Gramicidin is a membrane channel-forming antibiotic that is thoroughly investigated. The peptide monomer is embedded into a single monolayer of a bilayer membrane. The through channel is formed by transmembrane dimerization of two peptide molecules. The details of the monomer interaction remain unknown. Using continuous elastic model we studied the interaction of two gramicidin monomers embedded into a lipid bilayer. The calculated dependencies of dimer formation frequency on membrane tension and channel lifetime on membrane thickness proved to be in perfect agreement with available experimental data. The energy profile of the interaction was calculated for peptides located in the same monolayer and in the opposite monolayers of lipid membrane. We found out that the energy of the system had a minimum when two gramicidin peptides were separated by a few nanometers for both cases. The calculated interaction energy profile was used to analyze the gramicidin molecules ensemble behavior. The simplest model of 2D Van der Waals gas was applied to calculate the critical temperature of the ensemble condensation. The calculated temperature was found to be approximately 3 times higher than the physiological temperature, which indicates that gramicidin peptides in membrane could form clusters, in agreement with recent experimental data. The designed elastic theory is general and may be used for the analysis of membrane-mediated interactions of the inclusions of different nature: transmembrane molecules, amphipathic peptides, etc. The work was supported by the Russian Foundation for Basic Research (project # 17-04-02070).