Acute muscular syndrome associated with administration of clofibrate

Effects of exercise and lovastatin on serum creatine kinase activity

Vigorous physical activity and lovastatin (Mevacor) a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, have both been independently associated with elevated creatine kinase (CK) levels. To determine the effect of lovastatin plus exercise on serum CK activity, we measured CK levels before and after maximal treadmill exercise in 14 men (51.6 +/- 17.3 years, mean +/- SD) and 6 women (48.5 +/- 7.4 years) before and after 4 weeks of lovastatin treatment (20 mg/d). Blood samples were obtained before, immediately after, and 24 hours after exercise. Individual subjects were exercised for the same duration on each test. Preexercise CK levels and the average CK response to treadmill exercise did not differ before and after lovastatin treatment. In two men taking lovastatin, however, CK levels increased by 183% and 242% 24 hours after exercise during lovastatin administration. We conclude that low-dose lovastatin treatment plus exercise does not affect average CK activity but that this combination may markedly increase CK levels in certain individuals.

Effects of HMG-CoA reductase inhibitors in hypercholesterolemic patients on hemodialysis

The efficacy of lovastatin and simvastatin, competitive inhibitors of 3-hydroxy-3-methyl glutaryl coenzyme A reductase, was investigated in 40 hemodialysis (HD) patients displaying hypercholesterolemia and moderate hypertriglyceridemia (selection of 40 patients required screening of 700 hemodialysis patients). After a four-week placebo period, lovastatin or simvastatin was administered to two groups of 20 patients in increasing doses over a period of three months. Thirty-six patients completed the study. Lovastatin (1st month 20 mg; 2nd and 3rd months 40 mg day-1) and simvastatin (1st month 10 mg, 2nd month 20 mg and 3rd month 40 mg day-1) reduced total serum cholesterol from 280.3 +/- 9.4 to 213.0 +/- 6.7 (-24%) and 295.0 +/- 12.2 to 202.3 +/- 8.9 mg/dl (-31.4%), LDL cholesterol from 161.9 +/- 10.7 to 112.1 +/- 7.9 (-30.8%) and 181.8 +/- 14.7 to 107.4 +/- 8.1 mg/dl (-40.9%), as well as apolipoprotein B (apo B) from 116.0 +/- 6.6 to 83.3 +/- 3.7 (-28.2%) and 134.4 +/- 8.2 to 84.1 +/- 5.3 mg/dl (-37.4%), respectively. Furthermore, the ratio of LDL apo B/LDL cholesterol increased significantly (0.63 +/- 0.02 vs. 0.71 +/- 0.05 and 0.63 +/- 0.02 vs. 0.66 +/- 0.02, respectively). Another remarkable effect was the reduction of cholesterol concentration in VLDL (72.4 +/- 8.9 vs. 47.3 +/- 6.8 [lovastatin] and 78.3 +/- 11.1 vs. 50.7 +/- 8.8 mg/dl [simvastatin], respectively). Therefore, the ratio of triglycerides/cholesterol in VLDL increased (3.2 +/- 0.2 vs. 3.8 +/- 0.3 and 3.2 +/- 0.2 vs. 4.0 +/- 0.2, respectively), indicating VLDL formation poor in cholesterol and rich in triglycerides.(ABSTRACT TRUNCATED AT 250 WORDS)

[Hyperlipidemia and osteoarticular manifestations]

Hyperlipoproteinaemia, notably types II and IV, may give rise to various musculoskeletal disorders. Mono-, oligo- or polyarthritis, or even simple arthralgias, are often encountered in patients with severe type IIa hyperlipoproteinaemia, the most satisfactory tentative explanation for this being a microcrystalline pathology. Tendinitis is also frequent, particularly in children. The same manifestations have also been reported, although more occasionally, in type IV hyperlipoproteinaemia. Skeletal lesions, such as xanthoma or lipoma ossificans, are extremely rare. Other musculoskeletal disorders, including gout and aseptic osteonecrosis, are often associated with hyperlipidaemia. Some diseases may induce secondary hyperlipidaemia but have their own rheumatological manifestations. Finally, lipid-lowering drugs, such as fibrates and statines, sometimes induce disabling myalgias.

Effects of clofibrate on basal and insulin-activated glucose uptake in fast and slow skeletal muscles of rats

1. The basal uptake of glucose was increased significantly in the extensor digitorum longus muscle (EDL) of rats by clofibrate administration. 2. The insulin-activated uptake of glucose was increased in the soleus muscle (Sol) by clofibrate. 3. The insulin-induced increment of glucose uptake was increased significantly in Sol and decreased significantly in EDL by clofibrate.

