Polymorphism in Piroxicam

Piroxciam is a polymorphic drug. However, reports on the number and nomenclature of the polymorphs of
piroxicam and the complete hydrogen-bonding patterns of piroxicam molecules in the crystal forms are in conflict and are
sources of confusion, which we attempt to clarify. The difference in energy of the two polymorphs, I and II, of piroxicam
arises predominantly from the difference between their lattice energies, rather than between their conformational energies.
The detailed hydrogen-bonding networks of the two polymorphs are described and compared. Despite stabilization of the
polymorphs by hydrogen bonds, a loss of polymorphic memory was observed upon cryogrinding the two polymorphs, leading
to differences in recrystallization behavior between amorphous piroxicam prepared from polymorphs I and II.

吡罗昔康（piroxicam）属于多晶型药物。然而，目前关于吡罗昔康多晶型的数量、命名规则，以及各晶型中吡罗昔康分子完整氢键模式的相关报道存在分歧且易引发混淆，本研究旨在厘清这一问题。吡罗昔康的两种晶型I与II之间的能量差主要源于晶格能的差异，而非构象能的不同。本文对这两种晶型的氢键网络细节进行了描述与对比。尽管氢键可对晶型起到稳定作用，但在对两种晶型进行低温研磨后，均观察到多晶型记忆的丧失，进而导致由晶型I和晶型II制备得到的无定形吡罗昔康呈现出不同的重结晶行为。