Atorvastatin and atorvastatin calcium are chemically very similar. The key difference lies in the presence of a calcium ion (Ca2+).
Atorvastatin (Free Acid)
Atorvastatin itself is a lactone, containing a specific ring structure with various functional groups attached. These include a hydroxyl (-OH), various methyl (-CH3) groups, and a carboxyl (-COOH) group. The precise arrangement of these groups determines its pharmacological activity.
- Chemical Formula: C33H35NO7 Molar Mass: Approximately 560 g/mol
Atorvastatin Calcium
Atorvastatin calcium is a salt. Two molecules of atorvastatin bind to one calcium ion, forming a salt complex. This calcium salt increases the solubility of atorvastatin, which is significant for formulation and absorption in the body.
- Chemical Formula: C66H70CaN2O14 Molar Mass: Approximately 1160 g/mol (approximately double that of free atorvastatin due to the presence of two atorvastatin molecules)
Structural Variations and Implications
The calcium salt form is typically more easily formulated into tablets and capsules due to enhanced solubility compared to the free acid form. This improved solubility is often reflected in better bioavailability, meaning more of the drug reaches the bloodstream to exert its effects.
Improved solubility leads to better absorption. Better absorption can result in consistent therapeutic effects. Variations in formulation can affect individual patient responses.
In Summary
While chemically very similar, the presence or absence of a calcium ion dictates solubility and formulation properties. The calcium salt (atorvastatin calcium) is generally preferred for its improved bioavailability.
