The primary objective is to determine the efficacy of Lidocaine Patch 1.8% in reducing the severity of symptoms in participants with moderate-to-severe pain from Carpal Tunnel Syndrome.

This is a prospective, randomized, double-blind, cross-over study. Following informed consent, participants fulfilling entry criteria will be randomly assigned into one of two treatment cohorts. Cohort 1 will be treated with active lidocaine study patch for 1 week following FDA approved dosing recommendations, i.e. 12 hours during each 24-hour daily cycle. Following a 1-week washout period, provided participants continue to meet criteria to proceed, they will then be treated with a placebo topical patch for 1 week. A final visit after another 1-week washout period will complete the study. Participants assigned to the Cohort 2 will be evaluated in the same way except they will enter the placebo arm first and then, after 1-week washout, they will enter the active treatment arm, provided to continue to meet criteria to proceed.

For all measures, participants will serve as their own matched control. Comparisons will be made between significant improvements on active versus placebo treatment arms. The first two-week treatment period is Arm 1; the second two-week period is considered the cross-over arm.

Participants failing treatment will be offered standard of care treatment of steroid injection. All participants will wear a brace for the duration of the study per standard clinical practice.

Inclusion Criteria:

Participants must meet all of the following inclusion criteria to be eligible for enrollment into the study:

• Male and female participants, 18 years or older at Screening;
• Participants with Carpal Tunnel Syndrome, confirmed by CT6;
• Pain score of at least 4, based on an 11-point numeric rating scale (NRS) (scale of 0-10), at the screening (baseline) visit;
• Able and willing to provide a written informed consent;
• Able and willing to follow study instructions;
• Able and willing to return to clinic for follow-up visits;
• Able and willing to complete a daily diary;
• Intact skin over the affected wrist;
• Woman of childbearing age agreeing to use 2 forms of contraception.

Exclusion Criteria:

Participants presenting with any of the following exclusion criteria will not be enrolled into the study

• Participants must NOT have had prior steroid injection for CTS, CTS surgery, or other intervention/injury to the wrist that might interfere with assessments in the previous 30 days;
• Participants must not have pain at other sites that interfere with their ability to report site-specific pain related to the study (bilateral CT is an exclusion);
• Participants must NOT have cognitive or psychological impairment that interferes with the ability to complete study related assessments;
• Participants with mild (NRS less than 4) or no pain (only numbness) at baseline prior to randomization;
• Opioid tolerance (receiving at least 1 week of oral morphine 60 mg/day OR transdermal fentanyl 25 mcg/hour OR oral oxycodone 30 mg/day OR oral hydromorphone 8 mg/day OR an equianalgesic dose of any other opioid);
• History of sensitivity or allergy to lidocaine or ZTLIDO;
• Irritated, abraded, or otherwise non-intact skin over the affected wrist;
• Concurrently taking tocainide, mexiletine, or local anesthetics;
• Participants with history of or at significant risk for methemoglobinemia;
• Participation in another study of investigational drugs or devices within 30 days before screening, or previous participation in a Lidocaine Patch study;
• Known to or suspected of not being able to comply with the study protocol;
• Any clinically significant condition that would, in the investigator's opinion, preclude study participation for instance alcohol, medication or drug dependency, neurotic personality, psychiatric illness, epilepsy or suicide risk;
• Pregnancy or nursing mother;
• Woman in childbearing age without satisfactory contraception;
• Presence of possible other cause/s for hand pain (i.e., radicular pain, arthritis, injury, surgery) that could confound assessment or self-evaluation of the pain due to Carpal Tunnel Syndrome;
• Participants using topically applied analgesic compounds on the affected area;

Double-Blind