Study to Assess the Safety, Tolerance and Efficacy of Tezampanel in Patients With Acute Migraine

Primary: • Headache relief (headache response) defined as the percentage of patients in each treatment group who experience a decrease in pain from moderate or severe intensity pre-dose (baseline) to mild or no pain 2 hours after study drug administration and prior to use of rescue medication. Secondary: * Percentage of patients in each treatment group who are pain-free two hours after study drug administration, prior to the use of any rescue medication * Sustained headache response rate (percentage of patients in each treatment group with headache response at Hour 2 and no rescue medication or headache recurrence from 2 through 24 hours) * Sustained pain-free rate (percentage of patients in each treatment group who are pain free at Hour 2 with no rescue medication or headache recurrence from 2 through 48 hours) * Recurrence rate (percentage of patients in each treatment group with an Hour 2 mild response or pain-free response who subsequently develop a headache rated as moderate to severe in intensity within 2 to 24 hours) * Relapse rate (percentage of patients in each treatment group with an Hour 2 pain free response who subsequently develop a headache rated as moderate to severe in intensity within 2 to 48 hours