2933.33.01.00 - Alfentanil (INN), anileridine (INN), bezitramide (INN), bromazepam (INN), carfentanil (INN), difenoxin (INN), diphenoxylate (INN), dipipanone (INN), fentanyl (INN), ketobemidone (INN), methylphenidate (INN), pentazocine (INN), pethidine (INN), pethidine (INN) intermediate A, phencyclidine (INN) (PCP), phenoperidine (INN), pipradrol (INN), piritramide (INN), propiram (INN), remifentanil (INN) and trimeperidine (INN); salts thereof

This HTS category specifically encompasses a defined list of synthetic opioids and related compounds, primarily characterized by their analgesic properties and complex chemical structures. The inclusion of terms like "(INN)" (International Nonproprietary Name) signifies internationally recognized names for these pharmaceutical substances. This heading is reserved for the precise substances enumerated within its description, including alfentanil, fentanyl, remifentanil, and their direct salts.

Distinguishing this category from its siblings is crucial. For instance, while sibling categories may cover basic pyridine or piperidine compounds and their salts (2933.31 and 2933.32 respectively), or other specific fentanyl derivatives (2933.34), this particular subheading is strictly limited to the named compounds. It does not extend to general pyridine derivatives or other classes of nitrogenous heterocyclic compounds that might share structural similarities but are not explicitly listed.

As this is a leaf node in the HTS classification, there are no further subcategories. Classification under this heading relies solely on identifying the presence of one of the listed specific substances or their salts. Therefore, meticulous verification against the provided list of INNs is the primary determinant for correct classification within this detailed subheading.