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Different amorphous solid-state forms of roxithromycin: A thermodynamic and morphological study.

Marnus Milne1, Wilna Liebenberg1, Marique Elizabeth Aucamp1

  • 1Centre of Excellence for Pharmaceutical Sciences, North-West University, Potchefstroom Campus, Potchefstroom 2520, South Africa.

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Summary

Different preparation methods significantly alter amorphous roxithromycin forms, impacting their thermodynamic and morphological properties. This study clarifies polyamorphism by distinguishing true forms from pseudo-polyamorphism.

Keywords:
AmorphousAtypical polyamorphismPolyamorphismPreparation methodPseudo-polyamorphismRoxithromycin

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Area of Science:

  • Pharmaceutical Science
  • Materials Science
  • Solid-State Chemistry

Background:

  • Amorphous solid-state forms are crucial for drug efficacy.
  • Polyamorphism, the existence of multiple amorphous forms, requires further investigation.
  • Understanding preparation impacts is key to controlling drug properties.

Purpose of the Study:

  • To investigate the influence of preparation techniques on amorphous roxithromycin forms.
  • To analyze physico-chemical differences between these amorphous forms.
  • To define polyamorphism and differentiate true polyamorphism from pseudo-polyamorphism.

Main Methods:

  • Preparation techniques: melt, solution, solution-mechanical disruption, and hot air (novel).
  • Characterization: Differential Scanning Calorimetry (DSC), X-ray Powder Diffraction (XRPD), Hot-Stage Microscopy (HSM), Scanning Electron Microscopy (SEM), and vapor sorption.
  • Analysis of thermodynamic and morphological properties.

Main Results:

  • Four distinct amorphous roxithromycin forms were produced.
  • Significant thermodynamic differences were observed between the forms.
  • Preparation methods notably influenced powder morphology and physico-chemical properties like solubility and dissolution.

Conclusions:

  • Preparation techniques critically impact amorphous solid-state form characteristics.
  • The study provides a framework for understanding and classifying polyamorphism.
  • Control over amorphous form preparation is essential for optimizing drug performance.