Solvent influences on metastable polymorph lifetimes: real-time interconversions using energy dispersive X-ray...

Area of Science:

• Crystallization science
• Materials science
• Pharmaceutical chemistry

Background:

• Piracetam (2-oxo-pyrrolidineacetamide) is a nootropic drug with known polymorphs and hydrate forms.
• Controlling crystallization is vital for pharmaceutical manufacturing, impacting drug efficacy and stability.

Purpose of the Study:

• To investigate the influence of various solvents on piracetam polymorph and hydrate crystallization.
• To characterize the crystal growth profiles and transformation kinetics of piracetam polymorphs in different solvents.

Main Methods:

• In situ energy dispersive X-ray diffraction (EDXRD) was used to monitor crystallization.
• Time-resolved diffraction snapshots were collected across different solvent systems (water, methanol, 2-propanol, isobutanol, nitromethane).
• Crystal growth profiles were constructed to analyze polymorph formation and conversion.

Main Results:

• Solvents influenced the lifetime, rate, and temperature of piracetam polymorph conversions (Form I to II to III).
• Isopropanol and nitromethane favored the kinetically stable Form I, while inhibiting Form II to III transformation.
• Aqueous solutions yielded novel piracetam hydrate forms, distinct from the known monohydrate, involving transient structures.

Conclusions:

• Solvent selection is a critical parameter for controlling piracetam's solid-state forms.
• Understanding solvent-mediated crystallization pathways is essential for reproducible pharmaceutical production.
• Novel hydrate forms of piracetam were identified, expanding knowledge of its solid-state chemistry.