Pharmaceutical companies that spend billions of dollars to develop new drugs do not want competitors to profit from inexpensive generic copies of blockbuster medicines. To avoid rivals, they fight for patent extensions, seek new uses for old products and, sometimes, prevent generic drug companies from obtaining samples.

Dr. Scott Gottlieb, the commissioner of the Food and Drug Administration, calls this "gaming the system," and has vowed to stop it as part of the government's campaign to lower drug prices.

On Thursday, the F.D.A. took a new tack and began posting a list of makers of brand-name drugs that have been the target of complaints, to persuade them to "end the shenanigans," in the commissioner's words.

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Dr. Gottlieb calls it transparency, but this approach is better known among ethicists as naming and shaming.

Congressional efforts to force the companies to hand over samples of their drugs to generic competitors have not been successful. Recent proposals to ensure generic access to drug samples would save the federal government $3.8 billion over 10 years, according to the Congressional Budget Office, partly by lowering Medicare and Medicaid spending on prescription drugs.

The Federal Trade Commission has also been investigating the practice.

Some brand-name drug makers say the legislation is not needed. The F.D.A. has been speeding up approval of generic drugs, and nearly 90 percent of prescriptions are filled with generic drugs.

But others point to the ways in which major pharmaceutical companies have managed to keep patents on certain expensive drugs for years longer than necessary.

Generic drug developers usually need between 1,500 to 5,000 units of the brand drug to develop their product and test it, to show that it is effective and can be absorbed at the same rate as the brand drug, according to the agency. Both the F.D.A. and the Federal Trade Commission say securing the samples can be difficult, because major drug firms can invoke safety concerns — real or unreal — to avoid providing the materials.

The F.D.A.'s new list includes drug companies the agency said may be pursuing gaming tactics to delay generic competition. Along with the name of each business, the agency noted how many inquiries it received from generic drug companies seeking supplies. The names of the generic companies were not provided.

While Celgene tops the list, other companies that the F.D.A. named as the subject of complaints included GlaxoSmithKline, Pfizer, Valeant Pharmaceuticals International, BioMarin Pharmaceutical, Gilead Sciences and Novartis Pharmaceuticals.

Celgene, which makes drugs to treat cancer and immune-inflammatory diseases, was named as the subject of 31 inquiries from companies seeking access to Revlimid (lenalidomide), its treatment for multiple myeloma and related diseases; Pomalyst (pomalidomide); and Thalomid (thalidomide).

Celgene has been embroiled in lawsuits for several years with companies seeking access to the drugs. It recently sued Dr. Reddy's Laboratories Ltd., an Indian company, to block it from selling generic copies of Revlimid, the company's biggest product, and has been fending off an attempt by Mylan to also get into the generic Revlimid business. At a court hearing last year, a lawyer for Mylan, Jonathan M. Jacobson, told a federal district judge that the drug costs dying patients $20,000 a month — a price that would decline if generics were available.

Greg Geissman, a spokesman for Celgene, said the company had not prevented generic companies from obtaining their products.

"We have sold and will sell our groundbreaking products to generic manufacturers for the purposes of bioequivalence testing, subject to reasonable safety-related and business requirements," Mr. Geissman said. "Generic versions of Thalomid and Revlimid are expected to enter the market in coming years."

Geissman also said that Celgene supports federal efforts to promote access to samples at reasonable prices, as long as there is appropriate safety and liability protection for the seller.

The next biggest target, with 26 inquiries, is Actelion Pharmaceuticals Ltd., a Johnson & Johnson company, which is accused of blocking access to four drugs. There were 14 inquiries about getting supplies of Tracleer (bosentan), a medication prescribed for high blood pressure in the vessels of the lungs, known as pulmonary arterial hypertension. The F.D.A. also received eight complaints about lack of access to Opsumit (macitentan), which is also used to treat pulmonary arterial hypertension. There were also several complaints about a lack of access to Actelion's Zavesca (miglustat) and Veletri (epoprostenol sodium). Veletri is also used to treat pulmonary arterial hypertension and Zavesca is indicated for Gaucher disease.

An average one-month supply of Tracleer costs just over $12,000, and a supply of Opsumit runs $8,900 to $10,000, according to GoodRx, which tracks drug prices. Both prices are based on the patient presenting a free discount coupon.

Many pharmaceutical companies sell both brand-name and generic drugs, leading to a situation in which a company like Mylan, still fighting Celgene in court, can be on the receiving end of generic company complaints.

The F.D.A.'s list of shame notes three inquiries from companies trying to get access to Mylan's Amnesteem (isotretinoin), used to treat severe cystic acne that has not responded to antibiotic treatment.