[Fenofibrate induced polymyositis]

In a 65-year old man complaining of myalgias and loss of muscular strength, the creatine phosphokinase level was found to be 35 times higher than normal values. The electromyogram was of the diffuse myogenic type. Muscle biopsy showed necrotic lesions of the muscle fibres associated with perivascular infiltrates of mononuclear cells, leading to the diagnosis of polymyositis. This patient had been treated for 10 years with fenofibrate for hyperlipidaemia; during the last 32 months he had taken this drug in doses of 600 mg per day. Eight days after fenofibrate was discontinued, all clinical and laboratory abnormalities had disappeared. A reintroduction test performed 6 weeks later raised the creatine phosphokinase level up to 43 times the normal value. Withdrawal of fenofibrate therapy resulted in rapid and lasting recovery. This case shows that fenofibrate should be added to the list of drugs that are responsible for iatrogenic polymyositis.

Clinical features, pathogenesis and management of drug-induced rhabdomyolysis

Striated musculature is considered unusually tolerant to all kinds of injuries, and rhabdomyolysis associated with drug overdose or chronic drug intake is a rare event. This may be because striated musculature, in contrast to other tissues such as liver and kidney, shows little affinity for most drugs. Several different types of drug-induced rhabdomyolysis may be distinguished, and the clinical features of the condition may vary widely, from moderate myalgia to involvement of groups of muscles to involvement of the total skeletal musculature. In clinically asymptomatic rhabdomyolysis, early diagnosis is only made if routine laboratory tests include determination of serum creatine kinase. Determination of myoglobin in serum and urine is more sensitive and allows earlier diagnosis of muscle necrosis. Myoglobinaemia may lead to toxin-induced tubular necrosis, and impairment of renal function or even acute renal failure. About 10% of all cases of acute renal failure are due to rhabdomyolysis. Fulminant rhabdomyolysis may be associated with excessive hyperkalaemia and hypocalcaemia which may induce further life-threatening complications. Therefore, early diagnosis of rhabdomyolysis is most important for prevention of its potentially life-threatening sequelae. Therapy of rhabdomyolysis consists of supportive and specific measures. Early diagnosis may help to prevent life-threatening sequelae like acute renal failure, electrolyte imbalance and shock. Withdrawal of the incriminated drug or detoxification in drug overdose should be followed by supportive measures including infusion therapy and correction of dehydration and electrolyte imbalances. Forced diuresis with sodium bicarbonate may protect the kidney function from acidosis and precipitation of myoglobin in tubules. Elimination of myoglobin from plasma may be enhanced by plasmapheresis. In patients with acute renal failure, haemodialysis is necessary. In malignant hyperthermia, immediate infusion of dantrolene sodium is required. This drug also seems to have a beneficial effect in neuroleptic malignant syndrome. The repair mechanisms of striated musculature function extremely well. The prognosis of muscular atrophy after the acute stage of rhabdomyolysis is excellent. The same is true for the prognosis of acute renal failure. However, the extent of complications or survival of the acute stage of rhabdomyolysis strongly depend on early diagnosis and start of adequate therapy.

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 the hyperlipidemia of the nephrotic syndrome: a controlled trial

The hyperlipidemia of the nephrotic syndrome is often associated with elevated total and low-density lipoprotein (LDL) cholesterol levels and low or normal high-density lipoprotein (HDL) cholesterol levels. This pattern of hyperlipidemia has been associated with an increased risk of accelerated atherosclerosis in other populations. Despite extensive studies of diet and drug therapy in other populations, few such therapeutic studies exist in patients with the nephrotic syndrome. To investigate the effect of diet and lipid-lowering drugs on the lipoprotein-lipid profile of patients with unremitting nephrotic syndrome and marked hyperlipidemia, we conducted a controlled trial using two such drugs: colestipol and probucol. Colestipol lowered the mean total fasting plasma cholesterol of seven patients from 397 +/- 27 to 317 +/- 37 mg/dL, a 20.2% decrease, and lowered the LDL cholesterol from 398 +/- 28 to 203 +/- 18 mg/dL, a 31.9% decrease. It did not affect the HDL cholesterol level, and thus lowered the LDL-to-HDL cholesterol ratio. Probucol lowered the mean total cholesterol from 439 +/- 72 to 339 +/- 60 mg/dL, a 22.6% decrease, and the LDL cholesterol from 282 +/- 43 to 215 +/- 26 mg/dL, a 23.8% decrease. Although the HDL cholesterol was lowered from 49 +/- 9 to 43 +/- 7 mg/dL by probucol, a 12.2% decrease, the LDL-to-HDL cholesterol ratio still declined. Both drugs were well tolerated and proved safe in this short-term trial. Antihyperlipidemic therapy may well be indicated in certain patients with unremitting nephrotic syndrome.

