Aciclovir, a nucleoside analogue, is a potent antiviral medication widely used in the treatment of herpes simplex virus (HSV) infections, including oral and genital herpes, as well as varicella-zoster virus (VZV) infections like chickenpox and shingles. The drug works by inhibiting viral DNA replication, thus curbing the spread of the virus within the body. Aciclovir is available in various formulations, including oral tablets, intravenous injections, and topical creams. For recurrent herpes simplex infections, oral aciclovir is often prescribed to reduce the frequency and severity of outbreaks. In severe cases, particularly in immunocompromised individuals, intravenous aciclovir may be administered for more effective control of the viral infection. Additionally, topical aciclovir creams are commonly used to alleviate symptoms and promote faster healing of herpes lesions. While generally well-tolerated, aciclovir may cause side effects such as nausea, headache, and dizziness. Long-term use may also lead to the development of drug-resistant strains of the virus. Regular monitoring, dosage adjustments, and careful consideration of patient factors are crucial in optimizing the efficacy and safety of aciclovir therapy.