Ezetimibe

Impact of efavirenz on intestinal metabolism and transport: insights from an interaction study with ezetimibe in healthy volunteers

Hypercholesterolemia frequently occurs in patients treated with efavirenz who cannot be treated adequately with statins because of drug interactions. These patients may benefit from cholesterol-lowering therapy with ezetimibe. This study determined the influence of single-dose and multiple-dose efavirenz (400 mg/day for 9 days) on the pharmacokinetics and sterol-lowering of ezetimibe (10 mg) in 12 healthy subjects. In addition, the influence of efavirenz on genome-wide intestinal expression and in vitro function of ABCB1, ABCC2, UGT1A1, and OATP1B1 was studied. Efavirenz (multiple dose) had no influence on the pharmacokinetics and lipid-lowering functions of ezetimibe. Intestinal expression of enzymes and transporters (e.g., ABCB1, ABCC2, and UGT1A1) was not affected by chronic efavirenz. Efavirenz (single dose) slightly increased ezetimibe absorption and markedly decreased exposure to ezetimibe-glucuronide (single dose and multiple dose), which may be explained by inhibition of UGT1A1 and ABCB1 (in vitro data). Ezetimibe had no effect on the disposition of efavirenz. Consequently, ezetimibe may be a safe and efficient therapeutic option in patients with HIV infection.

Dietary intake of plant sterols stably increases plant sterol levels in the murine brain

Plant sterols such as sitosterol and campesterol are frequently administered as cholesterol-lowering supplements in food. Recently, it has been shown in mice that, in contrast to the structurally related cholesterol, circulating plant sterols can enter the brain. We questioned whether the accumulation of plant sterols in murine brain is reversible. After being fed a plant sterol ester-enriched diet for 6 weeks, C57BL/6NCrl mice displayed significantly increased concentrations of plant sterols in serum, liver, and brain by 2- to 3-fold. Blocking intestinal sterol uptake for the next 6 months while feeding the mice with a plant stanol ester-enriched diet resulted in strongly decreased plant sterol levels in serum and liver, without affecting brain plant sterol levels. Relative to plasma concentrations, brain levels of campesterol were higher than sitosterol, suggesting that campesterol traverses the blood-brain barrier more efficiently. In vitro experiments with brain endothelial cell cultures showed that campesterol crossed the blood-brain barrier more efficiently than sitosterol. We conclude that, over a 6-month period, plant sterol accumulation in murine brain is virtually irreversible.

Intestinal sterol transporters and cholesterol absorption inhibition

PURPOSE OF REVIEW

Statin therapy is the mainstay of lipid-lowering therapy; however, many patients, particularly those at high risk, do not achieve sufficient LDL-cholesterol (LDL-C) lowering. Thus, there remains an unmet medical need for more effective and well tolerated lipid-lowering agents. Guidelines recommend combining additional lipid-lowering agents with a complementary mode of action for these patients. One approach to complementing statin therapy is combination with inhibitors that block the intestinal absorption of dietary and biliary cholesterol. This review summarizes what is currently known about intestinal sterol transporters and cholesterol absorption inhibitors (CAIs).

RECENT FINDINGS

The only lipid-lowering agent currently available that specifically targets an intestinal sterol transporter (Niemann-Pick C1-like 1) is the CAI, ezetimibe. It is effective in lowering LDL-C, both when given alone and when combined with a statin. Clinical outcome data with ezetimibe combined with simvastatin have recently become available, and definitive evidence that the incremental LDL-C lowering attributable to the ezetimibe component reduces cardiovascular events beyond simvastatin alone is currently under study. Other novel CAIs have been evaluated based upon the structure and properties of ezetimibe, but none remain in development.

SUMMARY

Additional lipid-lowering agents are needed to fulfill an unmet medical need for those patients who do not achieve optimal LDL-C goals on statin monotherapy. The inhibition of cholesterol absorption is an important therapeutic strategy to reduce cholesterol levels. Based upon the demonstrated lipid-altering efficacy and safety of ezetimibe, several CAIs have been identified; all to date have been discontinued due to limited efficacy.

