scholarly journals Pharmaceutical solvates, hydrates and amorphous forms: A special emphasis on cocrystals

2017 ◽  
Vol 117 ◽  
pp. 25-46 ◽  
Author(s):  
Anne Marie Healy ◽  
Zelalem Ayenew Worku ◽  
Dinesh Kumar ◽  
Atif M. Madi
Keyword(s):  
Amorphous Forms

Polymorphism of pharmaceuticals

2020 ◽  
pp. 342-375
Author(s):  
Joel Bernstein
Keyword(s):  
Ionic Liquids ◽  
Pharmaceutical Preparations ◽  
Phase Changes ◽  
New Techniques ◽  
Solvent Selection ◽  
Crystal Forms ◽  
Rate Of Dissolution ◽  
Amorphous Forms ◽  
Stable Forms ◽  
Chemical Microscopy

Chapter 7 deals with polymorphism in pharmaceuticals. Following a discussion of the problem of determining the statistics of the occurrence of polymorphism in pharmaceuticals, I present a discussion and examples of the connection between polymorphism and the rate of dissolution and solubility, bioavailability, and the importance of phase changes and mixtures of forms in pharmaceutical preparations. I survey some of the considerations and techniques involved in screening for crystal forms: solvent selection, specific screening for solvates and hydrates, gel crystallization, crystallization in ionic liquids, the challenge of difficult to obtain stable forms and unstable new forms, and the outlook on new techniques and conditions for crystallization. The chapter also deals with polymorphism in pharmaceutical co-crystals, excipients, and amorphous forms and the importance and utility of chemical microscopy in the study of polymorphism of pharmaceuticals.

Absence of amorphous forms when ice is compressed at low temperature

Nature ◽  
2019 ◽  
Vol 569 (7757) ◽  
pp. 542-545 ◽  
Author(s):  
Chris A. Tulk ◽  
Jamie J. Molaison ◽  
Adam R. Makhluf ◽  
Craig E. Manning ◽  
Dennis D. Klug
Keyword(s):  
Low Temperature ◽  
Amorphous Forms

scholarly journals Pressure-induced amorphization and existence of molecular and polymeric amorphous forms in dense SO2

2020 ◽  
Vol 117 (16) ◽  
pp. 8736-8742
Author(s):  
Huichao Zhang ◽  
Ondrej Tóth ◽  
Xiao-Di Liu ◽  
Roberto Bini ◽  
Eugene Gregoryanz ◽  
...  
Keyword(s):  
Ab Initio Molecular Dynamics ◽  
X Ray Diffraction ◽  
Multiple Bonds ◽  
Local Structures ◽  
Polymeric Chains ◽  
Diamond Anvil ◽  
Amorphous Forms ◽  
Simple Molecules ◽  
Dynamics Simulations ◽  
Reversible Structural Transformation

We report here the pressure-induced amorphization and reversible structural transformation between two amorphous forms of SO2: molecular amorphous and polymeric amorphous, with the transition found at 26 GPa over a broad temperature regime, 77 K to 300 K. The transformation was observed by both Raman spectroscopy and X-ray diffraction in a diamond anvil cell. The results were corroborated by ab initio molecular dynamics simulations, where both forward and reverse transitions were detected, opening a window to detailed analysis of the respective local structures. The high-pressure polymeric amorphous form was found to consist mainly of disordered polymeric chains made of three-coordinated sulfur atoms connected via oxygen atoms, with few residual intact molecules. This study provides an example of polyamorphism in a system consisting of simple molecules with multiple bonds.

Comparison of the mechanical properties of the crystalline and amorphous forms of a drug substance

2002 ◽  
Vol 241 (1) ◽  
pp. 73-85 ◽  
Author(s):  
Bruno C Hancock ◽  
Glenn T Carlson ◽  
Dauda D Ladipo ◽  
Beth A Langdon ◽  
Matthew P Mullarney
Keyword(s):  
Mechanical Properties ◽  
Drug Substance ◽  
Amorphous Forms

Physicochemical Properties and Stability of Two Differently Prepared Amorphous Forms of Simvastatin

2008 ◽  
Vol 8 (1) ◽  
pp. 128-135 ◽  
Author(s):  
Kirsten A. Graeser ◽  
Clare J. Strachan ◽  
James E. Patterson ◽  
Keith C. Gordon ◽  
Thomas Rades
Keyword(s):  
Physicochemical Properties ◽  
Amorphous Forms

scholarly journals Dissolution profile evaluation of solid pharmaceutical forms containing chloramphenicol marketed in Brazil

2007 ◽  
Vol 50 (1) ◽  
pp. 57-65 ◽  
Author(s):  
Humberto Gomes Ferraz ◽  
Leticia Norma Carpentieri ◽  
Sayuri Pereira Watanabe
Keyword(s):  
United States ◽  
Dissolution Profile ◽  
United States Pharmacopoeia ◽  
Amorphous Forms ◽  
Independent Model

The dissolution profile for solid pharmaceutical forms containing chloramphenicol 250 mg available in Brazil was determined using a method from the American Pharmacopoeia (United States Pharmacopoeia, 2004) and then compared. Two different methods of dissolution profile comparison were used: ANOVA, and an independent model. Differences between the formulations were reflected in the dissolution profiles. The presence of metastable polymorphs or amorphous forms of chloramphenicol palmitate might be responsible for variations in the concentration of the drug observed within formulations.

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