Drug interactions with colesevelam hydrochloride, a novel, potent lipid-lowering agent

Colesevelam - a bile acid sequestrant for treating hypercholesterolemia and improving hyperglycemia

INTRODUCTION

Low density Lipoprotein cholesterol)LDL-C) levels show a clear relationship with cardiovascular disease (CVD). Statins are first line agents to reduce LDL-C and CVD risk. However, combination lipid-lowering therapy is often required to achieve large reductions in LDL-C.

AREA COVERED

Colesevelam HCl is a bile acid sequestrant (BAS), which reduces LDL-C by 16-22% in monotherapy and adds a further 12-14% reduction in LDL-C when combined with other lipid-lowering drugs. Like statins, colesevelam reduces C-reactive protein levels by 16% in monotherapy and additional 6% when added to statins. Colesevelam also reduced HbA_1c by 4mmol/mol (0.5%) when used alone and added to other hypoglycaemic drugs in studies of patients with diabetes .

EXPERT OPINION

Bile acid sequestrants reduce LDL-C and HbA_1c and have some CVD outcome evidence. The uses of these agents are limited in patients with gastrointestinal disease or high triglycerides due to adverse effects on gut function and raising triglycerides and they interfere with the absorption of lipid-soluble drugs. Colesevelam has a higher bile acid binding capacity, and fewer adverse effects than other BAS. Colesevelam may be useful as a third line agent for treatment of hypercholesterolemia with some additional specific benefits on glycemic control.

Effects of medicines used to treat gastrointestinal diseases on the pharmacokinetics of coadministered drugs: a PEARRL Review

OBJECTIVES

Drugs used to treat gastrointestinal diseases (GI drugs) are widely used either as prescription or over-the-counter (OTC) medications and belong to both the 10 most prescribed and 10 most sold OTC medications worldwide. The objective of this review article is to discuss the most frequent interactions between GI and other drugs, including identification of the mechanisms behind these interactions, where possible.

KEY FINDINGS

Current clinical practice shows that in many cases, these drugs are administered concomitantly with other drug products. Due to their metabolic properties and mechanisms of action, the drugs used to treat gastrointestinal diseases can change the pharmacokinetics of some coadministered drugs. In certain cases, these interactions can lead to failure of treatment or to the occurrence of serious adverse events. The mechanism of interaction depends highly on drug properties and differs among therapeutic categories. Understanding these interactions is essential to providing recommendations for optimal drug therapy.

SUMMARY

Interactions with GI drugs are numerous and can be highly significant clinically in some cases. While alterations in bioavailability due to changes in solubility, dissolution rate, GI transit and metabolic interactions can be (for the most part) easily identified, interactions that are mediated through other mechanisms, such as permeability or microbiota, are less well-understood. Future work should focus on characterising these aspects.

Pharmacokinetic Variability of Drugs Used for Prophylactic Treatment of Migraine

In this review, we evaluate the variability in the pharmacokinetics of 11 drugs with established prophylactic effects in migraine to facilitate 'personalized medicine' with these drugs. PubMed was searched for 'single-dose' and 'steady-state' pharmacokinetic studies of these 11 drugs. The maximum plasma concentration was reported in 248 single-dose and 115 steady-state pharmacokinetic studies, and the area under the plasma concentration-time curve was reported in 299 single-dose studies and 112 steady-state pharmacokinetic studies. For each study, the coefficient of variation was calculated for maximum plasma concentration and area under the plasma concentration-time curve, and we divided the drug variability into two categories; high variability, coefficient of variation >40%, or low or moderate variability, coefficient of variation <40%. Based on the area under the plasma concentration-time curve in steady-state studies, the following drugs have high pharmacokinetic variability: propranolol in 92% (33/36), metoprolol in 85% (33/39), and amitriptyline in 60% (3/5) of studies. The following drugs have low or moderate variability: atenolol in 100% (2/2), valproate in 100% (15/15), topiramate in 88% (7/8), and naproxen and candesartan in 100% (2/2) of studies. For drugs with low or moderate pharmacokinetic variability, treatment can start without initial titration of doses, whereas titration is used to possibly enhance tolerability of topiramate and amitriptyline. The very high pharmacokinetic variability of metoprolol and propranolol can result in very high plasma concentrations in a small minority of patients, and those drugs should therefore be titrated up from a low initial dose, depending mainly on the occurrence of adverse events.

Dietary Administration of Colesevelam Hydrochloride Does Not Affect Fertility or Reproductive Performance in Rats

Colesevelam hydrochloride (HCl) (WelChol; Sankyo Pharma) is a novel, highly potent, bile acid-binding polymer used for the treatment of hypercholesterolemia. The primary aim of this study was to determine the effects of dietarily administered colesevelam HCl on fertility and reproductive performance parameters. To assess these effects, sexually mature Sprague-Dawley rats were randomized to one of five treatment groups: feed alone, feed plus control article (SigmaCell), or feed plus colesevelam HCl 200, 1000, or 2000 mg/kg/day. Male and female rats were administered the appropriate group agent for 28 and 15 days, respectively, and were subsequently paired together for cohabitation and mating. Females continued to receive the test agent in their dietary formulation through presumed gestation day (GD) 7. Presumed pregnant females underwent cesarean section on GD 20. Food consumption rate, body weight, gross necropsy, and standard preclinical tests for reproduction and fertility were performed for each test animal. No statistically significant differences were found between control and drug-treated groups for any tested endpoints of reproduction. All animals placed in cohabitation successfully mated. Uterine and litter end points were unaffected by dosages of colesevelam HCl as high as 2000 mg/kg/day. There were no significant differences between treatment group litter averages in the number of corpora lutea, implantation sites, litter size, live fetuses, body weights, early/late resorptions, and the number of dams with viable fetuses. In addition, no external alterations of fetal morphology were attributable to treatment with colesevelam HCl when administered up to the embryo implantation stage. In male animals, no significant differences were found between the colesevelam HCl and control study groups in the average caudal epididymal sperm count or sperm concentration, total number of motile and nonmotile sperm, and the total percentage of motile sperm. Based on these data, colesevelam HCl does not have any significant adverse reproductive or fertility effects in rats, even when administered at doses approximately 30 times greater than the approved clinical dose.

Role of the Pharmacist in the Management of Dyslipidemia

Dyslipidemia is one of a number of independent risk factors for cardiovascular disease. Numerous large-scale, randomized clinical trials demonstrate the benefit of aggressive lipid-modifying therapy in reducing the mortality and morbidity associated with cardiovascular disease. Despite these data and the wide dissemination of clinical practice guidelines outlining management strategies for patients with dyslipidemia, particularly those at the greatest cardiovascular risk, studies indicate that a significant proportion of patients are not screened, initiated on appropriate therapy, or treated to target lipid levels. Pharmacists, as part of the multidisciplinary team, can play a vital role in assisting in the management of patients with dyslipidemias. This article reviews published studies that have evaluated the pharmacist's role in lipid management, reviews the process for managing a patient with dyslipidemia, and provides suggestions on how pharmacists can become more involved in lipid management.

