Known brand names include Zovirax.
An antiviral for herpes viruses. Tablets treat shingles, chickenpox, and genital herpes, and the IV form treats severe herpes infections, including herpes of the brain and herpes in newborns. It can harm the kidneys, especially when given IV, so good hydration matters.
Acyclovir and other antivirals are not on the ISMP acute care high-alert list.
Sources: [1]
The label does not describe a narrow therapeutic index or direct dosing by measured blood levels of the drug.
No specific antidote. Overdoses up to 20 g have caused agitation, lethargy, seizures, and coma, and drug crystals in the renal tubules can cause acute renal failure. Give supportive care with attention to fluids; hemodialysis lowers plasma levels about 60% over a 6-hour session and may help in acute renal failure with anuria.
Doses come from the FDA label. Study tool, not for clinical decisions.
Adjust by creatinine clearance (mL/min/1.73 m2). Oral: 800 mg every 4 hours becomes every 8 hours at 10 to 25 and every 12 hours at 0 to 10; at 0 to 10, 200 mg every 4 hours becomes every 12 hours and 400 mg every 12 hours becomes 200 mg every 12 hours. IV: full dose every 12 hours above 25 to 50, every 24 hours above 10 to 25, and half the dose every 24 hours at 10 or less. Hemodialysis lowers plasma levels about 60% over 6 hours, so give an extra dose after each session.
A synthetic purine nucleoside analogue. Viral thymidine kinase in HSV- and VZV-infected cells converts it to the monophosphate, and cellular kinases form acyclovir triphosphate, which competitively inhibits viral DNA polymerase, is incorporated into viral DNA as a chain terminator, and inactivates the polymerase. Activity is greater against HSV than VZV because HSV thymidine kinase phosphorylates it more efficiently. Oral bioavailability is 10% to 20% and falls as the dose rises; half-life is 2.5 to 3.3 hours with normal renal function, 62% to 91% of an IV dose is excreted unchanged in urine, and CSF levels are about 50% of plasma.