- Hepatic impairments as evidenced by a three-fold increase from the upper limit of normal in alanine or aspartate transaminase. Impairment of renal function as evidenced by any elevation above the upper limit of normal for serum creatinine. History of hypersensitivity to acyclovir. Malabsorption or vomiting that would, in the investigators opinion, potentially limit the retention and absorption of oral therapy.