Effect of Bile Acid Sequestrants on the Risk of Cardiovascular Events: A Mendelian Randomization Analysis

BACKGROUND

Statins lower low-density lipoprotein cholesterol (LDL-C) and risk of coronary artery disease (CAD), but they may be ineffective or not tolerated. Bile acid sequestrants (BAS) reduce LDL-C, yet their clinical efficacy on CAD remains controversial.

METHODS AND RESULTS

We conducted a systematic review and meta-analysis of randomized controlled trials to assess the effect of cholestyramine and colesevelam. We then used Mendelian randomization to estimate the effect of BAS on reducing the risk of CAD. First, we quantified the effect of rs4299376 (ABCG5/ABCG8), which affects the intestinal cholesterol absorption pathway targeted by BAS and then we used these estimates to predict the effect of BAS on CAD. Nineteen randomized controlled trials with a total of 7021 study participants were included. Cholestyramine 24 g/d was associated with a reduction in LDL-C of 23.5 mg/dL (95% confidence interval [CI] -26.8,-20.2; N=3806) and a trend toward reduced risk of CAD (odds ratio 0.81, 95% CI 0.70-1.02; P=0.07; N=3806), whereas colesevelam 3.75 g/d was associated with a reduction in LDL-C of 22.7 mg/dL (95% CI -28.3, -17.2; N=759). Based on the findings that rs4299376 was associated with a 2.75 mg/dL decrease in LDL-C and a 5% decrease in risk of CAD outcomes, we estimated that cholestyramine was associated with an odds ratio for CAD of 0.63 (95% CI 0.52-0.77; P=6.3×10(-6)) and colesevelam with an odds ratio of 0.64 (95% CI 0.52-0.79, P=4.3×10(-5)), which were not statistically different from BAS clinical trials (P>0.05).

CONCLUSIONS

The cholesterol lowering effect of BAS may translate into a clinically relevant reduction in CAD.

Lack of effect of colesevelam HCl on the single-dose pharmacokinetics of aspirin, atenolol, enalapril, phenytoin, rosiglitazone, and sitagliptin

AIMS

Drug interactions with bile acid sequestrants are primarily due to the potential of these agents to bind to concomitant drugs. Six clinical studies were performed to determine the effects of colesevelam on the pharmacokinetics of aspirin, atenolol, enalapril, phenytoin, rosiglitazone, and sitagliptin.

METHODS

All six studies enrolled healthy subjects aged 18-45 years. The phenytoin study used a single-dose, three-period crossover design (phenytoin alone, phenytoin simultaneously with colesevelam, and phenytoin 4h before colesevelam). The other studies used a two-period crossover design (test drug alone and test drug simultaneously with colesevelam). Colesevelam (3750mg once daily) was dosed throughout the pharmacokinetic sampling period. After each single dose of the test drug, serial blood samples were collected for determination of plasma drug concentrations and calculation of pharmacokinetic parameters.

RESULTS

For all six test drugs, 90% CIs for geometric least-squares mean ratios of AUC and Cmax for the measured analytes were within specified limits, indicating no interaction between the test drug and colesevelam.

CONCLUSIONS

Aspirin, atenolol, enalapril, rosiglitazone, and sitagliptin may be taken with colesevelam. Although the phenytoin study indicated no pharmacokinetic interaction, phenytoin should continue to be taken ≥4h before colesevelam in accordance with current prescribing information.

Safety and efficacy of colesevelam HCl in the treatment of elderly patients

BACKGROUND AND OBJECTIVES

Colesevelam significantly lowers cholesterol in patients with hypercholesterolemia, and both cholesterol and hemoglobin A1C (A1C) in patients with type 2 diabetes mellitus (T2DM). The purpose of this post hoc analysis was to evaluate the efficacy and safety/tolerability of colesevelam in older (≥65 years) and younger (<65 years) adults.

METHODS

We conducted post hoc analyses of pooled clinical trial data from seven phase II and III randomized, double-blind, placebo-controlled, primary hyperlipidemia and T2DM clinical trials. The hyperlipidemia safety/tolerability analysis included seven studies (≥65 years, n = 154; <65 years, n = 381); the efficacy analysis utilized one study with sufficient patients in both age groups for meaningful comparison. The T2DM analyses included four studies (safety/tolerability: ≥65 years, n = 249; <65 years, n = 880) or three studies (efficacy). In the hyperlipidemia studies, patients received colesevelam 1.5-4.5 g/day or placebo, alone or with a statin, for 4 weeks to 6 months. In the T2DM studies, colesevelam 3.75 g/day or placebo was added to existing antidiabetes therapies for 16 or 26 weeks. Low-density lipoprotein cholesterol (LDL-C), A1C, and adverse events were assessed.

RESULTS

In the hyperlipidemia analysis, colesevelam versus placebo produced similar mean reductions from baseline in LDL-C in older (-16.6 vs. +0.5 %) and younger (-13.7 vs. +0.4 %) patients. In the T2DM analysis, older and younger patients had similar reductions from baseline in A1C (treatment difference -0.59 and -0.54 %, respectively; both p < 0.001) and LDL-C (-14.7 and -15.5 %, respectively; both p < 0.001) with colesevelam. In both analyses, adverse event incidence was generally similar between subgroups. In the T2DM analysis, hypoglycemia was slightly more frequent with colesevelam versus placebo in older patients (5.8 vs. 2.3 %); no reports of hypoglycemia were considered serious adverse events.

CONCLUSIONS

In primary hyperlipidemia and in T2DM, colesevelam appeared to be generally as safe, well tolerated, and efficacious in patients aged ≥65 years as in those aged <65 years.

A reappraisal of the risks and benefits of treating to target with cholesterol lowering drugs

Atherosclerotic cardiovascular disease (CVD) is the number one cause of death globally, and lipid modification, particularly lowering of low density lipoprotein cholesterol (LDLc), is one of the cornerstones of prevention and treatment. However, even after lowering of LDLc to conventional goals, a sizeable number of patients continue to suffer cardiovascular events. More aggressive lowering of LDLc and optimization of other lipid parameters like triglycerides (TG) and high density lipoprotein cholesterol (HDLc) have been proposed as two potential strategies to address this residual risk. These strategies entail use of maximal doses of highly potent HMG CoA reductase inhibitors (statins) and combination therapy with other lipid modifying agents. Though statins in general are fairly well tolerated, adverse events like myopathy are dose related. There are further risks with combination therapy. In this article, we review the adverse effects of lipid modifying agents used alone and in combination and weigh these effects against the evidence demonstrating their efficacy in reducing cardiovascular events, cardiovascular mortality, and all cause mortality. For patients with established CVD, statins are the only group of drugs that have shown consistent reductions in hard outcomes. Though more aggressive lipid lowering with high dose potent statins can reduce rates of non fatal events and need for interventions, the incremental mortality benefits remain unclear, and their use is associated with a higher rate of drug related adverse effects. Myopathy and renal events have been a significant concern with the use of high potency statin drugs, in particular simvastatin and rosuvastatin. For patients who have not reached target LDL levels or have residual lipid abnormalities on maximal doses of statins, the addition of other agents has not been shown to improve clinical outcomes and carries an increased risk of adverse events. The clinical benefits of drugs to raise HDLc remain unproven. In patients without known cardiovascular disease, there is conflicting evidence as to the benefits of aggressive pursuit of numerical lipid targets, particularly with respect to all cause mortality. Certainly, in statin intolerant patients, alternative agents with a low side effect profile are desirable. Bile acid sequestrants are an effective and safe choice for decreasing LDLc, and omega-3 fatty acids are safe agents to decrease TG. There remains an obvious need to design and carry out large scale studies to help determine which agents, when combined with statins, have the greatest benefit on cardiovascular disease with the least added risk. These studies should be designed to assess the impact on clinical outcomes rather than surrogate endpoints, and require a comprehensive assessment and reporting of safety outcomes.

