termplot

I have used glm and stepAIC to choose a best model.  I can use termplot to
assess the contribution of each explanatory variable in the glm.  However
the final model after running stepAIC includes interaction terms, and when I
do termplot I get "Error in `[.data.frame`(mf, , i) : undefined columns
selected".  I also see the termplot detail saying "Nothing sensible happens
for interaction terms."   

Is it possilbe to determine explanatory power of final set of variables when
interactions are included?  
 
Thanks

- Bob