The effects of colestipol when combined with clofibrate in the treatment of severe hyperlipidemia. Short-term and long-term studies

Insulin resistance and cardiovascular drugs

Under certain circumstances the effect of insulin to promote glucose uptake in peripheral tissues is reduced because of a resistance to insulin action. This insulin resistance and the resulting hyperinsulinaemia are now recognised as common background factors that may be responsible for hypertension, hyperlipidaemia, decreased thrombolysis and also impaired glucose tolerance and diabetes. Hyperinsulinaemia has also been identified as an independent risk factor for coronary heart disease and promotes smooth muscle cell growth and plaque formation. A series of studies have now demonstrated that treatment with selective beta-blockers as well as thiazide diuretics impair insulin sensitivity by 15-30% and causes a compensatory increase in insulin concentrations. Furthermore, lipoprotein concentrations are affected in an unfavourable way. This is in contrast to the drugs belonging to ACE-inhibitors, calcium-channel blockers and alpha 1-blocker classes that are either neutral or may have the opposite effects in these respects.

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)

Changes in glucose tolerance and plasma insulin during lipid-lowering treatment with diet, clofibrate and niceritrol

In an effort to reduce serum lipids in patients with atherosclerotic manifestations, a combined treatment with a conventional lipid-lowering diet, clofibrate and niceritrol was used. The effect on glucose metabolism of such treatment was studied. Among the 106 patients 66 took the full dose of both drugs and of these 51 were weight-stable and non-diabetic. The effects of the diet and the drugs were evaluated in this subsample. Diet had no effect on fasting blood glucose concentration, the K value of an intravenous glucose tolerance test (IVGTT) and concentrations of serum insulin. Niceritrol treatment was associated with increased blood glucose, decreased K value, elevated fasting serum insulin and serum insulin at 60 min during IVGTT. Clofibrate had the opposite effects to niceritrol and when both drugs were combined, carbohydrate metabolism was unchanged compared with the pre-treatment state.

[Bezafibrate in primary hyperlipidemias (author's transl)]

The effect of long-term treatment over 40 weeks with Bezafibrate on lipids and lipoproteins was investigated in 27 patients with primary hyperlipoproteinemias (hlp) (12 patients with hlp type IV, 7 patients with type IIb, 3 patients with type IIa, 4 patients with type V and 1 patient with type III). Bezafibrate reduced total cholesterol by 16%, whereas HDL-cholesterol increased by 28% and 36% (p less than 0.05). Serumtriglycerides decreased by 59% (450 mg Bezafibrate daily) and by 66% (600 mg Bezafibrate daily) statistically significant (p less than 0.05). In hyperlipidemias type IV, IIb, IIa and V increases of HDL-cholesterol could be observed. The course of LDL-cholesterol was different in the various types of hlp. The postheparin-lipoprotein-lipase (PHLA) was activated by treatment with Bezafibrate from 10.5 +/- 0.7 to 14.7 +/- 0.7 and 15.5 +/- 0.8 mumol FFA/ml/h or by 30% (p less than 0.05). Only few side-effects during treatment with Bezafibrate could be ascertained.