Re: Herpes zoster

[sushantpatel_doc]

MANAGEMENT
Episodes of herpes zoster are generally self-limited and resolve without intervention. However, effective treatments do exist and can reduce the extent and duration of symptoms, and possibly the risk of chronic sequelae (ie, postherpetic neuralgia) as well. Treatment is of most benefit in those patient populations at risk for prolonged or severe symptoms, specifically, immunocompromised people and persons older than 50 years. The benefit of treating younger and healthier populations is unclear.

Uncomplicated zoster does not require inpatient care. Patients at high risk for disseminated zoster may benefit from intravenous (IV) acyclovir. Patients with disseminated zoster usually require admission for IV acyclovir. Inpatient care is also recommended for any patient demonstrating disseminated disease or ophthalmic or meningoencephalopathic involvement.

Pain Management for Acute Herpes Zoster
The majority of patients with acute herpes zoster experience pain. Primary treatments for acute zoster-associated pain include narcotic and non-narcotic analgesics (both systemic and topical), neuroactive agents, and anticonvulsant agents. While the efficacy of these treatments for general neuropathic pain has been well established, only a few of these modalities have been evaluated specifically for acute zoster-associated pain in controlled studies.

The oral narcotic oxycodone and the oral anticonvulsant gabapentin, as well as the topical analgesics aspirin and lidocaine, have all demonstrated the ability to reduce acute zoster-associated pain in double-blind, placebo-controlled studies. On the other hand, the oral anticonvulsant pregabalin failed to show any statistically significant effect in relieving acute zoster pain in a small double-blind, placebo-controlled study. Although, it should be noted this medication has demonstrated efficacy in treating the pain of postherpetic neuralgia in other controlled studies.

Antivirals and corticosteroids have also been shown to accelerate resolution of zoster-associated pain.

Nonpharmacologic therapies for acute zoster-associated pain include sympathetic, intrathecal, and epidural nerve blocks and percutaneous electrical nerve stimulation. Although well-controlled studies are few, meta-analyses and clinical trials suggest these treatments are effective in treating acute zoster-associated pain.

Antiviral Therapy for Uncomplicated Herpes Zoster
The goals of antiviral therapy in herpes zoster are to decrease pain, inhibit viral replication and shedding, promote healing of skin lesions, and prevent or reduce the severity of postherpetic neuralgia. Three antiviral agents, acyclovir, valacyclovir, and famciclovir, have been approved for treatment of herpes zoster in the United States. The mechanism of action for all of these agents is the prevention of varicella-zoster virus (VZV) replication through inhibition of the viral DNA polymerase.

Oral forms of all 3 agents have been shown in clinical trials to reduce viral shedding and accelerate resolution of symptoms, including pain, in uncomplicated herpes zoster. Some studies have suggested superiority of valacyclovir and famciclovir compared with acyclovir in terms of resolution of pain and acceleration of cutaneous healing. In addition, both valacyclovir and famciclovir have increased bioavailability over acyclovir and, as a result, require less frequent dosing.

The controlled studies of antiviral use in herpes zoster have only evaluated the efficacy of initiation of therapy within 48-72 hours of rash onset, and they have demonstrated no loss of effectiveness when medications are started at any point during that period. Several observational studies have shown antiviral therapy capable of reducing zoster pain, even when started beyond the traditional 72-hour therapeutic window. Thus, antiviral therapy should be considered for acute zoster treatment regimens, regardless of the time of presentation.

The duration of antiviral treatment in studies has varied from 7-21 days. Based on current literature, for immunocompetent patients, acyclovir for 7-10 days or a 7-day course of the newer agents is appropriate. Longer courses may be needed in immunocompromised patients.