In Reply:—

We would like to thank Dr. Nigrovic for his interest in our article. We fully agree that the very high doses of muscle relaxant used in dose-ranging studies may not be suitable for deriving EC50estimates. This was fully discussed and acknowledged in our report. We are not proposing multiple values for the EC50but are reporting a dose dependency of the EC50estimates. In our opinion, the example proposed by Dr. Nigrovic does not fully account for the multiplicity of factors involved. Unlike sodium concentrations, effect compartment concentrations are not measured but derived mathematically by combining the time courses of plasma concentration and effect. This complicates the interpretation and deserves further studies.