Acupuncture can reduce the likelihood of vomiting 24 hours after chemotherapy, according to a new review of recent studies -  in which participants also took anti-vomiting medication.

Acupuncture is a 2,000-year-old Chinese medical procedure used to treat a variety of ailments by stimulating certain anatomical points on the body, usually with very thin needles that penetrate the skin.

Electroacupuncture, in which a small electrical current is passed through the inserted needle, was the only technique that reduced the incidence of vomiting directly after chemotherapy, Jeanette Ezzo, Ph.D., of James P. Swyers Enterprises and colleagues found.

However, the electroacupuncture studies were also the only studies that did not use state-of-the-art anti-vomiting drugs such as Zofran and Anzemet that have become recommended treatment for chemotherapy-related nausea.

“All trials also gave anti-vomiting drugs, but the drugs used in the electroacupuncture trials were not the most modern drugs, so it is not known if electroacupuncture adds anything to modern drugs,” Ezzo said.

The review appears in the current issue of The Cochrane Library, a publication of The Cochrane Collaboration, an international organization that evaluates medical research. Systematic reviews draw evidence-based conclusions about medical practice after considering both the content and quality of existing medical trials on a topic.

Information pooled from nine studies found that 22 percent of patients (155 of 714 patients) who received acupuncture had acute vomiting the first day after chemotherapy, compared with 33 percent (154 of 500 patients) of those who did not receive acupuncture.

Ezzo and colleagues also evaluated acupressure, in which acupuncture points are stimulated by gentle pressure from the fingers or a studded wristband, as well as mild electrical stimulation at the acupuncture points from electrodes placed on the skin.

Acupressure was the only technique among all acupuncture treatments reviewed to reduce the likelihood of nausea the day after chemotherapy, although it did not affect vomiting.

“If our finding is correct, then acupressure offers a no-cost, convenient, self-administered intervention for chemotherapy patients to reduce acute nausea,” Ezzo said, while acknowledging that the placebo effects of all nausea treatments “can be substantial.”

Electrical stimulation did not affect either nausea or vomiting. None of the acupuncture studies had enough data to determine whether any anti-nausea or anti-vomiting effects lasted beyond the first 24 hours after chemotherapy.

Despite a growing number of acupuncture studies, researchers are still not exactly sure how the technique affects the body. In the Chinese tradition, acupuncture aids the flow of “qi” or vital energy along pathways called meridians that run throughout the body. According to Tong Joo Gan, M.D., a clinical anesthesia researcher at Duke University Medical Center, acupuncture may work by stimulating the release of hormones or the body’s natural painkillers.

Ezzo and colleagues are unsure why electroacupuncture reduced vomiting while needles-only acupuncture did not. Differences existed in how many acupuncture points were stimulated and how long the stimulation lasted among the largest studies, which may have affected the results, the Cochrane reviewers say.

Gan has studied the effects of electroacupuncture for postoperative nausea and vomiting in breast cancer patients. He says electroacupuncture, which he uses in the operating room, “enhances or heightens the effects of traditional acupuncture.”

Since all the acupuncture studies in the Cochrane review also used anti-vomiting medication, the research doesn’t offer a clear answer as to whether acupuncture would be helpful for patients who get no relief from the drugs, Ezzo said.

“The clinician can relay what is known and leave it to the patient to decide,” she said.

James P. Swyers Enterprises, Ezzo’s employer, is a Baltimore company that develops complementary and alternative medicines. The review was supported in part by the Danish Cancer Society and ViFab of Denmark, the National Cancer Institute and the National Center for Complementary and Alternative Medicine.

Ezzo JM, et al. Acupuncture-point stimulation for chemotherapy-induced nausea or vomiting. The Cochrane Database of Systematic Reviews 2006, Issue 2.

The Cochrane Collaboration is an international nonprofit, independent organization that produces and disseminates systematic reviews of health care interventions and promotes the search for evidence in the form of clinical trials and other studies of interventions. Visit http://www.cochrane.org for more information.