Pharm 101: Aciclovir

Class

Antiviral agent


Pharmacodynamics
  • 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

Pharmacokinetics
  • 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)

Precautions/contraindications
  • Concurrent administration of nephrotoxic agents may enhanced potential for nephrotoxicity

References

Pharm 101 700

Pharmacology 101

Top 200 drugs

MBBS (UWA) CCPU Emergency Medicine Trainee with interests in medical education, ECG interpretation, and the use of point-of-care ultrasound in the undifferentiated patient. Co-author of the LITFL ECG Library | Twitter

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