Reduction of serum cholesterol and triglyceride levels by the combined administration of neomycin and clofibrate

Cardiovascular Actions of the Peroxisome Proliferator-Activated Receptor-Alpha (PPAR?) Agonist Wy14,643

This review examines the various effects of Wy14,643, a hypolipidemic agent that activates peroxisome proliferator-activated receptor-alpha (PPARalpha), on the cardiovascular system. An emphasis has been placed on the specific cellular processes affected by Wy14,643 as they relate to vascular and cardiac function. Although the topic of this discussion is limited to vascular and cardiac tissues, the importance of circulating lipids on cardiovascular disease requires that a description of the indirect actions of this compound on liver metabolism also be included. Finally, the pharmacology of Wy14,643 is discussed within the context of PPARalpha-dependent and -independent mechanisms.

A comparative review of the adverse effects of treatments for hyperlipidaemia

Various lipid-lowering drugs have been shown to reduce serum cholesterol and serum triglycerides effectively. In view of trials indicating that lipid-lowering drugs may reduce cardiac morbidity and mortality but not the overall mortality in the study group, increased attention must be focused on potential harmful side effects during treatment with these agents. The adverse effects of many of the principal drugs in this category are discussed. Gastrointestinal symptoms, usually self-limited and reversible, are the most common side effects. Potential harmful adverse effects include drug interactions (cholestyramine), myopathy and hepatic injury (HMG-CoA reductase inhibitors), and increased gallstone formation and ventricular arrhythmias (clofibrate). Not all lipid-lowering drugs have been studied adequately on a long term basis, so that medications given for an indefinite period must be reevaluated frequently. However, there are several agents that lower serum lipid levels effectively and that have been used for more than 20 years without serious side effects.

Adverse effects of hypolipidaemic drugs

Cholestyramine, colestipol, clofibrate, gemfibrozil, nicotinic acid (niacin), probucol, neomycin, and dextrothyroxine are the most commonly used drugs in the treatment of hyperlipoproteinaemic disorders. While adverse reaction data are available for all of them, definitive data regarding the frequency and severity of potential adverse effects from well-controlled trials using large numbers of patients (greater than 1000) are available only for cholestyramine, clofibrate, nicotinic acid and dextrothyroxine. In adult patients treated with cholestyramine, gastrointestinal complaints, especially constipation, abdominal pain and unpalatability are most frequently observed. Continued administration along with dietary manipulation (e.g. addition of dietary fibre) and/or stool softeners results in diminished complaints during long term therapy. Large doses of cholestyramine (greater than 32 g/day) may be associated with malabsorption of fat-soluble vitamins. Most significantly, osteomalacia and, on rare occasions, haemorrhagic diathesis are reported with cholestyramine impairment of vitamin D and vitamin K absorption, respectively. Paediatric patients have been reported to experience hyperchloraemic metabolic acidosis or gastrointestinal obstruction. Concurrent administration of acidic drugs may result in their reduced bioavailability. Serious adverse reactions to clofibrate will probably limit its role in the future. Of particular concern are ventricular arrhythmias, induction of cholelithiasis and cholecystitis, and the potential for promoting gastrointestinal malignancy which far outweigh the reported benefits in preventing new or recurrent myocardial infarction, cardiovascular death and overall death. Patients with renal disease are particularly prone to myositis, secondary to alterations in protein binding and impaired renal excretion of clofibrate. Drug interactions with coumarin anticoagulants and sulphonylurea compounds may produce bleeding episodes and hypoglycaemia, respectively. Nicotinic acid produces frequent adverse effects, but they are usually not serious, tend to decrease with time, and can be managed easily. Dermal and gastrointestinal reactions are most common. Truncal and facial flushing are reported in 90 to 100% of treated patients in large clinical trials. Significant elevations of liver enzymes, serum glucose, and serum uric acid are occasionally seen with nicotinic acid therapy. Liver enzyme elevations are more common in patients given large dosage increases over short periods of time, and in patients treated with sustained release formulations.(ABSTRACT TRUNCATED AT 400 WORDS)

Treatment of hypercholesterolemia

After discussing the indications for treatment of familial hypercholesterolemia and the importance of a differential diagnosis, the authors describe drug therapy for the disorder with special attention to combined drug regimens. The surgical treatment of hypercholesterolemia and the treatment of homozygous and other forms of hypercholesterolemia are also detailed.

Effect of neomycin sulphate alone and in combination with D-thyroxine on serum lipoproteins in hypercholesterolaemic subjects

Treatment with neomycin sulphate 1.5 g/d for 8 weeks significantly lowered total serum cholesterol by an average of 19% in 15 out of 19 patients with primary hypercholesterolaemia and LDL-cholesterol by 21%, without significantly changing the corresponding triglyceride and HDL-cholesterol concentrations. Combined treatment with neomycin sulphate 1.5 g/d and d-thyroxine 6 mg/d for 8 weeks lowered total serum cholesterol in the same patients by an average of 30%, LDL-cholesterol by 27% and serum triglycerides by 18%, without significantly changing the HDL-cholesterol concentration. Continued treatment for 10 patients with neomycin sulphate 1.5 g/d for up to 13 months did not further change the reduced serum cholesterol level. 10 of 19 patients complained of side effects after 4-8 weeks of treatment with neomycin: 8 of recurrent diarrhoea, abdominal pain or poor appetite, and 4 of acute attacks of vertigo with nystagmus. All side effects were reversed a few days after stopping the neomycin treatment. No additional serious side effects due to d-thyroxine were observed. These serious side effects of neomycin sulphate limit its use to selected high risk patients with hypercholesterolaemia, who have failed to respond successfully to other LDL-cholesterol-lowering drugs. They stress the necessity for frequent monitoring for the side effects described.

