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Carbamazepine — Polymorphism

Polymorphism is the ability of solid crystalline anhydrous materials to exist in various structural forms (or modifications).

A directly related term is pseudo-PolymorphismPolymorphism is the ability of a solid material to form different crystalline structures (synonyms:  forms, modifications).polymorphism which concerns hydrates or solvates.

Different polymorphic forms exhibit different physico-chemical properties such as melting temperatures or specific heat capacities. This, in turn, has often an impact on the stability or bioavailability of the drug substance.

In the example, 1.23 mg of carbamazepine of modification III (with a theoretical Melting Temperatures and EnthalpiesThe enthalpy of fusion of a substance, also known as latent heat, is a measure of the energy input, typically heat, which is necessary to convert a substance from solid to liquid state. The melting point of a substance is the temperature at which it changes state from solid (crystalline) to liquid (isotropic melt).melting temperature of 176°C) was heated at 10 K/min in a nitrogen atmosphere using Al crucibles.
At around 160°C (peak temperature), modification III converts into modification I which finally melts at approx. 190°C (melt onset temperature = extrapolated onset temperature).