CHICAGO – Internet ads for “ultrarapid detox” using anesthesia promise pain-free withdrawal from heroin and prescription painkillers.

But the technique can be life-threatening, is not pain-free and has no advantage over other methods, a new study of 106 patients found.

The study, the most rigorous to date on the method, showed that patients’ withdrawal was as severe as those of addicts undergoing other detox approaches.

“Anyone who tells you it’s painless can only honestly be referring to the period the person is under anesthesia,” said co-author Dr. Eric Collins of Columbia University Medical Center.

The study appears in today’s Journal of the American Medical Association.

Patients, all heroin addicts, were divided into three treatment groups. Those receiving ultrarapid detox were anesthetized for about four hours while they got a large dose of a drug that blocks the brain’s opioid receptors.

In an awake patient, the initial dose would cause severe withdrawal symptoms, Collins said. The anesthesia is meant to mask the symptoms.

Patients underwent withdrawal when they awoke, even though they were given additional medications for withdrawal symptoms that included anxiety, insomnia, achy muscles and joints, diarrhea and vomiting.

“People think this is a nice, pleasant way to sleep through the misery of opiate detoxification,” said Dr. Susan Stine, who trains addiction psychiatry residents at Wayne State University School of Medicine and was not involved in the new study. “This is research that’s been needed for some time.”

The method also struck out on keeping addicts clean. Eighty percent of the anesthesia patients dropped out of follow-up treatment, a dropout rate slightly higher than for another method in the study.

And three of 35 anesthesia patients suffered life-threatening events, despite painstaking safety measures.

Since it began about 15 years ago, the method has been linked with several deaths. In one case, New Jersey regulators fined and gave two-year license suspensions to two doctors practicing the method, although the doctors were cleared of negligence in seven deaths.