Normalization of low-density-lipoprotein levels in heterozygous familial hypercholesterolemia with a combined drug regimen

We studied the effect of th bite acid sequestrant colestipol, alone and in combination with clofibrate or niacin, in patients with heterozygous familial hypercholesterolemia who were given a diet low in cholesterol and saturated fat. With colestipol alone, mean cholesterol levels in serum decreased 16 to 25 per cent. The addition of clofibrate produced a total mean decrement of only 28 per cent. In contrast, serum cholesterol levels fell 45 per cent when colestipol as combined with niacin. Low-density-lipoprotein (LDL) cholesterol decreased 55 per cent with colestipol and niacin, whereas high-density-lipoprotein (HDL) cholesterol increased. Mean LDL cholesterol was lower in patients given this regimen than in matched normal controls eating an unrestricted diet. Tendinous xanthomas, measured by quantitative xeroradiography, were significantly reduced (P < 0.01), indicating that this regimen mobilized cholesterol from tissue pools with slow turnover. Colestipol plus niacin promises to be useful in the treatment of patients at high risk from elevated levels of LDL.

Combined effects of clofibrate and diosgenin on cholesterol metabolism in rats

Groups of male rats were fed various doses of clofibrate and diosgenin, both alone and in combination for 1 week. Clofibrate suppressed the diosgenin-induced increase in hepatic cholesterol synthesis but did not alter the effectiveness of diosgenin in reducing cholesterol absorption. Diosgenin did not affect the bioavailability of CPIB. Clofibrate reduced the diosgenin induced increase in biliary levels of cholesterol; none of the regimens altered biliary bile acids. The combination produced greater decreases in LDL cholesterol than did either compound alone; the diosgenin-induced elevation in HDL cholesterol was partially reversed by clofibrate. The data provide a basis for the combined use of clofibrate and diosgenin in the control of hyperlipoproteinemia.

[Drug treatment of primary hyperlipoproteinemia (author's transl)]

Cardiovascular disease has become the major cause of death in the Western countries. There is strong evidence that elevations of serum lipids contribute to the pathogenesis of premature atherosclerosis. The classification of the hyperlipoproteinemias has been most beneficial as a guide to development of dietary and pharmacological regimens for lowering serum lipid concentrations. The results of dietary and drug prevention trials are discussed. Insight into the mechanisms involved in lipoprotein metabolism as well as the mode of action and of side-effects of hypolipidemic drugs is reviewed. Using present knowledge of heart disease research, it is reasonable to suggest dietary and drug treatments for the high risk patient.

Long-term kinetics of serum and xanthoma cholesterol radioactivity in patients with hypercholesterolemia

In four patients with hypercholesterolemia (type II hyperlipoproteinemia) and xanthomatosis the decay of serum cholesterol specific activity was followed for 53-63 wk after pulse labeling. Specific activity of biopsied xanthoma cholesterol was measured four times in the course of the study. The xanthoma specific activity curve crossed and thereafter remained above the serum specific activity curve. The average ratio of xanthoma to serum specific activity was 4.7 at the end of the study. The final half-time of the xanthoma decay curves was significantly greater (average: 200 days) than the slowest half-time of serum specific activity decay (average: 93 days). The data were analyzed by input-output analysis and yielded the following results. The average value for the total input rate of body cholesterol (I(T)) (sum of dietary and biosynthesized cholesterol) was 1.29 g/day. The average size of the rapidly miscible pool of cholesterol (M(a)) was 55.7 g. and of the total exchangeable body mass of cholesterol (M) 116.5 g. The average value of M - M(a) (remaining exchangeable mass of cholesterol) was 60.8 g. The derived values for exchangeable masses of cholesterol, in the present patients with marked hypercholesterolemia, were significantly larger than in a group of patients with normal serum lipids in previous studies. One of the four patients died of a sudden acute myocardial infarction 53 wk after pulse labeling. Specific activity of aortic wall and atheroma cholesterol was 3.12 times that of serum. The ratio was close to 2 for adipose tissue and spleen, and was slightly above 1 or was close to unity in most other organs studied, with the exception of brain which showed a ratio of 0.19.

Action of neomycin on the intraluminal phase of lipid absorption

Administration of a single 1 g dose of neomycin sulfate to five healthy subjects simultaneously with a test meal caused a marked increase in the proportion of fatty acid and bile acid in the ultracentrifuged deposit of aspirated intestinal contents. Labeled cholesterol was precipitated in a similar manner in two hypercholesterolemic patients. Neomycin had no effect on the pancreatic lipase concentration or on the pH of intestinal contents. These results confirm that the ability of neomycin to precipitate micellar lipids is due to interaction between the polybasic neomycin molecule and ionized fatty acids and bile acids. This mechanism provides an explanation for both the steatorrhea and hypocholesterolemia induced by this compound.