SHOULD THE United States permit American drug companies to sell to foreign governments drugs that have not been approved for use in this country? That's the Depo Provera question. It's available for use in this country in treating certain types of cancer. But last month the Food and Drug Administration banned its use here as a contraceptive, after finding in a four-year study that it may cause other types of cancer, irregular uterine bleeding and possible birth defects. Federal regulations bar export of any drug not approved for use at home.

Some underdeveloped nations nonetheless wish to buy the drug direct from its American manufacturer. It's cheap and, because it need to be injected only once every 90 days, it's attractive to countries where illiteracy and a shortage of medical personnel inhibit the use of other types of contraceptives. Officials of those countries resent the American ban, viewing it as a vote of no confidence in their ability to judge what's best for them. They criticize the United States for not exporting something the government considers too risky for Americans to use.

We do not believe on principle that drugs barred from certain uses in this country should necessarily be barred from export to foreign countries. But there is a big "if": They should not be barred from export if the transactions follow guidelines proposed in the Carter administration's drug-regulation bill now before Congress. These would require foreign governments to certify their request for the drugs, and American producers and sellers to disclose the results of all testing of that drug. In addition, the secretary of health, education and welfare could veto any sale determined not to be in the American public interest.

Those guidelines, in our view, would guard against blatantly fraudulent deals while allowing foreign countries to acquire - at their own risk, well known to them in advance - the drugs they feel they need to deal with what they perceive to be urgent social and medical problems.