Pravastatin-d3 is intended for use as an internal standard for the quantification of pravastatin by GC- or LC-MS. Pravastatin is a potent and competitive HMG-CoA reductase inhibitor (Ki = 2.3 nM for the active, open ring form of the molecule) that is a ring-hydroxylated metabolite of mevastatin . In vivo, pravastatin reduces total plasma cholesterol levels by 29% in dogs when administered at a dose of 20 mg/kg per day for five weeks. Formulations containing pravastatin have been used to reduce LDL cholesterol and triglyceride levels and increase HDL cholesterol in the prevention of cardiovascular disease.