We need to modify the radial dependence of the coupling form-factors to account partially for the effect of ignoring the difference of centrifugal potentials of the channels coupled together in coupled-channel calculations. In order to determine the modeified form-factors, the difference of the exact and approximate first-order demiclassical scattering amplitudes is minimized for each scattering angle. Analytic expressions for the Coulomb dipole and quadrapole coupling are obtained. We obtain local L-independent dynamic polarization potentials that describe the effect of coupling to excited states. This is accomplished by minimizing the difference between the first-order semiclassical scattering amplitudes of the polarization potential is determined. We have applied our results to study the effect in 18O+184W of the quadrupole Coulomb coupling of the 2+ state in 184W. Comparisons with exact coupled-channel calculations and other approximate treatments in the literature have been made.