Long-term effects of colestipol (U-26,597 A) on plasma lipids in familial type II hyperbetalipoproteinaemia

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)

Effect of probucol treatment on lipoprotein cholesterol and drug levels in blood and lipoproteins in familial hypercholesterolemia

Twelve patients with mild and 3 with severe hypercholesterolemia were stabilized with an isocaloric diet containing less than 300 mg cholesterol daily with a P/S ratio of 1.8, and placebo period of 4 weeks. They were administered 1000 mg probucol daily for 12 weeks, followed by placebo for 6 weeks. In patients with mild disease, a significant cholesterol reduction was achieved in serum, LDL, and HDL (maximum decrease, 17%, 13%, and 31%, respectively). While HDL3 cholesterol was reduced significantly throughout the period (P less than 0.001), HDL2 cholesterol showed a significant decrease only at the 4th week of treatment (P less than 0.001), and returned to basal levels at the 8th and 12th treatment weeks. Serum apo B levels decreased only slightly, but the HDL-apo A-I fall was significant with a reduction in the HDL-CH/HDL-apo A-I ratio throughout the treatment period. In 3 patients with severe disease, cholesterol decrease in serum and in VLDL, LDL and HDL fractions varied, but on the whole was lower than in patients with mild disease. A decrease in VLDL-CH and HDL-CH was present in all 3, but LDL-CH levels were only slightly lowered in 2 patients, and unchanged in the third. Serum probucol levels fell 66% from the 4th to the 12th treatment week, and in parallel, the percentage of lipoprotein-bound drug increased about 2-fold. It is suggested that these changes in pharmacokinetics as well as the cholesterol-lowering effect of the drug may be due to a change in lipoprotein composition or structure.

[Relation between serum lipoprotein metabolism and biliary lipid metabolism]

This review concern with recent results regarding interrelationships between serum lipoprotein and bile acid metabolism. First, changes in bile acid metabolism in primary hyperlipoproteinaemia type II and type IV are described. In addition, influences of lipid-lowering drugs such as sitosterol, cholestyramine/colestipol, neomycin, nicotinic acid, clofibrate and thyroxin on serum lipoproteins and biliary lipid metabolism are discussed. Changes in lipoprotein metabolism in disorders of bile acid metabolism and effects of primary and secundary bile acids on lipoprotein metabolism, hepatic cholesterol metabolism and intestinal cholesterol absorption are described. In the final discussion interrelationships between very low density lipoprotein - triglycerides and cholic acid metabolism as well as low density lipoprotein and chenodeoxycholic acid metabolism are stressed. The positive correlation between serum triglycerides and lithogenicity of bile is underlined and the possible significance of high density lipoprotein-cholesterol as precursor of biliary cholesterol is discussed.

The bile acid binding and hypocholesterolemic action of two water-soluble polymers

The in vitro bile acid binding properties of 2 water-soluble, linear, cationic resins, poly-[(dimethylimino)trimethylene chloride] or 3,3-ione C1, and poly-diallyldimethylammonium chloride) or CAT-FLOC were determined. Both polymers were substantially more active than cholestyramine. All were compared for hypocholesterolemic effect in normo-cholesterolemic dogs. CAT-FLOC and 3,3-ionene C1, administered at 1.8 and 1.2 g/day, respectively, exhibited cholesterol-lowering action equivalent to cholesteryramine given at 12 g/day. The results of this study suggest that effective reduction of plasma cholesterol may be achieved with significantly lower doses of bile acid sequestrants.

Colestipol: a review of its pharmacological properties and therapeutic efficacy in patients with hypercholesterolaemia

Colestipol is an anion exchange resin with bile acid sequestering properties resembling those of cholestyramine, another lipid-lowering binding resin. In daily doses of 15 to 30g colestipol reduces total plasma cholesterol concentrations (primarily low density lipoprotein cholesterol) by about 15 to 30%, but plasma triglyceride concentrations may be unchanged or in some patients increased. Thus, like cholestyramine, colestipol is of benefit in patients with primary hypercholesterolaemia without associated hypertriglyceridaemia (type IIa hyperlipoproteinaemia). Colestipol is odourless and tasteless, and is said by some to be more readily tolerated by patients than cholestyramine, leading to improved compliance, but such data has not been documented in most studies. Side effects of colestipol treatment are primarily gastrointestinal in nature since the drug is essentially unabsorbed. As with cholestyramine, colestipol may bind with other concomitantly administered drugs reducing their absorption or enterohepatic recirculation; dosage intervals of other concurrent medications should be adjusted to minimise the potential for such an interaction.

Abnormal low density lipoproteins in children with familial hypercholesterolemia--effect of polyanion exchange resins

In 20 children and adolescents with familial Type II a hyperlipoproteinemia, serum lipids and lipoproteins were examined before and during treatment with polyanion exchange resins. The composition of LDL was compared to that of helthy siblings. The patients were given Colestyramine (0.6 g/kg body weight) and Colestipol (0.5 g/kg body weight) in a cross-over study for 8 weeks each, after they had been under dietary treatment for at least 12 months. In 6 children, drug treatment had to be stopped due to side-effects. The most common complaints were gastrointestinal discomfort and constipation. Cholesterol, triglycerides and phopholipids were measured in whole serum and cholesterol, triglycerides and Apolipoprotein-B in isolated lipoprotein fractions after ultracentrifugation. Apo-B was determined by radial immunodiffusion. The Apo-B: cholesterol ratio in whole serum and in the LDL fraction was identical in the patients and in the controls. The LDL triglyceride: Apo-B ratio, however, was about 50% lower in the patients. This abnormal LDL composition was not altered by therapy with polyanion exchange resins. HDL cholesterol levels were significantly lower in the patients than in healthy children, and remained low during therapy. The decrease of total and LDL cholesterol (25%) and Apo-B (20%) was similar under both Colestipol and Colestyramine. Triglycerides and phospholipids showed no significant changes in therapy.

Long-term trial with colestipol plus clofibrate in familial hypercholesterolemia

Twenty subjects with familial hypercholesterolemia (12 Type IIa and 8 Type IIb), previously treated with Colestipol for 16 months, were subjected to therapy with Colestipol (15 g/day) + clofibrate (2 g/day) for 15 months. During the second treatment period these patients continued to follow the isocaloric hypocholesterolemic diet initiated during the original trial. In Type IIa patients, the association of these drugs enhanced the decrease in plasma cholesterol levels. The total mean decrease was -40 +/- 17 mg/dl (P less than 0.05). In Type IIb patients, on the other hand, the association of clofibrate with Colestipol induced an increase in plasma cholesterol levels. The total mean increase was +24 +/- 7 mg/dl (P less than 0.05). A markedly significant decrease in plasma triglyceride levels was observed in this group (- 107 +/- 30; P less than 0.01). These results seem to indicate that, in Type IIa, clofibrate increased the resin's hypocholesterolemic effect. In Type IIb, on the other hand, the association of these drugs did not seem to be indicated since a marked hypotriglyceridemic effect was accompanied by an increase in plasma cholesterol levels. These results are briefly discussed in the light of recent data obtained on the effects of Colestipol and clofibrate on lipoprotein metabolism.