Ezetimibe: its novel effects on the prevention and the treatment of cholesterol gallstones and nonalcoholic Fatty liver disease

The cholesterol absorption inhibitor ezetimibe can significantly reduce plasma cholesterol concentrations by inhibiting the Niemann-Pick C1-like 1 protein (NPC1L1), an intestinal sterol influx transporter that can actively facilitate the uptake of cholesterol for intestinal absorption. Unexpectedly, ezetimibe treatment also induces a complete resistance to cholesterol gallstone formation and nonalcoholic fatty liver disease (NAFLD) in addition to preventing hypercholesterolemia in mice on a Western diet. Because chylomicrons are the vehicles with which the enterocytes transport cholesterol and fatty acids into the body, ezetimibe could prevent these two most prevalent hepatobiliary diseases possibly through the regulation of chylomicron-derived cholesterol and fatty acid metabolism in the liver. It is highly likely that there is an intestinal and hepatic cross-talk through the chylomicron pathway. Therefore, understanding the molecular mechanisms whereby cholesterol and fatty acids are absorbed from the intestine could offer an efficacious novel approach to the prevention and the treatment of cholesterol gallstones and NAFLD.

Quantitative prediction of intestinal glucuronidation of drugs in rats using in vitro metabolic clearance data

UDP-glucuronosyltransferase (UGT) is highly expressed in the small intestine and catalyzes the glucuronidation of small molecules, which may affect the oral bioavailability of drugs. However, no method of predicting the in vivo observed fraction of absorbed drug (F(a)F(g)) affected by UGT has yet been established. Here, we investigated the relationship between F(a)F(g) and in vitro clearance of nine UGT substrates (ketoprofen, tolcapone, telmisartan, raloxifene, entacapone, resveratrol, buprenorphine, quercetin, and ezetimibe) via UGT in intestinal microsomes (CL(int, UGT)) in rats. F(a)F(g) was calculated from pharmacokinetic parameters after intravenous and oral administration or using the portal-systemic concentration difference method, with values ranging from 0.027 (ezetimibe) to 1 (tolcapone). Glucuronides of model compounds were observed in the portal plasma after oral administration, with CL(int, UGT) values ranging from 57.8 (tolcapone) to 19,200 µL/min/mg (resveratrol). An inverse correlation between F(a)F(g) and CL(int, UGT) was observed for most compounds and was described using a simplified intestinal availability model reported previously. This model gave accurate predictions of F(a)F(g) values for three in-house compounds. Our results show that F(a)F(g) in rats is affected by UGT and can be predicted using CL(int, UGT). This work should hasten the development of a method to predict F(a)F(g) in humans.

Treatment of atherogenic liver based on the pathogenesis of nonalcoholic fatty liver disease: a novel approach to reduce cardiovascular risk?

Nonalcoholic fatty liver disease (NAFLD), which spans a spectrum of conditions ranging from simple steatosis to progressive nonalcoholic steatohepatitis (NASH), is the most common chronic liver disease and a relevant public health issue. The prevalence of NAFLD depends on adiposity, age, gender and ethnicity. The natural history of liver disease in those with NAFLD critically depends on liver histological changes. However, cardiovascular mortality is increased in NAFLD, particularly in middle-aged adults. Against such a background, this review consists of three sections. First, data on NAFLD as a novel mechanism of increased cardiovascular risk via hyperinsulinism, pro-thrombotic potential, and subclinical inflammation are summarized. Next, the role of atherogenic liver in the development of manifestations of oxidative stress and atherosclerosis is emphasized. Finally, whether and how treating NAFLD will mechanistically result in reduced cardiovascular risk through ameliorated metabolic syndrome is discussed.

Combinations of ezetimibe with nonstatin drug regimens affecting lipid metabolism

In this article we discuss the available data on the effects of combined therapy of ezetimibe with agents affecting lipid metabolism other than statins. We consider studies evaluating the effects of combined therapy of ezetimibe with bile acid sequestrants, fenofibrate, niacin, n-3 fatty acids, plant sterols, orlistat, metformin, acarbose and glitazones. Combination of ezetimibe with bile acid sequestrants (especially colesevelam) was shown to have additional effects on lipid parameters in patients with hyperlipidemia. Combination of ezetimibe with fenofibrate may be a good approach to improve the overall lipid profile of patients with mixed hyperlipidemia. The addition of ezetimibe to niacin-based therapy can be useful for high-risk patients with dyslipidemia who are not achieving their assigned treatment goals. For patients who cannot tolerate statins there are useful combinations of ezetimibe with other drugs affecting lipid metabolism. These combinations improve many metabolic parameters, but more trials should be carried out to reach more robust conclusions about their effects on cardiovascular disease prevention.

