A Pharmacokinetic Study of Valacyclovir in Pediatric Oncology Patients

In this study, patients will receive a single dose of oral valacyclovir. Blood samples will
be drawn to evaluate the pharmacology (how the body handles the drug). Blood samples (less
than one teaspoon each) will be obtained before receiving the drug and at 0.5, 1, 1.5, 2, 5,
6, and 8 hours after receiving the drug. The total amount of blood drawn from patients for
all blood work including routine blood tests as well as pharmacokinetics will not be greater
than 5% of the total blood volume.

We will also have all urine output collected for 8 hours starting at the time patients
receive the dose of valacyclovir. A 5cc sample of urine will be collected and analyzed to
determine how the body handles the drug at hours 2, 4, 6, and 8.

Inclusion criteria:

- Age: Patients must be > / = 2 and < / = 18 years old.

- Life Expectancy: Patients must have a life expectancy of > 8 weeks

- Subjects must have a diagnosed malignancy, and must currently be receiving
consolidation or maintenance chemotherapy

- Hepatic/Renal Function: Patients must have adequate hepatic function (bilirubin < / =
1.5 mg/dl: SGPT < 3x normal) and adequate renal function (creatinine < / = 1 mg/dl:
BUN < 20 )

- Medication Tolerance: Patients must be able to swallow pills or tolerate a suspension
of the medication

- Fluid Tolerance: Children must be able to retain liquids at the time of enrollment

- Informed Consent: Written informed consent will be obtained from all patients and/or
their parents prior to enrollment

- Pregnancy: Women of childbearing age must have a negative serum pregnancy test at the
time of study entry

Exclusion criteria:

- More than one prior chemotherapy regimen.

- Patients with uncontrolled infections.

- Subjects with known history of adverse reaction to acyclovir in the past.

- Patients with concurrent infections requiring treatment with valacyclovir or
acyclovir.