Colesevelam hydrochloride in the management of dyslipidemia

Dyslipidemia is a highly heterogeneous group of disorders strongly influenced by both genetic and environmental factors. Dyslipidemia significantly increases risk for atherosclerotic disease and all of its various clinical manifestations. Identifying patients with dyslipidemia and initiating therapies aimed at normalizing the lipid profile has been demonstrated to significantly reduce the risk for myocardial infarction, stroke and cardiovascular mortality in both the primary and secondary prevention settings. Guidelines in Europe, Canada and the USA emphasize the need to reduce the burden of atherogenic lipoproteins in serum and to raise levels of high-density lipoproteins in patients at risk for cardiovascular events. Statins have emerged as front-line therapy for managing dyslipidemia, especially in patients with elevated serum levels of low-density lipoprotein cholesterol. As guidelines emphasize the need to reduce serum low-density lipoprotein cholesterol to lower levels, goal attainment can be challenging. The use of combination therapy increases the likelihood of therapeutic success for many patients. Furthermore, a significant percentage of patients with dyslipidemia either cannot achieve goals on statin monotherapy, choose not to take a statin or do not tolerate these drugs due to adverse side effects, such as myalgias, weakness or hepatotoxicity. This article summarizes the pharmacology, clinical efficacy and safety of colesevelam hydrochloride, a bile acid-binding resin. Bile acid-binding resins are orally administered anion-exchange resins that are not absorbed systemically. These agents bind bile acids and reduce their reabsorption at the level of the terminal ileum and prevent their enterohepatic recirculation. Colesevelam has a favorable side effect and toxicity profile and significantly impacts serum levels of lipoproteins when used as monotherapy or when used in combination with either statins or ezetimibe.

Bile acid sequestrants: glucose-lowering mechanisms and efficacy in type 2 diabetes

Bile acids are synthesized in the liver from cholesterol and have traditionally been recognized for their role in absorption of lipids and in cholesterol homeostasis. In recent years, however, bile acids have emerged as metabolic signaling molecules that are involved in the regulation of lipid and glucose metabolism, and possibly energy homeostasis, through activation of the bile acid receptors farnesoid X receptor (FXR) and TGR5. Bile acid sequestrants (BASs) constitute a class of drugs that bind bile acids in the intestine to form a nonabsorbable complex resulting in interruption of the enterohepatic circulation. This increases bile acid synthesis and consequently reduces serum low-density lipoprotein cholesterol. Also, BASs improve glycemic control in patients with type 2 diabetes. Despite a growing understanding of the impact of BASs on glucose metabolism, the mechanisms behind their glucose-lowering effect in patients with type 2 diabetes remain unclear. This article offers a review of the mechanisms behind the glucose-lowering effect of BASs, and the efficacy of BASs in the treatment of type 2 diabetes.

Role of colesevelam in combination lipid-lowering therapy

Hyperlipidemia is associated with an increased risk of cardiovascular events; reducing low-density lipoprotein cholesterol (LDL-C), the primary target for cholesterol-lowering therapy, lowers the risk for such events. Although bile acid sequestrants were the first class of drugs to show a mortality benefit related to LDL-C lowering, statins are now considered first-line pharmacological therapy for reducing LDL-C levels because of their potency and their remarkable record of successful outcomes studies. Nevertheless, a substantial proportion of patients do not achieve LDL-C goals with statin monotherapy. In addition, because of adverse effects (primarily myopathy), some patients may be unwilling to use or unable to tolerate statin therapy at all or may not tolerate a full therapeutic statin dose. Also, statins may increase risk of new-onset diabetes in patients at high risk for diabetes. Thus, there remains a need for other lipid-lowering drugs to be used in combination with or in place of statins. The purpose of this article is to review available data from the literature on the use of colesevelam, a second-generation bile acid sequestrant, in combination with other lipid-lowering agents. Colesevelam has been studied in combination with statins, niacin, fibrates, and ezetimibe (including some three-drug combinations). An additive reduction in LDL-C was seen with all combinations. Other observed effects of colesevelam in combination with other lipid-lowering drugs include reductions in apolipoprotein (apo) B (with statins, fibrates, ezetimibe, statin plus niacin, or statin plus ezetimibe) and high-sensitivity C-reactive protein (with statins), and increases in apo A-I (with statins, ezetimibe, or statins plus niacin). Triglyceride levels remained relatively unchanged when colesevelam was combined with statins, fibrates, ezetimibe, or statin plus ezetimibe, and decreased with the triple combination of colesevelam, statin, and niacin. Colesevelam offset the negative glycemic effects of statins and niacin in subjects with insulin resistance or impaired glucose tolerance. Colesevelam was generally well tolerated when added to other lipid-lowering therapies in clinical trials, with gastrointestinal effects such as constipation being the predominant adverse events. Since colesevelam is not absorbed and works primarily in the intestine, it has a low potential for systemic metabolic drug-drug interactions with other drugs. Colesevelam has been shown to not interact with the lipid-lowering drugs lovastatin and fenofibrate; where interaction may be anticipated, separating dosing times by 4 h reduces the impact of any interaction. Available data confirms that colesevelam has additive cholesterol-lowering effects when used in combination with other lipid-lowering therapies. Furthermore, in some patient populations, the additional glucose-lowering effect of colesevelam may be beneficial in offsetting hyperglycemic effects of other lipid-lowering drugs.

Comparative evaluation of in vitro efficacy of colesevelam hydrochloride tablets

CONTEXT

Colesevelam hydrochloride is used as an adjunct to diet and exercise to reduce elevated low-density lipoprotein (LDL) cholesterol in patients with primary hyperlipidemia as well as to improve glycemic control in patients with type 2 diabetes. This is likely to result in submission of abbreviated new drug applications (ANDA).

OBJECTIVE

This study was conducted to compare the efficacy of two tablet products of colesevelam hydrochloride based on the in vitro binding of bile acid sodium salts of glycocholic acid (GC), glycochenodeoxycholic acid (GCDA) and taurodeoxycholic acid (TDCA).

METHODS

Kinetic binding study was carried out with constant initial bile salt concentrations as a function of time. Equilibrium binding studies were conducted under conditions of constant incubation time and varying initial concentrations of bile acid sodium salts. The unbound concentration of bile salts was determined in the samples of these studies. Langmuir equation was utilized to calculate the binding constants k1 and k2.

RESULTS

The amount of the three bile salts bound to both the products reached equilibrium at 3 h. The similarity factor (f2) was 99.5 based on the binding profile of total bile salts to the test and reference colesevelam tablets as a function of time. The 90% confidence interval for the test to reference ratio of k2 values were 96.06-112.07 which is within the acceptance criteria of 80-120%.

