What is the research on ketamine (ketamine hydrochloride) and its efficacy in treating chronic pain syndrome?

From the Guidelines

Ketamine infusion is a potential treatment option for chronic pain syndrome, but its use is controversial due to limited evidence and potential adverse effects. The medication has been used to treat chronic pain syndromes at subanesthetic doses, with the added benefit of reducing opioid requirements 1. Ketamine can be used as adjunctive analgesic therapy for certain conditions, such as erythromelalgia, and some pain centers offer a combination of ketamine and lidocaine infusions. However, evidence supporting its use is limited, and its potential for abuse and adverse effects, such as dissociation and hallucinations, must be carefully considered.

Some key points to consider when evaluating the use of ketamine for chronic pain syndrome include:

• The dose and duration of ketamine infusion can vary, but typical protocols involve intravenous infusions at doses ranging from 0.1-1.0 mg/kg administered over 1-4 hours 1.
• The use of ketamine may be beneficial for patients who have not responded to conventional treatments, but its effectiveness can vary depending on the individual and the specific condition being treated.
• Patients should be closely monitored for potential side effects, and those with a history of psychosis, uncontrolled hypertension, or severe cardiac disease may not be suitable candidates for this therapy.

It is essential to weigh the potential benefits and risks of ketamine infusion for chronic pain syndrome and to consider the limited evidence supporting its use. As noted in a recent study published in the Mayo Clinic Proceedings, the use of ketamine infusion for chronic pain syndrome is controversial, and its effectiveness is not well established 1. Therefore, ketamine infusion should only be considered as part of a comprehensive treatment plan, under the close supervision of a qualified healthcare provider.

From the FDA Drug Label

CLINICAL PHARMACOLOGY Ketamine is a rapid-acting general anesthetic producing an anesthetic state characterized by profound analgesia... The research on ketamine (ketamine hydrochloride) and its efficacy in treating chronic pain syndrome is not directly addressed in the provided drug label.

• The label discusses the use of ketamine as a general anesthetic and its applications in various surgical and diagnostic procedures.
• It highlights the drug's ability to produce profound analgesia, but does not specifically mention its use in treating chronic pain syndrome.
• Therefore, based on the provided information, no conclusion can be drawn about the efficacy of ketamine in treating chronic pain syndrome 2.

From the Research

Overview of Ketamine and Chronic Pain Syndrome

• Ketamine has been used to treat various chronic pain syndromes, especially those with a neuropathic component 3, 4, 5.
• Low-dose ketamine produces strong analgesia in neuropathic pain states, presumably by inhibition of the N-methyl-D-aspartate receptor 3, 5.
• Ketamine's efficacy in treating chronic pain syndrome has been explored in randomized controlled trials, with some studies demonstrating improved pain symptoms, patient satisfaction, and quality of life 4, 6.

Conditions Treated with Ketamine

• Neuropathic pain: ketamine has been shown to produce potent analgesia in neuropathic pain states 3, 5.
• Fibromyalgia: ketamine has been explored as a treatment option for fibromyalgia, with some studies suggesting improved pain symptoms and quality of life 4.
• Complex regional pain syndrome (CRPS): ketamine has been used to treat CRPS, with some studies demonstrating significant analgesic benefit 6.
• Cancer pain: ketamine has been used to treat cancer pain, with some studies suggesting improved pain symptoms and quality of life 4.

Side Effects and Risks

• Psychotropic side effects: ketamine can cause psychedelic symptoms, such as hallucinations, memory defects, and panic attacks 3, 5.
• Nausea and vomiting: ketamine can cause nausea and vomiting, especially at high doses 3.
• Cardiovascular stimulation: ketamine can cause increased heart rate and blood pressure 3.
• Hepatotoxicity: ketamine can cause liver damage, especially with long-term use 3.

Current Research and Future Directions

• Further research is needed to assess the long-term safety profile and risk-benefit analysis of ketamine for chronic pain syndrome 3, 5, 6.
• Larger, multicenter studies with longer follow-ups are needed to better select patients and determine the optimal treatment protocol 6.
• The use of ketamine in combination with other treatments, such as benzodiazepines or α2-agonists, may facilitate its clinical application and reduce side effects 5.