7.1.3 Considerations for multiple-dose studies
In certain situations multiple-dose studies may be considered appropriate.
Multiple-dose studies in patients are most useful in cases where the API being studied is considered to be too potent and/or too toxic to be administered to healthy volunteers, even in single doses (see also 7.1.1). In this case, a multiple-dose, cross-over study in patients may be performed without interrupting therapy. The dosage regimen used in multiple-dose studies should follow the usual dosage recommendations. Other situations in which multiple-dose studies may be appropriate are as follows:
cases where the analytical sensitivity is too low to adequately characterize the pharmacokinetic profile after a single dose;
extended-release dosage forms with a tendency to accumulate (in addition to single-dose studies).
In steady-state studies the wash-out of the last dose of the previous treatment can overlap with the approach to steady state of the second treatment, provided the approach period is sufficiently long (at least five times the terminal half-life). Appropriate dosage