Zovirax 400 Tablet contains Acyclovir 400 mg, an antiviral medication primarily used for the treatment of infections caused by herpes viruses, including herpes simplex virus types 1 and 2, varicella-zoster virus, and cytomegalovirus. Acyclovir acts by inhibiting viral DNA synthesis, thereby preventing viral replication and reducing the severity and duration of outbreaks. It is commonly prescribed for the management of genital herpes, cold sores, shingles (herpes zoster), and chickenpox. Zovirax 400 Tablet is indicated for both initial and recurrent episodes of herpes infections and may also be used prophylactically in immunocompromised patients to prevent viral reactivation. The medication is administered orally, with dosage and duration tailored according to the specific infection and patient condition. Common side effects are generally mild and may include headache, nausea, diarrhea, and abdominal discomfort. Patients with renal impairment should use caution, as dose adjustment may be necessary to prevent accumulation and toxicity. Zovirax 400 Tablet should be used under medical supervision, and patients are advised to complete the full course of therapy even if symptoms improve early. It is contraindicated in individuals with known hypersensitivity to acyclovir or valacyclovir.