The elastic scattering, Stark transitions and Coulomb deexcitation of excited antiprotonic hydrogen atom in collisions with hydrogenic atom have been studied in the framework of the fully quantum-mechanical close-coupling method for the first time. The total cross sections $sigma_{nl to nl}(E)$ and averaged on the initial angular momentum $l$ cross sections $sigma_{nto n}(E)$ have been calculated for the initial states of $(bar{p}p)_{n}$ atoms with the principal quantum number $n=3 - 14 $ and at the relative energies $E=0.05 - 50$ eV. The energy shifts of the $ns$ states due to the strong interaction and relativistic effects are taken into account. Some of our results are compared with the semiclassical calculations.