Efficacy and Safety of Intravenous Dexamethasone Palmitate Treatments in Acute and Subacute Herpes Zoster Pain

This is a randomized, prospective, multicenter, open-label, blinded-endpoint study investigating the efficacy and safety of dexamethasone palmitate (DXP) for treating acute and subacute herpes zoster (shingles) pain. The study consists of four parallel sub-studies, each designed to answer a specific question: Study 1: Compares intramuscular (IM) vs. intravenous (IV) administration of DXP (8mg) against standard therapy alone. Study 2: Compares two different IV doses of DXP (4mg vs. 8mg) against standard therapy. Study 3: For HZ on the body trunk, compares IM injection vs. tender point infiltration vs. paravertebral nerve block (all containing 8mg DXP). Study 4: For HZ on the face (trigeminal nerve), compares IM injection vs. tender point infiltration vs. trigeminal nerve block (all containing 8mg DXP). Approximately 558 adult patients with HZ rash onset within 90 days and significant pain (VAS ≥7) will be enrolled across the studies. All patients receive standard background therapy, including antiviral medication (famciclovir), pregabalin, and rescue analgesics. The primary outcome is the change in pain intensity (Visual Analogue Scale, VAS) over 6 months. Secondary outcomes include the incidence of postherpetic neuralgia (PHN) at 3 and 6 months, consumption of pain medications, patient satisfaction, quality of life, and safety. The goal is to determine if DXP, through its targeted anti-inflammatory action, provides superior pain relief and PHN prevention compared to standard care, with a favorable safety profile across different administration routes.

Inclusion Criteria: \- 1. Patients with onset of HZ rash less than 90 days. 2. HZ affected the trigeminal nerves (ophthalmic/ maxillary/ mandibular nerve). 3. Aged 18 to 75 years (inclusive). 4. Pain intensity ≥ 7 cm on a visual analogue scale (VAS) with 0= 'no pain' to 10='unbearable pain'. 5\. Tender point count \> 4. 6. Agreed to sign the informed consent form. Exclusion Criteria: 1. Infection at the puncture site. 2. Poor general situation unable to be treated. 3. A history of abuse of narcotics. 4. Non-compliance or inability to complete the self-evaluation questionnaires. 5. Pregnancy or lactation. 6. Patients using immunosuppressants and those with severe systemic diseases such as hematological malignancies, cancers, or autoimmune disorders.