A Reference Listed Drug (RLD), as goes by its words itself means is a Food and Drug Administration-approved drug that can be referred to by a generic drug manufacturer while filing for an Abbreviated New Drug Application (ANDA). An RLD is mainly useful to ascertain bioequivalence of the product with reference to that of an already approved one.
When a generical manufacturer is applying for an ANDA, they should follow the FDA RLD in the application explaining that the proposed generic drug is the same all the aspects in comparison to the :
1)Active ingredient(s),
2)Dosage form,
3)Route of administration
4)Compositions, Strength, labeling, and Indications, etc.
Generally, the first innovator of the product or brand name product is assigned as an RLD. But once the innovator brand gets off-patent and generic products are widely available in the market the brand name products eventually get out of the market. In that case, FDA assigns one of the ANDA holders, who is the generic market leader at that time, as a new RLD.
In such cases, ANDA RLD gets all the similar responsibilities as of the original RLD like active ingredient(s), dosage form, route of administration, compositions, strength, labeling, and Indications, etc.