Definition of polymorphism:
The ability of a drug substance to exist in multiple crystalline forms with different arrangements or conformations.
Types:
Enantiotropic Polymorphs: Can reversibly transform from one form to another based-on temperature or pressure.
Monotropic Polymorphs: Irreversible transformation; one form is more stable than others.
Impact on Drug Properties:
Solubility: Different polymorphs have different dissolution rates.
Stability: Some polymorphs may degrade faster under storage conditions.
Bioavailability: A more soluble polymorph can lead to faster absorption.
Example:
Ritonavir faced formulation challenges due to a polymorphic transformation leading to decreased solubility and bioavailability.
Carbamazepine has multiple polymorphic forms with different dissolution profiles.