We have developed an instantaneous inelastic energy loss algorithm for use in molecular dynamics simulations of sputtering. This algorithm uses distance-of-closest-approach (DCA) criteria to initiate inner-shell electronic excitation, and subsequent removal of the excitation energy following hard atom-atom and ion-atom collisions. The DCA criteria used in the algorithm are based on the electron promotion models of Fano and Lichten [Phys. Rev. Lett. 14 (1965) 627] and Barat and Lichten [Phys. Rev. A 6 (1972) 211]. The amount of energy removed in these hard atom-atom and ion-atom collisions is determined by the energy needed to excite one or more inner-shell electrons to the continuum. This algorithm has been used to stimulate inelastic energy loss effects for the Ar +-Cu(100) and Ar +-Cu(111) systems at bombarding energies between 1 keV and 5 keV. Significant reductions in sputtering yields are produced above a bombarding energy threshold of approximately 2 keV. Polar-angle distributions of atoms sputtered from the Cu(100) surface also are changed significantly by this instantaneous inelastic energy loss model.