varicella-zoster%20virus%20infection
VARICELLA-ZOSTER VIRUS INFECTION
Varicella, also known as chickenpox, is a self-limited benign disease caused by primary varicella-zoster virus (VZV) infection characterized by fever, malaise, and generalized pruritic vesicular rash.
The average incubation period is 14-16 days. It is transmitted via direct contact with vesicular fluid or inhalation of aerosolized respiratory secretions or via droplet route during face-to-face contact.
Hallmark sign is pruritic rash that begins in the scalp and face which eventually spreads to the trunks and extremities.

Pharmacotherapy

Symptomatic Therapy

Antipruritics

  • Calamine lotion, tepid baths, cool compresses

Antipyretics

  • Eg Paracetamol
    • Aspirin should not be used in children because of its association with Reye’s syndrome
  • Provide symptomatic relief of fever

Analgesics

  • Eg Paracetamol, nonsteroidal anti-inflammatory drugs (NSAIDs); opioids may be considered in severe pain
  • May be used for relief of pain in herpes zoster infections

Corticosteroids

  • Benefits include acute pain reduction and rapid early healing
  • Should be administered with antiviral therapy due to its immunosuppressive properties
    • Concomitant use does not reduce incidence of postherpetic neuralgia (PHN)

Antivirals for Varicella

  • In otherwise healthy children, varicella is often benign and requires symptomatic care only
  • Varicella in otherwise healthy adolescents and adults and in immunocompromised patients tends to be more severe and they may be treated with antivirals preferably within 24 hours of rash onset
  • Not recommended as prophylaxis after exposure to varicella

Aciclovir [Oral/Intravenous (IV)]

  • Aciclovir is recommended in varicella-zoster virus (VZV) infections in immunocompromised patients and pregnant human immunodeficiency virus (HIV)-infected women with uncomplicated shingles
    • May be considered in patients with chronic cutaneous disorders, in patients with diseases that can be exacerbated by VZV infection (eg cystic fibrosis), otherwise healthy children >12 years or secondary household contacts, adolescents and adults, patients receiving a course of corticosteroids or chronic salicylate therapy
  • IV therapy should be used in severely immunocompromised patients, with severe infections and in pregnant women who exhibit signs & symptoms of VZV pneumonitis
    • High-dose oral Aciclovir may be sufficient for mildly immunocompromised patients
    • Show clinical improvement in 48-72 hours
    • Can decrease the risk of contralateral eye involvement when administered for ≥3 months for patients with acute retinal necrosis
  • Actions: Aciclovir is a guanosine analogue that is a competitive inhibitor of viral DNA polymerase
    • Limits viral replication and stops further spread of the virus to other cells
  • Effects: Shortens the duration of viral shedding, halts the formation of new lesions more quickly, accelerates the rate of healing in both immunocompetent and immunocompromised patients
    • This improvement is modest in the healthy individual but can reduce life-threatening complications in high-risk individuals

Famciclovir/Valaciclovir

  • Have been used in place of Aciclovir in otherwise healthy adults and adolescents

Antivirals for Herpes Zoster

  • Oral antiviral therapy is recommended in immunocompetent patients with ophthalmic or other nontruncal dermatomal rash, patients ≥50 years, and in patients suffering moderate to severe pain or rash
  • IV Aciclovir is typically recommended in immunocompromised patients
    • Oral antivirals may be acceptable in patients who are only mildly to moderately immunocompromised
    • IV Foscarnet may be an alternative for Aciclovir-resistant VZV
  • Primary goal of treatment in herpes zoster is to reduce acute pain and PHN
  • Therapy for herpes zoster should accelerate healing, limit the severity & duration of acute and chronic pain, reduce complications
  • When taken within 72 hours of symptom onset, oral antivirals have been shown to reduce severity and duration of symptoms
    • Most viral replication has ceased by 72 hours after the onset of rash but this may be substantially extended in immunocompromised patients
    • After 72 hours, antivirals should be considered if new vesicular lesions are continuing to appear or if complications arise
  • Choice of agent depends on availability, cost, dosing schedule and patient preference

Aciclovir

  • Actions: Guanosine analogue that is a competitive inhibitor of viral DNA polymerase
    • Limits viral replication and stops further spread of the virus to other cells
  • Effects: Several studies have shown that high-dose oral Aciclovir accelerates resolution of acute lesions and may reduce the risk for prolonged pain
  • Intravenous Aciclovir should be initiated and continued until clinical improvement of extensive cutaneous lesions or patients with suspected visceral involvementIntravenous route may be shifted oral once no new cutaneous lesions are noted and signs and symptoms are improving

Famciclovir

  • Actions: Famciclovir is the diacetyl prodrug of Penciclovir; Famciclovir has higher bioavailability than Penciclovir and is rapidly converted to Penciclovir in gastrointestinal tract (GIT), blood and liver
    • Penciclovir has similar mechanism of action as Aciclovir but has a longer half-life
  • Effects: Efficacy is similar to Aciclovir

Valaciclovir

  • Actions: Valaciclovir is the valine ester derivative of Aciclovir with improved oral absorption and it is immediately transformed to Aciclovir after absorption
    • Has the same mode of action as Aciclovir
  • Effects: Efficacy is similar to Aciclovir

Famciclovir or Valaciclovir is preferable to Aciclovir because of convenient dosing and higher antiviral drug activity

Alternative Treatment for Herpes Zoster

Brivudine (Brivudin)

  • Actions: A thymidine nucleoside analogue that competitively inhibits viral DNA replication by blocking DNA polymerases
  • Brivudine is a treatment option for immunocompetent patients with herpes zoster
  • Effects: Several studies have shown that patients given Brivudine had shorter time to last new-lesion formation and full crusting, and with less experienced pain

Non-Pharmacological Therapy

Skin/Wound Care

  • Keep skin lesions dry and clean to prevent bacterial superinfection
    • Shower at least twice a day with soap and water
  • Nails should always be trimmed short and kept clean
  • Avoid peeling lesion crust and let it slough off naturally
  • Soft or liquid diet may be preferred for patients with lesions near the mouth
  • Sterile wet dressings may decrease discomfort from lesions
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