Medical management of hyperlipidemia and the role of probucol

Recent experimental and epidemiologic evidence has dispelled all doubts about the need to treat patients with hyperlipidemia. Therapy should focus on 3 areas: control of concomitant risk factors for atherosclerosis, reduction of lipid levels through diet and, if response to diet proves inadequate, administration of lipid-lowering agents. There are 4 categories of first-line drugs: resins, fibrates, nicotinic acid and probucol. Probucol has a sustained effect, additive to that of a lipid-lowering diet; it can reduce total serum cholesterol and cause xanthoma regression even in patients with receptor-defective homozygous familial hypercholesterolemia. It is effective when used alone and has an additive effect when combined with resins or nicotinic acid. Compared with many other lipid-lowering medications, it is well tolerated. Although the combination of probucol and clofibrate may cause a significant decrease in high density lipoproteins, there is no evidence that this decrease carries any adverse consequences for the underlying disease process.

Propylthiouracil-induced hypothyroid hyperlipidemic chick: a model for clofibrate-induced toxicity

An animal model for clinically observed clofibrate (p-chlorophenoxy isobutyrate, CPIB)-induced toxicity has been tested. It is demonstrated that propylthiouracil-induced hypothyroid-hyperlipidemic chick develops severe toxic manifestations following clofibrate administration. Toxic symptoms are characterized by listlessness, drowziness, and extreme muscular weakness. This is associated with elevation of blood urea nitrogen, creatine phosphokinase, uric acid and glutamic oxaloacetic transaminase. Histological examination of muscle specimen from chicks exhibiting toxic syndrome showed degeneration and vacuolization of muscle fibers. The biochemical and histological changes observed are quite similar to those reported in clinical practice in some patients given clofibrate. It is suggested that this chick model could be used to investigate the biochemical basis of clofibrate toxicity.

Effect of clofibrate on branched-chain amino acid metabolism

Clofibric acid inhibited the oxidative decarboxylation of 4-methyl-2-oxopentanoate and 3-methyl-2-oxobutanoate in mitochondria and homogenates of rat liver and quadriceps muscle. In rat hemidiaphragms clofibric acid inhibited the oxidative decarboxylation of 4-methyl-2-oxopentanoate and had no effect on that of 3-methyl-2-oxobutanoate. Clofibric acid displaced branched-chain 2-oxo acids from bovine serum albumin. Clofibrate-treatment of rats decreased the actual activity and activity state of the branched-chain 2-oxo acid dehydrogenase complex in quadriceps muscle, and increased the total activity in heart and liver without a change of the activity state. All interactions of clofibric acid with the metabolism of branched-chain amino acids appear to relate to its structural resemblance to the branched-chain 2-oxo acids. Both reduced plasma and muscle concentrations of branched-chain amino acids and reduced muscle oxidation may play a role in the myopathic side-effects of clofibrate-treatment.

Mitochondrial myopathy--a result of clofibrate/etofibrate treatment? Case report

A 66-year-old man had developed a myopathy while undergoing several periods of etofibrate and clofibrate therapy over the past 5 years. Discontinuation of etofibrate treatment failed to reverse his muscle illness which, however, did not progress. A muscle biopsy revealed a chronic myopathy marked by abundant, abnormally structured muscle mitochondria. His mitochondrial myopathy may represent a forme fruste of the Kearns-Sayre syndrome or other types of mitochondrial myopathy, clinically made evident by the etofibrate/clofibrate therapy, or a permanent, adverse side effect of clofibrate treatment. If the latter assumption proves to be correct, it will indicate that clofibrate therapy may induce an acutely painful but reversible neuromuscular illness, or also, though rarely, a chronic mitochondrial myopathy.

