Clinical StudyKetamine for acute neuropathic pain in patients with spinal cord injury
Introduction
Patients with neuropathic pain often manifest decreased physical, psychological, and social functioning and their sleep and daily activities may be affected negatively.1, 2, 3 Their pain also directly contributes to their disability by reducing their capacity to participate in rehabilitation and to return to work.3, 4, 5 Consequently, patients with neuropathic pain experience a lower quality of life and decreased life satisfaction.6, 7, 8
Neuropathic pain may be due to increased neuronal excitability. While local anesthetics and N-methyl-d-aspartic acid (NMDA) receptor antagonists are used to reduce abnormal excitability, and opioids, antiepileptics and antidepressants are administered to increase inhibitory mechanisms, in many patients it is difficult to gain adequate pain control.7, 9, 10
Ketamine (ketamine hydrochloride) is an NMDA receptor antagonist which blocks the calcium channel that opens when glutamic acid, an excitatory amino acid, unites with the NMDA receptor. It is useful for the treatment of neuropathic pain.11, 12, 13, 14, 15, 16, 17, 18, 19 The administration of ketamine must be continued in the chronic phase of neuropathic pain, and to our knowledge there are no reports on its efficacy in the acute phase.11, 12, 13, 14, 15 We report our experience with the ketamine treatment of patients with acute-phase neuropathic pain due to spinal cord injury (SCI).
Section snippets
Materials and methods
This study includes 13 patients with acute neuropathic pain due to SCI who were treated at our institute between August 2006 and April 2010. Informed prior consent was obtained from all patients. They were eight men and five women ranging in age from 36 years to 81 years (mean, 59.7 years). All suffered severe neuropathic pain and underwent ketamine treatment. Based on the criteria of the American Spinal Injury Association (ASIA) the neurological classification of all patients was “D”.20 To obtain
Results
Upon test challenge, there was a decrease in pain by 79.2 ± 9.6% (range, 6.8 ± 1.9 to 1.5 ± 0.8 on the VAS). All 13 patients responded positively to the test challenge, ketamine administration was continued (Table 1), and all experienced pain alleviation. The administration period was 17.2 ± 13.1 days (range, 7–59 days); it was longest (59 days) in a patient (Patient 1) treated in the subacute phase. At the termination of ketamine therapy, pain was decreased by 74.7 ± 16.4% (range, 5.8 ± 1.6 to 1.4 ± 0.8 on the
Discussion
Mechanisms that involve transmitters and receptors are related to neuropathic pain.7 Repeat peripheral nociceptive stimulation up-regulates the reaction of posterior column cells in the spinal cord at each stimulation (wind-up phenomenon)24 and they become hypersensitive and react to even weak stimulation (central sensitization).25 The NMDA receptor is thought to have a central role in this phenomenon, in the manifestation of neuropathic pain, allodynia, and hyperalgesia.26, 27
Ketamine is
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2014, Disease-a-MonthCitation Excerpt :The TCAs remain the first-choice treatment for neuropathic pain.86,312 However, no head-to-head comparisons between ADMs and other analgesics have been done.86,230,237–239,247–249,313,314 Tramadol appears to be a global utilized analgesic for chronic non-cancer pain of all types available in multiple dosage forums.