The antiviral drug used against AIDS in France, and reportedly used to treat film star Rock Hudson, is expected to be available for experimental and perhaps "compassionate" use in this country in a few weeks, according to the Food and Drug Administration.

A formal application for acceptance of the drug, HPA23, is expected to be filed with the FDA by Aug. 15 and testing could begin within days after that, an FDA spokesman said.

It has been used experimentally at the Institut Pasteur where Hudson was treated after his acquired immune deficiency syndrome diagnosis a year ago. Hudson entered the American Hospital in Paris after collapsing at his hotel, and he was treated for a liver problem. The cause of Hudson's liver problem is unknown, but among the possible causes is the treatment, since HPA23 is associated with liver dysfunction, according to a National Institutes of Health spokesman.

In order to get the drug into this country, the manufacturer, the French pharmaceutical house Rhone-Poulenc, has already made a preliminary application for FDA approval. That makes the drug available for limited use, principally testing.

An additional possibility is that the drug -- if the company allows it and FDA approves -- may be made available for "compassionate" use for some patients.

If it is approved for "compassionate use," it could be provided to terminal AIDS patients at the request of their physician. It is up to the manufacturer to allow such compassionate use. Many do not because regulations require that it be provided to all who request the drug, and supplies of experimental drugs are often limited. No antiviral drugs are available now for compassionate use, although one agent being tested for its enhancing effect on the immune system -- isoprenasine -- is available.

The rush to find treatments includes not only French drugs, but Mexican drugs, and others which attack the AIDS virus.

But treatments have not proved effective, and an official for the National Institute of Allergy and Infectious Diseases at NIH, said, "There is no reason to believe that HPA23 is any better than any one of several antiviral agents already under investigation at NIH."

The disease is both fatal and without a cure; there are only palliatives and stopgaps. It also is spreading unchecked around the world.

In the United States, 11,871 people have been identified as AIDS victims, according to the federal Centers for Disease Control in Atlanta. By next April, that number is expected to double.

In addition, half a million to 1 million people not counted as having AIDS are believed to have been infected. About 5 to 10 percent of those infected will come down with the full disease during the following five years. Another 25 percent may become ill with a range of typical AIDS-related symptoms, including weight loss, lymph node enlargement, diarrhea and sometimes fever, according to Dr. Harold Jaffe of the CDC's AIDS project.

HPA23 and similar drugs work on the AIDS virus by preventing it from reproducing. Researchers in this country are experimenting with drugs called suramin and ribavirin as well as alpha-interferon.

Specialists like Anthony S. Fauci, director of NIAID, emphasize that such antiviral agents alone are not enough to treat AIDS victims, because the virus infects and destroys the body's immune system. Even if the AIDS virus were eliminated from a victim's body, the damaged immune system would be unable to protect the body against a host of other illnesses, including cancer.

AIDS, which was detected only about five years ago, has struck steadily in the same proportions among several high-risk groups: homosexual men account for three-quarters of the victims, intravenous drug abusers about 20 percent, and hemophiliacs for a small percentage. A small percentage of victims come from the general population, and the percentage is not increasing. But the total number of cases continues to rise, raising concern about where the plague will stop.

It is thought to be spread primarily through sexual contact, but may also be spread through contact with needles, blood or other body fluids. It is not, however, thought to be spread through casual contact.