The most important issue in starting treatment is the speed at which the curve reaches steady state, within the therapeutic window. If you give a fixed dose per unit of time, this speed is only determined by the half-life of the drug. On a fixed dosage schedule, steady state is reached after about 4 half-lives (Figure 16). In case of a long half-life it may therefore take some time for the drug to reach a therapeutic concentration. If you want to reach the window quicker, you can use a loading dose (see below).
Figure 16: Steady state is reached after 4 half-lives