Trigeminal neuralgia (TN) is characterized by sudden, severe, usually unilateral, transient, stinging, recurrent electrocute-like shock in one or more divisions of the trigeminal nerve, lasting from a few seconds to less than 2 minutes.Simple daily-life activities, such as washing the face, brushing the teeth, eating, and talking, or the slight touch of trigger points may trigger the attack of pain of TN, resulting in a decline in the patient's quality of life (QoL). Trigger zones predominantly locate in the perioral and nasal region. Paroxysmal pain is associated with triggers in virtually all patients with TN. TN may be caused by abnormality of the trigger zone and the blockade of Na+ channel of trigger zone may be a novel and effective treatment methods for TN. Currently, most patients with TN may not achieve adequate pain relief with a single therapeutic agent. Multiple analgesics targeting different mechanisms of the pain pathway are often used.5% lidocaine medicated plaster (LMP) is a white hydrogel plaster containing adhesive material. LMP was approved for post-herpetic neuralgia (PHN) treatment by the United States Food and Drug Administration (FDA) in 1999. Tamburin et al reported that 2 patients with primary TN who stopped oral drugs because of side effects or refused surgical procedures. Both patients were instructed to wear LMP over the affected area and LMP resulted in reduction of pain intensity and the number of pain paroxysms without side effects. However, due to limitations of these open-label design studies, the observed reductions in pain intensity may have been due to treatment effect, placebo effect, changes in underlying disease state, or a combination of these factors. Therefore, randomized controlled trials will be need to be performed to draw about the efficacy of the LMP in TN.

The PATCH trial is a prospective, double-blinded, vehicle-controlled, parallel-group, multicenter, enriched enrolment with randomized withdrawal (EERW) trial aimed at estimating the efficacy and safety of LMP in patients with TN. After providing informed consent and completing a baseline evaluation, patients will participate in an initial open-label treatment period of LMP (active patches). This openly titrated process is close to clinical practice and can provide data on the proportion of responders and non-responders, the optimal dose of the analgesic drug, and the proportion of withdrawal due to adverse effects. A responder at the end of the open-label treatment phase will be included in the subsequently double-blind treatment phase.

Inclusion Criteria:

• Occurrence of episodes of intense facial paroxysmal pain in the distribution(s) of one or more divisions of the trigeminal nerve, triggered by innocuous stimuli;
• Average daily pain intensity ≥ 4 by a brief pain inventory-short form (BPI-SF) Item 5 score (0-10 rating scale of average pain) in the preceding 24-hour period;
• Concomitant analgesic regimens that include 14 days of stable doses with systemic analgesics rather than topical agents for relief of PHN will be permitted
• Normal neurologic examination;
• Normal neuroimaging analysis.

Exclusion Criteria:

• Atypical pain location (eg, no specific trigger points) or trigger zones in the mouth;
• Proposed surgical intervention due to preference of the patient;
• Any condition known to interfere with the correct execution of the sensory tests (eg, peripheral or central neurological dysfunction or cognitive impairments);
• Presence of any other acute or chronic pain disorder with the need of systemic analgesic medication for more than 10 days in the last 3 months;
• Inability to discontinue the use of another lidocaine-containing products or a class I anti-arrhythmic drug during the study period;
• History of hypersensitivity to an amide-type local anesthetic agent, or other contents of the lidocaine or vehicle patch;
• History of surgical intervention or neurological ablation to treatment TN;
• Participation in another clinical trial within 30 days of the study;
• Any patient who was judged to be unreliable or unable to understand the protocol procedures;
• Any abnormality of the skin or of vascular origin at application site;
• Pregnancy or breastfeeding;.