Heading 3003 covers mixed medicinal preparations that have not yet been put up in measured doses or in forms for retail sale — bulk pharmaceutical blends awaiting further processing. Heading 3004 covers the same types of preparations once they are in tablet, capsule, ampoule, or other measured-dose form, or packaged for retail. The physical presentation and packaging state at the time of importation determine which heading applies.

Finished drug products must originate from an FDA-registered foreign establishment that has been inspected and approved. Importers file entry through FDA's PREDICT system, and shipments may be subject to physical examination or sampling. Products without an approved New Drug Application (NDA), Abbreviated NDA (ANDA), or Biologics License Application (BLA) are generally inadmissible, and importers should maintain documentation of the product's regulatory status.

Classification depends on the reagent's composition and function. Diagnostic reagents that are chemically defined compounds or simple mixtures without a therapeutic purpose often fall in Chapter 38. However, reagents based on blood products, antisera, or immunological components may fall under heading 3002. Finished in-vitro diagnostic kits packaged for retail or professional use can also land in Chapter 38 or Chapter 90 depending on their form. A binding ruling is advisable for borderline products.