These substances enter as pharmaceutical active ingredients and are subject to FDA admissibility review at the port of entry. The foreign manufacturing site must be registered with FDA, and the API should be covered by an active Drug Master File or included in an approved drug application. Shipments may be detained for sampling if the facility has outstanding FDA observations. Consult a licensed customs broker or regulatory counsel for admissibility guidance.

The presence of one or more halogen atoms (typically fluorine or chlorine) on the steroid nucleus is the defining structural criterion. Non-halogenated corticosteroids and their salts/esters classify elsewhere in heading 2937, while halogenated forms are specifically captured here. Borderline cases — such as mixed-substituent compounds — may require a binding ruling from CBP to confirm the correct 10-digit line.