CONCLUSION

It is concluded from the results that the test and reference tablets of colesevelam hydrochloride showed a similar in vitro binding profile and capacity to bile salts.

Ezetimibe and bile acid sequestrants: impact on lipoprotein metabolism and beyond

PURPOSE OF REVIEW

Several lines of evidence indicate that the enterocyte plays a pivotal role in cholesterol homeostasis. The development of the selective inhibitor of cholesterol absorption ezetimibe and bile acid sequestrants (BAS) interrupting the enterohepatic circulation of bile salts has expanded the options for preventing and treating cardiovascular disease. We discuss here a selection of recently published studies that evaluated the effects of ezetimibe and BAS on lipoprotein metabolism.

RECENT FINDINGS

Although significant progress has been made in recent years in elucidating the impacts of ezetimibe and BAS on lipoprotein metabolism, underlying mechanisms are not completely understood. Important new insights have been provided by using in-vivo kinetic studies of apolipoproteins labelled with a stable isotope. Other reports indicated that ezetimibe and BAS modulate the expression of several key genes involved in intestinal lipoprotein metabolism. Many of these effects have been related to the local effects of ezetimibe and BAS on intestinal cholesterol homeostasis.

SUMMARY

A substantial effort is being made by researchers to fully understand the mechanisms by which ezetimibe and BAS improve lipid profile. The efficacy of combination therapy of statins with ezetimibe or BAS for the prevention of cardiovascular disease remains to be confirmed in clinical endpoint studies.

A review of the efficacy and safety of oral antidiabetic drugs

INTRODUCTION

Additional oral antidiabetic agents to metformin, sulfonylureas (SU) and thiazolidinediones (TZD) are approved for the treatment of type 2 diabetes.

AREAS COVERED

The efficacy and safety of metformin, SUs, TZDs, dipeptidyl peptidase-IV (DPP-4) inhibitors, meglitinide analogs, α-glucosidase inhibitors (AGIs), bile-acid sequestrants (BAS) and bromocriptine will be reviewed.

EXPERT OPINION

Several new oral agents have been approved for type 2 diabetes management in recent years. It is important to understand the efficacy and safety of these medications in addition to the older agents to best maximize oral drug therapy for diabetes. Of the recently introduced oral hypoglycemic/antihyperglycemic agents, the DPP-4 inhibitors are moderately efficacious compared with mainstay treatment with metformin with a low side-effect profile and have good efficacy in combination with other oral agents and insulin. They are a recommended alternative when metformin use is limited by gastrointestinal (GI) side effects or when SU treatment results in significant hypoglycemia or weight gain. Meglitinide analogs are limited by their frequent dosing, expense and hypoglycemia (repaglinide > nateglinide), while AGIs are also limited by their dosing schedule and GI side-effect profile. BAS and bromocriptine have the lowest efficacy with regard to HbA(1c) reduction, also are plagued by GI adverse reactions, but have a low risk of hypoglycemia.

Colesevelam hydrochloride: evidence for its use in the treatment of hypercholesterolemia and type 2 diabetes mellitus with insights into mechanism of action

Colesevelam hydrochloride is a molecularly engineered, second-generation bile acid sequestrant demonstrating enhanced specificity for bile acids which has been approved for use as adjunctive therapy to diet and exercise as monotherapy or in combination with a β-hydroxymethylglutaryl-coenzyme A reductase inhibitor for the reduction of elevated low-density lipoprotein cholesterol in patients with primary hypercholesterolemia. It is also the only lipid-lowering agent currently available in the United States which has been approved for use as adjunctive therapy in patients with type 2 diabetes mellitus whose glycemia remains inadequately controlled on therapy with metformin, sulfonylurea, or insulin. With the recent emphasis upon drug safety by the Food and Drug Administration and various consumer agencies, it is fitting that the role of nonsystemic lipid-lowering therapies such as bile acid sequestrants – with nearly 90 years of in-class, clinically safe experience – should be reexamined. This paper presents information on the major pharmacologic effects of colesevelam, including a discussion of recent data derived from both in vitro and in vivo rodent and human studies, which shed light on the putative mechanisms involved.

Bile acid sequestrants: more than simple resins

PURPOSE OF REVIEW

Bile acid sequestrants (BAS) have been used for more than 50 years in the treatment of hypercholesterolemia. The last decade, bile acids are emerging as integrated regulators of metabolism via induction of various signal transduction pathways. Consequently, BAS treatment may exert unexpected side-effects. We discuss a selection of recently published studies that evaluated BAS in several metabolic diseases.

RECENT FINDINGS

Recently, an increasing body of evidence has shown that BAS in addition to ameliorating hypercholesterolemia are also effective in improving glycemic control in patients with type 2 diabetes, although the mechanism is not completely understood. Furthermore, some reports suggested using these compounds to modulate energy expenditure. Many of these effects have been related to the local effects of BAS in the intestine by directly binding bile acids in the intestine or indirectly by interfering with signaling processes.

SUMMARY

A substantial effort is being made by researchers to fully define the mechanism by which BAS improve glycemic control in type 2 diabetic patients. A new challenge will be to confirm in clinical trials the recent discoveries coming from animal experiments suggesting a role for bile acids in energy metabolism.

Colesevelam: an improved bile acid sequestrant for treating hypercholesterolemia and improving diabetes

There is a well-established association between serum cholesterol and coronary heart disease. Statins are the first-line agents for the treatment of hypercholesterolemia, yet combination therapy is required to achieve the desired reduction in low-density lipoprotein cholesterol (LDL-C). Niacin and bile acid sequestrants were among the first lipid-lowering drugs developed to lower LDL-C and have been established to be effective both in monotherapy and in combination therapy. However, tolerability and compliance issues have limited their use. Colesevelam HCl is the newest bile acid sequestrant and reduces LDL-C by 16-22% in monotherapy and adds 12-14% in combination dual therapy with statins, fibrates and ezetimibe or in triple therapy with statin and ezetimibe. It reduces C-reactive protein levels by 16-19% in monotherapy or by 23% in combination with statins and other lipid-lowering therapies. In addition, it consistently reduces hemoglobin A_1c by 0.5% in addition to other hypoglycemic drugs in studies of patients with diabetes. Compared with other bile acid sequestrants it has a higher bile acid-binding capacity, reduced adverse effects and, therefore, has better compliance. Colesevelam HCl is thus a useful addition to the lipid-lowering formulary as a second-line agent, particularly for patients with metabolic syndrome requiring extra reduction in LDL-C.

Combination therapy of dyslipidemia

Clinical trials have demonstrated the benefit of low-density lipoprotein (LDL) cholesterol reduction and, with less robust evidence, reduction of triglyceride levels and increased high-density lipoprotein (HDL) cholesterol in the prevention of atherosclerotic cardiovascular disease. Although the statins are the cornerstone of lipid-lowering therapy, they may not be adequate to accomplish all of the changes in lipid and lipoprotein levels called for in current guidelines. Combinations of one or more lipid-modifying drugs in addition to lifestyle changes are now part of clinical guidelines and are being used extensively in practice. Clinicians need to be familiar with the individual drugs and how they interact. There is also a need for outcome data with combination therapy, especially for statin-fibrate and statin-niacin combinations. Several clinical trials are underway and should provide further evidence for the benefit of combination therapy of dyslipidemia. New drug classes have the potential to provide additive effects with currently available medications to provide substantial LDL reduction and increased HDL level that may lead to a substantial reduction in the burden of atherosclerotic vascular disease.

