From their site:
Vivarin® is not a substitute for sleep. You need sleep. (I know I do.) Vivarin is not for children under 12.
One Vivarin® tablet contains as much caffeine as a cup of coffee. Limit your use of caffeine in medications, foods and drinks while taking Vivarin® because too much caffeine may cause nervousness, irritability, sleeplessness, and, occasionally, rapid heartbeat. For occasional use only. Not a substitute for sleep. If drowsiness persists, consult a doctor. Not for children under 12.
Thank you, Dee Riedel-Bennett, for passing this along!