The bill aims to allow doctors and patients to see on the label exactly where a medication was made — details that had largely been withheld until now, even from Congress. Current generic drug labels often include only the location of the packager or distributor, which can be thousands of miles away from the actual manufacturer.

One provision made the law particularly strong, experts said: The label was supposed to include a unique code that the Food and Drug Administration uses to identify factories. That code would have made it easier for researchers and the public to track the regulatory histories of specific facilities.

The requirements also were supposed to take effect as early as a year after the bill’s passage.

Senators have now struck both of those provisions. People familiar with the deliberations said lawmakers worried the requirements would raise drug prices and weaken national security by revealing the precise locations where lifesaving medications are made.