A case report on use of Mexiletine as panacea for opioid induced hyperalgesia
Chauhan G, Loomba V, Upadhyay A, Sibai N. A case report on use of Mexiletine as panacea for opioid induced hyperalgesia. Regional Anesthesia and Pain Medicine 2017; 42(6).
Regional Anesthesia and Pain Medicine
Introduction OIH is a recognized complication of opioid therapy. It is a pro-nociceptive process which is related to, but different from, tolerance. This focused review will elaborate on the neurobiological mechanisms of OIH as well as summarize the pre-clinical and clinical studies supporting the existence of OIH. In particular, the role of the excitatory neurotransmitter, N-methyl-D-aspartate appears to play a central, but not the only, role in OIH. Other mechanisms of OIH include the role of spinal dynorphins and descending facilitation from the rostral ventromedial medulla. The pain practitioner has several options when confronted with a demonstrated lack of opioid efficacy. Rational polypharmacy to include non-opioid medication should be utilized when treating any patient with intractable pain. This strategy helps minimize the dose of opioid used, thus reducing the possibility of side effects and therefore, OIH. Neuropathic pain tends to preferentially respond to non-opioid medications such as antidepressants and anticonvulsants. Results/Case report We present a case of a 31-year-old female that presented to our pain clinic with chronic myofascial pain since last 6 years. The pain was located in neck bilaterally and radiated to head along with generalized weakness in the whole body. She underwent various opioid rotations over the years and was recently placed on Methadone 10 mg daily. She rated her pain 10/10 on Methadone and was scheduled initially for IV lidocaine infusion therapy. In lieu of prolonged QTc the decision was made to substitute IV Lidocaine for Mexiletine 150 mg per oral. We tapered the Methadone to 10 mg per day and gradually increase Mexiletine to 150 mg three times a day. She responded to this treatment regimen and her NRS score decreased to 2/10 with functional improvement in her daily activities and sleep. This is the first report of its kind in which Mexiletine therapy was successful in ameliorating the symptoms of Opioid-induced Hyperalgesia.