A 1-Year Survey of Zoster-Associated Pain after Amenamevir Treatment

Introduction Amenamevir is a new anti-varicella-zoster virus drug that inhibits the helicase-primase complex involved in viral replication. Amenamevir has the same effect as valaciclovir on acute pain and skin eruption, but no studies have examined the presence of long-term zoster-associated pain (ZAP) or postherpetic neuralgia (PHN) after amenamevir treatment. Methods A total of 785 herpes zoster patients treated with amenamevir were followed up for 12 months. Patients recorded their pain status on a questionnaire once a month. Results The proportion of patients with pain was 20.8% at 90 days, 8.0% at 180 days, 3.8% at 270 days, and 2.7% at 360 days after treatment. The median residual pain duration was 48 days. ZAP resolution rate slowed between 90 and 120 days, suggesting that the main feature of ZAP is a shift from nociceptive pain to neuropathic pain. Older age and more severe skin symptoms at the first visit were associated with a higher risk of developing PHN. Median ZAP duration was high for the head, face, and upper back and chest. Regarding the nature of pain, sudden pain attacks that felt like electric shocks, sensation of numbness, burning sensation, and cold/heat pain tended to remain as PHN. Conclusions Although conclusions must remain tentative without further comparative studies, amenamevir seems to have a similar effect on PHN as conventional nucleoside analogs, despite having a different action mechanism.