What Is Ketamine?
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Ketamine was approved for use by the United States Food and Drug Administration (FDA) in 1970. It is a derivative of phencyclidine hydrochloride, which is better known as PCP or angel dust. It is a white, crystalline powder or clear liquid. Ketamine is primarily used by veterinarians as a horse tranquilizer. It is one-tenth as potent as PCP and was originally used as an anesthetic agent in humans.
Today, its use as an anesthetic agent is waning. Instead, many are beginning to question the role of ketamine used for pain relief. This is especially for severe neuropathic pain, and as a treatment for a common comorbid condition of chronic pain: depression.
Does Ketamine For Pain Relief Work?As of late, interest has grown in researching ketamine for pain. In this case, it is used in low doses to provide pain relief, as opposed to the high doses used for anesthesia.
Ketamine in pain management may be used for relief of acute or chronic pain. A single intravenous dose of the medication prior to skin incision was found to decrease postoperative pain and reduce morphine consumption. Ketamine can also be used to counter postoperative pain in patients with:
- Decreased responsiveness to opioids (tolerance)
- Increased sensitivity to pain (hyperalgesia)
- Pain caused by stimuli that are not usually painful (allodynia)
Ketamine’s use for acute pain is recommended as an addition to traditional narcotic pain relievers. It is not meant to be used alone for acute pain relief. The optimal dose of ketamine for pain has not been established. But it is known that a narrow window exists between the optimal dose for pain relief and the dose for anesthesia causing loss of consciousness.
Ketamine For Pain Management ResearchMore research needs to be done before ketamine for pain management can be widely prescribed. There are ketamine side effects and risks for abuse that we’ll discuss below. Some studies have shown positive benefits of use, however.
A Korean study concluded that a small dose of ketamine provided pain relief proportional to fentanyl, a very potent narcotic pain reliever, in the management of acute postoperative pain.
A study done in India concluded that low-dose ketamine provided superior pain relief, and resulted in less sedation, and less nausea and vomiting than intermittent morphine, in patients suffering from musculoskeletal trauma.
A 2014 study from the British Journal of Clinical Pharmacology, noted that while ketamine was well-tolerated in clinical settings, it’s potential for abuse required more research into its efficacy as a pain management solution. The researchers did note that it was a treatment option for patients with therapy-resistant severe neuropathic pain.
Chronic Pain Conditions For Ketamine UseMost of the clinical trials exploring the use of ketamine in the treatment of chronic pain have been related to neuropathic, or nerve, pain. An Australian trial concluded that ketamine had efficacy comparable to placebo with respect to chronic neuropathic pain.
Ketamine has been tested in other chronic pain disorders including:
- Atypical tooth pain
- Pain from decreased blood flow (ischemia) to tissues
- Complex regional pain syndrome, which can affect a limb after injury
- Fibromyalgia, which is a form of widespread musculoskeletal pain, including back pain
- Facial pain
- Phantom limb pain experienced after amputation
- Post herpetic neuralgia, which is nerve pain after the resolution of shingles
- Poststroke pain
- Spinal injury
- Temporomandibular joint (TMJ) pain
Unfortunately, the evidence for the efficacy of ketamine in the treatment of chronic pain is weak to moderate. Nevertheless, it deserves consideration as a third-line agent when first and second-line agents such as narcotics, anti-seizure medications, and anti-depressants do not adequately relieve chronic pain. Overall, the lack of evidence regarding efficacy, and poor safety profile, do not support the routine use of ketamine for pain management for the majority of chronic pain patients.
Most of the existing studies examining whether or not ketamine is helpful with cancer pain look at its use in combination with opioid, or narcotic, pain relievers. In studies, ketamine has been shown to have an opioid or morphine sparing effect, but no significant effect on the intensity of pain. Other studies have shown improvement in pain when ketamine is added to opioid pain interventions such as patient-controlled morphine. Evidence for the use of ketamine for cancer pain is limited and conflicting.
Ketamine For DepressionThe direct use of ketamine for pain management is important, however, ketamine for depression may be another opportunity for treatment. We’ve written extensively on the relationship between chronic pain and depression, but most importantly in this case, many patients who reduce symptoms of one can effectively reduce symptoms of the other condition.
When it comes to ketamine for depression, early research, including a small study in 2009 published in Biological Psychiatry, found severely depressed patients who received intravenous ketamine experienced a reduction in suicidal thoughts.
