Mode of Action of Chlorophenoxyisobutyric Acid on Cholesterol Metabolism in Man

In short-term trials chlorophenoxyisobutyric acid (CPIB) (Atromid-S) reduced the plasma cholesterol and triglyceride levels in eight subjects with type II and IV hyperlipidemias to an equal extent. In these subjects, who were maintained on constant solid food diets, CPIB administration resulted in increased excretion of fecal neutral and acidic sterols in the type II subjects only. There was an immediate increase in specific activity of plasma cholesterol in seven of the eight subjects, and a reduced rate of fall of specific activity in many of the subjects. It is suggested that CPIB inhibits the synthesis of cholesterol in vivo, and that the subsequent fall in plasma cholesterol is responsible for the release of cholesterol with higher specific activity from tissues into the plasma pool.