The effects of lowering LDL cholesterol with simvastatin plus ezetimibe in patients with chronic kidney disease (Study of Heart and Renal Protection): a randomised placebo-controlled trial

BACKGROUND

Lowering LDL cholesterol with statin regimens reduces the risk of myocardial infarction, ischaemic stroke, and the need for coronary revascularisation in people without kidney disease, but its effects in people with moderate-to-severe kidney disease are uncertain. The SHARP trial aimed to assess the efficacy and safety of the combination of simvastatin plus ezetimibe in such patients.

METHODS

This randomised double-blind trial included 9270 patients with chronic kidney disease (3023 on dialysis and 6247 not) with no known history of myocardial infarction or coronary revascularisation. Patients were randomly assigned to simvastatin 20 mg plus ezetimibe 10 mg daily versus matching placebo. The key prespecified outcome was first major atherosclerotic event (non-fatal myocardial infarction or coronary death, non-haemorrhagic stroke, or any arterial revascularisation procedure). All analyses were by intention to treat. This trial is registered at ClinicalTrials.gov, NCT00125593, and ISRCTN54137607.

FINDINGS

4650 patients were assigned to receive simvastatin plus ezetimibe and 4620 to placebo. Allocation to simvastatin plus ezetimibe yielded an average LDL cholesterol difference of 0·85 mmol/L (SE 0·02; with about two-thirds compliance) during a median follow-up of 4·9 years and produced a 17% proportional reduction in major atherosclerotic events (526 [11·3%] simvastatin plus ezetimibe vs 619 [13·4%] placebo; rate ratio [RR] 0·83, 95% CI 0·74-0·94; log-rank p=0·0021). Non-significantly fewer patients allocated to simvastatin plus ezetimibe had a non-fatal myocardial infarction or died from coronary heart disease (213 [4·6%] vs 230 [5·0%]; RR 0·92, 95% CI 0·76-1·11; p=0·37) and there were significant reductions in non-haemorrhagic stroke (131 [2·8%] vs 174 [3·8%]; RR 0·75, 95% CI 0·60-0·94; p=0·01) and arterial revascularisation procedures (284 [6·1%] vs 352 [7·6%]; RR 0·79, 95% CI 0·68-0·93; p=0·0036). After weighting for subgroup-specific reductions in LDL cholesterol, there was no good evidence that the proportional effects on major atherosclerotic events differed from the summary rate ratio in any subgroup examined, and, in particular, they were similar in patients on dialysis and those who were not. The excess risk of myopathy was only two per 10,000 patients per year of treatment with this combination (9 [0·2%] vs 5 [0·1%]). There was no evidence of excess risks of hepatitis (21 [0·5%] vs 18 [0·4%]), gallstones (106 [2·3%] vs 106 [2·3%]), or cancer (438 [9·4%] vs 439 [9·5%], p=0·89) and there was no significant excess of death from any non-vascular cause (668 [14·4%] vs 612 [13·2%], p=0·13).

INTERPRETATION

Reduction of LDL cholesterol with simvastatin 20 mg plus ezetimibe 10 mg daily safely reduced the incidence of major atherosclerotic events in a wide range of patients with advanced chronic kidney disease.

FUNDING

Merck/Schering-Plough Pharmaceuticals; Australian National Health and Medical Research Council; British Heart Foundation; UK Medical Research Council.

First-pass metabolism via UDP-glucuronosyltransferase: a barrier to oral bioavailability of phenolics

Glucuronidation mediated by UDP-glucuronosyltransferases (UGTs) is a significant metabolic pathway that facilitates efficient elimination of numerous endobiotics and xenobiotics, including phenolics. UGT genetic deficiency and polymorphisms or inhibition of glucuronidation by concomitant use of drugs are associated with inherited physiological disorders or drug-induced toxicities. Moreover, extensive glucuronidation can be a barrier to oral bioavailability as the first-pass glucuronidation (or premature clearance by UGTs) of orally administered agents usually results in the poor oral bioavailability and lack of efficacies. This review focused on the first-pass glucuronidation of phenolics including natural polyphenols and pharmaceuticals. The complexity of UGT-mediated metabolism of phenolics is highlighted with species-, gender-, organ- and isoform-dependent specificity, as well as functional compensation between UGT1A and 2B subfamily. In addition, recent advances are discussed with respect to the mechanisms of enzymatic actions, including the important properties such as binding pocket size and phosphorylation requirements.

