The management of patients suffering from pain that is refractory to opioids remains an important challenge for healthcare workers. Patients experiencing pain with a neuropathic component, those experiencing an isolated neuropathic component, and those experiencing mixed pain including neuropathic and nociceptive components, are of particular concern. Some therapies such as tricyclic antidepressants, anticonvulsants, or antiarrhythmics, have already demonstrated efficacy but may require a few weeks to be fully effective. Analgesic interventions with more rapid action would be valuable.
The analgesic effect of intravenous (IV) sodium channel blockers, such as lidocaine, could be a viable alternative as they suppress the ectopic discharges recorded in a neuroma . However, some experimental studies performed on animals and humans have also provided evidence of a central action of lidocaine, possibly through N-methyl-D-aspartate (NMDA) receptor binding . Even if central neurological (generalized seizures and convulsive events) and cardiovascular adverse effects are well-documented with IV lidocaine, low doses do not cause significant hemodynamic changes.
Previous randomized controlled trials (RCTs) have already assessed the efficacy of IV lidocaine on non-cancer neuropathic pain such as diabetic neuropathy [3, 4], postherpetic neuralgia [5, 6], spinal cord injury , peripheral nerve injury [8, 9], post-amputation pain , sciatica , and neuralgia . In neuropathic cancer pain only three randomized placebo-controlled studies reported the use of IV lidocaine [13–15], with discordant findings. Two did not find any significant difference in pain between the lidocaine and placebo groups, but those studies were performed on a small sample (10 patients in each trial) [13, 14]. The third, most recent study, which was performed on a larger sample (n = 50), demonstrated a significant analgesic effect of IV lidocaine compared with the placebo .
Only one retrospective study specifically evaluated the needs of the palliative care unit population . The study found that among 82 patients admitted to palliative care and suffering from opioid-refractory cancer pain, 91% had a major response to parenteral lidocaine. These preliminary uncontrolled results need to be confirmed by RCTs.
Since 2010, despite a limited amount of evidence, the French drug and device regulation agency (Agence Nationale de Sécurité du Médicament, ANSM) has recommended local anesthetics given parenterally for palliative care. Lidocaine can be used to treat cancer pain that is refractory to standard opiates in the hospital at the medical staff’s discretion. The maximum dose is 8 mg/kg per day. Monitoring for toxicity should be implemented, specifically for the occurrence of a metallic taste in the mouth, numbness of the lips and tongue, hot and/or cold feelings, and headache leading to lidocaine discontinuation.
These observations prompted us to establish a multicenter, prospective, two-group, placebo-controlled, double-blind, randomized study with the primary objective of assessing the analgesic efficacy of IV lidocaine in patients in palliative care suffering from opioid-refractory cancer pain with a neuropathic component. The secondary objectives are to assess the tolerance of, symptomatology, and patient satisfaction with this therapeutic approach.