Study to Evaluate the Safety and Pharmacokinetics of Topically Applied 40% Lidocaine Gel Compared with Placebo in Subjects With Acute Herpes Zoster (Shingles) Pain

This study is testing a high-strength lidocaine gel (40%) applied to the skin to relieve pain from shingles (herpes zoster). Shingles causes a painful rash and can lead to severe nerve pain. The gel is applied directly to the area where you feel the allodynia — a type of pain where even light touch, like brushing clothing against the skin, is very painful. Participants are randomly assigned to use either the lidocaine gel or a placebo gel and researchers track how their pain changes. You may be eligible if: - You are between 18 and 85 years old - You have been diagnosed with shingles (herpes zoster) - Your rash appeared within the last 20 days - Your rash is on your trunk or limbs (not face, head, neck, or genital area) and covers less than 300 cm2 - Your pain score is 4 or above out of 10 You may NOT be eligible if: - Your shingles rash is on your face, head, neck, or genital/rectal areas - You are allergic to lidocaine or local anaesthetics - The rash area is broken, inflamed, or not intact - You take Class I antiarrhythmic heart medications Talk to your doctor about whether this trial might be right for you.