The Role of Colesevelam Hydrochloride in Hypercholesterolemia and Type 2 Diabetes Mellitus

Objective:

To evaluate the safety and efficacy of colesevelam hydrochloride for the treatment of hypercholesterolemia and type 2 diabetes mellitus.

Data Sources:

Literature retrieval was accessed through MEDLINE/PubMed (1950–March 2010), Web of Science (1980–March 2010), and International Pharmaceutical Abstracts (1977–March 2010) using the terms colesevelam, dyslipidemia, hypercholesterolemia, and type 2 diabetes mellitus. References from publications identified were reviewed for additional resources. In addition, abstracts presented at the most recent (2009) American Diabetes Association, American Association of Clinical Endocrinologists, and European Association for the Study of Diabetes annual meetings were searched for relevant original research.

Study Selection and Data Extraction:

All articles in English identified from the data sources were evaluated. All relevant studies evaluating the safety and efficacy of colesevelam in hypercholesterolemia and/or type 2 diabetes mellitus were included. Priority was placed on data obtained from human randomized controlled trials.

Data Synthesis:

Seventeen clinical trials were reviewed and evaluated. Of the clinical trials evaluating colesevelam in hypercholesterolemia, 3 evaluated monotherapy, 4 evaluated combination therapy with hydroxymethylglutaryl coenzyme A (HMG-CoA) reductase inhibitors, and 6 evaluated combination therapy with other lipid-lowering therapies. In the type 2 diabetes mellitus trials, colesevelam was evaluated in combination with metformin, sulfonylureas, insulin, and rosiglitazone and sitagliptin. A review of the clinical trials provided evidence that colesevelam monotherapy effectively reduces low-density lipoprotein cholesterol (LDL-C). Additionally, the use of colesevelam in combination with other lipid-lowering therapies further reduces LDL-C. Colesevelam also effectively reduces hemoglobin A1c in patients with type 2 diabetes mellitus. The safety and tolerability of colesevelam appear to be improved from that of older-generation bile acid sequestrants, with adverse effects similar to those with placebo in monotherapy and type 2 diabetes mellitus trials.

Conclusions:

Colesevelam is a safe and effective option for the treatment of hypercholesterolemia and type 2 diabetes mellitus. It can fulfill a useful role in combination with HMG-CoA reductase inhibitors for hypercholesterolemia and should be considered in patients with type 2 diabetes mellitus with concomitant hypercholesterolemia.

Colesevelam lowers glucose and lipid levels in type 2 diabetes: the clinical evidence

Simultaneous control of blood glucose and other risk factors such as hypertension and dyslipidaemia is essential for reducing the risk of complications associated with type 2 diabetes mellitus (T2DM). As relatively few patients with T2DM have their risk factors managed to within the limits recommended by the American Diabetes Association, American College of Endocrinology or National Cholesterol Education Program Adult Treatment Panel III guidelines, treatment that can simultaneously control more than one risk factor is of therapeutic benefit. Clinical studies have shown that bile acid sequestrants have glucose-lowering effects in addition to their low-density lipoprotein cholesterol-lowering effects in patients with T2DM. The bile acid sequestrant colesevelam hydrochloride is approved as an adjunct to antidiabetes therapy for improving glycaemic control in adults with T2DM. This review examines data from three phase III clinical trials that evaluated the glucose- and lipid-lowering effects of colesevelam when added to the existing antidiabetes treatment regimen of patients with T2DM.

Effect of the bile acid sequestrant colesevelam on the pharmacokinetics of pioglitazone, repaglinide, estrogen estradiol, norethindrone, levothyroxine, and glyburide

The purpose of this study was to assess effects of colesevelam on the pharmacokinetics of glyburide, levothyroxine, estrogen estradiol (EE), norethindrone (NET), pioglitazone, and repaglinide in healthy volunteers. Six drugs with a potential to interact with colesevelam were studied in open-label, randomized clinical studies. The presence of a drug interaction was concluded if the 90% confidence intervals for the geometric least squares mean ratios of AUC(0-t) (AUC(0-48) for levothyroxine) and C(max) fell outside the no-effect limits of (80.0%, 125.0%). Concomitant administration of colesevelam had no effect on the AUC(0-t) or C(max) of pioglitazone but significantly decreased the AUC(0-t) and C(max) of glyburide, levothyroxine, and EE and the C(max) of repaglinide and NET. AUC(0-t) and C(max) of glyburide and EE, but not repaglinide or NET, were significantly decreased when the drug was given 1 hour before colesevelam. When glyburide, EE, or levothyroxine was given 4 hours before colesevelam, no drug interaction was observed. Although colesevelam has a cleaner drug interaction profile than other bile acid sequestrants, it does interfere with absorption of some drugs. A 4-hour window appears sufficient to eliminate these interactions.

Colesevelam hydrochloride for the treatment of type 2 diabetes mellitus

BACKGROUND

Colesevelam hydrochloride is a bile acid sequestrant approved in January 2008 by the US Food and Drug Administration (FDA) for the treatment of adult patients with type 2 diabetes mellitus (DM) in combination with a sulfonylurea, metformin, and/or insulin therapy.

OBJECTIVE

The purpose of this article was to review the pharmacology, pharmacokinetics, efficacy, adverse effects and tolerability, drug-drug interactions, contraindications/precautions, dosage and administration, pharmacoeconomics, and the overall role of colesevelam in the management of adult patients with type 2 DM.

METHODS

A literature search using MEDLINE (1966-October 27, 2008), PubMed (1950-October 27, 2008), Science Direct (1994-October 27, 2008), Web of Science (1980-October 27, 2008), American Diabetes Association Scientific Abstracts (2004-2008), and International Pharmaceutical Abstracts (1970-October 27, 2008) was performed using the term colesevelam. English-language, original research and review articles were examined, and citations from these articles were assessed. Manufacturer prescribing information and the FDA review of the new drug application for colesevelam were also examined.

RESULTS

Colesevelam is a hydrophilic, water-insoluble polymer, with negligible absorption and systemic distribution, that is excreted primarily in the feces. Through a mechanism still under investigation, colesevelam effectively lowers glycosylated hemoglobin (HbA(1c)) when used in combination with a sulfonylurea, metformin, and/or insulin therapy. Three completed, published Phase III clinical trials investigating colesevelam for the treatment of type 2 DM were evaluated for information, data, and conclusions. At dosing of 1.875 g BID or 3.75 g once daily in combination with one of the aforementioned agents versus placebo, reductions in HbA(1c) in all 3 Phase III clinical trials of colesevelam ranged from 0.5% to 0.7% (P < 0.02). In clinical trials, colesevelam was well tolerated, with hypoglycemia occurring in approximately 3% of studied patients.

