Final answer:
The first number in the NDC identifies the labeler, which is the entity like the manufacturer or distributor of the drug. This is part of a unique three-segment numerical code regulated by the FDA.
Step-by-step explanation:
The first number in the National Drug Code (NDC) represents the labeler code, which is assigned by the U.S. Food and Drug Administration (FDA). This labeler code uniquely identifies the manufacturer, repackager, or distributor of the drug. The NDC itself is a unique identifier for human drugs in the United States. The code is a three-segment number, where the first segment is the labeler code, the second set of numbers represents the product code, which identifies a specific strength, dosage form, and formulation for a particular firm, and the third set, the package code, identifies package sizes and types.