An FDA watchdog group criticized the agency's recent approval of a new electrical stimulation device for depression Monday. It says that the device has not been proven to work and may increase patients' risk of suicide.

Read Web MD's "What Is Vagus Nerve Stimulation?"

The device, called a Vagus Nerve Stimulator (VNS), was approved for U.S. sales Friday. But Public Citizen, an FDA and medical industry monitoring group, says that the device does not meet government standards for safety and efficacy and has not been adequately studied.

The device is also the subject of an ongoing investigation on Capitol Hill, where some lawmakers are questioning its approval.

VNS is a small electrical generator that is surgically implanted under the skin, where it delivers an electrical pulse every five seconds through wires wrapped around the vagus nerve. The vagus nerve runs from the neck to the brain. The nerve is thought to have some control over mood regulation.

John O'Reardon, MD, a psychiatrist and a paid consultant for the manufacturer, called the approval "a reasonable scientific decision." Severely depressed patients run a long-term risk of suicide attempts of nearly 20 percent, meaning they are already in danger without treatment, says O'Reardon, chief of the treatment-resistant depression clinic at the University of Pennsylvania.

"It won't help every patient. If it helps 30 percent of my severely ill patients that makes them a lot better off then they were previously," O'Reardon says.

Read Web MD's "FDA Panel Recommends Device for Depression."

Device Rejected Last Year

FDA expert advisers voted 5-2 last year to recommend approval of the device for treatment-resistant depression despite a study showing it failed to help severely depressed patients after three months. In another study, 30 percent to 40 percent who used VNS for one to two years had some improvement in their depression, according to manufacturer Cyberonics Inc.

Several experts at the time expressed concern over data suggesting that some patients who use VNS could be at increased risk for worsening depression or even suicide.

Thirty-one of 235 participants in one study had bouts of deepening depression, many reporting more than one episode. Twenty-five patients using VNS also attempted suicide in several company studies.

The FDA rejected the device in August 2004, a decision that was appealed by the manufacturer. The agency defended the reversal, noting that the surgically implanted device was approved as a last resort for severely ill patients who get no help from other treatments.

Read Web MD's "Your Guide to Depression."

Questioning Approval

Peter Lurie, MD, Public Citizen's deputy director, called the approval "one of the most questionable regulatory decisions made by the agency in recent memory.

"Devices for which medical claims are made should meet the same approval criteria as drugs. In effect, the FDA has lowered the approval bar for this device. There is simply no convincing evidence that this device works. Until and unless such data are generated, patients are better off without this device."

Cyberonics, a WebMD sponsor, declined to comment on Public Citizen's criticism of the approval.

The Senate Finance Committee, which has spent the last year and a half probing approval and safety practices at the FDA, several months ago launched an investigation into the FDA's handling of Cyberonics' application for VNS's approval.

The committee's senior Republican and Democrat noted in a joint statement Friday that they would continue their inquiry. "Both the effectiveness and the safety of medical devices must be ensured prior to their approval by the Food and Drug administration," say Sen. Charles E. Grassley (R-Iowa) and Sen. Max Baucus (D-Mont.).

VNS has been on the U.S. market since 1997 as a treatment for severe epilepsy. More than 22,000 patients have used the device, according to Cyberonics.

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FDA Defends Approval

The FDA rejected Public Citizen's complaint that the agency lowered its standards for approving VNS for depressed patients. FDA regulations require manufacturers to show "a reasonable assurance of safety" to get devices cleared, while drugs must be shown to be "safe and effective," says FDA spokeswoman Julie Zawisza.

"This device was approved for a very small subset of patients who are very, very sick and have failed all other treatment options and have no other options," she says.

VNS devices will carry "black box" warnings alerting doctors to use the device only in patients who have failed to improve after four or more other types of treatment, Zawisza says.

Richard P. Malone, MD, who served on the expert panel that scrutinized the VNS data, says he was not convinced that the device met the agency's standard for a reasonable assurance of safety or efficacy.

"The only controlled study was negative. So benefit is clearly a problem. The studies did show safety concerns, but I don't think they showed benefit," says Malone, a professor of psychiatry at Drexel University who voted against approving VNS.

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By Todd Zwillich, reviewed by Michael W. Smith, MD

SOURCES: Peter Lurie, MD, deputy director, Public Citizen Health Research Group. Sen. Charles E. Grassley (R-Iowa). Sen. Max Baucus (D-Mont.). Julie Zawisza, FDA spokesperson. Richard P. Malone, MD, professor of psychiatry, Drexel University College of Medicine. John O'Reardon, MD, assistant professor of psychiatry, University of Pennsylvania.