Most prostaglandin and leukotriene compounds are chemically labile — susceptible to hydrolysis, oxidation, and isomerization — and require refrigerated or frozen storage throughout transit. Temperature excursions can degrade potency and alter impurity profiles, potentially triggering FDA detention for out-of-specification material. Importers should include temperature-monitoring records with the entry documentation and confirm storage requirements with the supplier's Certificate of Analysis.

Heading 2937 captures both natural and synthetic prostaglandins and their derivatives, so synthetic analogues such as latanoprost or bimatoprost generally classify here alongside naturally occurring forms. However, if a prostaglandin analogue is formulated into a finished pharmaceutical preparation, it would reclassify under Chapter 30. The key distinction is whether the imported article is a bulk API or a finished dosage form. A binding ruling from CBP is advisable for novel synthetic analogues with structural modifications that could place them in other chemical headings.