Lack of clinically relevant drug-drug interactions when dalcetrapib is co-administered with ezetimibe

AIMS

Dalcetrapib, which targets cholesteryl ester transfer protein activity, is in development for prevention of cardiovascular events. Because dalcetrapib will likely be prescribed with other lipid-modifying therapies such as ezetimibe, a study was performed to investigate potential pharmacokinetic interactions between dalcetrapib and ezetimibe. Lipids changes and tolerability were secondary endpoints.

METHODS

Co-administration of dalcetrapib 900 mg (higher than the phase III dose) with ezetimibe was investigated in a three period, three treatment crossover study in healthy males: 7 days of dalcetrapib, 7 days of dalcetrapib plus ezetimibe, 7 days of ezetimibe alone. A full pharmacokinetic profile was performed on day 7 of each treatment.

RESULTS

Co-administration of dalcetrapib with ezetimibe was associated with minimal changes in dalcetrapib exposure compared with dalcetrapib alone. Least squares mean ratio (LSMR) (90% confidence interval) was 93.6 (87.1, 100.7) for AUC(0,24 h) and 99.0 (85.2, 115.0) for C(max) . Ezetimibe exposure was reduced with co-administration of ezetimibe with dalcetrapib compared with ezetimibe alone: LSMR 80.3 (74.6, 86.4) for AUC(0,24 h) and 88.9 (80.9, 99.9) for C(max) for total ezetimibe. High-density lipoprotein cholesterol increases associated with co-administration of dalcetrapib with ezetimibe (+29.8%) were comparable with those with dalcetrapib alone (+25.6%), while the reduction in low-density lipoprotein cholesterol with co-administration (-35.9%) was greater than with ezetimibe alone (-20.9%). Dalcetrapib was generally well tolerated when administered alone and when co-administered with ezetimibe.

CONCLUSION

Co-administration of dalcetrapib with ezetimibe was not associated with clinically significant changes in pharmacokinetic parameters or tolerability and did not diminish the lipid effects of either drug.

Pleiotropic effects of ezetimibe/simvastatin vs. high dose simvastatin

BACKGROUND

In the setting of stable coronary artery disease (CAD), it is not known if the pleiotropic effects of cholesterol reduction differ between combined ezetimibe/simvastatin and high-dose simvastatin alone.

OBJECTIVE

We sought to compare the anti-inflammatory and antiplatelet effects of ezetimibe 10mg/simvastatin 20mg (E10/S20) with simvastatin 80 mg (S80).

METHODS AND RESULTS

CAD patients (n=83, 63 ± 9 years, 57% men) receiving S20, were randomly allocated to receive E10/S20 or S80, for 6 weeks. Lipids, inflammatory markers (C-reactive protein, interleukin-6, monocyte chemoattractant protein-1, soluble CD40 ligand and oxidized LDL), and platelet aggregation (platelet function analyzer [PFA]-100) changes were determined. Baseline lipids, inflammatory markers and PFA-100 were similar between groups. After treatment, E10/S20 and S80 patients presented, respectively: (1) similar reduction in LDL-C (29 ± 13% vs. 28 ± 30%, p=0.46), apo-B (18 ± 17% vs. 22 ± 15%, p=0.22) and oxidized LDL (15 ± 33% vs. 18 ± 47%, p=0.30); (2) no changes in inflammatory markers; and, (3) a higher increase of the PFA-100 with E10/S20 than with S80 (27 ± 43% vs. 8 ± 33%, p=0.02).

CONCLUSIONS

These data suggest that among stable CAD patients treated with S20, (1) both E10/S20 and S80 were equally effective in further reducing LDL-C; (2) neither treatment had any further significant anti-inflammatory effects; and (3) E10/S20 was more effective than S80 in inhibiting platelet aggregation. Thus, despite similar lipid lowering and doses 4× less of simvastatin, E10/S20 induced a greater platelet inhibitory effect than S80.

