What Is It?
Ketamine is a medication invented in the 1960’s as an anesthetic agent often used during invasive operations. In low doses, ketamine is used for chronic pain management and the treatment of depression.
What Does It Do?
Ketamine manages chronic pain by acting on a receptor of the central and peripheral nervous system called N-methyl-D-aspartate as an antagonist. NMDA promotes the amplification of nerve signals, central sensitization and opioid tolerance. By antagonizing the NMDA receptor, ketamine provides pain-relieving effects.
What Is It Used For?
Ketamine infusions can be used for patients with chronic pain that is not well-managed with commonly used pain medication or other noninvasive treatment options. Its analgesic effects have been shown in patients with CRPS, neuropathy (nerve pain), cancer pain, fibromyalgia, postherpetic (Shingles) neuralgia and diabetic neuropathy.
Evidence
In a retrospective series study, conditions that effectively responded to the ketamine infusions were most commonly CRPS, refractory back pain and intractable headache. All of these chronic pain conditions experienced analgesic effects of the ketamine of varying durations. Half of the conditions received pain relief for 3 weeks.
In a study on cancer-related neuropathic pain, 7 out of 9 patients who received an oral dose of 0.5 mg/kg ketamine 3 times a day in addition to their already established morphine routine reported a decreased pain score greater than 3 points. 4 patients experienced nausea as a side effect, 2 a loss of appetite, and 8 sedation. The results demonstrate that in low doses, ketamine can be an effective treatment option for refractory neuropathic pain management in cancer patients.
A retrospective review of 33 patients with CRPS treated with a ketamine infusion, 76% of patients had complete pain relief and 18% had partial pain relief. For all 12 patients who received a second course of treatment, complete pain relief was achieved.