Faced with an acute shortage of two drugs for American soldiers in the Persian Gulf, the Defense Department has taken the unprecedented step of buying from overseas companies large quantities of medicines not licensed for sale in the United States.

Defense officials say they are confident that the drugs -- gamma globulin, used to prevent hepatitis A, and an anti-malarial drug known as chloroquine phosphate -- are safe and effective.

They said any risk associated with the foreign-made drugs, which have not been subjected to the testing and evaluation required by the Food and Drug Administration, is far outweighed by the need to treat the hundreds of thousands of U.S. troops deployed to Saudi Arabia.

Federal law prohibits dispensing pharmaceuticals in the United States before they have been approved by the FDA. Because of this, defense officials ordered that the drugs be routed directly to Saudi Arabia from Europe. The services prohibit the use of non-FDA approved drugs on soldiers overseas, and they will have to decide whether Operation Desert Shield warranted an exception.

Officials said the drugs will be held in Saudi Arabia pending a final decision by the Pentagon on their use. The FDA will test batches of the gamma globulin, review other tests about both drugs and data on the firms producing them and then advise the Defense Department of its analysis.

A Pentagon spokesman said, "Certainly we're not going to do anything if there is strong evidence that this is not a safe move to make."

"We haven't had the need for anywhere near the quantities of vaccines and medications that we currently do and, therefore, we're running into a different set of problems than we've ever had before," said Brig. Gen. Ronald R. Blanck of the Army Surgeon General's Office.

FDA officials declined to comment about their discussions with the Defense Department. One defense source said contingency plans are being made by the two agencies to expedite future such procedures.

The troops are living in conditions that tend to promote the spread of illness, officials said. The Army's policy has been to inject each departing soldier with 5 ccs of gamma globulin that afford five months of protection, officials said, but the shortage meant smaller doses had to be given. Although the drug still possessed the same strength, it only afforded three months protection.

Since the U.S. deployment began in August, the Defense Department has bought up nearly all the domestic supplies of gamma globulin, which is manufactured by a single U.S. firm, Armour Pharmaceutical, in Blue Bell, Pa. Hospitals have reported shortages for civilian use and Armour has increased production to try to deal with the crisis.

With the advent of the second deployment of more than 200,000 troops in November, Armour's production could not satisfy the demand. After a worldwide search, Defense Department logistics officials bought 500,000 vials of gamma globulin for $1 million from Sclavo of Siena, Italy. To meet a similar shortage in the anti-malaria drug, it bought 8 million pills from Bayer AG of Leverkusen, Germany.

Some preliminary gamma globulin test data has been sent to the FDA from Sclavo and samples will be airlifted soon to the agency, a source said.

One source who is familiar with the discussions between the Defense Department and the FDA said the FDA was wary about granting full approval absent the normal process, because if anything went wrong -- a soldier became ill or suffered a side effect that could be attributed to the medication -- the FDA might be blamed.

The FDA "is not going to approve it or endorse it. The decision to use or not to use is going to be DOD's," the source said.

At the same time, defense officials had no desire to use unapproved medication without some support from scientists at FDA.

"No {military} surgeon general wants to be called before a congressional committee and asked to explain why he approved the use of a foreign-manufactured product where it resulted in injury to American citizens," the source said.

According to one federal source, during the search for alternative sources of gamma globulin, which is derived from blood plasma, there was concern raised that foreign producers might not adequately screen donors for HIV infection, raising the possibility of the infection being transmitted to U.S. soldiers.

However, Defense Department officials were assured by Sclavo that its plasma is obtained from FDA-approved U.S. blood banks that have strict screening requirements. Scientists here also confirmed that HIV infection cannot survive the process by which gamma globulin typically is made.

Riccardo Vanni, director of Sclavo's biopharmaceutical division in Siena, said yesterday in a telephone interview that his firm is pleased "to be able to offer this production to the defense, the American defense. . . . We are a group of people who are pursuing a high quality of production and we are very proud."

Bayer's U.S.-based spokesman, Ralph Abrahams, said "it was a special event" to be enlisted to assist the Defense Department and that his firm "offered to do whatever is necessary to make this medication available to the U.S. military."