Since having prostate brachytherapy i now have e d is viagra (sildenafil) beneficial and is it covered by pbs ?

Individualized: Every insurance program has multiple program/plans, each with its own formulary ("allowabe" medication panel). ED is a recognized risk/side-effect associated with any treatment for documented prostate cancer. Unfortunately, pRacticing MDs do not control/manage your insurance: it is up to the discretion of your insurer as to the degree of "coverage" re: your post-op situation.