Need mental energy to power through? Vivarin is one of the best ways to get the energy you need to tackle your days OR nights.Its 200mg of caffeine in one swallow.One Vivarin tablet contains about 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.