Influence of clofibrate on thyroid hormone and muscle protein turnover

Clofibrate, a hypolipidemic agent, has been shown to increase muscle protein degradation. The possible role of thyroid hormones in this phenomena was examined. Clofibrate treatment of rats for 2 weeks resulted in a significant decrease in total thyroxine and triiodothyronine levels in serum. Reverse T3 and resin uptake values remained unchanged. When exogenous thyroxine was co-administered with clofibrate, serum TSH levels were suppressed, but the increased muscle protein degradation was not reversed. Equilibrium dialysis and Scatchard analysis of the binding of 125I-thyroxine to serum proteins indicated that clofibrate competitively inhibits the binding of thyroid hormone to serum proteins by decreasing its apparent binding affinity. In the presence of lower total thyroid hormone concentrations and an elevated free thyroxine fraction, the total free hormone levels are estimated to be in the normal range in the serum of clofibrate treated rats. Clofibrate seems to act like thyroid hormone since it binds to and displaces T4 from plasma proteins. Because free thyroid hormone levels are in the normal range, the thyroid hormone-like effects of clofibrate on the cell may be additive to the T4 effects, and are probably responsible for the hypermetabolic state seen in the muscle of clofibrate-treated animals. Our data suggest that the effects of clofibrate in muscle are complex. In addition to competitively altering the binding of thyroxine to serum proteins, this substance may also exert a hitherto unrecognized thyroid-hormone-like subcellular effect resulting in increased muscle protein degradation, and in augmented ouabain-sensitive ATPase activities.

The short term effects of bezafibrate on the hypertriglyceridaemia of moderate to severe uraemia

Hypertriglyceridaemia, an atherogenic risk factor, is a well recognised complication of uraemia, and is present in the earliest stages of the disease. Bezafibrate is an effective hypolipidaemic agent, and its effect in moderate to severe uraemia is documented in this study. Significant reductions in serum triglyceride and cholesterol have been achieved after 1 month's therapy with a reduced dosage of bezafibrate. A reduction in the hyperinsulinaemia was also seen, but no change in the fractional removal rate of injected lipid emulsion (K2) was observed. An accelerated decline in some patients' renal function was observed, which was partially reversed on cessation of treatment. Reversible elevations in the serum creatinine phosphokinase were also seen, but no patient exhibited the myositis-like syndrome associated with clofibrate.

Treatment of common lipoprotein disorders

The pathogenesis of arteriosclerosis is not yet fully understood. The growing body of scientific information strongly indicates that the plasma lipoproteins are playing a crucial role in the development of this disease. We now have conclusive information that dietary cholesterol can produce arteriosclerosis in animals and its removal from the diet can result in regression of these lesions. Most importantly, we know that reducing plasma cholesterol in humans will prevent mortality and morbidity related to the clinical sequelae of arteriosclerosis. A diet can be prescribed that can produce profound reductions in lipoprotein levels in many individuals. The rate of success in achieving modifications that reduce plasma cholesterol is very high. Most patients over time find a diet with reduced cholesterol and saturated fat to be quite palatable. As food suppliers become more active in emphasizing low fat, low cholesterol products, and as restaurants see a demand for healthier entrees, the task for the physician and nutritionist will become much easier. Achieving sustained weight reduction is a much more difficult problem, but this too can be accomplished in many patients if the health professionals maintain a hopeful supportive approach. Ultimately, it is the patient's responsibility to bring about these lifestyle changes. It is the physician's and nutritionist's job to monitor the process and provide sound information and encouragement. For individuals with severe lipoprotein disorders such as familial hypercholesterolemia where diet therapy is helpful but not adequate, the use of medications is now indicated (bile acid binding resins and nicotinic acid). Other medications that promise additional effectiveness and safety are under development (Compactin, Mevinolin). It is our belief that control of coronary heart disease and stroke requires appropriate treatment of lipoprotein disorders and the methods for a strong beginning in this endeavor are at hand.

[Bezafibrate-induced myolysis and myoglobinuria in patients with impaired renal function]

A muscular syndrome has been described in patients on clofibrate and fenofibrate therapy. The present paper describes four patients with impaired renal function in whom symptoms and signs of skeletal muscle damage developed during treatment with another clofibrinic acid derivative, bezafibrate. The syndrome was characterized by variable degrees of muscular cramps and paresis, excessive elevation of muscle enzymes in serum, myoglobinemia and myoglobinuria. Transient deterioration of renal function was also common. All patients had been overdosed with bezafibrate with regard to their renal function. It is concluded that bezafibrate like other lipid lowering agents of the clofibrate type may induce muscle damage, at least if doses are not adjusted to renal function. Extreme caution is warranted when treating patients with renal impairment with bezafibrate and strict dose adjustment to kidney function is necessary to avoid muscle damage.

