We study theoretically the smectic mediated interactions between pointlike inclusions in a lamellar phase. The two-body interaction is derived and we discuss the virial expansion in the limits of weak and strong interactions. The leading order finite density corrections to the interaction potential are calculated using a mean field theory, which allows the particle density, potential, and effective smectic moduli to be calculated self-consistently. The effective bending modulus of the membranes is found to increase linearly with the particle density. We also give the structure factor S(q) for small but finite particle density.