Valacyclovir is an antiviral drug. Valacyclovir is a precursor drug to acyclovir, which is metabolized into acyclovir when it enters the body. Acyclovir can enter the herpes-infected cells and inhibit the synthesis of herpes virus DNA, thus exerting an antiviral effect. The clinical use of valacyclovir is mainly for the treatment of varicella and herpes simplex virus infections. Valacyclovir may cause side effects such as respiratory distress, joint pain, liver function impairment, etc. Oral administration of valacyclovir may also cause nausea, vomiting, diarrhea, abdominal pain, stomach discomfort, loss of appetite, and thirst. Long-term use of valaciclovir may cause mental and neurological symptoms such as dizziness, headache, insomnia, confusion, tremor, hallucinations, and excitement. Valaciclovir may also cause symptoms of acute renal impairment such as proteinuria and elevated urea nitrogen.