a stable, monogamous heterosexual relationship for at least one year.
2. Patients must have a primary diagnosis of Hypoactive Sexual Desire Disorder for at least six months.
3. Patients must be naturally postmenopausal women of any age with at least one ovary.
4. Patients may participate whether or not they are currently taking systemic hormone therapy provided the therapy was not prescribed for treatment of low sexual desire. Hormone therapy must be at a stable dose for at least six months.

Exclusion criteria:

1. Patients with a history of drug dependence or abuse within the past twelve months.
2. Patients who have been previously treated with flibanserin.
3. Patients who have sexual dysfunctions other than Hypoactive Sexual Desire Disorder, such as: Sexual Aversion Disorder, Substance-Induced Sexual Dysfunction, Dyspareunia, Vaginismus, Gender Identity Disorder,Paraphilia, or Sexual Dysfunction due to a general medical condition.
4. Patients who indicate that their sexual partner has inadequately treated organic or psychosexual dysfunction that could interfere with a patients response to treatment.
5. Patients whose sexual function was impaired, in the investigators opinion, by abdominal or vaginal hysterectomy, oophorectomy or any other pelvic, vaginal, or urologic surgery.
6. Patients with pelvic pain, pelvic inflammatory disease, endometriosis, urinary tract or vaginal infection/vaginitis, cervicitis, interstitial cystitis, vulvodynia, symptomatic vaginal atrophy or any other gynecological pathology requiring further evaluation.
7. Patients with a history of unexplained vaginal bleeding within the past twelve months.
8. Patients with a history of Major Depressive Disorder within six months prior to Screening; ; active suicidal ideation with intent in the past ten years or suicidal behavior at any time.
9. Patients with a history of any other psychiatric disorder that could impact sexual function, increase risks to patient safety, or impair patient compliance. Such disorders include but are not limited to bipolar disorder, psychotic disorders, severe anxiety, eating disorders, and antisocial personality disorders.
10. Clinically significant electrocardiogram abnormalities at Screening.
11. Patients with a history of dementia or other neurodegenerative disease; organic brain disease; stroke; transient ischemic attacks; multiple sclerosis; spinal cord injury; brain surgery; significant brain trauma; peripheral neuropathy; and epilepsy.
12. Patients with ongoing hepatic impairment (cirrhosis, hepatic tumor, or other hepatic disease); peptic ulcer within six months prior to Screening; elevated liver enzymes ; inflammatory bowel disease; gastrointestinal bleeding within two months prior to Screening; Patients who have had bariatric surgery for obesity.
13. Patients with a history of angina; atherosclerotic cardiovascular disease; congestive heart failure; cardiomyopathy; symptomatic cardiac valve disease; arrhythmia; hypertension.
14. Patients with a history of renal failure; known history of chronic glomerulonephritis.
15. Patients with a history of chronic obstructive pulmonary disease, chronic bronchitis, or asthma not well controlled with medication taken twice daily or less.
16. Patients with a history of gonadotrophic hormone disorders or uncontrolled diabetes mellitus.
17. Uncorrected hypothyroidism or hyperthyroidism.
18. Patients with a history of uncontrolled glaucoma.
19. Patients with known Human Immunodeficiency Virus infection, Acquired Immunodeficiency Syndrome, other clinically significant immunological disorders or auto-immune disorders such as lupus or scleroderma.
20. Patients with a history of any cancer within the past ten years, other than non-invasive, previously resected basal cell carcinoma of the skin.