The physicochemical properties of digoxin

Area of Science:

• Pharmaceutical Sciences
• Solid-State Chemistry

Background:

• Digoxin is a cardiac glycoside used to treat heart conditions.
• Variations in commercial digoxin powder properties necessitate understanding its solid forms.

Purpose of the Study:

• To investigate the physicochemical properties of digoxin powder from various commercial sources.
• To characterize different solid forms of digoxin, including crystalline and amorphous states.

Main Methods:

• Recrystallization of digoxin under various conditions.
• Characterization of amorphous and crystalline digoxin forms.
• Solubility and stability studies under compression and aqueous contact.

Main Results:

• A pure amorphous form of digoxin was obtained under specific conditions, with no polymorphs observed.
• The amorphous form exhibited higher solubility and stability under compression but rapidly crystallized in water.
• Presence of crystalline digoxin traces significantly reduced the amorphous form's dissolution rate and stability.
• Thermal behavior variations in commercial samples are attributed to amorphous content and thermal decomposition above 160°C.

Conclusions:

• Digoxin exists in both crystalline and amorphous forms, with the amorphous form being more soluble and stable under compression.
• The amorphous form's stability is compromised by water contact and crystalline impurities.
• Understanding these solid-state properties is crucial for consistent digoxin formulation and therapeutic efficacy.