The purpose of this study is to determine if the relative difference in PK between extensive metabolizers (EMs) and poor metabolizers (PMs) is the same with desvenlafaxine SR and venlafaxine ER when a single dose is administered.

Inclusion Criteria:

• Healthy men and women between 18 to 55 years of age
• Healthy as determined by the investigator on the basis of medical history and physical examination, laboratory test results, vital signs, and no clinically significant abnormalities on 12-lead electrocardiogram (ECG)
• History of nonsmoker for at least 1 year

Exclusion Criteria:

• Presence or history of any disorder or significant cardiovascular, hepatic, renal, respiratory, gastrointestinal, endocrine, immunologic, dermatologic, hematologic, neurologic, any severe conditions of the ears, eyes or throat (such as glaucoma or increased intraocular pressure), or psychiatric disease that may prevent the completion of the study
• Known or suspected alcohol abuse or consumption of more than 2 standard units per day within past 6 months or known or suspected abuse of prohibited drugs or other substances
• Use of any over-the-counter, prescription, hormonal therapy or investigational medications within 30 days of study day -1 until the end of the study