The Food and Drug Administration moved yesterday to require manufacturers to report immediately on health problems resulting from all prescription drugs, including more than 4,000 products marketed without government approval.

Health and Human Services Secretary Margaret M. Heckler called it "an important step in protecting the public health because it will complete FDA's early warning system for drugs."

The proposed regulation would help close a legal loophole. Last year 30 premature babies died after receiving a new intravenous Vitamin E solution, E-Ferol, that the FDA had not approved for marketing.

"By broadening the reporting requirements to cover all marketed prescription drugs, today's proposed regulations should eliminate such tragic health consequences," Dr. Frank E. Young, the food and drug commissioner, said.

Currently, the law requires that manufacturers report adverse reactions to prescription drugs that have undergone the required FDA review for safety and effectiveness, about 90 percent of the drugs on the market.

But this requirement has not applied to at least 4,200 drugs, including those sold before 1938 when the law was changed to require premarket clearance as well as more recent drugs that are claimed to be exempt because they are identical or similar to older drugs.

Under the new proposal, manufacturers of all prescription drugs, regardless of their status, would have to report any serious, unexpected adverse reaction to a drug or any significant increase in serious reactions within 15 working days.

Had such a requirement been in place, FDA officials said they might have learned earlier of infants' adverse reactions to E-Ferol after it was first marketed in late 1983. FDA did not hear of the problem until the Centers for Disease Control was asked to investigate. During a follow-up investigation, however, the FDA learned that the drug's distributor previously had received adverse reaction reports but had not alerted the government.

While the FDA was aware that E-Ferol was being marketed without approval, it initially said that it failed to take action because the drug was thought to be similar to older drugs on the market. FDA officials later acknowledged in congressional hearings that this had been in error.

A spokesman for Rep. Ted Weiss (D-N.Y.), chairman of the House Government Operations subcommittee on intergovernmental relations and human resources, yesterday praised the proposed rule as a "step in the right direction," but urged that it be extended to drugs sold over the counter.