drude lorentz model

i am working on wave optics module and using metal layer in my model for this layer when i gave permitivity in terms of real and imaginary part let epsilon=5+8i and use this value in VARIABLES for K=5+8i*ewfd.k0 it works (i used relative permitivity model to solve metal in this case) but when i want to use drude lorentz model which gives epsilonr then how i will use this value in my VARIABLE equation K.if i use ewfd.epsilonrxx value then it gives me three components how i can use this in my equation . in short how cai use the value calculated from drude model in my variable form or it works without using ?

Thanks