Transmit power control to minimize transmit power for multi-user distributed antenna systems (MU-DASs) is necessary to improve spectrum efficiency. In previous work, distributed transmit power control (DTPC) algorithm for cellular MIMO systems has been developed based on uplink-downlink duality. The performance of this DTPC algorithm in MU-DASs is evaluated in this paper because MU-DASs is different from cellular MIMO systems in terms of an effect of the co-channel interference (CCI). Computer simulations show that the sum of transmit power is decreased because of uplink-downlink duality assumption. In addition to this, an advantage of MU-DAS is shown. However, it is shown that the sum of transmit power is not always minimized without optimization of clustering.