This will place more emphasis on fitting the higher concentrations and may ignore the lowest concentrations. The log transformation that is done will reduce this problem, but will not eliminate it. Despite this problem you will likely find almost identical slopes if you use weighted nonlinear regression on the same points selected for determination of terminal slope. Moreover, some nonlinear fitting methods are unstable when only 3-4 points are available over a narrow time range. This often occurs with the last measured concentration.
Assumptions are always necessary regardless of the method used for analyzing the data.
The half-life calculated from the terminal portion is an appropriate measure regardless of the number of other terms or the multiphasic nature of the curve. The usual limitation is, of course, that you have sufficiently good data over the terminal time points. See, for example, Anesthesiology. PST Dear Dr. You would get the same value for this parameter even if you use compartmental analysis.