Updated from 9:25 a.m. EDT

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Cyberonics

(CYBX)

fell again Friday after a major selloff Thursday that was triggered by the Food and Drug Administration's decision to overrule the advice of an advisory panel and reject the company's application to market a pacemaker-like device to treat depression.

The decision, announced by Cyberonics yesterday, flattened the stock of the Houston, Texas-based company, which had been hoping for a positive FDA response in October. The company cited an advisory panel's support of the device, in a 5-to-2 vote, as the source of its optimism. The company had been seeking approval of its VNS Therapy device for treating patients with long-term depression that isn't helped by medication, psychiatry or shock treatments.

The stock shed 33 cents, or 2.3%, to $14.03 Friday. Yesterday, it lost $9.59, or 40%. Some 27 million shares changed hands, about 10 times the stock's average volume.

Cyberonics responded angrily to the agency's ruling. "We are shocked and bewildered by FDA's decision to ignore its expert advisory panel's recommendation," said Robert P. Cummins, the company's chairman and chief executive, in a prepared statement.

In a conference call with analysts and investors Thursday morning, Cummins' comments were less measured. He attacked the FDA as "one of the most unpredictable groups we have dealt with" and repeatedly called the agency's decision "inexplicable."

He accused the agency of demanding clinical tests that he alleged are "inconsistent" with the FDA's regulations governing the testing of experimental medical devices. "This unprecedented decision was a mistake," he said.

Cummins said Cyberonics executives want to meet with FDA officials as soon as possible to discuss what additional research information would be needed to get the VNS Therapy device approved for marketing. Asked by one analyst how long it might take for Cyberonics to develop, conduct and evaluate the necessary research, Cummins said it could take three years, "give or take six months," to get the information to an FDA advisory panel again. "The rules seem to change at FDA's whim," he said.

The VNS Therapy device was recommended six years ago by the FDA for treating epilepsy.

Given the FDA's latest decision, Cummins said it will take a few weeks for the company to revise its financial guidance for the second quarter, which ends Oct. 31.