CONCLUSIONS

When used in combination with a sulfonylurea, metformin, and/or insulin therapy, colesevelam has been reported to significantly reduce HbA(1c) in adult patients with type 2 DM. Colesevelam's role in the management of type 2 DM remains undefined, however; further investigation into its mechanism of action and long-term efficacy and safety should be performed.

Improving glycemic and cholesterol control through an integrated approach incorporating colesevelam - a clinical perspective

Bile sequestrants have been used for almost 50 years to lower low density lipoprotein cholesterol (LDL-C). The advent of colesevelam in 2000 provided a more tolerable add-on LDL-C-lowering agent with an excellent safety record and with likely benefit for coronary heart disease events. Colesevelam lowers LDL-C approximately 15%, and has an additive effect when combined with statin or non-statin lipid-modifying agents. It also tends to increase triglyceride levels. The discovery that bile sequestrants also lower glucose levels led to definitive large-scale clinical trials testing the effect of colesevelam as a dual antihyperglycemic agent with LDL-C-lowering properties in type 2 diabetic subjects on metformin-, sulfonylurea- or insulin-based therapy with inadequate glycemic control. Colesevelam was found to lower hemoglobin A1c (HbA1c) by approximately 0.5% compared to placebo over the 16- to 26-week period, and had similar effects on the lipid profile in these diabetic subjects, as had previously been demonstrated in non-diabetic individuals. Colesevelam was well tolerated, with constipation being the most common adverse effect, and did not cause weight gain or excessive hypoglycemia. Colesevelam thus combines antihyperglycemic action with LDL-C-lowering properties, and should be useful in the management of type 2 diabetes.

Lowering low-density lipoprotein cholesterol: statins, ezetimibe, bile acid sequestrants, and combinations: comparative efficacy and safety

Statins, ezetimibe, and bile acid-binding resins can be used individually or in combination for lowering low-density lipoprotein cholesterol (LDL-C) levels. Statins are the most potent drugs for lowering LDL-C and are well tolerated in most patients. The addition of a bile acid sequestrant or ezetimibe to a statin produces additional LDL-C reduction allowing many patients to reach LDL-C targets. This article discusses the efficacy and safety of available statins, bile acid sequestrants, and ezetimibe in the treatment of hyperlipidemia.

Low-dose combination therapy with colesevelam hydrochloride and lovastatin effectively decreases low-density lipoprotein cholesterol in patients with primary hypercholesterolemia

BACKGROUND

Colesevelam hydrochloride is a novel, lipid-lowering agent that binds bile acids with high affinity. A multicenter, randomized, double-blind, placebo-controlled, parallel-design study was conducted to assess the efficacy and tolerability of combination low-dose colesevelam and lovastatin treatment in patients with primary hypercholesterolemia.

HYPOTHESIS

Combination therapy with low doses of colesevelam and lovastatin decreases low density (LDL) cholesterol with minimal adverse events.

METHODS

Following a 4- to 6-week dietary lead in, 135 patients were randomized into five groups for a 4-week treatment period: placebo, colesevelam 2.3 g at dinner, lovastatin 10 mg at dinner, the combination of colesevelam and lovastatin given at dinner (dosed together), and combination treatment with colesevelam given at dinner and lovastatin administered at bedtime (dosed apart).

RESULTS

Combination colesevelam and lovastatin treatment decreased LDL cholesterol by 34% (60 mg/dl, p < 0.0001) and 32% (53 mg/dl, p < 0.0001) when colesevelam and lovastatin were dosed together or dosed apart, respectively. Both combination therapies were superior to either agent alone (p < 0.05). Decreases in LDL cholesterol exceeded the combined decreases observed for colesevelam alone (13 mg/dl, 7%) and lovastatin alone (39 mg/dl, 22%). Both combination treatments reduced total cholesterol by 21% (p < 0.0001) and apolipoprotein B by 24% (p < 0.0001). Neither combination treatment significantly altered high-density lipoprotein cholesterol or triglycerides. Adverse side effects were not significantly different among randomized groups.

CONCLUSIONS

Combination colesevelam and lovastatin was efficacious and well tolerated, resulting in additive decreases in LDL cholesterol levels whether or not both agents were administered simultaneously.

Novel pathways for glycaemic control in type 2 diabetes: focus on bile acid modulation

Type 2 diabetes is a common disorder with high risk of macrovascular and microvascular complications. These complications are largely driven by hyperglycaemia, dyslipidaemia and hypertension, for which aggressive treatment is thus warranted. Achieving and maintaining control of all three risk factors is especially difficult, however, and new therapeutic approaches could be useful. Bile acids have a well-established and important role in cholesterol homeostasis. Normally, their levels are maintained primarily by ileal reabsorption and enterohepatic recycling. Bile acid sequestrants bind bile acids in the intestine, reduce this recycling and deplete the bile acid pool, thereby stimulating use of hepatic cholesterol for bile acid synthesis, which leads to accelerated removal of LDL from the plasma and a decrease in LDL-cholesterol levels. Interestingly, recent evidence suggests that bile acid sequestrants can lower glucose levels to a clinically meaningful degree. This review presents this evidence and the possible mechanisms by which these glucose-lowering effects occur and discusses the apparently unique ability of bile acid sequestrants among lipid-lowering agents to significantly improve two cardiovascular risk factors, hyperglycaemia and dyslipidaemia. There is renewed interest in the use of bile acid sequestrants in individuals with type 2 diabetes, most of whom would benefit from additional reductions in both LDL-cholesterol and glycaemia.

Colesevelam hydrochloride in clinical practice: a new approach in the treatment of hypercholesterolaemia

OBJECTIVE

Hypercholesterolaemia is a major risk factor for atherosclerosis and coronary heart disease. Treatment with lipid lowering agents reduces the risk of vascular events. Colesevelam is a novel bile acid sequestrant (BAS) indicated for the treatment of hypercholesterolaemia, either as monotherapy or in combination with statins.

SCOPE

This article reviews the efficacy, tolerability and safety of colesevelam in clinical practice. The literature search was based on a PubMed search up to January 2008.

FINDINGS

Colesevelam, used alone or in combination with other hypolipidaemic agents (statins, ezetimibe and fenofibrate), has an overall favourable effect on lipid profile. Specifically, colesevelam reduces total and low-density lipoprotein cholesterol (LDL-C) and apolipoprotein B levels and increases high-density lipoprotein cholesterol and apolipoprotein AI. However, colesevelam may slightly raise triglyceride levels. Colesevelam can improve glycaemic control in diabetic patients. Moreover, it may have anti-inflammatory properties, as it can reduce high sensitivity C-reactive protein concentration. Colesevelam almost lacks the intense side effects of previously used BASs, thus resulting in better patient compliance. However, the dose regimen consisting of up to 7 tablets/day and high cost may limit its use.

CONCLUSIONS

Colesevelam is a safe alternative for those intolerant to other lipid lowering medication. This BAS also provides an option for patients who do not reach their LDL-C goal despite treatment with a statin.

The biology and chemistry of hyperlipidemia

Coronary arterial diseases are responsible for more deaths than all other associated causes combined. Elevated serum cholesterol levels leading to atherosclerosis can cause coronary heart disease (CHD). Reduction in serum cholesterol levels reduces the risk for CHD, substantially. Medicinal chemists all around the world have been designing, synthesizing, and evaluating a variety of new bioactive molecules for lowering lipid levels. This review summarizes the disorders associated with elevation of lipids in blood and the current strategies to control them. The emphasis has been laid in particular on the new potential biological targets and the possible treatments as well as the current ongoing research status in the field of lipid lowering agents.