Effect of clofibrate feeding on palmitate and branched-chain 2-oxo acid oxidation in rat liver and muscle

Oxidation rates of palmitate (total and antimycin-insensitive), pyruvate, leucine, 4-methyl-2-oxopentanoate and 3-methyl-2-oxobutanoate and activities of two mitochondrial marker enzymes (citrate synthase and cytochrome c oxidase) were assayed in liver and muscle homogenates of fed, clofibrate-treated and 18 hr-starved rats. Significant alterations in the clofibrate-treated and the starved rats were predominantly observed in the liver. Clofibrate feeding increased antimycin-insensitive (peroxisomal) and antimycin-sensitive (mitochondrial) palmitate oxidation and 4-methyl-2-oxopentanoate and pyruvate oxidation in liver. In muscle, only the activities of citrate synthase and cytochrome c oxidase were slightly decreased. Short starvation increased antimycin-sensitive palmitate and 4-methyl-2-oxopentanoate oxidation in liver. The rates of pyruvate and 3-methyl-2-oxobutanoate oxidation were decreased in muscle homogenates. Results suggest that myopathic phenomena observed after chronic clofibrate administration are not related to changes in the capacity of oxidative metabolism of muscle.

Clofibrate does not alter cyclic nucleotide metabolism in muscle

Clofibrate is a hypolipidemic agent that causes muscle protein breakdown in rats, and an acute muscular syndrome in man. It also inhibits adenylate cyclase in fat tissue. Muscle protein metabolism has been shown to be regulated by cyclic nucleotides. In the present experiments were measured several parameters of cyclic nucleotide metabolism to determine the role that cyclic nucleotides play in clofibrate-induced muscle protein degradation. It was found that clofibrate treatment did not alter cyclic nucleotide levels, nor did it change the activities of basal or hormone-stimulated adenylate cyclase, or cyclic nucleotide phosphodiesterase in muscle. Our results suggest that muscle protein breakdown in clofibrate-treated rats is not regulated by cyclic nucleotides.

The mechanism of action of lipid-lowering drugs

In conclusion, many drugs have been used as lipid lowering agents. Only five currently combine efficacy and acceptable side effects. None of these, nicotinic acid, clofibrate, probucol, cholestyramine or colestipol, is without serious drawbacks. In using lipid lowering drugs, it is important to bear in mind the following. First, no patient should be committed to an indefinite period of drug therapy without an adequate trial of diet therapy. For overweight patients, caloric restriction and weight reduction should always be therapeutic goals. Second, as our understanding of lipoprotein metabolism increases, evaluation of new drugs must include not only their effects on triglyceride but also on lipoprotein and apoprotein levels. Third, our drug armamentarium is currently quite limited and there is a pressing need for the development of new, safe and effective hypolipidemic agents.

Hypothyroidism masquerading as polymyositis

A group of patients is described who presented with proximal muscle weakness and elevated muscle enzymes. They were initially believed to have polymyositis and one of them was even treated as such over a long period of time. The patients were subsequently found to have hypothyroidism and responded well to thyroid hormone replacement.

Hypothyroidism should always be considered in the differential diagnosis of polymyositis. A polymyositis-like picture has to be regarded as a symptom and not as a disease since it occurs in several metabolic, infectious, malignant and drug-induced diseases.

[Fat and renal failure--therapeutic aspects]

There is current debate as to whether or not the hyperlipidaemia seen in patients (1) with chronic renal insufficiency, (2) on regular dialysis treatment and (3) after successful renal transplantation should be specifically treated. The reduced HDL cholesterol fraction suggests that the risk of cardiovascular complications may be increased. Therapeutic possibilities include increased physical exercise and a reduction of carbohydrate intake. If these measures fail, then treatment with clofibrate or bezafibrate should be considered. The recommended dosage of clofibrate is 1.0-1.5 g/week (with CPK-control), and of bezafibrate is 400-500 mg/week in patients with chronic renal insufficiency (creatinin-clearance below 20 ml/min). In patients on regular dialysis treatment plasma lipids are reduced by adding carnitine. Most investigators believe that a specific therapy of the hypercholesterolaemia and hypertriglyceridaemia of patients with nephrotic syndrome is not necessary since the disturbances in fat metabolism are associated with an increased levels of HDL-cholesterol. With remission of the nephrotic syndrome an improvement of the hyperlipoproteinaemia is observed. If patients with acute renal failure are under parenteral nutrition fat infusion is recommended once per week to avoid a deficiency of essential fatty acids which is augmented by daily dialysis therapy.

