The purpose of this study is to test whether Rifampin affects blood levels of istradefylline in humans. Rifampin could possibly decrease istradefylline levels.

Inclusion Criteria:

• Healthy non-smoking male and post-menopausal female subjects
• Body Mass Index: 18.0-35.0 kg/m2, inclusive
• Subjects must not be taking drugs that are moderate to potent inhibitors of CYP3A4 or CYP1A2.
• Subjects without clinically significant medical history in the judgment of the investigator
• Subjects without clinically significant laboratory or ECG abnormalities

Exclusion Criteria:

• Females that are pregnant or lactating
• Administration of an investigational drug within 30 days or 5 elimination half-lives of such investigational drug, whichever is longer, prior to study drug administration, or planned administration of another investigational product or procedure during the subject's participation in this study;
• Known history of treatment for drug or alcohol addiction within the previous 12 months;
• Subjects with an average alcohol intake of more than 2 units per day or 14 units per week up to 48 hours prior to the istradefylline dose on Day 1. One unit of alcohol is ½ pint of beer (285 mL) or 1 glass of spirits (25 mL) or 1 glass of wine (125 mL);
• Donated or lost > 500 mL of blood within 3 months prior to istradefylline dose on Day 1 of Period 1;
• Positive test results for human immunodeficiency virus (HIV) or Hepatitis B surface antigen, or Hepatitis C;
• Positive test results for drugs of abuse at screening;
• Unable, or unwilling to tolerate multiple venipunctures;
• Difficulty fasting or eating the standard meals that will be provided;
• Use of tobacco or nicotine-containing products within 90 days of the study start to the Follow-up visit