Effect of colestipol,a new bile acid sequestrant,on the absorption of phenprocoumon in man

Summary The effect of colestipol, a basic anion-exchange resin, which lowers the serum cholesterol level, has been examined on the absorption of phenprocoumon in four human volunteers,in vivo. Plasma concentrations of phenprocoumon were determined after the simultaneous ingestion either of 8 g colestipol or 4 g placebo (microcrystalline cellulose) and 12 mg phenprocoumon according to a randomized crossover repetition design. The plasma levels were not affected by colestipol, suggesting that it had no effect on the absorption of phenprocoumon. —In vitro, the phenprocoumon-binding capacity of colestipol was the same as that of cholestyramine, except in buffers at pH 5 when there was a marked decrease in the colestipol binding.     

Bile acid sequestrants based on cationic dextran hydrogel microspheres. 2. Influence of the length of alkyl substituents at the amino groups of the sorbents on the sorption of bile salts

Cationic dextran hydrogel microspheres with pendant quaternary ammonium groups having alkyl substituents (C(2)-C(12)) at quaternary nitrogen were synthesized. The in vitro sorption of sodium salts of four bile acids (glycocholic, cholic, taurocholic, and deoxycholic acids) with these hydrogels was studied as a function of substituent alkyl chain length and bile acid hydrophobicity. Sorption experiments were performed in phosphate buffer solutions (pH 7.4) containing one bile salt (individual sorption) or mixtures of several bile salts (competitive sorption). Parameters for individual sorption were calculated taking into consideration the stoichiometric and cooperative binding of bile salts to oppositely charged polymer hydrogels. The results show that the increase in the length of the alkyl chain of the substituent leads to an increase in both ionization constant K(0) and overall stability constant of binding K, but decreases the cooperativity parameter u. The competitive sorption studies indicate that the hydrogels display a good affinity for both dihydroxylic and trihydroxylic bile salts. The molar ratio of maximum amounts bound for the two types of bile acid is 2 to 1, which is much lower than those reported for other cationic polymers recommended as bile acid sequestrants. The binding constants for the sorption of bile salts by some dextran hydrogels are 20-30 times higher than those obtained for cholestyramine under similar sorption conditions.     

Colesevelam hydrochloride.

The pharmacology, pharmacodynamics, clinical efficacy, drug interactions, adverse effects, and dosage and administration of colesevelam hydrochloride are reviewed. Colesevelam hydrochloride is a nonabsorbed lipid-lowering agent approved for use alone or in combination with hydroxymethylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors for the reduction of low-density-lipoprotein (LDL) cholesterol in patients with primary hypercholesterolemia. Colesevelam forms nonabsorbable complexes with bile acids in the gastrointestinal (GI) tract, resulting in changes in plasma lipid levels, including total, LDL, and high-density-lipoprotein cholesterol and triglycerides. Colesevelam has been reported to be four to six times as potent as traditional bile acid sequestrants (BASs), perhaps because of its greater binding affinity for glycocholic acid. Unlike cholestyramine and colestipol, colesevelam appears to reduce LDL cholesterol in a dose-dependent manner. In clinical trials, colesevelam demonstrated efficacy either alone or in combination with HMG-CoA reductase inhibitors in the treatment of primary hypercholesterolemia. Combination therapy appeared to be more effective than monotherapy. Although infection, headache, and GI adverse effects have been reported for colesevelam, the rates do not differ significantly from those occurring with placebo. The constipation that typically hinders compliance with traditional BASs is minimal. In one study, the rate of compliance with colesevelam was 93%. There is little evidence of clinically significant interactions involving colesevelam. The maintenance dosage is three 625-mg tablets twice daily or six tablets once daily, taken with meals. Colesevelam provides an effective alternative to cholestyramine and colestipol while offering the potential for fewer adverse effects and better compliance. Studies are needed to directly compare colesevelam with traditional BASs.     

