There may be reasons to use another schedule. In steady state the total amount of drug in the body remains constant. If you want to reach this state quickly you can administer at once the total amount of drug which is present in the body in steady state (Figure 19). What quantity is then needed? Theoretically you will need the mean plasma concentration, multiplied by the distribution volume. In the majority of cases these figures can be found in pharmacology books, or may be obtained from the pharmacist or the manufacturer. For several drugs fixed schedules exist, e.g. for digoxin.
Figure 19: Loading dose