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Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism

Factors Affecting Dissolution: Polymorphism, Amorphism and Pseudopolymorphism

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).
Some polymorphic crystals possess lower aqueous solubility than their amorphous counterparts, leading to incomplete absorption. For instance, the oral suspension of Chloramphenicol, which...

Pharmaceutical Alternatives: Polymorphic Form-Related and Particle Size-Related Therapeutic Nonequivalence

Pharmaceutical Alternatives: Polymorphic Form-Related and Particle Size-Related Therapeutic Nonequivalence

Changes in polymorphic forms can significantly influence the bioavailability of poorly soluble drugs. Although the FDA defines pharmaceutical equivalence based on having the same active ingredient, dosage form, and route of administration, it does not automatically disqualify products with different polymorphic forms. This means two products with different polymorphs can still be deemed pharmaceutically equivalent. However, polymorphic differences can affect properties like wettability,...

Stability of Substituted Cyclohexanes

Stability of Substituted Cyclohexanes

This lesson discusses the stability of substituted cyclohexanes with a focus on energies of various conformers and the effect of 1,3-diaxial interactions.
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For example, in...

Pharmaceutical Alternatives: Stability-Related Therapeutic Nonequivalence

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Generic intravenous (IV) drugs are considered bioequivalent to their branded counterparts due to their 100% bioavailability upon administration. However, variations in stability among different drug products can significantly influence their therapeutic performance, even if they are pharmaceutically equivalent.Cefuroxime, a prophylactic antimicrobial, is often used as a single-dose IV injection for patients undergoing coronary artery bypass grafting surgery. A 3 g dose typically provides...

Complexation Equilibria: Factors Influencing Stability of Complexes

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In complexation reactions, metal cations are the electron pair acceptors, and the ligands are the electron pair donors. The stability of the metal complexes depends primarily on the complexing ability of the central metal ion and the nature of the ligands. Generally, the complexing ability of the metal ion depends on the size and charge of the ion. As the metal ion size increases, the stability of the metal complexes decreases, provided that the valency of the metal ion and the ligands remain...

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Orally administered drugs primarily enter the systemic circulation via passive diffusion through the intestinal membranes. The drug's absorption is influenced by drug stability in the gastrointestinal GI tract, membrane permeability, the surface area available for absorption, luminal drug concentration, and residence time in the lumen. Drug permeability can be enhanced by adjusting the lipophilicity, polarity, or molecular size of the drug, promoting its passive transport across intestinal...

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Related Experiment Video

Updated: May 19, 2026

A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients

A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients

Published on: August 9, 2022

Solid state characterizations and analysis of stability in azelnidipine polymorphs.

Dong Li¹, Min Wang, Caiqin Yang

¹College of Life Sciences, Hebei University, Baoding 071002, China.

Chemical & Pharmaceutical Bulletin

|August 7, 2012

Summary

This study identified three crystal forms of azelnidipine, a calcium channel blocker, using various analytical techniques. Polymorph β is the thermodynamically stable form at room temperature, crucial for drug formulation.

Related Experiment Videos

Last Updated: May 19, 2026

A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients

A Package of Established Analytical Tools to Investigate the Solid-State Alteration of Lipid-Based Excipients

Published on: August 9, 2022

Area of Science:

Pharmaceutical Sciences
Solid-State Chemistry
Materials Science

Background:

Azelnidipine is a dihydropyridine calcium channel antagonist.
Understanding its crystal forms is essential for drug development and patent protection.

Purpose of the Study:

To identify and characterize the polymorphic and pseudopolymorphic crystal forms of azelnidipine.
To investigate the thermodynamic and kinetic properties of these crystal forms.

Main Methods:

Powder X-ray diffraction (PXRD)
Differential scanning calorimetry (DSC)
Spectroscopy (IR, Raman, THz, ss-NMR)
Solubility studies

Main Results:

Three distinct crystal forms of azelnidipine were identified (two polymorphic, one pseudopolymorphic).
Polymorph β was determined to be the thermodynamically stable form at room temperature.
Thermodynamic parameters (ΔG, ΔH, ΔS) and activation energies for decomposition were calculated.

Conclusions:

The study provides a comprehensive characterization of azelnidipine's solid-state forms.
Identification of the stable polymorph is critical for consistent drug manufacturing and efficacy.
The findings contribute to the understanding of azelnidipine's physical chemistry.