Study to Assess Drowsiness, Cognition, Fall Risk After Metaxalone 640 mg and Metaxalone 800 mg

The Screening-Baseline Visit will include vital signs and urine testing, and a discussion of medications and current medical history. Participants will be given written tests to measure drowsiness, reaction time and thinking process and will also be asked to take walking tests to assess fall risk. Visit 2 approximately one to two (1 to 2) week(s) later will be the first dosing day (Arm 1) after eating the high fat meal. The testing from Baseline will be repeated four (4) hours after the medication dose is taken. Visit 3 approximately one (1) week later will be the second dosing day (Arm 2) after eating the high fat meal. The testing from Baseline will be repeated four (4) hours after the medication dose is taken. The End of Study safety visit will take place one (1) week after Visit 3 by phone with a discussion of any side effects from the drug, recent medications, and any illness or injury experienced since the previous visit. Participants will be given end of study and discharge instructions.