Chronic pain syndromes have a wide range of causes and are defined by the experience of daily pain for a period of over 12 weeks. Chronic pain affects between 50-100 million adults in the U.S. yearly, and over 1.5 billion people worldwide. Approximately 1 in 10 adults report they have experienced pain daily for three months or more. Chronic pain is the leading cause of long-term disability in the U.S. today.
Up to 77% of individuals who experience chronic pain report feeling depressed due to pain. Large numbers of chronic pain patients suffer from comorbid and associated conditions of depression, chronic anxiety, and substance abuse problems. Current treatment regimens include opiate analgesics, nonsteroidal anti-inflammatory drugs (NSAIDs), and corticosteroid injections, as well as treatment with antidepressants and anti-seizure medications. Most people continue to suffer from chronic pain despite these treatments, and report minimal improvement in the level of their pain. All these treatments have the risk of significant side effects.
Traditionally, many patients with chronic pain are treated with opioid analgesics. Opioids bind to neuronal opiate receptors causing decreased activation of the neuronal pathways involved in the perception of pain. Unfortunately, these effects are short-lived, and over a relatively short period of time, the neurons involved respond by the overexpression of the opiate receptors, leading to decreased responsiveness and effectiveness to these medications.
Consequently, many people who are started on opioid analgesics, despite initial improvement in their daily pain levels, frequently require the need for escalating doses, increased frequency of dosing, and the use of more potent opioids to control their pain over time. The use of opioids to control chronic pain is, therefore, a treatment with diminishing returns, as the side effects and lack of efficacy rapidly start to overwhelm the benefits provided by this class of medications. Medication tolerance, dependence, and addiction are often the result.
Ketamine infusions have been shown to rapidly provide up to a 50% decrease in patient-reported pain levels, in patients that respond to these treatments. Ketamine is particularly effective for many chronic pain syndromes, particularly neuropathic pain syndromes, such as chronic regional pain syndrome (CRPS). Ketamine is thought to improve chronic pain in a novel way, by blocking the N-methyl-D-aspartate (NMDA) receptor. This NMDA blockade is thought to allow the pain pathways in the brain and spine to “reset,” allowing a more normal response to pain signals from the body’s nerves. This resetting of the pain pathways may last for weeks to months, and can be maintained with occasional booster treatments, as needed. Ketamine, by blocking and resetting these hyperstimulated pain pathways, allows not only a decrease in painful symptoms, but also a decrease in the need for opioid medications. In addition, there is a clear overlay of depressive symptoms and chronic anxiety for many patients suffering from chronic pain disorders. Ketamine’s ability to decrease the symptoms of depression and anxiety can lessen the compounding effect these conditions have on the patient’s pain level.