Acceptability of cholestyramine or colestipol combinations with six vehicles

Preferences for cholestyramine or colestipol in combination with orange drink, orange juice, grape juice, apple juice, water, or apple sauce were evaluated in 40 healthy adults. Each subject evaluated the taste, texture, and smell of 30-mL samples of 12 drug-vehicle combinations (two drugs, six vehicles) using modified five-point wine-tasting scales. Samples were prepared to contain either cholestyramine 1.0 g or colestipol hydrochloride 1.3 g. The products were tested at room temperature and were administered in a random order. Subjects and observers were blinded to the identity of the products. Acceptability scores for taste, texture, and smell were significantly higher for cholestyramine than for colestipol. Total mean preference scores for cholestyramine-vehicle combinations ranged from 9.9 to 11.7; for colestipol, 6.3 to 8.9. Orange drink, apple juice, grape juice, and orange juice were the preferred vehicles for cholestyramine. The preferred vehicles for colestipol were orange drink, apple sauce, and apple juice.     

Increasing the in vitro bile acid binding capacity of diethylaminoethylcellulose by quaternization.

Diethylaminoethylcellulose (DEAE-cellulose) was quaternized with methyl iodide (DEAE-cellulose-CH3I), and its in vitro binding capacity for sodium glycocholate, at room temperature, in water, Tris-HCl buffer (0.0015-0.0050 M, pH 7.0), and aqueous NaCl (0.0025 M) was determined by reversed-phase HPLC. Quaternization increased the in vitro bile salt binding capacity of DEAE-cellulose. On a molar basis, the binding capacity was greater than that of cholestyramine, a cholesterol-lowering agent. Increasing the ionic strength of the medium decreased the binding capacities, as expected if ionic interactions are important. However, conversion of DEAE-cellulose-CH3I to its chloride form did not change the binding capacity. The bile salt binding capacity of DEAE-cellulose-CH3I was similar for both sodium cholate and sodium glycocholate.     

Effects of resins and activated charcoal on the absorption of digoxin, carbamazepine and frusemide.

1. The interference of resins and activated charcoal with the absorption of digoxin, carbamazepine and frusemide was studied. 2. In a cross-over study consisting of four phases, single doses of colestipol hydrochloride (10 g), cholestyramine (8 g), activated charcoal (8 g) or water only were given to six healthy volunteers immediately after the simultaneous ingestion of digoxin (0.25 mg), carbamazepine (400 mg) and frusemide (40 mg). Plasma and urine concentrations of the test drugs and the urine volumes were determined up to 72 h. 3. The absorption of digoxin was not reduced by colestipol, moderately (30-40%, P less than 0.05) reduced by cholestyramine and greatly (96%) by charcoal. 4. The absorption of carbamazepine was not decreased by cholestyramine, slightly (10%) by colestipol and greatly (90%) by activated charcoal. 5. The absorption and the diuretic effect of frusemide were significantly diminished by all agents. The bioavailability was reduced by colestipol 80%, by cholestyramine 95% and by activated charcoal 99.5%. 6. The interference with the gastrointestinal absorption of most of the basic drugs by colestipol and cholestyramine seems to be minimal. On the other hand, the resins may seriously impair the absorption of certain acidic drugs, for example frusemide.     

The effect of drugs on bile flow and composition. An overview

Many drugs are eliminated via the hepatobiliary route, after biotransformation in the liver. Some of them may affect bile flow and/or the hepatic secretion of biliary lipids such as bile acids, cholesterol and phospholipids. Bile acids are the most potent agents which increase bile flow, especially unconjugated bile acids. Other drugs which increase bile flow include phenobarbitone (phenobarbital), theophylline, glucagon and insulin. In contrast, ethacrynic acid, amiloride, ouabain, oestrogens and chlorpromazine are among those agents which decrease bile flow. Biliary bile acid secretion is altered by a variety of drugs, including cheno- and ursodeoxycholic acids (CDCA and UCDA), the bile acid sequestrants cholestyramine and colestipol, and ethinyloestradiol. The composition of bile can also be altered by drug therapy. Thus, clofibrate increases biliary cholesterol secretion, and reduces bile acid concentrations, without altering biliary phospholipid concentrations. However, other clofibrate derivatives may produce changes of a different pattern, suggesting that the risk of developing gallstones may differ for each derivative. Nicotinic acid and d-thyroxine also increase biliary cholesterol saturation, while CDCA and UDCA reduce biliary cholesterol concentration. The potential consequences of drug-induced changes in bile flow and composition extend to the liver, the gallbladder and the intestine. If adverse effects are to be avoided, further study in this often overlooked area is required.     

