Quantization of non-Hamiltonian physical systems

We propose a general method of quantization of non-Hamiltonian physical systems. Applying it, for example, to a dissipative system coupled to a thermal reservoir described by the Fokker-Planck equation, we are able to obtain the Caldeira-Leggett master equation, the nonlinear Schrödinger-Langevin equation, and the Caldirola-Kanai equation (with an additional term), as particular cases.