Famvir Diagnosis Online - Famvir is prescribed to treat attacks of genital herpes and to prevent future flare-ups. For people with HIV infections, it is used as a treatment for both genital and oral herpes. For maximum benefit, take Famvir for the full time of treatment, even if your symptoms begin to clear up. Do not, however, take Famvir more often or for a longer time than your doctor directs. You may take Famvir with meals or in between.