Myopathy induced by epsilon-aminocaproic acid. Case report

The authors present a case of proximal myopathy secondary to epsilon-aminocaproic acid (EACA) administration. This well recognized entity does not occur immediately after institution of therapy, but follows a delay of several days and a cumulative dose. Its consequences include a spectrum of symptoms from myalgias to severe myopathy with rhabdomyolysis, myoglobinuria, and acute tubular necrosis. A presenting symptom of calf pain in a patient receiving EACA should not automatically imply deep vein thrombosis. Serial creatine phosphokinase measurements are essential in monitoring a patient undergoing EACA therapy, especially after 2 weeks of treatment and a total dose of greater than 500 gm.

Bezafibrate: lack of effect on creatinine excretion and muscular proteins

The effect of bezafibrate (200 mg t.i.d.) on renal and, to some degree, on muscular function was studied in nine patients with primary hyperlipoproteinemia. No signs of a reduction in creatinine excretion or an increase in muscular proteins could be found serving as a possible explanation for the slight increase in serum creatinine observed in a bezafibrate long-term study in more than 1,000 patients. Further studies are necessary for clarification.

Hypolipidemic and glycogenolytic effect of clofibrate (CPIB) in hypothyroid mice: role of insulin and glucagon

1. The role of endogenous glucagon and insulin on the hypolipidemic and glycogenolytic effect of clofibrate was determined in the euthyroid and propylthiouracil (PTU)-induced hypothyroid mice. 2. PTU was fed in diet (0.15%) for 2 weeks and then clofibrate added to diet (0.25%) for 4 weeks. 3. Both PTU and clofibrate significantly increased liver weight but had no effect on kidney weight. PTU significantly decreased plasma triglycerides (TG) and increased cholesterol (Ch). 4. Clofibrate had a significant hypotriglyceridemic effect in both euthyroid and hypothyroid mice but did not affect plasma cholesterol. 5. Clofibrate decreased hepatic glycogen in euthyroid but not in hypothyroid mice. 6. Glucose-6-phosphatase activity was not affected by either PTU or clofibrate. 7. Neither PTU nor clofibrate affected hepatic TG or Ch. 8. Biliary lipid changes due to PTU treatment were reversed by clofibrate administration. 9. Since plasma insulin and glucagon levels were not affected by clofibrate in either euthyroid or hypothyroid mice, our results suggest that the hypotriglyceridemic and glycogenolytic effect of clofibrate is not mediated by changes in circulating insulin and glucagon ratio. 10. Moreover, while the glycogenolytic effect of clofibrate seems to be dependent, the hypotriglyceridemic effect seems to be independent of thyroid hormones.

Clofibrate and vascular smooth muscle: actions on rabbit aorta preparations

Clofibrate (Atromid-S) has been found to inhibit the contractility of isolated rabbit aortic muscle rings produced by exposure to either norepinephrine, histamine or angiotensin. The inhibitory effect of clofibrate is seen optimally in Krebs medium containing low, 5 X 10-5 M, calcium but is not found in medium containing 2.5 X 10-3 M calcium. In contrast, clofibrate does not inhibit contractions triggered by depolarizing concentrations of K+, in either low or normal Ca medium. Since only receptor-mediated contractions are inhibited, it is suggested that the actions of clofibrate in aorta influence an event common to receptor-linked contractions, possibly by interfering with the utilization of membrane-bound calcium.

[Myopathy caused by propoxyphene: report of 2 cases with muscle histochemistry]

The cases of a 43 years old-man with gout and a 24 years-old woman with severe back pain who developed dextro-propoxyphene addiction during pain treatment are reported. They had severe edema and fibrosis of skin, subcutaneous tissue and muscle involving the upper and lower limbs. ESR was elevated, CPK and LDH were normal. EMG in proximal muscles showed decreased duration and voltage of potentials, excess of short polyphasics and increased recruitment (BSAP), with positive waves and fibrillations; distal muscles had fasciculations, fibrillations, positive waves, normal voluntary potentials, decreased recruitment. Lymphography indicate delayed progression of contrast media and obstruction in the thighs. Muscle biopsy on fresh-frozen section and histochemistry showed extensive connective tissue proliferation with intense acid and alkaline phosphatase activity in the perimysial and endomysial area, infiltration of lymphocytes near and around small vessels and capillaries. There were perifascicular and type II fiber atrophy. After discharge the patients returned to propoxyphene addiction and the symptoms who subsided during drug withdrawal come back again. New admission, new drug withdrawal and they were discharged free of symptoms and pathologic changes.

