WASHINGTON — Massive doses of a steroid drug given within hours of a spinal cord injury can significantly reduce paralysis for patients who previously had seemed beyond help, a government study reported Friday.

The study, conducted at 10 centers around the United States, proved that the drug methylprednisolone was able to restore some feeling and movement in virtually all spinal cord injury patients, marking the first time that an effective treatment for such paralyzing injuries has been found, federal officials said.

“We now know that paralysis after spinal cord injury can be reduced by early treatment,” said Michael B. Bracken, a professor at the Yale University School of Medicine who directed the study. “We were never certain about that before this study.”

Clinical trials of the drug involved 487 spinal injury patients. The study compared the results of 162 treated with methylprednisolone with 154 treated with naloxone and 171 who received a placebo.

The results, said, Bracken, show that methylprednisolone is “an effective treatment for reducing some of the neurological damage of a spinal injury.”

Officials who monitored the study said its results could have an important effect on the lives of some 10,000 Americans annually who suffer acute spinal cord injury. Automobile accidents are the most common source of such injuries.

Most such injuries occur in men under the age of 30 and most such patients will spend their lives permanently disabled.

Methylprednisolone has been used for years to treat shock, to prevent swelling of the brain from injury or stroke and to stabilize membranes after injury. For the spinal injury study, researchers at the clinical centers gave patients 10 to 100 times the normal dosage within a 23-hour period.

The result, said Bracken, is that virtually all patients receiving the drug improved to some degree. The improvement was significantly greater than for patients with similar injuries who received other treatment.

Bracken said the study results have been evaluated by reviewers and will be published in May in the New England Journal of Medicine. He said the announcement was made in advance of publication in hopes that patients can benefit immediately.

Federal officials said doctors may obtain information about treatment with the drug by calling 301-496-5751 during working hours. Weekends, the number to call is 800-633-3425.

The drug works only if it is given within eight hours after a spinal cord injury. About 95 percent of all spinal cord patients are admitted to hospitals within eight hours, which means that most can benefit from this therapy, Bracken said.

Some patients in the study reported remarkable and unexpected recovery from serious spinal injuries.

In Phoenix, doctors credit the drug with saving Denise Shoblom, owner of several Arizona broadcast outlets, from possible paralysis.