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Polymorphism refers to the existence of a drug substance in multiple crystalline forms, known as polymorphs. Recently, this term has been expanded to include solvates (forms containing a solvent), amorphous forms (non-crystalline forms), and desolvated solvates (forms from which the solvent has been removed).
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Angina pectoris, a primary symptom of ischemic heart disease, requires careful pharmacological interventions. In this context, calcium channel blockers (CCBs) and ranolazine have emerged as crucial pharmacotherapeutic agents, providing deep insights into the complexities of angina management.
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Amorphous Solid Forms of Ranolazine and Tryptophan and Their Relaxation to Metastable Polymorphs.

Joana F C Silva1, Pedro S Pereira Silva2, Manuela Ramos Silva2

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Researchers explored methods to create amorphous ranolazine, improving its solubility and stability. A co-amorphous ranolazine-tryptophan mixture showed enhanced properties, offering a promising approach for drug formulation.

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Area of Science:

  • Pharmaceutical Sciences
  • Materials Science
  • Solid-State Chemistry

Background:

  • Ranolazine is a sparingly soluble anti-anginal drug.
  • Developing stable amorphous forms of poorly soluble drugs is crucial for bioavailability.
  • Understanding solid-state transformations is key for drug development.

Purpose of the Study:

  • To investigate various amorphization techniques for ranolazine.
  • To characterize novel amorphous and crystalline forms of ranolazine.
  • To develop a stable, co-amorphous formulation of ranolazine with improved properties.

Main Methods:

  • Mechanochemistry, quench-cooling, and solvent evaporation were used for amorphization.
  • Cryo-milling and differential scanning calorimetry (DSC) were employed for characterization.
  • X-ray diffraction and structural analysis were utilized to solve crystal structures.

Main Results:

  • Amorphous ranolazine with low glass transition temperatures was obtained via cryo-milling and quench-cooling.
  • Two new metastable polymorphs (II and III) were identified during amorphous phase relaxation.
  • A binary co-amorphous ranolazine-tryptophan mixture exhibited enhanced glass transition temperature, kinetic stability, and aqueous solubility.
  • The crystal structure of the stable polymorph I was solved.

Conclusions:

  • Amorphization techniques can yield novel solid forms of ranolazine.
  • Co-amorphous formulation with tryptophan significantly enhances ranolazine's stability and solubility.
  • This study provides insights into solid-state behavior and formulation strategies for sparingly soluble drugs.