Effects of clofibric acid on amino acid metabolism in cultured rat skeletal muscle

Well-differentiated cultured skeletal muscle cells (myotubes) obtained from adult rats were incubated for up to 48 h in Dulbecco's modified Eagle's medium. Medium glucose decreased from 4.9 +/- 0.1 mM at 0 h to 13 +/- 1 microM by 24 h; approximately 60% of glucose was converted to lactate. Pyruvate, alanine, and citrate were continuously produced, even during the period of 24-48 h when no glucose or lactate utilization was observed. Branched-chain amino acid utilization increased more than fourfold during the incubation period of 24-48 h; during this time, intracellular ATP, pyruvate, alpha-ketoglutarate, malate, and citrate levels were constant despite the absence of glucose or lactate consumption. Incubation of muscle cells with 2 mM clofibric acid resulted in a 76% inhibition of leucine metabolism. Coincident with the drug-induced inhibition of a branched-chain amino acid utilization, alanine and citrate production was blocked, and cell levels of pyruvate, alpha-ketoglutarate, malate, and citrate were markedly reduced. These studies suggest branched-chain amino acids contribute significantly to anaplerotic pathways in cultured skeletal muscle cells and that these pathways lead to the net production of alanine and citrate during periods of minimal carbohydrate utilization.

Branched chain amino acid oxidation in cultured rat skeletal muscle cells. Selective inhibition by clofibric acid

Leucine metabolism in skeletal muscle is linked to protein turnover. Since clofibrate is known both to cause myopathy and to decrease muscle protein content, the present investigations were designed to examine the effects of acute clofibrate treatment on leucine oxidation. Rat skeletal muscle cells in tissue culture were used in these studies because cultivated skeletal muscle cells, like muscle in vivo, have been shown to actively utilize branched chain amino acids and to produce alanine. The conversion of [1-(14)C]leucine to (14)CO(2) or to the [1-(14)C]keto-acid of leucine (alpha-keto-isocaproate) was linear for at least 2 h of incubation; the production of (14)CO(2) from [1-(14)C]leucine was saturable with a K(m) = 6.3 mM and a maximum oxidation rate (V(max)) = 31 nmol/mg protein per 120 min. Clofibric acid selectively inhibited the oxidation of [1-(14)C]leucine (K(i) = 0.85 mM) and [U-(14)C]isoleucine, but had no effect on the oxidation of [U-(14)C]glutamate, -alanine, -lactate, or -palmitate. The inhibition of [1-(14)C]leucine oxidation by clofibrate was also observed in the rat quarter-diaphragm preparation. Clofibrate primarily inhibited the production of (14)CO(2) and had relatively little effect on the production of [1-(14)C]keto-acid of leucine. A physiological concentration-3.0 g/100 ml-of albumin, which actively binds clofibric acid, inhibited but did not abolish the effects of a 2-mM concentration of clofibric acid on leucine oxidation. Clofibrate treatment stimulated the net consumption of pyruvate, and inhibited the net production of alanine. The drug also increased the cytosolic NADH/NAD(+) ratio as reflected by an increase in the lactate/pyruvate ratio, in association with a decrease in cell aspartate levels. The changes in pyruvate metabolism and cell redox state induced by the drug were delayed compared with the nearly immediate inhibition of leucine oxidation. These studies suggest that clofibric acid, in concentrations that approximate high therapeutic levels of the drug, selectively inhibits branched chain amino acid oxidation, possibly at the level of the branched chain keto-acid dehydrogenase.

Clofibrate-induced muscular syndrome. Report of a case with clinical, electromyographic and pathologic observations

In this report the clinical features of a case of clofibrate-induced muscular syndrome, as well as the electromyographic, histochemical, light- and electron-microscopic findings are described. The clinical features are similar to those of previously reported cases. Electromyography was consistent with a myopathy. Histochemical profile was normal. The myopathology included breakdown of contractile material, deranged mitochondria, dilated sarcoplasmic reticulum profiles, accumulation of membrane bound dense bodies, discontinuities in sarcolemma and thickening of capillary basement membrane. Macrophages invaded severely affected fibers.