High-density lipoprotein (HDL) cholesterol: leveraging practice-based biobank cohorts to characterize clinical and genetic predictors of treatment outcome

Over the past decade, large multicenter trials have unequivocally demonstrated that decreasing low-density lipoprotein (LDL) cholesterol can reduce both primary and secondary cardiovascular events in patients at risk. However, even in the context of maximal LDL lowering, there remains considerable residual cardiovascular risk. Some of this risk can be attributed to variability in high-density lipoprotein (HDL) cholesterol. As such, there is tremendous interest in defining determinants of HDL homeostasis. Risk prediction models are being constructed based upon (1) clinical contributors, (2) known molecular determinants and (3) the genetic architecture underlying HDL cholesterol levels. To date, however, no single resource has combined these factors within the context of a practice-based data set. Recently, a number of academic medical centers have begun constructing DNA biobanks linked to secure encrypted versions of their respective electronic medical record. As these biobanks combine resources, the clinical community is in a position to characterize lipid-related treatment outcome on an unprecedented scale.

Assessment of potential pharmacokinetic interactions of ezetimibe/simvastatin and extended-release niacin tablets in healthy subjects

BACKGROUND

Efforts to lower plasma lipid levels sometimes require multiple agents with different mechanisms of action to achieve results specified by national treatment guidelines.

METHODS

This was an open-label, randomized, three-period, multiple-dose crossover study that assessed the potential for pharmacokinetic interaction between extended-release niacin and ezetimibe/simvastatin and their major metabolites. Eighteen adults received three randomized treatments: (A) extended-release (ER) niacin 1000 mg/day for 2 days, followed by 2000 mg/day for 5 days; (B) ezetimibe/simvastatin 10 mg/20 mg/day; (C) coadministration of Treatments A and B. Treatments were given once a day after a low fat breakfast for a total of 7 days, with a 7-day inter-dose period.

RESULTS

There were small (mean ≤35%) increases in drug exposure for all analytes after coadministration of ER niacin and ezetimibe/simvastatin 10 mg/20 mg. The least-square mean between treatment C(max) (maximum plasma concentration) ratios (×100) were 97, 98, and 109% for ezetimibe, simvastatin and niacin, respectively. The corresponding ratios for total ezetimibe, simvastatin acid, and nicotinuric acid were 99, 118, and 110%. The AUC((0-24)) (area under the plasma concentration-time curve from time zero to 24 h after dosing) ratios for ezetimibe, simvastatin, and niacin were 109, 120, and 122%, respectively, and the corresponding ratios for total ezetimibe, simvastatin acid, and nicotinuric acid were 126, 135 and 119%.

CONCLUSION

There is a small pharmacokinetic drug interaction between ER niacin and ezetimibe/simvastatin and although this is not considered to be clinically significant, the concomitant use of these drugs should be appropriately monitored, especially during the niacin titration period.

Synergistic influence of Abcb1 and Abcc2 on disposition and sterol lowering effects of ezetimibe in rats

Pharmacokinetics of the sterol-lowering drug ezetimibe (EZ) is influenced by intestinal ABCB1 and ABCC2. This study in Lew.1W rats with "chemical" and genetic Abcb1 and Abcc2 deficiency was initiated to evaluate the individual contribution of both efflux carriers to the overall disposition and sterol-lowering effects of EZ. Disposition and sterol-lowering effects of EZ (5 mg/kg, 14 days) were measured in wild-type (WT) and Abcc2-deficient (Abcc2-) rats (N = 8 per group) and in animals treated with PSC833 (20 mg/kg) to generate "chemical" Abcb1-deficiency (Abcb1-, Abcb1-/Abcc2-). EZ serum levels decreased in the order WT (3.11 +/- 1.09 ng/mL), Abcb1- (1.94 +/- 1.10 ng/mL), Abcc2- (1.42 +/- 0.42 ng/mL, p = 0.003 vs. WT), Abcb1-/Abcc2- (1.17 +/- 0.53 ng/mL, p = 0.002 vs. WT) whereas the serum EZ glucuronide levels increased as follows: WT (23.2 +/- 24.6 ng/mL), Abcb1- (119 +/- 74.5 ng/mL, p = 0.002 vs. WT), Abcc2- (195+/-76.5 ng/mL, p < 0.001 vs. WT), Abcb1-/Abcc2- (676 +/- 207 ng/mL, p < 0.001 vs. WT, Abcb1- and Abcc2-). Abcb1 and Abcc2 protein deficiency resulted synergistically in lower fecal but increased renal excretion of total EZ although to a much lower extent. The sterol-lowering effects of EZ were significantly correlated to serum levels of EZ. In conclusion, Abcb1 and Abcc2 deficiency leads to lower levels of the active EZ and in turn to decreased sterol-lowering effects.

