Actual stimulation is much more limited than the half life of the substance would suggest, as it is with most other stimulant drugs. Even if much of the substa

Actual stimulation is much more limited than the half life of the substance would suggest, as it is with most other stimulant drugs. Even if much of the substance remains unchanged by the liver the stimulation effect is front loaded. After a short time, typically 2-3 hours, physiological stimulation decreases rapidly unless even more stimulant is added.