Author: Nick Hatch, M.D. Educational Pearls Acyclovir toxicity can uncommonly cause altered mental status, low blood glucose, hallucinations and myoclonic jerks. Toxicity often occurs in the setting of renal insufficiency, as it is cleared by the kidneys. Acyclovir is often used to treat shingles, which can also cause similar symptoms as acyclovir toxicity due to encephalitis - rule this out in the setting of a concomitant shingles infection. References: http://www.rxlist.com/zovirax-drug.htm