Effects of cholestyramine and colestipol on the plasma concentrations of propranolol

The effect of equivalent hypolipidaemic doses of cholestyramine (8 g) or colestipol (10 g) on the plasma concentrations of propranolol and 4'-hydroxypropranolol was studied in 12 normal volunteers following the oral administration of 120 mg of normal release propranolol tablets. When two doses of either cholestyramine or colestipol were administered prior to the propranolol, the peak plasma concentrations and area under the curve for both propranolol and the metabolite 4'-hydroxypropranolol were reduced significantly (P less than 0.05). We conclude that the drug interaction between cholestyramine or colestipol and propranolol leads to significant reductions in plasma concentrations of propranolol and 4'-hydroxypropranolol which may cause a clinically diminished effect for a given dosage. Therefore, patients should be observed when either of these resins are added to or deleted from a therapeutic regimen.     

Bile acid sequestrants: Mechanisms of action on bile acid and cholesterol metabolism

Summary Interruption of the enterohepatic circulation of bile acids by cholestyramine or colestipol influences the hepatic metabolism of cholesterol in many ways. The synthesis of bile acids is increased, as reflected by a several-fold increase in the activity of the cholesterol 7 hydroxylase, the rate-determining enzyme in bile acid synthesis. The increased metabolism of cholesterol to bile acids causes an enhanced demand of cholesterol in the hepatocytes, which respond with both new synthesis of cholesterol, as reflected in a several-fold increase of the HMG-CoA reductase activity, and increased expression of LDL receptors. As a consequence, the plasma level of LDL-cholesterol is lowered. The hepatic secretion rate of VLDL particles is increased. Cholestyramine therapy does not affect the output of biliary lipids or the cholesterol saturation of bile, indicating that treatment with bile acid sequestrants should not be associated with any increased risk of gallstone formation.     

Patent Evaluation: Polyamide bile acid sequestrants are more potent than cholestyramine

Summary

Novelty: Amide polymers, potentially useful in the treatment of hypercholesterolaemia, are claimed. The polymers form ionic and hydrogen bonds with bile acids, preventing reabsorption and facilitating their excretion. The compositions have greater efficacy than the known therapeutic agents, cholestyramine and cholestipol, which have a similar mode of action.

Biology: A six month in vivo canine study evaluating the ability of the compounds to lower plasma cholesterol levels is described (animals were fed on a semi-synthetic, low cholesterol diet with and without a bile acid sequestrant). The results indicate that the compounds are effective for the control of blood cholesterol levels and show superior activity to cholestyramine.

Chemistry: Dimethylaminopropylmethacrylamide (DMAPMA) is one of thirty-four polymers specifically claimed. Preparative details using standard techniques are presented.     

The effect of colestipol dose on postprandial serum bile acid concentration: assessment by an enzymic bioluminescence procedure

A dose-response study was performed with three doses of colestipol, using postprandial serum bile acid levels to assess bile acid sequestering activity in 40 volunteers with asymptomatic hyperlipidaemia. Subjects who entered the study had total serum cholesterol concentrations greater than 220 mg/dl and triglyceride concentrations less than 200 mg/dl. They were randomly assigned to one of four parallel treatment groups: (a) placebo b.d., (b) colestipol (as Colestid hydrochloride granules) 2.5 g b.d., (c) colestipol 5 g b.d., and (d) colestipol 7.5 g b.d. Subjects were maintained on a constant repeating solid diet throughout the 6-day study period, and colestipol was ingested 30 min before breakfast and dinner. No drug was administered on Days 1-3; baseline (pre-treatment) serum bile acid concentration profiles were determined on Day 3. The above treatments were given on Days 4-6, and total serum bile acid concentrations were determined at 30- or 60-min intervals for 10 h on Days 4 and 6. Serum bile acids were measured using a bioluminescence procedure which enzymically measures total 3 alpha hydroxy bile acids. Serum bile acid concentrations were significantly decreased from the pretreatment period by 5.0 and 7.5 g/day as compared to 2.5 g/day or placebo. Differences from the pre-treatment period in the area under the serum bile acid time curve revealed the same trends in the data as analysis of percentage difference (Day 6 vs pre-treatment period) in serum bile acid concentrations. These results indicate that postprandial serum bile acid concentrations are influenced by colestipol in a dose-related manner, with doses of 5 and 7.5 g b.d. having a significantly greater effect than 2.5 g b.d. The dose of 7.5 g b.d. had an identical effect on serum bile acid patterns as a dose of 5.0 g t.d.s., which was previously reported. Our findings also show that changes in serum bile acid concentrations may be used to follow the immediate effects of bile acid sequestration in hypercholes terolaemic subjects, and that the bioluminescence enzyme technique is sufficiently sensitive to detect such changes.     

