THE RESPONSE OF HYPERLIPOPROTEINEMIAS TO ATROMID AND ETHYL CHLOROPHENOXYISOBUTYRATE

Clofibrate in type II hyperlipoproteinemia

As a part of a double-blind randomized study, the safety and the lipid- and uric acid-lowering effect of clofibrate have been evaluated in 28 patients with type II hyperlipoproteinemia (HLP). A highly significant reduction of serum cholesterol occurred in type IIa and of serum triglyceride and choelsterol in type IIb HLP throughout the 60-week observation period (p less than 0.01). Of the patients with types IIa and IIb HLP, 65% had at least a 25% reduction of serum cholesterol. Uric acid was significantly reduced only during the first period of treatment (p less than 0.05). In the laboratory measurements concerning safety, a persistent, slight reduction was observed in Hb, hematocrit and alkaline phosphatase. No significant clinical side-effects were noted. Clofibrate is considered effective as a lipid-lowering agent in many cases of type II HLP.

The effects of clofibrate and 3-amino-1,2,4-triazole on liver catalase and lipid metabolism in mice

Clofibrate-treated mice showed a significant decrease in plasma triacylglycerols and a parallel elevation of liver catalase. Repeated administration of aminotriazole to clofibrate-treated mice effectively abolished the elevated catalase activity, but had no significant effect on the reduced plasma triacylglycerol levels. In mice, the hypolipidemic effect of clofibrate may be dissociated from its capacity to elevate liver catalase. Repeated administration of aminotriazole to control mice resulted in significantly lowered carcass fat and plasma triacylglycerol levels even though the liver catalase activity was greatly depressed. The livers of clofibrate-treated mice showed an increase in phospholipid content. Livers of aminotriazole-treated mice showed a decrease in total lipid content, with a profound decrease in free fatty acids and triacylglycerols and a slight increase in phospholipids. The composition of the individual free fatty acids of the liver triacylglycerols showed a shift towards the shorter fatty acids and the nutritionally essential alpha-linolenic acid in clofibrate-treated mice.

A rapid gas chromatographic method for the determination of chlorophenoxyisobutyric acid in plasma and urine

A rapid gas chromatographic method is described for the determination of chlorophenoxyisobutyric acid (the active metabolite of clofibrate) in plasma and urine. The assay involves an extraction into toluene and back-extraction of the chlorophenoxyisobutyric acid and the internal standard (2-naphthoic acid) into the methylating reagent (trimethylanilinium hydroxide). Concentrations of 1 mug/ml in plasma and urine can easily be measured; the precision of the method is 3.3 +/- 0.7% for plasma and 2.7 +/- 0.4% for urine. There is no interference from endogenous compounds or from drugs commonly prescribed together with clofibrate.

Dose-response effect of single and combined clofibrate (Atromidin) and niceritrol (Perycit) treatment on serum lipids and lipoproteins in type II hyperlipoproteinaemia

The dose-response effects of clofibrate and niceritrol on serum cholesterol and triglycerides (TG) were studied in 29 patients with Type IIa and IIb hyperlipoproteinaemia. In 17 patients, clofibrate and niceritrol were then given as combined treatment, and the effects of this combination on serum lipoproteins were studied. Clofibrate was given in three doses: 1.5,2 and 2.5 g/day. The optimum effect on serum TG and cholesterol in patients with Type IIa was observed with the 1.5 g dose and higher doses did not lower the serum lipids further. In patients with Type IIb the optimal clofibrate dose was 1.5-2 g/day. Niceritrol was then given in three doses: 3,45 and 6 g/day. In patients with Type IIa the serum TG concentration was not significantly affected by any dose used, whereas the reduction of the serum cholesterol concentration was dose dependent. In patients with Type IIb the reduction of both serum TG and cholesterol was dose dependent. Combined treatment with 2 g clofibrate and 3 g niceritrol resulted in a normal lipoprotein pattern i 15 out of 17 patients. The reduction of the serum lipids was approximately the same as during treatment with 6 g niceritrol/day. No additional side-effects were observed during combined treatment.

Lack of effect of cholestyramine on the pharmacokinetics of clofibrate in man

The study was undertaken to determine whether cholestyramine (16 g daily) interfered with clofibrate absorption when the two drugs were given together. Fifteen patients taking 1 g of clofibrate twice daily (for 2 to 416 weeks) participated in the study. Clofibrate (as the acid, p-chlorophenoxyisobutyric acid, CPIB) was quantified by thin-layer and gas-liquid chromatography. In patients taking clofibrate only, mean plasma CPIB concentration before the morning dose of clofibrate was 123 mug/ml. Peak levels were reached 3.5 hours after drug intake, the mean peak plasma CPIB concentration being 193 mug/ml. Absorption of CPIB exceeded 99%. Ninety-eight percent of the daily CPIB-intake was excreted in the urine, 61% being conjugated. In vivo degradation of CPIB did not occur. Free and conjugated CPIB was present in bile (mean fasting level being 55 mug/ml. The decay of radioactive CPIB in plasma was not log-linear: the mean t 1/2 of the first exponential was 0.45 hours, and of the second 15.1 hours. The pool size in 3 patients 3 hours after the morning dose of clofibrate was 1054 mg. CPIB was not detectable in adipose tissue, and kinetic data gave no hint of drug accumulation in patients on long-term therapy. In 6 patients given cholestyramine together with clofibrate, there was no significant alteration in fasting plasma CPIB levels, 24-hour urinary and faecal excretion of CPIB or in the half-life and pool size of the drug. A short delay in reaching peak plasma CPIB levels was the only consistent finding.

The hyperlipoproteinaemias

Elevated plasma lipids have been associated with an increased risk of ischaemic heart disease. However, regimens which reduce plasma lipids may decrease the recurrence rate of myocardial infarction. Accurate diagnosis of patients with elevated lipids and their families may be important in both secondary and primary prevention of atherosclerosis.

Classification of hyperlipoproteinaemias, the methods of diagnosis and an approach to dietary and drug therapy are discussed.

Functions and interrelationships of different classes of plasma lipoproteins

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The combined use of CPIB and thyroxine in treatment of hyperlipoproteinemias

The combined effect of CPIB and levothyroxine on lipoprotein concentrations in 13 patients with various types of hyperlipoproteinemias has been investigated. Analysis of long-term observations indicates the following: (1) CPIB lowers Sf 20-10 5 concentrations profoundly regardless of the initial lipoprotein distribution. (2) Addition of levothyroxine to CPIB produces no further significant effect on Sf 20-10 5 concentrations. (3) The effect of CPIB on Sf 0-20 concentrations appears to depend on the initial lipoprotein distribution. In carbohydrate-sensitive hyperlipemias CPIB can markedly increase Sf 0-20 levels, whereas it has no such effect in other hyperlipoproteinemias. On occasion, a marked Sf 0-20 lowering effect occurs in patients with Sf 0-20 hyperlipoproteinemias. Two such instances are reported in detail. (4) In combined Sf 0-20 and Sf 20-10 5 hyperlipoproteinemias the combination of CPIB and thyroxine is often more effective than either agent used separately in reducing total lipoprotein concentrations.