This paper considers the problem of adaptive subcarrier allocation, power control, and power allocation for multiuser frequency division duplex-discrete multitone (FDD-DMT) systems in a Gaussian interference channel. Assuming perfect knowledge of all channel and crosstalk transfer functions, we formulate the problem as an optimization problem to maximize jointly the sets of downstream and upstream bit rates for given user priorities. We show that the optimization problem belongs to the class of nonlinear mixed-integer optimization problems. We explain that for the multiuser FDD-DMT systems such problems can not be solved with existing algorithms. Instead, this paper introduces a new suboptimal normalized-rate iterative algorithm of low complexity.