Fecal bile acid excretion and liver cholesterol synthesis after sucralfate and cholestyramine administration in the rat

The relative ability of the resin cholestyramine and sucralfate (disucrose octasulfate) to bind bile acids in the gastro intestinal tract and increase fecal bile acid excretion has been studied in normal rats under standard diet. Plasma and liver cholesterol concentrations and in vitro cholesterol synthesis from 14C-acetate by liver slices, have been determined before and after one and three weeks of drug administration (0.5 or 1.0 g/100 g food). Plasma and liver cholesterol levels were unchanged after one week of treatment, but a moderate decrease in liver cholesterol content was observed after 3 weeks administration of cholestyramine and, to a lesser extent of sucralfate. Both drugs increase fecal bile acid excretion with a definitely higher effect of cholestyramine at either dose or period of administration. However, the resin produced a higher bile acid excretion after one week than after three weeks, whereas sucralfate effect increases with the time of administration. In vitro cholesterogenesis was clearly increased by cholestyramine and moderately by sucralfate although 14C-acetate incorporation into cholesterol was not quantitatively correlated to the amount of bile acid excreted in feces. The potential interest of sucralfate as bile acid sequestrant and hypocholesterolemic agent in man deserves further investigations.     

The acceptability of resin therapy to patients attending a hospital lipid clinic.

Low dose cholestyramine ('Questran A') and colestipol ('Colestid Orange') were compared in a blinded two period crossover study of 55 patients attending a hospital lipid clinic. Colestipol was rated higher on a combined acceptability/palatability score. Both treatments reduced low density lipoprotein (LDL) cholesterol to a similar extent.     

Pravastatin. A review of its pharmacological properties and therapeutic potential in hypercholesterolaemia.

Pravastatin is an HMG-CoA reductase inhibitor which reduces plasma cholesterol levels by inhibiting de novo cholesterol synthesis and increasing the receptor-mediated catabolism of low density lipoprotein (LDL). Several large multicentre placebo-controlled trials have shown that pravastatin reduces total and LDL-cholesterol levels in a dose-proportional manner in patients with familial or nonfamilial hypercholesterolaemia. Reductions in LDL-cholesterol levels reported in the largest study were 18% (10 mg/day), 23% (20 mg/day) and 31% (40 mg/day) after 12 weeks. Once-daily administration appears to be as effective as two daily doses. Pravastatin consistently increases HDL-cholesterol levels and decreases levels of total triglycerides but these changes are not dose dependent. At the study dosages used, the antihypercholesterolaemic effects of pravastatin were superior to those of bezafibrate and clinofibrate, and were similar to those of simvastatin, lovastatin, gemfibrozil and cholestyramine although in some studies a trend towards a superior effect with pravastatin was seen. Pravastatin did not reduce HDL-cholesterol like probucol, or increase triglyceride levels like cholestyramine. Combined treatment with pravastatin and cholestyramine or colestipol enhances the cholesterol-lowering effects of either drug administered alone and offsets the increase in total triglyceride levels seen with cholestyramine or colestipol therapy. Pravastatin is well tolerated during treatment of up to 24 months but longer term tolerability has not yet been established. The effect of provastatin on cardiovascular events related to elevated plasma cholesterol levels is under investation in several large scale regression and primary and secondary prevention trials.(ABSTRACT TRUNCATED AT 250 WORDS)     

Bile acid sequestrants

The bile acid sequestrants, cholestyramine and colestipol, are the drugs of choice for the treatment of patients with hypercholesterolemia caused by increases in LDL-cholesterol levels without concurrent hypertriglyceridemia (type IIA and type IIB hyperlipoproteinemia). Longitudinal clinical studies with these drugs have shown their ability to slow the progression of atherosclerosis and to limit the consequences of the disease. Bile acid sequestrants can be used with other lipid-lowering drugs such as nicotinic acid or HMG CoA reductase inhibitors, to maximize the cholesterol-lowering effects. The side effect profile of the bile acid sequestrants is tolerable, with most complaints related to effects on the gastrointestinal tract and the bulkiness of the resins.     