Safety considerations with gastrointestinally active lipid-lowering drugs

Gastrointestinally active agents such as cholesterol absorption inhibitors (CAIs) (eg, ezetimibe) and bile acid sequestrants (BAS) (the resins cholestyramine and colestipol, or colesevelam, a nonabsorbable polymer) offer important options for lipid-lowering therapy. Ezetimibe is a novel CAI that inhibits the absorption of dietary and biliary cholesterol without affecting the absorption of triglycerides or fat-soluble vitamins. In clinical trials, there has been no evidence of increased rates of myopathy or rhabdomyolysis associated with ezetimibe, whether in use as monotherapy or in a combination with statin therapy, although there exist case reports of possible ezetimibe-associated myopathy. Ezetimibe alone does not appear to increase liver transaminase levels significantly, but the coadministration of a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin) with ezetimibe marginally increases this risk. However, reported increases in liver enzymes have not been associated with clinically meaningful symptoms and often return to baseline levels after the discontinuation of therapy or with continued treatment. To date, no cases of liver failure, liver transplantation, or death have been reported. BAS have been used clinically since the 1960s for lowering low-density lipoprotein cholesterol. Because they are not absorbed from the gastrointestinal tract into the blood, these agents do not contact most body organs and are therefore systemically safe. However, case reports and pharmacokinetic data disclose 3 kinds of adverse effects: (1) the decreased absorption of concomitant medications and sometimes of certain vitamins; (2) the physicochemical alteration of intestinal contents leading to constipation and, very rarely, intestinal obstruction; and (3) modest increases in plasma triglyceride levels due to the alteration of hepatic lipid metabolism. The newest BAS, colesevelam, has greater specificity for bile acids compared with the older agents cholestyramine and colestipol, eliminating most drug interactions and reducing the tendency for constipation. Overall, CAIs and BAS have excellent systemic safety profiles when used alone or in combination with other lipid-lowering drugs.

Bile acid salt binding with colesevelam HCl is not affected by suspension in common beverages

It has been previously reported that anions in common beverages may bind to bile acid sequestrants (BAS), reducing their capacity for binding bile acid salts. This study examined the ability of the novel BAS colesevelam hydrochloride (HCl), in vitro, to bind bile acid sodium salts following suspension in common beverages. Equilibrium binding was evaluated under conditions of constant time and varying concentrations of bile acid salts in simulated intestinal fluid (SIF). A stock solution of sodium salts of glycochenodeoxycholic acid (GCDC), taurodeoxycholic acid (TDC), and glycocholic acid (GC), was added to each prepared sample of colesevelam HCl. Bile acid salt binding was calculated by high-performance liquid chromatography (HPLC) analysis. Kinetics experiments were conducted using constant initial bile acid salt concentrations and varying binding times. The affinity, capacity, and kinetics of colesevelam HCl binding for GCDC, TDC, and GC were not significantly altered after suspension in water, carbonated water, Coca-Cola, Sprite, grape juice, orange juice, tomato juice, or Gatorade. The amount of bile acid sodium salt bound as a function of time was unchanged by pretreatment with any beverage tested. The in vitro binding characteristics of colesevelam HCl are unchanged by suspension in common beverages.

Lipoprotein effects of combined ezetimibe and colesevelam hydrochloride versus ezetimibe alone in hypercholesterolemic subjects: a pilot study

Two drug classes act in the intestine to lower cholesterol. Ezetimibe inhibits cholesterol absorption, whereas bile acid-binding resins enhance cholesterol excretion via enhanced conversion to bile acids. Combining these 2 classes may be beneficial, but cholestyramine binds ezetimibe, and the combined effect of colesevelam hydrochloride and ezetimibe was little studied. The aim of the study was to determine if adding colesevelam HCl to ezetimibe provides additional lowering of low-density lipoprotein- and apolipoprotein B-containing lipoproteins or alters ezetimibe levels. Twenty subjects with low-density lipoprotein cholesterol (LDL-C) levels of 130 mg/dL or higher were enrolled and taught a National Cholesterol Education Program Step I diet. At a second baseline visit, lipoproteins were measured and subjects were randomly allocated to (1) ezetimibe 10 mg daily with placebo colesevelam HCl twice daily (E) or (2) ezetimibe 10 mg daily with 1.875 g colesevelam HCl twice daily (E + C). Lipoproteins were measured 6 and 12 weeks after initiating treatment. Baseline characteristics (mean +/- SD) were statistically indistinguishable in E vs E + C: LDL-C (mg/dL), 167 +/- 26 and 158 +/- 27; triglyceride, 134 +/- 75 and 140 +/- 67; and BMI, 29.4 +/- 4.9 and 27.8 +/- 6.6 kg/m(2), respectively. Percent changes after 12 weeks in E vs E + C were as follows: LDL-C, -24 +/- 12 vs -30 +/- 11 (P = .102); triglyceride, -19 +/- 34 vs 36 +/- 85 (P = .054; at 6 weeks, P = .009); total cholesterol, -19 +/- 9 vs -15 +/- 8 (P = .50); non-high-density lipoprotein cholesterol, -25 +/- 10 vs -21 +/- 11 (P = .70); apolipoprotein B, -31 +/- 14 vs -22 +/- 14 (P = .41). Plasma ezetimibe levels at 12 weeks were 21% lower in E + C vs E, a nonsignificant difference (P = .54). In conclusion, in the short term, colesevelam HCl may not consistently add cholesterol-lowering benefit to ezetimibe. This observation requires confirmation.

Cholesterol absorption inhibitors as a therapeutic option for hypercholesterolaemia

The development of cholesterol-lowering drugs (including a variety of statins, bile acid-binding resins and recently discovered inhibitors of cholesterol absorption) has expanded the options for cardiovascular prevention. Recent treatment guidelines emphasise that individuals at substantial risk for atherosclerotic coronary heart disease should meet defined targets for LDL cholesterol concentrations. Combination therapy with drugs that have different or complementary mechanisms of action is often needed to achieve lipid goals. Existing approaches to the treatment of hypercholesterolaemia are still ineffective in halting the progression of coronary artery disease in some patients despite combination therapies. Other patients are resistant to conventional drug treatment and remain at high risk for the development and progression of atherosclerotic cardiovascular disease and alternative approaches are needed. The discovery and development of ezetimibe (a novel, selective and potent cholesterol absorption inhibitor) has advanced the treatment of hypercholesterolaemia. New agents including the phytostanol preparation FM-VP4 and inhibitors of acyl coenzyme A:cholesterol acyltransferase, the apical Na(+)-dependent bile acid transporter and microsomal triglyceride transfer protein may also play a future role in combination therapy. This review focuses on the recent progress in the molecular mechanisms of intestinal cholesterol absorption and transport, and novel therapeutic approaches to inhibit the cholesterol absorption process.

