The effective collision frequency relevant to the problem of current drive (CD) is evaluated taking into account the radiative slowing down due to (spontaneous) electron cyclotron (EC) emission as well as an ion charge state Z ⩾ 1. The efficiency of CD by EC radiation from high temperature plasmas is obtained straight-forwardly on the basis of the salient properties of the single electron emissivity at mildly relativistic energies. The CD degradation due to radiative slowing down is evaluated and the relevant scaling with respect to Z is discussed