FDA Panel Recommends Device for Depression
Experts Want Device Restricted to Most Severely Ill Patients
Experts say they are encouraged by the data, but not all were convinced that VNS is effective.
"I think there are certainly hints to efficacy. I think it's not been proved," says Kyra J. Becker, MD, a neurologist at the University of Washington School of Medicine in Seattle and chairwoman of the FDA panel.
Some experts also express worry that the company had not done enough to show that VNS was responsible for the improvements in depression symptoms. Many patients in the trial knew that they were receiving VNS stimulation, making them vulnerable to a placebo effect. Patients in the studies were also allowed to take antidepressant drugs and other medications, which could have skewed the results, they say.
Some panelists asked the company to go back and perform a randomized trial of patients with VNS against those receiving a sham surgery in which no stimulation is delivered.
"We can guess all we want, we can speculate. But I don't find this at the acceptable level of a randomized, controlled trial," says Richard P. Malone, MD, a professor of psychiatry and epidemiology at Brigham and Women's Hospital in Boston and a member of the panel.
The committee asked the FDA to require labeling that confines VNS to patients who have gotten no benefit out of at least four existing medical depression treatments. They also want the FDA to require that psychiatrists receive special training before using the device to treat patients.
Safety in Question
Up to two-thirds of patients using VNS for depression or epilepsy experience alterations in their voice because of the electrical pulses to the vagus nerve. Many patients also experience mild side effects including persistent cough. Patients can deactivate the device with a magnet if they become uncomfortable or want to alleviate the voice alterations.
About 1% of patients using the device for epilepsy have to have it removed due to infections, according to the company.
But the experts are more uneasy about suggestions that the implants may carry risks for some patients. Thirty-one patients in one study of 235 subjects had episodes of deepening depression, and many had two or more episodes of worsening depression, according to the company.