Omacor acts on the plasma lipids by lowering triglyceride levels resulting in a fall in VLDL (very low density lipoprotein), and the substance is also active on haemostasis and blood pressure. Omacor reduces the synthesis of triglycerides in the liver because EPA and DHA are poor substrates for the enzymes responsible for triglyceride synthesis and they inhibit esterification of other fatty acids. The increase in peroxisomes of β-oxidation of fatty acids in the liver also contributes to the fall in triglycerides, by reducing the quantity of free fatty acids available for their synthesis. The inhibition of this synthesis lowers VLDL. Omacor increases LDL-cholesterol in some patients with hypertriglyceridaemia. Rises in HDL-Cholesterol are only small, significantly smaller than seen after administration of fibrates, and not consistently.