Post-herpetic neuralgia in elderly: Can topical capsaicin 8% patch be considered as first-line therapy?

Abstract

Post-Herpetic Neuralgia (PHN) is a painful and debilitating complication of Herpes Zoster or Shingles (HZ). HZ is caused by reactivation of Varicella-Zoster Virus (VZV) and manifests as painful skin rash. Persistent pain for three or more months after the healing of HZ rash is termed as PHN. Elderly patients are more susceptible to develop HZ due to age related decline in immunity, a factor attributed to the reactivation of VZV residing in Dorsal Root Ganglion (DRG) after the first exposure. Older age, increased rash severity, severe pain, and female sex are some of the major risk factors for developing PHN following HZ. The risk of having PHN is five times higher in older adults of more than 80 years age while more than 50% of adults older than 70 years with HZ may develop PHN. Treatment of PHN in elderly is a complex and challenging task. The risk of serious adverse events with oral medications is high due to factors such as polypharmacy for multi morbidity (drug interaction) and altered pharmacodynamic and pharmacokinetic profile (unexpected response, delayed clearance, etc.). Topical Capsaicin 8% patch is a safe and effective therapy for PHN in elderly patients. It significantly reduces pain for months after single application for 60 minutes and well tolerated even on repeated applications. Capsaicin 8% minimally absorbed into systemic circulation and rapidly metabolized in the liver, therefore the risk of drug interaction is negligible. The pharmacokinetic and pharmacodynamic properties of Capsaicin 8% patch make it a suitable choice to be considered as first line therapy of PHN in elderly patients.