  We present a generalized Drude analysis of the in-plane optical conductivity
$\sigma_{ab}$($T$,$\omega$) in cuprates taking into account the effects of
in-plane anisotropy. A simple ansatz for the scattering rate
$\Gamma$($T$,$\omega$), that includes anisotropy, a quadratic frequency
dependence and saturation at the Mott-Ioffe-Regel limit, is able to reproduce
recent normal state data on an optimally doped cuprate over a wide frequency
range. We highlight the potential importance of including anisotropy in the
full expression for $\sigma_{ab}$($T$,$\omega$) and challenge previous
determinations of $\Gamma$($\omega$) in which anisotropy was neglected and
$\Gamma$($\omega$) was indicated to be strictly linear in frequency over a wide
frequency range. Possible implications of our findings for understanding
thermodynamic properties and self-energy effects in high-$T_c$ cuprates will
also be discussed.
