Atorvastatin and atorvastatin calcium share similar pharmacokinetic profiles, with minor differences primarily related to bioavailability due to the calcium salt’s higher molecular weight. Both are rapidly absorbed after oral administration, reaching peak plasma concentrations within 1-2 hours.
Absorption and Bioavailability
Atorvastatin absorption is highly variable and is reduced by concomitant food intake, suggesting administration on an empty stomach is preferable. Atorvastatin calcium exhibits slightly lower absolute bioavailability (approximately 12-14% lower) compared to atorvastatin, likely due to its slower dissolution rate.
Metabolism and Elimination
Both compounds undergo extensive hepatic metabolism primarily via cytochrome P450 3A4 (CYP3A4) isoenzyme. This means that interaction with drugs that inhibit or induce CYP3A4 can significantly alter atorvastatin levels. The primary metabolites are inactive.
Elimination primarily occurs via biliary excretion, with minimal renal excretion. The half-life is approximately 14 hours, leading to once-daily dosing regimens.
Key Pharmacokinetic Differences Summarized
| Absorption Rate | Rapid | Slightly slower |
| Bioavailability | Higher | Lower (approx. 12-14% less) |
| Metabolism | Extensive hepatic metabolism via CYP3A4 | Same |
| Elimination | Primarily biliary | Primarily biliary |
| Half-life | ~14 hours | ~14 hours |
Clinical Implications
These pharmacokinetic differences, while not substantial, warrant consideration when switching between formulations or when managing patients with impaired hepatic function or those taking concomitant medications that interact with CYP3A4. Always consult prescribing information for specific dosage recommendations.
