  We analyze the outcomes of an extended-Drude-model approach to the optical
spectra of pnictides, where the multiband nature of the electronic excitations
requires a careful analysis of the role of interband processes in the optical
conductivity.Through a direct comparison between model calculations of the
intraband optical spectra and experimental data, we show that interband
transitions,whose relevance is shown by first-principle calculations,give a non
negligible contribution already in the infrared region. This leads to a
substantial failure of the extended-Drude-model analysis on the measured
optical data without subtraction of interband contributions.
