Herpes zoster (HZ) is an acute herpetic skin disease caused by the reactivation of the varicella-zoster virus (VZV) latent in the sensory ganglia. Postherpetic neuralgia (PHN) often occurs after herpes zoster heals and persists for a long time. At present, clinically anticonvulsants (such as gabapentin, pregabalin) and antidepressants (such as amitriptyline) are clinically first-line drugs for the treatment of PHN, which are not usually effective to treat PHN well, as well as to alleviate patients' bad mental symptoms. Esketamine, as a well-known N-methyl-D-aspartate receptor inhibitor, has both analgesic and antidepressant effects with extremely few incidence of respiratory depression, delirium, hallucinations, nausea and vomiting. Therefore, we hypothesize that esketamine could relieve PHN and Anxiety and depression-like symptoms symptoms in patients with PHN. This study intended to compare the efficacy of pregabalin, amitriptyline combined with esketamine therapy and pregabalin combined with amitriptyline therapy for alleviating PHN, and to further explore the feasibility and safety of esketamine in the treatment of PHN as well as underlying the mechanism of esketamine on the PHN.

Inclusion Criteria:

• 18-80 years old; Patients with post-herpetic neuralgia with anxiety and depression; NRS ≧4 points; A and (or) D ≧8 points in the Hospital Anxiety and Depression Scale (HADS) ; The course of disease ≧3 months; Patients with invalid conventional treatment (pregabalin or gabapentin combined with anti-anxiety depression, anti-epileptic dugs).

Exclusion Criteria:

• Present acute and chronic pain caused by other disease during treatment; Serious systemic disease; Severe infection, history of heart, lung, liver and kidney dysfunction, tumor, immunodeficiency and other serious diseases, or currently receiving or have recently received immunosuppression or cytotoxic drug treatment; A history of mental illness such as epilepsy, depression, Alzheimer's, multiple sclerosis, Parkinson, etc., and a history of head trauma; Participating in another clinical trial.