Valacyclovir in Immunocompromised Children

Patients with shingles: Patients with shingles will receive oral Valacyclovir three times a day for 5 to 10 days. For the first 24 hours of treatment, patients will be admitted to the hospital for close monitoring. If there are no problems after the first 24 hours then the patient may be discharged to take the medicine at home. After discharge patients will be seen and examined in clinic daily for the first 5 days, then on day 7 and after that every other day until the shingles show evidence of healing. A final physical exam and blood tests occur on day 21. A small amount of fluid will be taken from one of the shingles lesions using a very fine needle to verify the presence of the virus that causes shingles. This will be done before the first dose of Valacyclovir and 3 days later. Blood tests (no more than 2 teaspoons) will be performed twice a week to monitor for toxic effects of the drug. Blood samples will be drawn to evaluate the pharmacology of this drug(how the body handles the drug). Nine blood samples (less than one teaspoon each) will be obtained over 24 hours during the first day of treatment. The total amount of blood to be drawn is 9 teaspoons (3 tablespoons). For children that are toilet trained, urine will be collected for 12 hours at the start of the study. This urine will be used to evaluate kidney function, and the pharmacology of valacyclovir. If there are unacceptable side effects or if there is evidence that the disease is spreading, despite being on Valacyclovir for more than 48 hours, then you will be taken off the study and started on acyclovir by vein. Patients Undergoing Bone Marrow Transplantation: Patients undergoing a bone marrow transplant will receive a single dose of valacyclovir in place of their first scheduled dose of acyclovir. They will then receive acyclovir as outlined by their physician. Blood samples will be drawn to evaluate the pharmacology (how the body handles the drug) of the study drug. Fifteen blood samples (less than one teaspoon each) will be obtained over 24 hours during the first day of treatment. The total amount of blood to be drawn is 9 teaspoons (3 tablespoons. The total amount of blood drawn for all blood work including routine blood tests as well as pharmacokinetics will not be greater than 5% of the patients total blood volume. This amount of blood loss is a safe amount even for small children