Colesevelam: Potential Uses for the Newest Bile Resin

Colesevelam is the newest bile resin with a unique chemical structure. It binds to bile acids with higher affinity than traditional bile acid sequestrants and has fewer gastrointestinal side effects and drug interactions. Colesevelam is safe and efficacious alone or in combination with HMG-CoA reductase inhibitors (statins) in reducing low-density lipoprotein cholesterol (LDL-C) levels. Despite this, the role of colesevelam in the treatment of hyperlipidemia remains limited, particularly in the face of new lipid lowering agents. As guidelines for cholesterol control become more stringent, the need to maximize therapeutic benefit through combination therapy will become increasingly more important. Colesevelam has a dose-sparing effect on statin therapy, potentially decreasing the risk of unwanted side effects or drug-drug interactions associated with statin use. This makes colesevelam a viable option for addition to a statin regimen when goal LDL-C levels cannot be achieved with a statin alone. Additionally, anecdotal reports indicate that colesevelam may have potential benefits in certain patient populations that cannot tolerate other lipid lowering therapies, including organ transplant recipients, cholestatic liver disesase, and end-stage renal disease. By recognizing the potential utility of colesevelam, clinicians can better manage those patients who are not able to tolerate first-line therapies.

Clinical utility of bile acid sequestrants in the treatment of dyslipidemia: a scientific review

Bile acid sequestrants (BAS) continue to command a position in the treatment of dyslipidemias 25 years after their introduction. Partial diversion of the enterohepatic circulation using BAS depletes the endogenous bile acid pool by approximately 40%, thus stimulating an increase in bile acid synthesis from cholesterol, which lowers low-density lipoprotein cholesterol (LDL-C) by 15 to 26%. Three BAS are currently used for treating hypercholesterolemia in the United States: the conventional sequestrants, cholestyramine and colestipol, and the specifically engineered BAS, colesevelam hydrochloride (HCl). Compared with conventional BAS, colesevelam HCl has enhanced specificity, greater affinity, and higher capacity for binding bile acids, due to its polymer structure engineered for bile acid sequestration. BAS are not absorbed by the intestine and thus have no systemic drug-drug interactions, but may interfere with the absorption of some drugs. Although BAS monotherapy effectively lowers LDL-C, combination therapy, especially with BAS and statins, is becoming increasingly common due to complementary mechanisms of action. Low-dose statin plus BAS combinations lead to greater or similar LDL-C reductions compared with high-dose statin monotherapy and may have a better safety profile. Combinations of BAS with nonstatin lipid-lowering agents, including niacin, fibrates, and cholesterol absorption inhibitors, may be useful in those patients who require intensive lipid-lowering, but are statin intolerant. BAS treatment can significantly reduce coronary artery disease (CAD) progression and the risk of CAD-associated outcomes. It is also becoming clear that BAS and other therapies that manipulate the bile acid synthetic pathway may have clinically useful therapeutic effects on other metabolic disorders including type 2 diabetes.

Safety and efficacy of colesevelam hydrochloride in combination with fenofibrate for the treatment of mixed hyperlipidemia

OBJECTIVE

The aim of this study was to evaluate the amount of low-density lipoprotein cholesterol (LDL-C) reduction achieved by adding the specifically engineered bile acid sequestrant (SE-BAS) colesevelam HCl to a stable dose of fenofibrate in patients with mixed hyperlipidemia.

RESEARCH DESIGN AND METHODS

Patients with mixed hyperlipidemia (n = 129) were enrolled in a randomized, double-blind, placebo-controlled, parallel-group study investigating the efficacy of fenofibrate plus colesevelam HCl versus fenofibrate monotherapy. After a 4- to 8-week washout period, subjects received fenofibrate 160 mg/day for 8 weeks and were then randomized to receive colesevelam HCl 3.75 g/day or placebo, in addition to fenofibrate 160 mg/day, for 6 weeks.

MAIN OUTCOMES MEASURES

The primary efficacy endpoint was mean percent change in LDL-C during randomized treatment. Secondary endpoints included absolute and percent changes in mean levels of LDL-C, triglycerides (TGs), high-density lipoprotein cholesterol (HDL-C), non-HDL-C, total cholesterol (TC), and apolipoproteins (apo) A-I and B during randomized treatment and from washout to end of randomized treatment.

RESULTS

Of the 129 patients randomized to treatment, 119 completed the study. After 6 weeks of treatment, fenofibrate plus colesevelam HCl produced a mean percent change in LDL-C of -10.4% versus +2.3% with fenofibrate monotherapy (p < 0.0001). Fenofibrate plus colesevelam HCl was significantly more effective than fenofibrate alone at reducing levels of non-HDL-C, TC, and apo B (p < or = 0.0002). Colesevelam HCl did not significantly affect the TG-lowering effects of fenofibrate. Both treatment regimens were safe and well tolerated.

CONCLUSIONS

Compared with fenofibrate monotherapy in patients with mixed hyperlipidemia, fenofibrate/colesevelam HCl combination therapy significantly reduced mean LDL-C, non-HDL-C, TC, and apo B levels without significantly affecting the TG-lowering or HDL-C-raising effects of fenofibrate. Fenofibrate/colesevelam HCl combination therapy is a safe, useful alternative for the treatment of mixed hyperlipidemia.

Management of dyslipidemia in women in the post-hormone therapy era

OBJECTIVE

Cardiovascular disease (CVD) is the leading cause of death for women in the United States and is largely preventable. The American Heart Association has recently released evidence-based guidelines for the prevention of CVD in women; these include gender-specific recommendations for the management of dyslipidemia. This article reviews these recommendations and the evidence supporting them.

DESIGN

This was a qualitative review of a systematic literature search related to lipid guidelines for women and discussion of rationale and evidence for new clinical recommendations.

MAIN RESULTS

Lifestyle modifications are the cornerstone of lipid management. Substantial evidence from randomized clinical trials supports the use of low-density lipoprotein cholesterol-lowering therapy (primarily statins) in all high-risk women and the use of niacin or fibrates when high-density lipoprotein cholesterol is low or non-high-density lipoprotein cholesterol is elevated. Fewer data are available for women at lower or intermediate risk.

CONCLUSIONS

Encouragement of lifestyle modification and appropriate use of lipid-altering therapy will have a substantial impact on reducing the burden of cardiovascular disease in women.

The clinical and nutritional implications of lipid-lowering drugs that act in the gastrointestinal tract

PURPOSE OF REVIEW

A new class of cholesterol-lowering therapy that reduces intestinal sterol absorption has recently been introduced. This increases the number of classes of lipid-lowering agents that directly affect gastrointestinal function and raises questions concerning the overall effect of these agents on absorption and nutritional status.

RECENT FINDINGS

A recent assessment notes a paucity of information concerning the factors that affect the bioavailability and intestinal absorption of lipophilic nutrients. By contrast, the specificity of the mechanisms of action of new drugs acting on the gastrointestinal tract may circumvent some of the detrimental effects on nutrient and drug bioavailability that have been noted with older forms of treatment.

SUMMARY

The clinical imperative for aggressive control of lipid and metabolic risk factors makes widespread use, alone or in combination, of lipid-lowering agents that affect the gastrointestinal tract seem increasingly likely. Whilst the opportunity for therapeutic synergy is attractive, care will be required to avoid interference with intestinal absorptive function.