The Supreme Court ruled yesterday that generic "copycat" drugs, imitations of brand-name products, must be screened for safety and effectiveness by the Food and Drug Administration before they are marketed.

The justices unanimously reversed an appeals court decision that had freed many of these drugs from pre-marketing scrutiny. The FDA said the lower court action would have "crippled" its authority and left consumers with no assurance that the generic "equivalents" were either equivalent or safe.

Generic copies, sometimes called "me-too" drugs, are versions of well-advertised brand-name drugs which claim to produce the same result at a lower price. Often they are designed to look exactly like the copied product so as to seem familiar to consumers. The generics, championed by consumer groups, now constitute over 14 percent of the prescription drug market.

The case began when the FDA moved against the Florida-based Generix Drug Corp. to stop it from distributing a variety of prescription drugs that have not been approved by the agency. The products purportedly used the same active ingredient as the brands copied, but employed different chemicals as binders and coaters.

Generix said the active ingredients had already been approved by the FDA at the time they were marketed by the original manufacturers, so its product was not a "new drug" as defined by the law requiring FDA approval.

The FDA said approval was required because the addition of the other substances could substantially alter the performance of the active ingredient, which often forms just 10 percent of the overall product.

After Generix won at the 11th Circuit Court of Appeals, the government appealed to the Supreme Court, which required only eight terse pages to reverse the lower court's ruling, saying the judges "misread the statutory text."

Justice John Paul Stevens, writing for the court, said the court of appeals "rested on the proposition that the statutory phrase 'any drug' does not include a complete drug product, but only an active ingredient. That proposition is simply untenable."

"....The term 'drug' is plainly intended throughout the act to include entire drug products, complete with active and inactive ingredients," Stevens wrote.

An FDA spokesman said yesterday that the ruling actually will help generic distributors by giving consumers confidence in the efficacy of their pharmaceuticals.

Dr. Sidney M. Wolfe, of the consumer-oriented Health Research Group, agreed, but said the FDA needed to speed up development of an abbreviated approval process to help bring the lower-priced generics on the market more quickly.