Potential therapeutic uses for ezetimibe beyond lowering LDL-c to decrease cardiovascular events

Ezetimibe is a relatively new drug that inhibits the absorption of dietary cholesterol in the small intestine. It is a low density lipoprotein-cholesterol (LDL-C) lowering medication that acts directly on the intestine by inhibiting Niemann-Pick C1 Like1 (NPC1L1). Recently, results of the ARBITER 6-HALTS trial (Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol 6-HDL and LDL Treatment Strategies) and the ENHANCE trial (Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression) showed that ezetimibe had no effect on atherosclerosis despite producing a marked decrease in LDL-C. Recent studies show a potential benefit of ezetimibe in treating insulin resistance, non-alcoholic fatty liver disease (NAFLD), gallstones and dyslipidaemia associated with chronic renal failure and organ transplantation. All of these conditions are known to be associated with an increase in risk of cardiovascular disease (CVD) and further studies are needed to assess the potential benefits of ezetimibe in these therapeutics areas.

Effects of UDP-glucuronosyltransferase polymorphisms on the pharmacokinetics of ezetimibe in healthy subjects

PURPOSE

Ezetimibe is the first lipid-lowering drug that inhibits the intestinal uptake of dietary and biliary cholesterol without affecting the absorption of fat-soluble nutrients. Ezetimibe is readily absorbed, and undergoes rapid and almost complete glucuronidation by UGT, particularly UGT1A1, in enterocytes during its first pass. Genetic polymorphisms of UGT1A1 may decrease ezetimibe glucuronidation. Therefore, we tested the effects of the UGT1A1*6 and *28 alleles on the pharmacokinetics of ezetimibe.

METHODS

Three hundred and ninety healthy Korean subjects (347 male and 43 female) were recruited and genotyped for UGT1A1 (*6 and *28 variants). Forty-three subjects among them participated in a pharmacokinetic study of ezetimibe. These 43 subjects were divided into three groups (UGT1A1*1/*1, UGT1A1*1/*X, and UGT1A1*X/*X; where *X = *6 or *28) according to the number of UGT1A1 variant alleles. All received a single 10-mg oral dose of ezetimibe. The concentrations of unchanged ezetimibe and ezetimibe-glucuronide in plasma were determined by LC-MS/MS.

RESULTS

The frequencies of the UGT1A1 genotypes were 47.69%, 23.85%, 19.49%, 3.33%, 3.33%, and 2.31% for the *1/*1, *1/*6, *1/*28, *6/*6, *6/*28, and *28/*28 genotypes respectively. Besides the C(max) of unchanged ezetimibe, no significant difference was found in any other pharmacokinetic parameter of unchanged ezetimibe or ezetimibe-glucuronide in the three groups. C(max) and AUC(0-48) in subjects with UGT1A1*28/*28 in the UGT1A1*X/*X group were significantly different from those in the wild-type.

CONCLUSIONS

The UGT1A1*6 allele was not found to significantly affect the pharmacokinetics of ezetimibe, but the UGT1A1*28 allele might.

Ezetimibe reverses the inhibitory effects of dietary cholesterol on mammary tumorigenesis in rats

There are concerns regarding increased cancer incidence in patients treated with ezetimibe, an inhibitor of the absorption of dietary cholesterol. Here we tested the hypothesis that ezetimibe will accelerate mammary tumorigenesis in rats. The drug was administered at a dose of 1 ppm in an AIN-93G diet that contained 0.3% cholesterol. This experimental diet and control diets that contained either no additions or cholesterol or ezetimibe only, were fed to groups of 30 Sprague-Dawley rats 3 days after they were treated with 50 mg/kg methylnitrosourea (MNU). All rats were euthanized 22 weeks after MNU administration. Tumor multiplicity was significantly smaller in rats fed cholesterol than those fed no cholesterol (1.84 +/- 0.42 vs. 3.86 +/- 0.86 respectively, P < 0.05), but was significantly greater in the cholesterol/ezetimibe group than the group fed only cholesterol (3.48 +/- 0.59 vs. 1.84 +/- 0.42 respectively, P < 0.04). The average weight of tumors/rat was also significantly larger in the cholesterol/ezetimibe group than those fed cholesterol alone (5.67 +/- 1.15 vs. 2.56 +/- 0.71 respectively, P < 0.04). As expected, ezetimibe prevented the cholesterol raising effect of the dietary cholesterol. These results show that ezetimibe reverses the inhibitory effect of dietary cholesterol on the development of rat mammary tumors.

