Gaining insights into the fluctuation-induced entropic pressure between membranes that mediates cell adhesion and signal transduction is of great significance for understanding numerous physiological processes driven by intercellular communication. Although much effort has been directed toward investigating this entropic pressure, there still exists tremendous controversy regarding its quantitative nature, which is of primary interest in biophysics, since Freund challenged the Helfrich's well-accepted results on the distance dependence. In this paper, we have investigated the entropic pressure between fluctuating membranes in multilayer systems under pressure and tension through theoretical analysis and Monte Carlo simulations. We find that the scaling relations associated with entropic pressure depend strongly on the magnitude of the external pressures in both bending rigidityand surface tension-dominated regimes. In particular, both theoretical and computational results consistently demonstrate that, in agreement with Helfrich, the entropic pressure p decays with inter-membrane separations c as p similar to c (-3) for the tensionless multilayer systems confined by small external pressures. However, our results suggest that the entropic pressure law follows to be p similar to c (-1) and p similar to c (-3), respectively, in the limit of large and small thermal wavelengths for bending fluctuations of the membranes in a tension-independent manner for the case of large external pressures.