Prices for a small but growing number of brand-name drugs have risen more than twofold in recent years as drug makers seek to squeeze greater profits out of often small-selling but vital medicines, according to Congressional investigators.

Medicines like Adderall for attention deficit disorder, Inderal for chest pain and Sumycin for infections were among 416 brand-name drug products whose makers or distributors raised prices at least once by 100 percent or more from 2000 to 2008, investigators found.

These substantial price increases are becoming increasingly common, according to the Government Accountability Office, which conducted the inquiry. In 2000, prices for 28 drug products rose by 100 percent or more. In 2008, 71 had similar increases.

In response to the investigators’ report, which will be released Monday, the Pharmaceutical Research and Manufacturers of America e-mailed a statement saying that drugs represent only 10 percent of the nation’s overall spending on health care.