Assessing the Efficacy of a High-Dose Lidocaine-Tetracaine Cream for the Treatment of Peripheral Neuropathic Pain

Assessing the Efficacy of High-Dose Lidocaine-Tetracaine Cream for the Treatment of Peripheral Neuropathic Pain: A Crossover Study in Elderly Patients Refractory to Pharmacological Treatments

The goal of this clinical trial is to learn if the topical anesthetic cream works to treat neuropathic chronic pain in older adults who have not found sufficient relief undergoing other pain treatments and/or medications. The safety of this drug has already been tested in other studies. The main questions it aims to answer are:

• Does the anesthetic cream lower the pain of participants?
• Can the participants return to daily activities that they have quit due to chronic pain?
• What medical problems do participants have when using this cream?

Researchers will compare the anesthetic cream to a placebo (a look-alike substance that contains no drug) to see if it works to treat neuropathic chronic pain.

Participants will:

• Use the anesthetic cream or a placebo every day for 14 days
• Visit the clinic once every 2 weeks for checkups and tests
• Keep a diary of their symptoms and the number of times they use the anesthetic cream.

This study is divided into two phases, separated by 30 days.

• Phase 1: Application of the active cream (Lidocaine 23% / Tetracaine 7%) twice daily: once in the morning upon waking and once at night before bed.
• Phase 2: Application of the placebo cream under the exact same conditions.

The order of administration (active/placebo) will be randomly assigned.

Procedure: Participants will sign the informed consent form. A baseline evaluation will be conducted, assessing VAS (Visual Analog Scale) score, functionality, and quality of life.

The use of other medications will be recorded. The creams will be applied at home with weekly telephone follow-up and daily patient self-reporting. Evaluations will be conducted on day 14 of each phase. Follow-up controls will occur one and two months after the treatment is suspended. Adherence and adverse effects will also be logged.

Inclusion Criteria:

• Age 60 years or older.
• Clinical diagnosis of peripheral neuropathic pain that has lasted for at least 6 months.
• Baseline Visual Analog Scale (VAS) pain score of 6 or higher.
• Ability to understand and sign the informed consent form.

Exclusion Criteria:

• Known hypersensitivity (allergy) to lidocaine, tetracaine, or any excipients (inactive ingredients) in the preparation
• Dermatological lesions (skin damage or sores) in the intended application area.
• Concomitant use of other topical therapies (creams, gels, patches) in the affected area.
• Severe cognitive impairment or unstable medical comorbidity.