The study of 61 patients found that almost 75 percent experienced an improvement in their migraine intensity after a three- to seven-day course of inpatient treatment with ketamine. The drug is used to induce general anesthesia but also provides powerful pain control for patients with many painful conditions in lower doses than its anesthetic use.

“Ketamine may hold promise as a treatment for migraine headaches in patients who have failed other treatments,” said study co-author Eric Schwenk, M.D., director of orthopedic anesthesia at Thomas Jefferson University Hospital in Philadelphia. “Our study focused only on short-term relief, but it is encouraging that this treatment might have the potential to help patients long-term. Our work provides the basis for future, prospective studies that involve larger numbers of patients.”

An estimated 12 percent of the U.S. population suffers from migraines — recurring attacks of throbbing or pulsing moderate to severe pain. A subset of these patients, along with those who suffer from other types of headaches, do not respond to treatment. During a migraine, people are often very sensitive to light, sound and may become nauseated or vomit. Migraines are three times more common in women than in men.

The researchers reviewed data for patients who received ketamine infusions for intractable migraine headaches — migraines that have failed all other therapies. On a scale of 0-10, the average migraine headache pain rating at admission was 7.5, compared with 3.4 on discharge. The average length of infusion was 5.1 days, and the day of lowest pain ratings was day 4. Adverse effects were generally mild.

Dr. Schwenk said while his hospital uses ketamine to treat intractable migraines, the treatment is not yet widely available. Thomas Jefferson University Hospital will be opening a new infusion center this fall that will treat more patients with headaches using ketamine. “We hope to expand its use to both more patients and more conditions in the future,” he said.

“Due to the retrospective nature of the study, we cannot definitively say that ketamine is entirely responsible for the pain relief, but we have provided a basis for additional larger studies to be undertaken,” Dr. Schwenk added.