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By Sarah Abedi, MD

Ketamine has been in the medical toolbox for a long time. With its first use as a surgical anesthetic in 1970, ketamine quickly also gained popularity for its ability to maintain hemodynamic stability on the battlefield. Unlike other anesthesia that can sometimes bring down blood pressure and respiratory rate, ketamine does not cause much fluctuation in hemodynamics. This is another reason why ketamine has become a popular choice in the emergency room for unstable patients as well as a frequent choice for sedating children during painful procedures. Ketamine is currently only approved by the food and drug administration (FDA) for short-term sedation and anesthesia and recently obtained FDA approved for a nasal spray ketamine version (Spravato) for treatment-resistant depression. We have also found ketamine to have psychedelic properties aiding in psychedelic assisted psychotherapy. But can ketamine help with chronic abdominal pain?

“There is another, less common condition of abdominal pain that is chronic or frequently recurring, which is not associated with changes in bowel habits.”

People with functional gastrointestinal (GI) disorders can have a variety of symptoms that range from painless diarrhea or constipation, to pain associated with diarrhea and/or constipation (usually called irritable bowel syndrome). There is another, less common condition of abdominal pain that is chronic or frequently recurring, which is not associated with changes in bowel habits. This condition is called Centrally Mediated Abdominal Pain Syndrome (CAPS).

There are no abnormal x-rays or laboratory findings to explain the pain. It occurs because of altered processing of nerve impulses in the central nervous system, and it is not associated with altered motility in the intestines. CAPS is characterized by continuous or frequent abdominal pain that is often severe. It has little or no relationship to events such as eating, defecation, or menses. For people with CAPS, the pain can be so all-consuming that it becomes the main focus of their life. Unfortunately, many patients end up on narcotics as the last resort.

Ketamine’s most important pharmacological properties are linked to its blocking effect on an important receptor in the brain and spinal cord that plays a crucial role in pain sensitization. This effect is a result of the drugs antagonism to the N-methyl-D-aspartate (NMDA) receptor. The NMDA receptor is involved in the amplification of pain signals, opioid tolerance and the development of sensitization of the spinal cord and brain to pain signals. Ketamine has also been noted to have anti-inflammatory properties with a systemic review showing intraoperative ketamine reducing postoperative cytokine levels and associated inflammatory response in surgical patients.

“Ketamine is increasingly being used for refractory chronic pain such as complex regional pain syndrome and fibromyalgia, the latter often being comorbid with CAPS.”

Ketamine is increasingly being used for refractory chronic pain such as complex regional pain syndrome and fibromyalgia, the latter often being comorbid with CAPS. Its practical use for these conditions is greatly limited by the fact that the medication is commonly given as intermittent IV infusions with studies showing that it may provide short-term pain relief. A single dose of ketamine does not appear to be sufficient for control of chronic pain, and current protocols appear to have multiple IV infusions lasting several hours. Although the research often has small sample sizes, there does appear to be a short-term benefit to infusions for some patients.

Another reason against the use of ketamine for CAPS is the fact that chronic ketamine abuse does appear to be associated with liver and bladder damage as well as addictive behavior. There is very little long-term data on the safety regarding ketamine in chronic pain use. Some patients that have suffered from chronic pain do see benefit with ketamine but usually as a last resort.

CAPS like all types of chronic pain can be an incredibly debilitating condition and when current FDA treatments for chronic pain syndromes do not help, we are seeing increasingly more off-label uses of ketamine in the hope of harnessing this potential relief.

Sarah Abedi, MD is an emergency medicine doctor practicing in Southern California. She completed her medical school at UC Irvine and finished her emergency medicine residency at Harbor UCLA. Her medical interests lie in the science of disease prevention which motivated her to create The Hidden Body Podcast.