Valtoval 500 Tablet is neither an antibiotic nor a corticosteroid. It is an antiviral medicine and acts against viruses. It is effective against herpes simplex virus (chickenpox, cold sores, and genital herpes), varicella-zoster virus (shingles), and cytomegalovirus (CMV). Valtoval 500 Tablet prevents the occurrence of CMV infection and disease after organ transplant.