Sorption of fluoroacetate (compound 1080) by Colestipol, activated charcoal and anion-exchange in resins in vitro and gastrointestinal decontamination in rats

The sorption of sodium fluoroacetate (FA) by activated charcoal (AC) and 5 anion exchange resins (AERs) was tested in 2 simulated gastrointestinal (GI) fluids. Each sorbent was incubated with FA in a shaker-water-bath at 37 C for 24 h. Supernatant was removed and filtered, and the concentration of FA was determined by gas chromatographic detection of the dichloroaniline derivative. Under simulated gastric conditions (0.1 M HCl at approximately pH 1.5), the sorbents removed the following proportions of FA from solution: Carbosorb AC, 87 +/- 2%; cholestyramine, 28 +/- 7%; colestipol, 96 +/- 0%; Amberlite IRA-96, 70 +/- 2%; DEAE-Sephadex, 7 +/- 4%; Chitosan, 66 +/- 2%. Under simulated intestinal conditions (0.05 M sodium phosphate at approximately pH 7.4), binding was as follows: Carbosorb AC, 68 +/- 4%; cholestyramine, 53 +/- 5%; colestipol, 46 +/- 2%; AmberliteIRA-96, 10 +/- 20%; DEAE-Sephadex, 64 +/- 7%; Chitosan, 5 +/- 2%. All findings differed significantly from control, with the exception of Amberlite IRA-96 and Chitosan in phosphate buffer, and DEAE-Sephadex in HCI. In a second study, rats were given 5 mg FA/kg, and then gavaged with 2 g/kg Carbosorb AC, colestipol or bentonite. Over 4 h, the area under the curve of serum FA versus time (AUC) decreased by 39% in the rats treated with colestipol and 42% in those treated with bentonite. In contrast, Carbosorb AC did not affect the AUC,yet increased Tmax In another study, mortality was assessed 96 h after rats were orally dosed with 5 mg FA/kg followed by gavage with 2 g/kg Carbosorb AC, colestipol or water immediatey or 30 min after dosing. When the sorbents were given immediately, mortality was the same as control (75%). Surprisingiy, the 30-min delay resulted in lower mortality in colestipol-treated rats, (approximately 38%) compared to 100% in the group treated with Carbosorb AC. Before any recommendation can be made regarding the use of colestipol as a GI decontaminant, the latter findings require confirmation in an intensive care setting. The potential for synergistic effects with 2 or more sorbents also warrant investigating.     

The effect of colestipol and cholestyramine on the systemic clearance of intravenous ibuprofen in rabbits

Abstract— The effect of oral administration of the non-absorbable anion-exchange resins cholestyramine and colestipol on the systemic clearance and other pharmacokinetic parameters of intravenously administered ibuprofen (25 mg kg^?1) was studied in rabbits. Single doses of colestipol hydrochloride (0·4 g kg^?1) or cholestyramine (0·17 g kg^?1) were given 30 min before ibuprofen administration. In cholestyramine-treated rabbits a significant reduction in ibuprofen plasma concentration was observed compared with both control (water only) and colestipol-treated rabbits. Cholestyramine treatment resulted in a significant decrease in the terminal elimination half-life and the mean residence time. Furthermore, a 31% increase in the systemic clearance and 23% decrease in the area under the plasma concentration-time curve were also observed in cholestyramine-treated rabbits. Colestipol treatment did not change these parameters. The volume of distribution parameters (Vd_ss and Vd_area) did not change following either treatment. The changes in the pharmacokinetic parameters are compatible with an acceleration of ibuprofen elimination induced by oral administration of cholestyramine and not by colestipol. This effect is thought to be due to augmentation of net biliary excretion through enteric binding.     

