Water clusters in amorphous pharmaceuticals

Area of Science:

• Pharmaceutical Science
• Materials Science
• Physical Chemistry

Background:

• Amorphous materials lack long-range order but exhibit local structure.
• Water is a ubiquitous component in amorphous pharmaceuticals.
• Water molecules can exist as unclustered entities or form aggregates (clusters).

Purpose of the Study:

• To review the distribution and clustering of water in amorphous pharmaceutical systems.
• To explore the impact of water clustering on pharmaceutical properties.
• To highlight the need for further research into water's role in amorphous drug stability.

Main Methods:

• Review of existing literature and experimental data.
• Analysis of evidence from neutron and X-ray scattering.
• Consideration of molecular dynamics simulations and water sorption isotherms.

Main Results:

• Water clustering is observed in various amorphous systems like carbohydrates, polymers, and proteins.
• Water clustering is concentration-dependent: unclustered at low concentrations, clustered at intermediate concentrations.
• The transition between clustered and unclustered water can alter pharmaceutical properties, including degradation rates.

Conclusions:

• A mechanistic understanding of water's impact on amorphous pharmaceutical stability requires systematic studies.
• Current investigations into water distribution and clustering in amorphous pharmaceuticals are insufficient.
• Further research is needed to elucidate the precise role of water clustering in drug degradation.