ROSUVASTATIN CALCIUM IS A SYNTHETIC LIPID-LOWERING AGENT. ROSUVASTATIN IS AN INHIBITOR OF 3-HYDROXY-3-METHYLGLUTARYL-COENZYME A (HMG-COA) REDUCTASE. THIS ENZYME CATALYZES THE CONVERSION OF HMG-COA TO MEVALONATE, AN EARLY AND RATE-LIMITING STEP IN CHOLESTEROL BIOSYNTHESIS. IN IN VIVO AND IN VITRO STUDIES, ROSUVASTATIN PRODUCES ITS LIPID-MODIFYING EFFECTS IN TWO WAYS. FIRST, IT INCREASES THE NUMBER OF HEPATIC LDL RECEPTORS ON THE CELL-SURFACE TO ENHANCE UPTAKE AND CATABOLISM OF LDL. SECOND, ROSUVASTATIN INHIBITS HEPATIC SYNTHESIS OF VLDL, WHICH REDUCES THE TOTAL NUMBER OF VLDL AND LDL PARTICLES. ROSUVASTATIN REDUCES TOTAL CHOLESTEROL (TOTAL-C), LDL-C, APOB, AND NONHDL-C (TOTAL CHOLESTEROL MINUS HDL-C) IN PATIENTS WITH HOMOZYGOUS AND HETEROZYGOUS FAMILIAL HYPERCHOLESTEROLEMIA (FH), NONFAMILIAL FORMS OF HYPERCHOLESTEROLEMIA, AND MIXED DYSLIPIDEMIA. ROSUVASTATIN ALSO REDUCES TG AND PRODUCES INCREASES IN HDL-C. ROSUVASTATIN REDUCES TOTAL-C, LDL-C, VLDL-CHOLESTEROL (VLDL-C), APOB, NONHDL-C AND TG, AND INCREASES HDL-C IN PATIENTS WITH ISOLATED HYPERTRIGLYCERIDEMIA.