In vitro binding of various biological substances by two hypocholesterolaemic resins. Cholestyramine and colestipol.

The ability of cholestyramine and colestipol, two hypocholesterolaemic resins, to bind in vitro several compounds such as vitamin B12, vitamin B12-intrinsic factor complex, folic acid, iron citrate and calcium chloride was investigated. Both resins bound to a high extent vitamin B12-intrinsic factor complex, folic acid and iron citrate; in addition, cholestyramine also caused appreciable binding of calcium. Throughout a large range of pH, there was no change in the binding capacity; however, at pH 2, cholestyramine exhibited a marked drop in the binding of tested substances (with exception of folic acid). By increasing the molarity of the solutions, the binding to the resins of vitamin B12-intrinsic factor complex and of calcium chloride was completely inhibited. In human gastric and duodenal juices, the uptake by the resins of the studied compounds depends on the molarity of the physiological medium tested and partly confirms the results obtained with aqueous solutions. These data obtained in vitro emphasize the necessity of regular monitoring these biochemical parameters during chronic treatment of hypercholesterolaemia conducted with these two resins.     

Tolerability and efficacy of colestipol hydrochloride for accelerated elimination of teriflunomide

Background: Teriflunomide is an oral disease modifying therapy approved for the treatment of relapsing forms of multiple sclerosis. Teriflunomide’ s pharmacokinetics (PK) contribute to its slow elimination, on average taking 6–8 months, though it can take up to 2 years in some instances. This slow elimination can become problematic in certain clinical situations – such as during pregnancy, when teriflunomide has potential teratogenic effects. In such scenarios, an accelerated elimination procedure (AEP) is recommended. Currently, AEPs with oral cholestyramine or activated charcoal are available but are restricted by adverse effects, limited administration routes, and dosing frequencies.

Methods: A single-center, PK interaction study was performed in a total of 14 healthy volunteers, to investigate colestipol hydrochloride (HCl) as an alternative to cholestyramine for the elimination of teriflunomide. Participants received teriflunomide for 14 days, followed by an AEP with colestipol HCl for 15 days.

Results and conclusions: The administration of colestipol HCl for 15 days was sufficient to reduce plasma teriflunomide concentrations by greater than 96%. Although colestipol HCl did not completely eliminate teriflunomide with the same effectiveness as cholestyramine, it may offer an alternative method for accelerated elimination of teriflunomide with potentially improved tolerability and more favorable dosing and administration options.     

DMP 504, a novel hydrogel bile acid sequestrant: I. equilibrium binding properties and computer simulation of human bile flow

DMP 504 is a novel bile acid sequestrant under development for the treatment of primary hypercholesterolemia. The resin is a soft-textured “hydrogel” that is synthesized from 1,10-dibromodecane and 1,6-diaminohexane. The equilibrium binding parameters for DMP 504 have been determined and compared to cholestyramine (CS) with respect to the major trihydroxy bile acid, glycocholate (GC), and the major dihydroxy bile acid, glycochenodeoxycholate (GCDC). DMP 504 had a greater maximum binding capacity (Bmax) than CS for GC (5.47 ± 0.06 vs. 2.76 ± 0.17 moles/kg) and GCDC (5.71 ± 0.14 vs. 3.26 ± 0.11 moles/kg). DMP 504 had a greater affinity, i.e., a lower Kd, than CS for GC (1.78 ± 0.04 vs. 5.24 ± 0.64 mM) and GCDC (0.19 ± 0.01 vs. 0.52 ± 0.06 mM). Similar values were obtained for the taurine conjugates of cholate and chenodeoxycholate. Since the interaction of bile acids with DMP 504 was highly cooperative, the binding isotherms were analyzed with a model that included a cooperativity parameter (W) to allow for interactions between adjacently bound bile acids. The DMP 504 binding isotherms showed greater cooperativity than CS for GC (5.10 ± 0.42 vs. 1.81 ± 0.47) and GCDC (6.28 ± 1.68 vs. 2.40 ± 0.76). A mathematical model of human bile flow, using the values for Bmax, Kd, and W determined in this study predicted that DMP 504 would be approximately threefold more potent than CS in a clinical setting. Drug Dev. Res. 41:58–64, 1997. © 1997 Wiley-Liss, Inc.