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Ketamine for Pain Management

What is ketamine?

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. 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.

 

Ketamine can now be used in the management of pain. It is a white, crystalline powder or clear liquid. The use of ketamine for pain management has been hindered by its adverse effects and risks.

Adverse effects of ketamine may include:​

As of late, interest has grown in the pain relief potential of ketamine. It is used in low doses to provide pain relief, as opposed to the high doses used for anesthesia. Ketamine can be given by various routes and vehicles. It can be injected into veins (intravenous), just beneath the skin (subcutaneous), or directly into muscle (intramuscular). It can also be given orally and topically. Vehicles for administration include creams, gels, liquids, and lozenges.​

  • Vivid dreams or nightmares

  • Hallucinations

  • Anxiety/panic attacks

  • Nausea/vomiting

  • Loss of appetite

  • Abdominal pain

  • Drowsiness

  • Elevated liver enzymes/liver damage

  • Headache

  • High blood pressure

  • Swelling of the cornea of the eye

  • Irregular heartbeat

  • Slowed breathing

  • Dizziness

  • Fainting

  • 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.​

Managing Pain With Ketamine

Ketamine 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), and pain caused by stimuli that are not usually painful (allodynia). 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. 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 control of acute 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.

Most of the clinical trials exploring the use of ketamine in the treatment of chronic pain have been related toneuropathic, 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

  • 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 antidepressants 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 in the management of chronic pain.

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.​

Conditions Related To Ketamine Use
Conclusion

Ketamine has the potential for use in the management of pain. 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 is limited, lacking, and at times conflicting. Researchers agree that more clinical trials are needed to confirm its pain-relieving role.​

References

  1. Visser E, Schug SA. The role of ketamine in pain management. Biomedicine and Pharmacotherapy. 2006 Aug; 60 (7): 341-348.

  2. Soo KL. The use of ketamine for perioperative pain management. Korean J Anesthesiol. 2012 Jul; 63 (1): 1-2.

  3. 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.

  4. 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.

  5. 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.

  6. Perrson J. Ketamine in pain management. CNS Science and Therapeutics. 2013 Mar; 19: 396-402.

  7. Hocking G, Cousins MJ. Ketamine in chronic pain management: an evidence-based review. Anesthesia and Analgesia. 2003 Dec; 97 (6): 1730-1739.

  8. Soto E. Relevance of ketamine in the management of cancer pain. Ann Palliat Med. 2013; 2 (1): 40-42.

  9. Blonk MI et al. Use of oral ketamine in chronic pain management: a review. Eur J Pain. 2009.

  10. Niesters M, Martini C, Dahan A. Ketamine for chronic pain: risks and benefits. Br J Clin Pharmacol. 2014 Feb; 77 (2): 357-367.

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