Herpes zoster, commonly known as shingles, occurs due to reactivation of the varicella-zoster virus (chickenpox virus). This virus remains in the dorsal root ganglion following primary infection with chickenpox. Almost one in three Australian adults who get chickenpox will develop shingles later in life. The risk of developing shingles increases with age (particularly over 50 years of age), when the body is immune compromised, or with disturbances of the spinal cord such as a tumour or radiotherapy.

Most people who develop shingles will only have one attack of shingles in their lifetime. For people who have never had chickenpox, coming into contact with a person with shingles places them at risk of developing chickenpox rather than shingles. The virus usually spreads by direct contact with the fluid from the lesions which may occur through touching the clothing or dressings containing fluid from the blisters. Shingles is less contagious than chickenpox, and the risk of transmission is low if the lesions remain covered.

Early symptoms of shingles may include tiredness, headache, and photophobia. The skin may also feel itchy, tender and painful. Any part of the body may be affected, including the face and trunk. It usually appears as a unilateral skin rash in a belt shape. This is because the virus works down the nerve root that branches out from the spinal cord. The affected skin later turns red, and blisters start to break out within two to three days. The rash usually lasts about 10-14 days with scaly crusts appearing later, often with skin depigmentation.

Treatment of herpes zoster should be initiated with oral antiviral therapy within 72 hours of rash onset for immunocompetent patients. Antiviral treatment should also be considered for all patients with ophthalmic herpes zoster and immunocompromised patients regardless of the duration of the rash. Timely initiation of an antiviral has been shown to reduce acute pain, duration of rash, viral shedding, and ophthalmic complications.

Recommended antiviral medication usually includes:

  • Oral aciclovir 800mg 5 times daily for 7 days, or
  • Oral famciclovir 250mg 8-hourly for 7 days*, or
  • Oral valaciclovir 1000mg 8-hourly for 7 days.

*Famciclovir 500mg 8-hourly for 10 days is recommended for immunocompromised patients

For pain relief, paracetamol should be the first-line therapy. More severe pain may respond to the addition of an oral corticosteroid, tricyclic antidepressant or an opioid.

Treating the skin rash

Calamine lotion has traditionally been used to soothe the discomfort of shingles. However, removal of dried calamine lotion can be painful. Patients should be advised not to over-treat the rash as this may increase the risk of infection. In order to remove crusts, the affected area can be bathed with saline three times a day. Topical corticosteroids should be avoided when lesions are active. The lesions should be covered in light, non-adherent dressing pads.

Other complications

Rare complications from herpes zoster infections include secondary bacterial skin infections or motor paralysis. Postherpetic neuralgia (PHN) is a common complication of shingles that occurs in around 10% of all patients with herpes zoster, but up to 75% of those over 70 years of age. It is caused by viral-mediated nerve damage to peripheral afferent neurons. The Therapeutic Guidelines define PHN as pain persisting for longer than four to six weeks after crusting of the vesicles.

Postherpetic neuralgia resolves within one year in 70-80% of cases, but it can persist for years in some people. PHN is characterised by excruciating pain, which may include spontaneous stabbing pain, constant burning pain, or electric shock-like pain.

Treatment of PHN includes:

  • Basic analgesics such as paracetamol or aspirin
  • Transcutaneous electrical nerve stimulation (TENS) applied as often as necessary for up to 16 hours a day for at least two weeks. It is particularly effective in combination with a tricyclic antidepressant (TCA) or anticonvulsant (off-label use)
      • Tricyclic antidepressants, e.g., oral amitriptyline 10-25mg at night, increasing to a usual maximum of 75-100mg at night, or
      • Pregabalin 75mg at night initially, then increased to a maximum tolerated dose of up to 300mg twice daily, or
      • Gabapentin 100-300mg orally at night initially, increasing to a maximum tolerated dose of up to 2400mg daily.
  • Topical medication:
      • Capsaicin 0.025% or 0.075% (Zostrix®) cream applied four times a day may provide pain relief.
      • Lignocaine 5% in an ointment or transdermal patch may also be beneficial.

References:

  1. Murtagh J. Murtagh’s General Practice. North Ryde: McGraw Hill Education; 2015.
  2. Rossi S (ed). Australian Medicines Handbook. Adelaide: AMH; 2018.
  3. Therapeutic Guidelines. eTG complete [internet]. Melbourne: Therapeutic Guidelines; 2018.

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