Researchers say the “club drug” ketamine might be effective against those painful migraine headaches. Here’s the reasons why it might.

Migraine pain is notoriously difficult to treat.

But a new study shows that the drug ketamine may provide some relief to patients for whom other drugs have been ineffective.

Researchers at Thomas Jefferson University Hospital in Philadelphia studied 61 patients who received continuous three-day to seven-day treatment with ketamine.

The drug is more commonly used as an anesthetic, a sedative, and to treat depression.

Ketamine also is sometimes used illicitly as a hallucinogenic “club drug” with the nickname “Special K.”

The study, which was presented at Anesthesiology 2017, the annual meeting of the American Society of Anesthesiologists, found that about three of four migraine patients reported improvements in their pain intensity at the end of the treatment period.

“These are patients for whom nothing worked at all or made a dent in their migraine pain,” Dr. Eric Schwenk, director of orthopedic anesthesia at Thomas Jefferson University Hospital and a study co-author, told Healthline.

Patients who received ketamine infusions for intractable migraine headaches — migraines that haven’t responded to any other therapies — rated their average migraine pain at 3.4 on a 10-point scale at discharge.

That’s compared with an average of 7.5 upon admission to treatment.

The lowest pain ratings were reported on the fourth day of treatment.

“Our study focused only on short-term relief, but it is encouraging that this treatment might have the potential to help patients long term,” said Schwenk in a press statement. “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.”

Schwenk and colleagues are preparing more data for release that looks at the lingering effects of ketamine treatments on patients at the point that they receive their first follow-up meeting with their doctor.

That’s typically one to three months after inpatient treatment.

Preliminary data shows that about 40 percent of patients in the study had sustained pain relief at 30 and 100 days after hospitalization. Almost 95 percent of these patients were chronic migraine sufferers.

Thomas Jefferson University Hospital is among a handful of facilities in the country currently offering ketamine as a treatment option for migraine pain.

The Jefferson Headache Center is also one of the few academic headache centers in the United States.

The hospital is opening a new ketamine infusion center this fall.

“We hope to expand its use to both more patients and more conditions in the future,” said Schwenk.

Ketamine has a reputation for having serious side effects such as hallucinations, “out of body” experiences, and vivid dreams.

This has limited the drug’s use as a pain medication.

However, adverse effects reported by people in the study group were generally mild.

Only one participant stopped their IV infusions due to the drug’s side effects, according to Schwenk.

That may be due to the low, slow dose of the drug given to patients compared to a single high dose when ketamine is used as an anesthetic, he said.

“The chance of side effects is substantially less for patients getting treatment for headaches,” said Schwenk.

About 12 percent of Americans have migraines, which are typified by intense pain, sensitivity to light and sound, and nausea.

Migraine headaches are three times more common among women than men, and their causes and treatments remain poorly understood.

Ketamine is sometimes used as an alternative to opiate-based painkillers because it targets N-methyl-D-aspartate (NMDA) receptors in the brain, not opiate receptor sites.

That makes it a valuable drug for treating pain patients with a history of opiate addiction, for example.

“Ketamine is a unique drug, and is experiencing a renaissance in emergency medicine right now,” said Rick Pescatore, DO, assistant director of emergency medicine research at Inspira Health Network.

Pescatore said he has used the drug to treat migraine patients in his own practice.

“We continue to find new ways to utilize it to the benefit of our patients, all with the benefit of avoiding the harmful and dangerous effects of opioids and other addicting medicines,” Pescatore told Healthline. “It has a host of properties that make it ideal for our environment, including hemodynamic support (it doesn’t drop the blood pressure like so many other medications), pain relief, and there’s even a growing body of literature that it can decrease depressive symptoms. It’s a great and versatile drug.”

However, he said, caution in prescribing the drug is warranted.

“For example, years ago we thought it was verboten in patients with head trauma. Now, there’s even literature suggesting it might be beneficial,” he said. “More saliently, ketamine exerts its effects through the NMDA receptor, a signaling molecule we’re only recently learning more about and finding dangers like encephalitis.”

Schwenk agrees that “we don’t have a good grasp of why ketamine works” and “who it works for particularly well,” although follow-up studies may provide answers.

“One of our questions is: Can we predict which patients are getting a sustained response?” he said.

Previous studies also found ketamine to hold promise as a migraine treatment.

In 2012, Dr. Magdalena Anitescu of the University of Chicago Medical Center and colleagues reported that all 49 patients who underwent ketamine infusions over a five-year period reported significant pain reduction.

In some cases, they lasted up to three weeks after treatment.

Other researchers have reported success in using a ketamine nasal spray to reduce the severity of migraine aura and flare-ups of migraine breakthrough pain.