Is valacyclovir (valacyclovir hydrochloride) effective for treating neuropathic pain following a herpetic infection, specifically postherpetic neuralgia?

From the Guidelines

Valacyclovir is not effective for treating established postherpetic neuralgia (PHN), and other medications such as gabapentin, pregabalin, tricyclic antidepressants, or lidocaine patches are usually more effective for this condition. The most recent and highest quality study, 1, suggests that valacyclovir may help prevent PHN if started within 72 hours of rash onset, but it is not the primary treatment for established PHN. For patients with existing PHN, medications like gabapentin (starting at 300 mg daily and titrating up to 1800-3600 mg daily in divided doses), pregabalin (150-600 mg daily in divided doses), tricyclic antidepressants like amitriptyline (10-25 mg at bedtime, increasing gradually), or lidocaine patches (5%) applied to the painful area are more effective.

Some key points to consider when treating PHN include:

• Gabapentin and pregabalin are effective for treating PHN, with a number needed to treat (NNT) of 4.39 and 4.93, respectively, as reported in 1.
• Tricyclic antidepressants, such as amitriptyline, are also effective for treating PHN, with an NNT of 2.64, as reported in 1.
• Lidocaine patches (5%) can be effective for treating PHN, especially for patients who cannot tolerate oral medications, with an NNT of 2, as reported in 1.
• Valacyclovir, on the other hand, is more effective for preventing PHN when started within 72 hours of rash onset, rather than treating established PHN, as suggested in 1.

It's essential to note that the evidence for valacyclovir in treating PHN is limited, and the most recent studies, such as 1, do not support its use as a primary treatment for established PHN. Instead, valacyclovir is typically used to treat acute herpes zoster infections, and its effectiveness in preventing PHN is more significant when started early in the course of the disease.

From the FDA Drug Label

In subjects aged less than 50 years, no difference was found with respect to the duration of pain after healing (post‑herpetic neuralgia) between the recipients of VALTREX and placebo In subjects aged greater than 50 years, among the 83% who reported pain after healing (post‑herpetic neuralgia), the median duration of pain after healing (95% CI) in days was: 40 (31,51), 43 (36,55), and 59 (41,77) for 7‑day VALTREX, 14‑day VALTREX, and 7‑day oral acyclovir, respectively.

Valacyclovir is not effective for treating neuropathic pain following a herpetic infection, specifically postherpetic neuralgia, as there was no difference in the duration of pain after healing between valacyclovir and placebo in subjects aged less than 50 years, and the median duration of pain after healing was not significantly reduced in subjects aged greater than 50 years 2.

From the Research

Effectiveness of Valacyclovir for Neuropathic Pain

• Valacyclovir has been studied as a potential treatment for postherpetic neuralgia, a complication of herpes zoster characterized by persistent pain after the resolution of the rash 3, 4, 5, 6, 7.
• A randomized clinical trial found that one year of suppressive treatment with valacyclovir was associated with a lower dosage of neuropathic pain medication and reduced pain duration in some patients with postherpetic neuralgia 3.
• The study also found that participants who were younger than 60 years at the onset of herpes zoster and had a chronic disease duration had lower pain scores in the valacyclovir group compared to the placebo group 3.
• Other studies have suggested that antiviral therapy, including valacyclovir, can reduce the risk and duration of postherpetic neuralgia in elderly patients 4, 5, 6, 7.
• Valacyclovir has been shown to be comparably effective to other antivirals, such as famciclovir and brivudine, in reducing the incidence and duration of zoster-associated pain and postherpetic neuralgia 6.

Treatment Guidelines

• The management of herpes zoster and postherpetic neuralgia typically involves a combination of antiviral therapy, pain management, and other treatments 4, 5, 7.
• Antiviral therapy, including valacyclovir, should be started as soon as possible after the onset of herpes zoster to reduce the severity and duration of the disease 4, 5, 6, 7.
• Pain management may involve the use of topical or systemic agents, such as lidocaine, capsaicin, gabapentin, pregabalin, and opioid analgesics 4, 5, 7.
• Vaccination is recommended as a preventive measure to reduce the incidence of herpes zoster and postherpetic neuralgia 7.