Acivir-400 DT Tablet is used to treat viral infections. It plays a vital role in treating cold sores (an inflamed blister in or near the mouth, caused by infection with the herpes simplex virus), genital herpes (a common sexually transmitted infection marked by genital pain and sores), and herpes zoster (a viral infection that causes a painful rash). In addition to this, it is also used to treat chickenpox. Acivir-400 DT Tablet does not cure herpes but does not allow the infection to spread and treat its symptoms.