A study promoting new therapeutic approach, which is "incredibly unique" and is safe and effective in some patients with intractable pain. Low doses of the hormone oxytocin along with the anesthetic ketamine may provide a unique and effective therapeutic approach to some patients with severe intractable pain. Dr Pedersen has found better ways to treat patients with very severe pain.

"If you put these two together, you could replace any short-acting opiate," Caron Pedersen, FNP-C, DC, BSN, BS-PT, a nurse practitioner, chiropractor, and physical therapist specializing in patients with spinal pain, told Medscape Medical News. Dr Pedersen said, "are pretty much opioid-dependent and have been for long time, and are not getting relief." A variety of antiseizure, antidepressant, and anti-inflammatory agents, as well as muscle relaxants and adrenergic blocking agents, provide mild to moderate pain relief.

But these approaches are not always a substitute for opioids in patients with severe pain. Both oxytocin and ketamine provide analgesia by mechanisms other than stimulating opioid receptors. Oxytocin receptors are found at multiple sites in the brain and throughout the spinal cord, said Dr Tennant. In addition to activating its own receptors and decreasing pain signals, oxytocin binds to opioid receptors and stimulates endogenous opioid release in the brain. In addition to relieving pain, oxytocin lowers serum cortisol and can produce a calming effect and improve mood.

Oxytocin can block "anticipatory pain," added Dr Pedersen. Patients with intractable pain are constantly waiting for "the next burse of pain" so are "in constant stress," she said. However, when they take oxytocin, "they may actually get a lot of relief since they are no longer having that anticipation."

Pain Free, No Side Effects

The investigators are working to determine optimal doses and routes of administration for oxytocin. They have experimented with combining oxytocin with low-dose naltrexone, benzodiazepines, neuropathic agents, opioids, and now ketamine, an N-methyl-D-aspartic acid receptor antagonist. There has been a resurgence of interest in ketamine as a possible therapy for chronic pain conditions, including neuropathic pain, complex regional pain syndrome, fibromyalgia, postherpetic neuralgia, migraines, and spinal cord injury. 

At relatively high doses, ketamine has significant psychomimetic and euphoric properties that have led to abuse. Oral ketamine, sometimes called Special K, has become a popular nightclub drug. About 15 minutes after receiving the oxytocin, patients then received 0.25 to 0.50 mL (12.5 to 25 mg) of liquid ketamine, also sublingually. While the use of oxytocin as an analgesic is supported by basic science.

Argoff said, "this study does not add significantly to the human studies already completed, given its size and design." He concludes that Adding ketamine "dampens enthusiasm" for this therapeutic approach because of concerns about dependency and side effects. Adverse effects of ketamine can include nausea, headaches, fatigue, and dysphoria.