Acyclovir (Zovirax®) is a drug used to treat infections caused by certain viruses. It does not cure the infection but it will help decrease pain and itching, help with healing, and may help reduce the number of out-breaks when taken on a regular basis. Acyclovir has been used to treat infections caused by herpes simplex virus (HSV), varicella zoster virus (VZV, chickenpox), and herpes zoster virus (shingles). It may also be used in patients with impaired immune function to help prevent infection with cytomegalovirus (CMV). It is available as tablets, capsules, solution, suspension, injection, and a topical ointment.