A nonadiabatic molecular dynamics is implemented in the framework of the time-dependent density functional tight binding method (TDDFTB) combined with Tully's stochastic surface hopping algorithm. The applicability of our method to complex molecular systems is illustrated on the example of the ultrafast excited state dynamics of microsolvated adenine. Our results demonstrate that in the presence of water, upon initial excitation to the S-3 (pi-pi*) state at 260 Bin, an ultrafast relaxation to the S-1 state with a time constant of 16 fs is induced, followed by the radiationless decay to the ground state with a time constant of 200 fs.