Polimorflar

Polimorflar (polymorphs) are different crystalline forms of the same chemical substance that share the same molecular composition but differ in the arrangement or conformation of molecules within the crystal lattice. These structural differences can lead to distinct physical properties, such as density, melting point, solubility, rate of dissolution, hardness, and chemical stability. Polymorphism occurs in many crystalline materials, including organic compounds, inorganic solids, minerals, and pharmaceuticals.

Polymorphs are commonly classified by their stability relationships. Enantiotropic polymorphs exhibit two forms whose relative stability changes with temperature, allowing one form to be more stable at one temperature range and the other form at another. Monotropic polymorphs have a fixed stability order under given conditions, with the less stable form tending to transform irreversibly to the more stable form. Solvates and hydrates are related phenomena where solvent molecules are incorporated into the crystal lattice, sometimes forming distinct polymorphic systems upon solvent loss.

In pharmaceuticals, polymorphism is especially important because different forms can have markedly different dissolution rates, bioavailability, and manufacturability. Regulatory agencies require thorough characterization and control of polymorph forms to ensure consistency, efficacy, and safety, and a new polymorph can have regulatory and patent implications.

Characterization techniques include X-ray diffraction (XRD) for crystal structure, differential scanning calorimetry (DSC) for thermal properties, thermogravimetric analysis (TGA), and solid-state nuclear magnetic resonance (NMR). Crystallization conditions—solvent choice, temperature, and pressure—strongly influence which polymorph forms.