Valaciclovir, also spelled valacyclovir, is an antiviral drug used in the management of herpes simplex, herpes zoster (shingles), and herpes B. It is a prodrug, which is converted to aciclovir in a persons body. Common adverse drug reactions (≥1% of patients) associated with valaciclovir therapy are the same as for aciclovir, its active metabolite, and include: nausea, vomiting, diarrhea and headache. Infrequent adverse effects (0.1–1% of patients) include: agitation, vertigo, confusion, dizziness, edema, arthralgia, sore throat, constipation, abdominal pain, rash, weakness and/or renal impairment. Rare adverse effects ( Valaciclovir belongs to a family of molecules first described and patented by Paolo Cornaglia Ferraris in 1982 (patents EP0077460 A2, CA1258149A1, DE3273785D1, EP0077460A3, EP0077460B1, US4567182). Valaciclovir is a prodrug, an esterified version of aciclovir that has greater oral bioavailability (about 55%) than aciclovir (10–20%). It is converted by esterases to the active drug aciclovir, as well as the amino acid valine, via hepatic first-pass metabolism. Valtrex will not cure herpes, but it can lessen the symptoms of the infection. It slows the growth and spread of the herpes virus so that the body can fight off the infection. Valtrex is used to treat infections caused by herpes viruses in adults and children. Illnesses caused by herpes viruses include genital herpes, cold sores, shingles, and chickenpox. Valtrex is used to treat cold sores in children who are at least 12 years old, and to treat chickenpox in children who are at least 2 years old. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Treatment with Valtrex should be started as soon as possible after the first appearance of symptoms (such as tingling, burning, blisters). This medication might not be as effective if you first start taking it 1 or 2 days after the start of your symptoms. Drink plenty of water while you are taking Valtrex to keep your kidneys working properly. Shake the oral suspension (liquid) well just before you measure a dose.
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