Continued studies of ketamine’s potential for treating depression confirmed early results. In 2014, Japanese researchers from the RIKEN Center for Life Science Technologies fed ketamine to monkeys and studied their brains with PET molecular imaging. Scientists discovered that the drug works to boosts serotonin activity, particularly in the area of the brain that regulates motivation.
The research has also caught the eye of a European subsidiary of health care conglomerate Johnson & Johnson that is working on a nasal spray version of ketamine to treat depression. A clinical trial of the drug conducted at Mt. Sinai Hospital resulted in a nearly 64% response rate among 72 depressed patients who had tried at least two other medications with no relief.
Ketamine for depression is attractive to researchers because it works fast—as quickly as 24 hours—and lasts a relatively long period of time. It works differently than typical anti-depressants and has proven particularly effective for people who have not experienced relief from traditional medications, such as serotonin reuptake inhibitors. Commonly used anti-depressants can take months to work, if they work at all, delaying relief for patients suffering from depression.
How To Use Ketamine For Pain ControlKetamine can be given by various routes and vehicles. It can be injected:
- Injected into veins (intravenous)
- Just beneath the skin (subcutaneous)
- Directly into muscle (intramuscular)
It can also be given orally and topically. Vehicles for administration include creams, gels, liquids, and lozenges. The use of ketamine for pain management, however, has been hindered by its adverse effects and risks.
Ketamine Side Effects And RisksAdverse effects of ketamine may include:
- Vivid dreams or nightmares
- Anxiety/panic attacks
- Loss of appetite
- Abdominal pain
- Elevated liver enzymes/liver damage
- High blood pressure
- Swelling of the cornea of the eye
- Irregular heartbeat
- Slowed breathing
- Difficulty urinating
Patients taking ketamine for prolonged periods are at high-risk for abuse. It has become a recreational drug of abuse. Abusers can inject, inhale, or smoke ketamine. It is referred to as special K or super K on the street. Ketamine is not as addictive as opioid, or narcotic, pain relievers however.
Avoiding these risks comes down to working with a highly-specialized, well-trained pain specialist. They’ll work directly with you to correctly diagnose your condition and then explain the treatment options that could work for you. If ketamine is suggested, they’ll work diligently to prescribe the appropriate dosage and put proper procedures in place to reduce your risk.
ConclusionKetamine for pain has the potential for reducing pain levels in patients. It is a medication with anesthetic and pain relieving properties. At low doses, ketamine’s pain relieving properties dominate. Evidence for the utility of ketamine in the management of pain however is limited, lacking, and at times conflicting. Researchers agree that more clinical trials are needed to confirm its pain-relieving role. The References listed below are a start and can be a resource for you to learn more about this pain management drug.
If you’re interested in learning more about how to manage your pain, safely and effectively, reach out to a pain doctor in your area today.
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- Soo KL. The use of ketamine for perioperative pain management. Korean J Anesthesiol. 2012 Jul; 63 (1): 1-2.
- Parikh B, Maliwad J, Shah VR. Preventative analgesia: effect of small dose of ketamine on morphine requirement after renal surgery. J Anesthesiol Clin Pharmacol. 2011; 27: 485-488.
- Gurnani A, Sharma PK, Rautela RS, Bhattacharya A. Analgesia for acute musculoskeletal trauma: low-dose subcutaneous infusion of ketamine. Anaesth Intensive Care. 1996; 24: 32-36.
- Ducharme J. No pain, big gain: effective pain management. Program and abstracts of the American College of Emergency Physicians 2011 Scientific Assembly; October 15-18, 2011; San Francisco, California.
- Perrson J. Ketamine in pain management. CNS Science and Therapeutics. 2013 Mar; 19: 396-402.
- Hocking G, Cousins MJ. Ketamine in chronic pain management: an evidence-based review. Anesthesia and Analgesia. 2003 Dec; 97 (6): 1730-1739.
- Soto E. Relevance of ketamine in the management of cancer pain. Ann Palliat Med. 2013; 2 (1): 40-42.
- Blonk MI et al. Use of oral ketamine in chronic pain management: a review. Eur J Pain. 2009.
- Niesters M, Martini C, Dahan A. Ketamine for chronic pain: risks and benefits. Br J Clin Pharmacol. 2014 Feb; 77 (2): 357-367.