Atorvastatin calcium, the substance known by the chemical name (R-(R*,R*))-2-(4-fluorophenyl)-β,δ-dihydroxy-5-(1-methylethyl)-3-phenyl-((phenylamino)carbonyl)-1H-pyrrole-1-heptanoic acid hemi calcium salt is known as HMG-CoA reductase inhibitor and is used as an antihypercholesterolemic agent. Atorvastatin in the pharmaceutical compositions available in the market, is usually prepared as its calcium salt since it enables atorvastatin to be conveniently formulated in the pharmaceutical formulations, for example, in tablets, capsules, powders and the like for oral administration. Atorvastatin calcium can exist in an amorphous form or in one of the at least four known crystalline forms (Form I, Form II, Form III and Form IV). Atorvastatin calcium is the substance which is sparingly soluble in water, with pKa 4,5, and it has been found that the crystalline forms are less soluble than the amorphous form, which may cause problems in bioavailability of atorvastatin in the body.The present invention solves the problem of providing therapeutic equivalence of atorvastatin pharmaceutical formulation regardless the form (crystalline, amorphous, mixture of both) of atorvastatin calcium used for its preparation.
