Characterization of piroxicam crystal modifications

Area of Science:

• Pharmaceutical Sciences
• Solid-State Chemistry
• Crystallography

Background:

• Piroxicam polymorphism has been extensively studied previously.
• Understanding crystal forms is vital for drug formulation and efficacy.
• Polymorphism influences physicochemical properties like solubility and stability.

Purpose of the Study:

• To re-evaluate piroxicam polymorphism.
• To characterize newly obtained crystal forms of piroxicam.
• To investigate factors influencing piroxicam crystal formation.

Main Methods:

• Crystallization from various solvents at different temperatures.
• Forced crystallization techniques (e.g., using dry ice).
• Infrared (IR) spectroscopy and crystal structure analysis.
• Evaluation of thermal and mechanical stability.
• Dissolution rate and wettability studies.

Main Results:

• Three new polymorphic forms (including a novel form III) and one monohydrate were obtained.
• Solvent polarity and crystallization temperature critically influenced polymorphic outcomes.
• Form I exhibited the highest melting point and superior stability.
• IR spectra differences correlated with hydrogen bonding variations.
• Form II was identified as the previously proposed alpha(2) form.
• Dissolution rates varied, with monohydrate showing highest wettability and form III the lowest.

Conclusions:

• Solvent polarity and crystallization rate are key determinants of piroxicam's solid-state forms.
• Piroxicam form I is the most stable polymorph under mechanical and thermal stress.
• Differences in crystal forms significantly impact piroxicam's wettability and dissolution characteristics.