PT  - JOURNAL ARTICLE
AU  - S Vickers
AU  - C A Duncan
AU  - I W Chen
AU  - A Rosegay
AU  - D E Duggan
TI  - Metabolic disposition studies on simvastatin, a cholesterol-lowering prodrug.
DP  - 1990 Mar 01
TA  - Drug Metabolism and Disposition
PG  - 138--145
VI  - 18
IP  - 2
4099  - http://dmd.aspetjournals.org/content/18/2/138.short
4100  - http://dmd.aspetjournals.org/content/18/2/138.full
SO  - Drug Metab Dispos1990 Mar 01; 18
AB  - The biosynthesis of cholesterol is mainly regulated by 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase. Because the liver is the major site of cholesterol synthesis, it is the primary target of the class of drugs known as HMG-CoA reductase inhibitors. Simvastatin (SV) is a lactone prodrug which undergoes reversible metabolism. In the hydroxy acid form (SVA) it is a potent inhibitor of HMG-CoA reductase. SV is well absorbed by rats, dogs, and humans. After an oral dose of SV, tissue distribution studies were consistent with high hepatic extraction of SV and relatively poor tissue penetration of SVA. The majority of a radioactive dose of SV is eliminated in bile. A high portal/systemic gradient for 6'-OH-SVA, an active biliary metabolite, suggests its probable reentry and indicates potential for prolongation of HMG-CoA reductase inhibition. AUC comparisons in dogs after simultaneous iv (3H) and intraportal (14C) infusions indicate that hepatic extraction is high with only 8% of SV reaching the systemic circulation unchanged. Approximately 98% and 96% of SV was bound to human and dog plasma protein, respectively. The physiological disposition of SV in dog appears to be a suitable paradigm for man. Because of its high hepatic extraction SV should be both specific and selective with respect to the inhibition of HMG-CoA reductase.