Measurement of clofibric acid (CPIB) metabolites in plasma of patients on clofibrate therapy

1. The metabolites of clofibric acid [CPIB;2-(chlorophenoxy)-2-methylpropionic acid] are present in the plasma of patients on clofibrate therapy. The highest plasma concentrations of CPIB in metabolite form (up to 51 micrograms/ml) were generally found in patients with renal disease. Negligible concentrations (less than or equal to 2 micrograms/ml) were found in only seven patients out of thirty-six studied. 2. The two conjugates of CPIB found in urine were present in plasma. 3. When measuring conjugated CPIB in plasma it is essential to take care in the handling and storage of specimens, and to select an assay method known to be specific for unmetabolized CPIB.

Metabolic effects of clofibrate in insulin-dependent ketosis-prone diabetic man

This study examined the effects of clofibrate therapy on basal plasma substrate and hormone concentrations in ketosis-prone insulin-dependent diabetic man. A double-blind crossover design was utilized during a 3-mo period in which clofibrate treatment (1 g b.i.d.) was compared to that of a lactose placebo (1 g b.i.d.). Our results demonstrate that clofibrate treatment resulted in a significant reduction in the concentration of plasma glucose, ketone bodies, free fatty acids, triglyceride, and cholesterol in diabetic man. These beneficial effects were observed without demonstrable changes in circulating concentrations of insulin and glucagon. These observations suggest that in ketosis-prone diabetic man, clofibrate therapy may provide an adjunct to exogenous insulin administration.

Clofibrate retardation of naturally-occurring arteriosclerosis in repeatedly-bred male and female rats

Repeatedly-bred, male and female Sprague-Dawley rats which develop hyperglycemia, hyperlipidemia, hypertension, and arteriosclerosis spontaneously were killed at sequential time intervals, i.e., when the females had completed 1, 2, 3 and 4 pregnancies. The control breeders received no treatment; the experimental animals were given 113 mg of clofibrate/100 g of b.w., subcutaneously, daily, 5 times per week. Clofibrate-treated breeders manifested reduction in blood pressure and in the incidence and severity of arterial disease characteristic of repeatedly-bred rats. The aortic lesions of the clofibrate-treated breeders showed attenuation of the usual severe ground substance alterations, the degenerative changes in connective tissue elements, e.g., fibrosis and elastosis, and absence of calcification and cartilaginous metaplasia. Clofibrate-treated breeders did not show any unusual elevation in serum enzymes, e.g., CPK, SGOT, SGPT and LDH, or significant reduction of their hyperlipidemia. They manifested a definite reduction in adrenocortical and medullary histopathology and their circulating corticosterone levels were subnormal compared to non-treated breeders. It is suggested that the protective effect of clofibrate was mediated through its ability to block normal adrenal steroidogenic pathways rather than through its antilipemic action.

Protective effects of clofibrate on isoproterenol-induced myocardial infarction in arteriosclerotic and non-arteriosclerotic rats

Male and female, arteriosclerotic and non-arteriosclerotic rats were treated with the anti-lipemic agent, clofibrate, for 8 days and then subjected to an acute myocardial infarction by injecting them with two large doses of isoproterenol spaced 24 hours apart. The animals were killed at sequential time intervals during the acute necrosis and early repair phases of myocardial infarction. Pre-treatment with clofibrate caused a definite improvement in survival, less shock and prostration, and ECG evidence of little or no ischemia. Increased SGOT levels, hepatic lipid and necrosis were indicative of advanced liver damage. Although clofibrate-treated animals showed little change in serum lipids during the acute cardiac necrosis phase, they were hyperglycemic and showed the greatest increase in BUN levels. Clofibrate-treated animals had higher serum corticosterone levels than those given isoproterenol alone. Despite superior survival rates, both the arteriosclerotic and non-arteriosclerotic, clofibrate-treated animals exhibited equally severe histopathologic evidence of myocardial damage. It is suggested that the protective effect of prophylactic treatment with clofibrate against isoproterenol-induced myocardial infarction in rats may be due to its ability to change corticosterone levels in the circulation.

[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.

Clofibrate-induced myopathy in the rat

Rats were given daily injections of 0.2 or 0.5 g/kg chlorophenoxyisobutyrate (clofibrate) for 9 to 46 days. Lower leg muscles were studied with light and electron microscopy. Daily treatment with 0.5 g/kg of the drug for 26--46 days caused myopathic changes.