By Pat Anson, PNN Editor

Low doses of ketamine are just as effective at treating trauma pain in emergency room patients as larger standard doses, according to a new study by researchers at Loyola University Medical Center in Chicago.

Ketamine is a non-opioid that’s been used for decades as a surgical anesthetic, but in recent years it’s increasingly being used to treat short-term acute pain in hospital emergency rooms. A standard dose of ketamine administered intravenously is 0.30 mg/kg, but Loyola researchers wanted to see if half the normal dose could be just as effective.

"We challenged the conventional ketamine dose used to treat pain," said lead study author Shannon Lovett, MD, an emergency physician at Loyola University Medical Center (LUMC). "Our study should help demonstrate that a lower dose is sufficient to treat pain."

Lovett and her colleagues recruited 98 patient volunteers who were in moderate to severe acute pain. Half received just 0.15 mg/kg of IV ketamine, while the other half received the standard dose. Both patients and providers were “blinded” on which dose was being administered.

After 15 minutes, patients in the standard dose group had a greater reduction in pain, but experienced more side effects such as dizziness, mood changes and hallucinations. After 30 minutes, adverse events and pain levels were similar in both dosing groups.

Asked if they would take ketamine again, 76% of patients in the low-dose group said yes, while only 62% in the standard dose group said they would.

"As we continue with our research, we hope to find data that supports diminished side effects with the lower dose of ketamine with equal efficacy in treating pain," said senior author Megan Rech, PharmD, an emergency medicine pharmacist at LUMC.

The study findings are reported in the journal Academic Emergency Medicine.

Researchers said there is “robust evidence supporting the use of ketamine as an alternative to traditional opioids across a wide range of doses,” but its effectiveness is usually short-lived. Ketamine does not have a significant analgesic effect after 60 minutes. It also puts patients into a hypnotic, dream-like state in which they appear awake, but are unresponsive. For that reason, ketamine is only administered under medical supervision.

A growing number of outpatient clinics provide off-label infusions of ketamine for depression, post-traumatic stress disorder (PTSD) and difficult chronic pain conditions such as Complex Regional Pain Syndrome (CRPS). The infusions are usually not covered by insurance.

A pilot study is underway to see if an oral version of ketamine and aspirin, combined in a tablet, could be used to treat pain at home.