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The hypolipidaemic effect of a new drug, gemfibrozil (CI-719), was studied for 20 weeks in 20 patients with primary type IIb, III, IV or V hyperlipoproteinaemia. Baseline recordings of serum cholesterol (9.1 mmol/l), triglyceride (3.79 mmol/l) and ultra-centrifugally isolated lipoproteins were obtained during a six-week pretreatment period with stable diet and body weight. With 800 mg of gemfibrozil per day given in two divided doses, the mean serum triglyceride and cholesterol levels were decreased by 44.6% and 10.5% respectively, during 20 treatment weeks. Only 2 patients were completely resistant to the hypolipidaemic action of the drug. Serum triglyceride was brought down to normal levels in 9 subjects. After 12 weeks of treatment the mean VLDL-triglyceride, VLDL-cholesterol, and LDL-triglyceride were reduced by 48.5%, 57.6%, and 22.7% respectively, while the HDL-cholesterol rose by 16%. The LDL-cholesterol increased slightly but significantly during treatment in type IV patients and decreased in type IIb patients. The change of LDL-cholesterol showed an inverse correlation with the initial LDL-cholesterol level (r=-0.87). The postheparin plasma lipoprotein lipase and hepatic lipase activities, determined separately by an immunochemical method, increased during four weeks of gemfibrozil treatment (+18.1% and +20.6% respectively), but neither of these changes was significantly correlated with the changes in any of the serum lipid or lipoprotein levels. Oral glucose tolerance was not influenced by the treatment, but one-hour plasma insulin increased slightly during administration of the drug. One patient discontinued the drug after eight weeks because of generalized allergic eczema, but no other side effects were recorded. It is concluded that gemfibrozil is highly effective in reducing elevated serum VLDL levels. The simultaneous elevation of LDL in type IV patients needs more attention and study. The mechanism of the hypolipidaemic action of the drug is so far obscure, but it might partly be due to an increased efficiency in VLDL removal by an increased activity of lipoprotein lipase.

Fat-mobilizing lipolysis was studied in rat and human adipose tissue during incubation in vitro by following the release of glycerol into the incubation medium. Gemfibrozil as well as clofibrate consistently and readily inhibited basal as well as noradrenaline-stimulated fat-mobilizing lipolysis in rat fat. With human adipose tissue no effect was observed with gemfibrozil and clofibrate on basal lipolysis. This may be due to the comparatively low rate of the nonstimulated fat-mobilizing lipolysis in human tissue incubated in vitro. When lipolysis was stimulated with noradrenaline as well as isoprenaline, however, both gemfibrozil and clofibrate significantly reduced the fat-mobilizing lipolysis. This inhibition of lipolysis was however not observed in all studies. When lipolysis had been stimulated with theophylline, no inhibition of lipolysis was obtained with either compound. The possibility that reduced fat-mobilizing lipolysis in adipose tissue may cause a lowering of plasma triglycerides by reducing the flow of FFA to the liver is discussed in some detail. It is also suggested that inhibition of lipolysis may be accompanied by increased activity of lipoprotein lipase as well as an increase in the FIAT process. However, the pharmacological implication of the above-mentioned findings, particularly for gemfibrozil, must await further studies, as fairly large doses, around 1 mg/ml of incubation medium, were needed to obtain inhibition of fat-mobilizing lipolysis.

Gemfibrozil (CI-719) has proved to be an effective agent in reducing the plasma triglyceride levels in experimental animals and in patients with endogenous hypertriglyceridaemia. We have confirmed these findings.