t max
The time taken following drug administration for the drug to reach its peak plasma concentration, Cmax, is referred to as tmax. The value for tmax is affected by many of the same drug and patient characteristics that determine the Cmax value, including administration route and formulation, as well as the relative rates of absorption, distribution and clearance. It might be expected that weak acids, which are absorbed rapidly and extensively from the stomach, may show tmax values shorter, on average, than do weak bases.
Drugs of abuse often have a short tmax, since a short time between administration and drug effect is more reinforcing of behaviour.