The life-prolonging but still experimental anti-AIDS drug AZT is well on its way to becoming an approved prescription drug that could soon be available to large numbers of AIDS victims.

But the question now facing the medical community is this: Will the cost of AZT be beyond the reach of the people who need it most?

Industry experts estimate that once the drug is approved by the Food and Drug Adminstration, AZT will cost anywhere from $7,000 to $15,000 for a year's supply.

Since many AIDS victims lose their jobs -- and their health insurance -- or have health insurance plans that do not cover prescription drugs, the concern is that many patients will not be able to afford the drug even if it is available.

"This is a question that will apply not only to the United States but to a larger area of the world as well," said Dr. Samuel Broder, head of the National Cancer Institute's Clinical Oncology program, which helped develop and test AZT.

It is an issue that will be debated this week in a special hearing by the House Energy and Commerce subcommittee on health and the environment.

So far, the drug has been taken by an estimated 4,500 AIDS patients who receive it at no cost because they are part of the experimental studies required by the FDA to test the new drug. Another 500 AIDS patients get AZT free of charge as part of clinical trials conducted at some 15 regional medical centers by the National Institutes of Health.

AZT (azidothymidine) is an anti-retroviral drug -- a class of drugs that appears to be effective in controlling the type of virus, known as a retrovirus, that causes acquired immune deficiency syndrome. Produced by the Burroughs Wellcome Co., AZT has gone from the laboratory bench to medical use in patients in less than two years.

The drug has been most useful in treating patients with pneumocystis carinii pneumonia, the deadly respiratory infection that claims some 60 percent of AIDS patients, said Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases.

As of March 2, 31,834 cases of AIDS had been reported to the federal government's Centers for Disease Control in Atlanta. Of those, 18,395 people have died, and more than 12,000 of the deaths were caused by pneumocystis carinii pneumonia.

In experimental clinical trials, AZT seems to prolong the lives of patients who began therapy within 90 days after having their first bout with pneumocystis. Experts do not yet know how much longer the average treated patient will live.

Studies are also under way to see if AZT is effective in treating other groups with AIDS or related conditions: children; those with AIDS-related complex, or ARC; patients suffering from neuropsychiatric symptoms associated with AIDS; and those with Kaposi's sarcoma, a type of cancer linked to AIDS.

If these studies show that AZT is effective in treating these other conditions associated with AIDS -- or if the drug is found to prevent the disease in asymptomatic carriers -- "then the implications of not having the drug easily accessible to a large number of people are even greater," Fauci said.

Exactly what will happen to AIDS patients who can no longer afford the drug is still unknown. "We can't say for sure what will happen," said Fauci. "But from what we know about the nature of the latency of the virus, it is very likely that if you stop the drug that the virus is going to {become active} again."

Taking away the drug, said Fauci, would be "tantamount to taking away the extended survival that we know is associated with use of AZT for certain forms of AIDS."

Burroughs Wellcome, which recently dubbed AZT with the new trade name Retrovir, estimates that it will cost less than $10,000 a year.

"We're predicting that the drug will cost $7,000 to $10,000 a year," said the company's public affairs official Kathy Bartlett. The price, she said, "will vary depending on a patient's dosage."

But some industry experts say that the prescription price of AZT is likely to be even higher. In a press release to other pharmaceutical companies, Burroughs Wellcome predicted that the wholesale cost of AZT will run about $188 for 100 capsules -- about an eight-day supply -- or about $9,700 a year. One industry watcher says that on average retailers and pharmacies add about 30 to 50 percent more to the wholesale price for drugs. That would place the cost of AZT at approximately $12,000 to $14,000 a year for consumers, depending on the doses needed.

"If patients can't pay for it, that's an issue that people will have to address," says the drug manufacturer's Bartlett.

"What it's going to come to I suppose," adds Jonah Shacknai, a Washington attorney whose law firm, Royer, Shacknai and Mehle, represents several pharmaceutical companies, "is whether or not the federal government finds itself paying for the chronic health care of AIDS patients. If so, it would seem abundantly sensible to make available to the patient drugs that might well reduce the costs associated with chronic care."

The debate over who will pay for AZT treatment for AIDS patients parallels an earlier dilemma for the medical community over the drug cyclosporin. This drug is used to help suppress the rejection of organs in transplant patients and must be taken for life.

Like AZT, cyclosporin was an experimental drug that showed very good results in clinical trials, and then gained FDA approval as a prescription drug. And like AZT, experts worried that many transplant patients would be unable to pay for cyclosporin once the drug went on the market.

To deal with that concern, special arrangements were made by Sandoz Pharmaceuticals Corp., the makers of cyclosporin, to supply the drug at no cost to patients who were part of a medical study. But transplant patients who had not been in one of the experimental programs faced a lifetime of bills averaging $6,000 to $8,000 a year for the drug.

Since cyclosporin first became available in November 1983, doctors have learned to maintain transplant patients on lower doses, and the annual cost of the drug has dropped to about $3,000 to $5,000 a year. Some insurance plans pay for prescription drugs.

Meanwhile, the federal government changed its policy of not paying for the drug and agreed to reimburse transplant patients who are dependent on cyclosporin. Some states will also pay for cyclosporin.

Health officials pointed out that the federal government was already paying for kidney dialysis and transplants when cyclosporin was introduced. With cyclosporin, the success rate of transplants went from the 65-70 percent range to 85 or 90 percent. "It was argued," says Shacknai, "that by reimbursing for cyclosporin and by extending its scope of use, the federal government would actually save money." Instead of paying for additional hospitalizations and further surgery when transplants failed, paying for the drug helped prevent organ rejection.

But until the federal policy was changed, Shacknai says, some doctors refused to do transplant operations on patients who were unable to pay for cyclosporin. "Patients were screened out of the transplant waiting line because they couldn't afford the drug that would make the transplants work," he says.

The concern with AZT is that until the cost drops -- or the federal government steps in to help pay for the drug -- many AIDS patients may face a similar restriction.

But unlike cyclosporin, AZT is not a miracle drug. It doesn't defeat AIDS altogether -- although it does buy time for some patients -- and the drug can cause some serious toxic side effects, most notably suppression of the immune system, in some AIDS victims.

"I think that the cost of anti-retroviral therapy {such as AZT} will almost assuredly fall with time," NCI's Broder predicts. "And if it can be shown that AZT reduces hospital stays and time lost from work, I think that one has to consider that as at least a potential offset."

In addition, Broder says, "it is quite likely that other drugs will be available in the foreseeable future" to help AIDS patients and to reduce the cost of treatment through competition.

One of the most promising is called di-deoxy cytidine (DDC). The patent for DDC is owned by the federal government, which has recently awarded a manufacturing license to Hoffmann-La Roche Inc.

"The DDC molecule is similar to AZT, but the restructuring of the molecule makes it more effective in the test tube at a much, much lower concentration," Fauci said. "The hope is that if you can suppress the virus with a lesser concentration of DDC, you may have lesser toxic side effects. We can't say that yet. It's still too early."