Case Report: Amantadine, an NMDA-receptor antagonist, for the treatment of neuropathic pain in a cat

This case report describes the presentation of neuropathic pain in cats, highlights the recognition of clinical signs such as allodynia and hyperalgesia and describes treatment with amantadine as part of an analgesic protocol for neuropathic pain relief. A cat found after a road traffic accident was presented at the emergency surgery of the University of Veterinary Medicine, Vienna. The cat had sustained a left oblique fracture of the ilium and a right sacroiliac joint subluxation. Shortly after surgery, the cat exhibited a severe wound infection at the surgical site with additional allodynia and hyperalgesia in the wound area up to the thoracolumbar region. The cat also showed signs of deterioration of the function of the ischiatic nerve in the left hind limb, with reduced proprioception and paroxysmal pain episodes. Although the cat was placed on a multimodal analgesic therapy, including oral tramadol 1 mg/ kg twice daily, meloxicam 0.1 mg/kg daily and gabapentin 10 mg/kg twice daily, only mild improvement of the neuropathic pain symptoms was achieved. Two and a half months after surgery the cat was admitted to the pain surgery at the University of Veterinary Medicine, Vienna. Gait observation revealed poor weight bearing of the left pelvic limb with dragging of the same paw. Muscle atrophy was present throughout the left pelvic limb and the cat still showed symptoms of neuropathic pain, including allodynia and hyperalgesia in the thoracolumbar area, which the cat licked excessively. Because neuropathic pain treatment can be challenging, the analgesic regime was changed. Oral amantadine 10 mg daily (3 mg/kg) was administered for 14 days in addition to oral meloxicam (0.025 mg/kg daily). Twenty-eight days after starting the new analgesic regime, the cat was markedly improved and no longer displayed clinical signs consistent with neuropathic pain. The meloxicam was stopped and the amantadine therapy continued for another 28 days. A month after discontinuing amantadine, hyperalgesia in the thoracolumbar area with excessive licking reoccurred. The signs resolved completely within seven days of resuming daily amantadine.