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.