The Evolving Role of Ketamine in Chronic Pain Management
Introduction
Ketamine hydrochloride, approved by the FDA in 1970, is primarily known as an anesthetic. Over the past two decades, it has gained traction for its efficacy in treating chronic pain. This article discusses the background, clinical applications, and practical considerations for using ketamine in pain management.
Background
Ketamine acts as a noncompetitive antagonist of the N-methyl-D-aspartate (NMDA) receptor for glutamate, a major excitatory neurotransmitter within the central nervous system. Initially indicated as an anesthetic induction agent with doses ranging from 1 mg/kg to 4.5 mg/kg, ketamine exists in two enantiomers: S and R structures. The S enantiomer is more potent due to its affinity for the PCP binding sites on the NMDA receptor. Structurally related to phencyclidine, ketamine has a lower incidence of hallucinations and minimal effect on respiratory function. It can produce dissociative sensations, leading to some non-medical use. Other effects include elevated blood pressure and bronchodilation. Recently, ketamine has become popular in treating chronic pain.
Ketamine for Treating Chronic Pain
Ketamine's use in chronic pain management is extensive. Since the 1990s, studies have suggested that IV ketamine infusions are effective for Complex Regional Pain Syndrome (CRPS) and other conditions involving central sensitization, such as postherpetic neuralgia, migraine, burns, fibromyalgia, and neuropathies.
- Sigtermans et al.: Patients treated for 4 days with a 22 mg/h/70 kg infusion experienced significantly lower pain scores over a 12-week evaluation period.
- Sheehy et al.: In a study involving children and adolescents with chronic pain, ketamine infusions (0.3 mg/kg/h for 4-8 hours over 3 days) showed significant pain reduction, particularly for CRPS.
- Swartzman et al.: A double-blind randomized controlled study found that ketamine (0.35 mg/kg/hr for 4 hours over 10 days) significantly reduced pain parameters for up to 90 days.
Clinicians have reported administering doses ranging from 50 to 800 mg per treatment, noting its effectiveness in reducing chronic pain.
Working With Ketamine
My interest in ketamine infusions began in 2000, driven by its intriguing infusion process and lasting pain relief effects. With an increase in inquiries from physicians and the proliferation of ketamine infusion clinics, here are some considerations for starting ketamine IV therapy:
- Dedicated Setting: Due to potential hallucinations and dissociative sensations, a dedicated treatment setting is essential.
- Staffing: Hire registered nurses or personnel with IV therapy experience.
- Supplies: Necessary supplies include IV cannulas (22-24G) or butterfly needles, IV tubing, IV piggyback (100-250ml), monitoring equipment, and medications for side effects.
- Insurance: Determine insurance coverage and reimbursement rates. Patients may be willing to pay out-of-pocket if insurance does not cover the therapy.
Conclusion
Ketamine is a versatile pharmaceutical with a reputation for effectively managing a variety of conditions. Despite its history of illicit use, its clinical benefits are well-documented, and ongoing studies continue to uncover more advantages. As ketamine gains popularity, its role in chronic pain management becomes increasingly prominent. For more insights into ketamine therapy, consider further reading and discussions with experienced clinicians.
Ketamine has come a long way from its anesthetic origins, evolving into a powerful tool for chronic pain management. Its unique properties and growing body of evidence make it a valuable option for patients suffering from various pain conditions.
- https://academic.oup.com/painmedicine/article/20/2/323/4925560
- https://academic.oup.com/painmedicine/article/16/5/943/2460721
- https://link.springer.com/article/10.1007/s11916-018-0664-x
- https://pubs.asahq.org/anesthesiology/article/133/1/13/109071/Ketamine-for-Chronic-PainOld-Drug-New-Trick
- https://pubmed.ncbi.nlm.nih.gov/34820225/
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