Pharm 101: Aciclovir


Antiviral agent

  • Guanosine derivative with activity against HSV-1 and HSV-2, and VZV (10x less potent)
  • In vitro activity against EBV, CMV and HHV-6 is present but weaker
  • Inhibits viral DNA synthesis
    • Selectively activated in virus cells by virus-specific thymidine kinase (three phosphorylation steps for activation)
    • Irreversibly binds to viral DNA polymerase
    • Incorporation into viral DNA with termination
  • Absorption unaffected by food
  • Low bioavailability 15-20%
  • Widely distributed
  • CSF concentrations 20-50% of serum values
  • Half-life 2-3 hours in normal renal function (5x daily dosing oral)
  • Renal clearance, mostly excreted unchanged in urine
Clinical uses
  • HSV encephalitis
  • Serious HSV or VZV infections
  • Immunocompromised patients with VZV
  • Topical administration for primary HSV infection (genital herpes)
Adverse effects
  • GI upset: nausea, vomiting, diarrhoea
  • Headache
  • IV infusion is associated with reversible renal toxicity or neurological effects (tremor, delirium, seizures)
  • Concurrent administration of nephrotoxic agents may enhanced potential for nephrotoxicity
Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS CCPU (RCE, Biliary, DVT, E-FAST, AAA) Rob is an Emergency Medicine Advanced Trainee based in Melbourne, Australia. He has special interests in medical education, ECG interpretation, and the use of diagnostic and procedural ultrasound in the undifferentiated and unwell patient.

Follow him on twitter: @rob_buttner | ECG Library |

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.