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HERPES SIMPLEX VIRUS INFECTION
Primary herpes simplex virus (HSV) infection is first infection with either herpes simplex virus-1 (HSV-1) or herpes simplex virus-2 (HSV-2) in individuals who do not have antibodies to either HSV-1 or HSV-2.
First episode-non primary infection is infection with either HSV-1 or HSV-2 in individuals who have previously existing antibodies against HSV-1 or HSV-2 respectively.
Recurrent HSV infection results from reactivation of latent virus. It is usually brought about by triggering factors eg UV light, immunosuppression.
Orolabial HSV disease is mostly caused by HSV-1 that occurs most commonly in children <5 years of age. It is transmitted through close contact with individuals who have active viral shedding.
Genital HSV disease is caused by HSV-2 that is the usual cause of herpes genitalis. It typically occurs in adults and transmitted through sexual contact.

Principles of Therapy

Primary Herpes Simplex Virus (HSV) Infection

  • If given within 72 hours of symptom onset, antivirals can be effective in reducing severity & duration of symptoms; however, early treatment of primary infection does not prevent recurrences
  • Choice of agent depends on cost, dosing schedule & patient preference

Recurrent Genital Herpes Simplex Virus (HSV) Infection

  • Episodic treatment for recurrent genital HSV disease may be given as a single-day patient-initiated treatment or for 5 days
  • Long-term suppressive treatment (prophylaxis) for frequent recurrences of genital HSV disease requires at least 3 months to 1 year of therapy to achieve any efficacy

Pharmacotherapy

Symptomatic Therapy

Analgesics (Oral)

  • Eg Paracetamol, Ibuprofen
  • Symptomatic relief of pain

Anesthetics (Topical)

  • Eg Benzocaine, viscous Lidocaine, Dyclonine
  • Symptomatic relief of pain
  • In theory, may cause sensitization but rarely happens in practice
  • Various topical anesthetics are available. Please see prescribing information for specific formulations in the latest MIMS

Oral Preparations

  • Symptomatic relief of ulceration & inflammation in orolabial herpes simplex virys (HSV) disease

Zinc Preparations

  • Eg Zinc oxide/glycine cream, Zinc sulfate gel
  • Shorten time of resolution of symptoms


Antiviral Therapy - Oral

Aciclovir

  • Acyclic purine nucleoside analogue that is a competitive inhibitor of viral DNA polymerase
  • Limits viral replication & stops further spread of the virus to other cells
  • Oral & Intravenous (IV) are both effective in treating HSV-1 & HSV-2
  • IV is usually reserved for severe disease or complications where hospitalization is necessary
  • Topical agent has limited efficacy for genital HSV, hence not recommended
  • Bioavailability is poor requiring frequent dosing

Famciclovir

  • Famciclovir is a prodrug of Penciclovir
  • Has higher bioavailability than Penciclovir & is rapidly converted to Penciclovir in gastrointestinal tract (GIT), blood & liver
  • Penciclovir has similar mechanism of action as Acyclovir

Valaciclovir

  • L-valine ester prodrug of Aciclovir, rapidly metabolized to Aciclovir by liver & intestine
  • Has better absorption after oral administration than Aciclovir making lower doses or lesser dosing frequency possible
  • Has been shown to decrease risk of transmission

Foscarnet

  • Pyrophosphate analogue that is a noncompetitive inhibitor of viral RNA & DNA polymerase
    • Foscarnet is virostatic & activation by thymidine kinase is not required
  • May be used for Aciclovir-resistant mucocutaneous HSV infections in immunocompromised patients

Methisoprinol or Inosiplex

  • Antiviral activity by modifying or stimulating cell-mediated immune process

Antiviral Therapy - Topical

Aciclovir - Same as above

  • Topical agent has shown limited efficacy

Cidofovir

  • May be used for Aciclovir-resistant genital infections

Docosanol

  • Inhibits fusion between the cell plasma membrane & HSV which prevents viral entry into cells & viral replication
  • Decreases healing time of recurrent herpes labialis

Penciclovir

  • Same mechanism of action as Aciclovir
  • Decreases healing time of recurrent herpes labialis

Tromantadine

  • Derivative of Amantadine w/ antiviral activity
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