Intravenous (IV) Ketamine is an exciting therapy.
It is being used for Complex Regional Pain Syndrome (CRPS, also known as Reflex Sympathetic Dystrophy, or RSD) and Major Depressive Disorder (MDD). It has also been used for radiculopathy, phantom limb pain, post herpetic neuralgia migraine, central neuropathic pain, chemotherapy induced neuropathy, fibromyalgia, painful limb ischemia, traumatic peripheral nerve injury, spinal cord injury, temporomandibular joint pain, trigeminal neuropathic pain and whiplash.
Ketamine is used when first-line treatments, such as tricyclic antidepressants (such as amitriptyline or Elavil) or reuptake inhibitors (such as duloxetine or Cymbalta) or “membrane stablizers,”(such as gabapentin or Neurontin or pregabalin or Lyrica) don’t work for CRPS or MDD. Up to 60% of patients with neuropathic pain can be unresponsive to standard treatment.
While rarely covered by insurance, IV ketamine can be an important and effective tool to treat chronic pain.
Ketamine was approved by the FDA in 1970 as an anesthetic. It was useful because it provided anesthesia and amnesia, while not decreasing either heart rate or breathing. Ketamine is called a dissociative anesthetic because it causes one to become dissociated from the pain. Occasionally, it can cause a very unpleasant experience of feeling like you are out of your body. For this reason, its use as an anesthetic is limited.
Ketamine does not work well when you take it by mouth because it gets broken down by the liver. While some people do give it by mouth, it is more effective when given intravenously.
There is no consensus on how to best give ketamine, including how much to give, how long to give it or how frequently to give it. High doses of ketamine can cause unpleasant, dissociative, symptoms during the infusion which need to be treated with drugs like benzodiazepines, such as midazolam or Versed.
We use low dose ketamine infusions because benzodiazepines can interfere with the effect of the ketamine and because we want to avoid the unpleasant side effects of ketamine.
Patients having ketamine infusion should be medically cleared.
Patients may be pretreated with ondansetron (Zofran) for nausea. Other drugs, such as clonidine and midazolam may be used. Meclizine can help with nystagmus. Rarely, Seroquel and Klonopin may be needed.
We will perform up to 4 infusions separated by a week. If necessary, we can perform daily infusions for up to 10 days. Our infusions last 2 hours. Patients will be monitored by an RN for the entire procedure.
Greater than 50% relief has been seen after a 10-day infusion with benefit up to 3 months, with “booster infusions“ of three infusions as needed.
Ketamine acts at the N-methyl-D-aspartate (NMDA) receptor. The NMDA receptor causes pain transmission to be increased. We believe that ketamine acts by blocking the NMDA receptor. Ketamine also works in the primitive part of the brain by causing activation of transmitters which block pain.