A 70-year-old man developed
herpes zoster over the right L5-S2 region for 3 days and was admitted for
acyclovir therapy. He had a medical history of
rectal cancer status post-
colostomy and
end-stage renal disease undergoing thrice weekly
hemodialysis. Without a prior loading dose,
acyclovir 500 mg (7.7 mg/kg) daily was given intravenously in two divided doses. On the third dosage, the patient became confused and agitated and developed
insomnia. Within the following 24 h,
delirium, visual and
auditory hallucinations, disorientation to place and time, as well as impaired recent memory occurred. At the same time, a transient low grade
fever (38 degrees C) was noted but resolved spontaneously after
ice pillow (Fig. 1). The etiology was vigorously explored. He had no history of any neurological or
psychiatric disorders.
Drug history was reviewed, but no other medications besides
acyclovir were currently being used. Physical examination revealed neither meningeal signs nor focal neurological deficits. Serum blood
urea nitrogen,
glucose, and
electrolytes were within normal limits except for an elevated
creatinine level at 6.2 and 5.7 mg/dl (before and after neuropsychotic symptoms, respectively). Complete blood count with differentiation was also unremarkable. Cerebrospinal fluid examination was not possible as the patient's family refused the lumbar puncture. Moreover, an electroencephalograph study and head computed tomography scan disclosed no abnormalities.
Acyclovir-induced neurotoxicity was suspected. Therefore,
acyclovir was discontinued. Subsequently, serum
acyclovir and
CMMG were checked by
enzyme-linked
immunosorbent assay. Serum
acyclovir level was 1.6 mg/l (normal therapeutic level, 0.12-10.8 mg/l) and
CMMG level was 5 mg/l. Emergent
hemodialysis (4-h/session) was given; the neuropsychotic symptoms, including agitation,
delirium, and visual and
auditory hallucinations, greatly abated after the second session. The patient fully recovered after three consecutive days of
hemodialysis; the serum was rechecked and revealed that the
acyclovir level was below 0.5 mg/l and the
CMMG level was undetectable. At the same time, his herpetic skin lesions resolved well.