Degradation kinetics of atorvastatin under stress conditions and chemical analysis by HPLC.

Atorvastatin is an antilipemic drug belonging to the statins class, whose reference drug is Pfizer's Lipitor®. It is used to reduce the levels of lipoproteins rich in cholesterol and reduce the risk of coronary artery disease. It is well-known that calcium atorvastatin (ATV), C₆₆H₆₈CaF₂N₄O₁₀•3H₂O, presents polymorphism. The drug in question is commonly sought after by pharmaceutical industries that produce generic drugs, due to the fact that the drug has a high value price, it is consumed globally, and its patent expired in late 2010. Many questions concerning this drug's pharmaceutical scope demonstrate its importance regarding stability studies and the identification of degradation products of drugs and pharmaceutical formulations. ATV has been found to degrade under acid and basic conditions, including a first order kinetic degradation under acid conditions, as compared to a zero order kinetic degradation under basic conditions, which tends to be less stable when studied within acid mediums. The rate constant (k) for degradation in acid medium was 1.88 × 10⁻² s⁻¹ (first order), while for basic medium k = 2.35 × 10⁻⁴ mol L⁻¹ s⁻¹ (zero order), demonstrating a lower stability of the drug within acid mediums.