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.

Ezetimibe therapy and its influence on oxidative stress and fibrinolytic activity

OBJECTIVE

The effect of ezetimibe on blood lipids, oxidative stress, and fibrinolytic activity in hyperlipidemic patients was investigated after three months of therapy.

METHODS

Thirty hyperlipidemic patients were treated for twelve weeks with ezetimibe 10 mg/day. A healthy control group with matching age and gender was also included. Fasting blood glucose, lipid parameters, paraoxonase (PON1), protein carbonyl (PCO), oxidized LDL (oxLDL), 8-isoprostane (ISOPR), total antioxidant capacity (TAC) levels, tissue-type plasminogen activator (tPA), plasminogen activator inhibitor type-1 (PAI-1), and PAI-1/t-PA levels were evaluated.

RESULTS

Ezetimibe therapy for twelve weeks led to changes in lipid profile in accordance with the literature. Fibrinolytic activity parameters, PAI-1/tPA and tPA-1 decreased, whereas PAI-1 levels did not change significantly. Antioxidant parameters, serum PON1 activity, and TAC levels increased significantly compared with the basal values. Oxidant parameters, oxLDL, ISOPR, and PCO (which is an indicator of oxidative protein damage) decreased significantly after therapy.

CONCLUSIONS

Ezetimibe therapy has beneficial effects on fibrinolytic activity and homeostasis between oxidant and antioxidant activity in hyperlipidemic patients This may be through lowering lipid levels or other mechanisms such as decreasing insulin resistance and the pleiotropic effects of the drug.

Ezetimbe as potential treatment for cholesterol gallstones: The need for clinical trials

Obesity is associated with insulin resistance, non-alcoholic fatty liver disease (NAFLD) and gallstones. High fat diets (unsaturated fats) rich in cholesterol have been demonstrated to produce not only gallstones but also NAFLD and insulin resistance. Interestingly, a high incidence of gallstones is being reported in association with insulin resistance and NAFLD. Laparoscopic cholecystectomy is the best definitive therapy for symptomatic gallbladder disease. Ezetimibe is a drug that inhibits the absorption of both dietary and biliary cholesterol in the small intestine. Importantly, ezetimibe showed potential benefit not only in treating and preventing gallstones but also in insulin resistance and NAFLD. Further studies are required before the use of ezetimibe for the treatment of gallstones can be advocated.

Stability Indicating RP-HPLC Method for Simultaneous Determination of Simvastatin and Ezetimibe from Tablet Dosage Form

A simple, specific and sensitive reverse phase high performance liquid chromatographic method was developed and validated for simultaneous determination of ezetimibe and simvastatin from pharmaceutical dosage forms. The method uses C18 ODS Hypersil column and isocratic elution. The mobile phase composed of acetonitrile:phosphate buffer (pH 4.5, 0.01M) in the ratio of 65:35 v/v was used at a flow rate of 1.0 ml /min. UV detector was programmed at 232 nm for first 10 min and at 238 nm for 10 to 20 min. All the validation parameters were in acceptable range. The developed method was effectively applied to quantitate amount of ezetimibe and simvastatin from tablets. The method was also applied suitably for determining the degradation products of ezetimibe and simvastatin.

Pleiotropic effects of ezetimibe: do they really exist?

Ezetimibe represents a new lipid lowering agent which inhibits cholesterol absorption. It effectively reduces low-density lipoprotein cholesterol when administered either alone or in combination with statins. However, its effect on cardiovascular mortality remains under question since it failed to demonstrate any significant changes in the primary endpoints of the recently published ENHANCE and SEAS studies. A possible explanation for this unsuccessful outcome is that ezetimibe lacks pleiotropic effects. This article aims to review the potential pleiotropic effects of the drug mainly on inflammation markers, lipoprotein subfractions and endothelial function.

Comparison of the efficacy of administering a combination of ezetimibe plus fenofibrate versus atorvastatin monotherapy in the treatment of dyslipidemia

Background

This trial compares the efficacy of administering a combination of ezetimibe plus fenofibrate as an alternative to statin monotherapy for the treatment of dyslipidemia. In this randomized, unblinded crossover study, 43 patients with documented hypercholesterolemia requiring pharmacotherapy were randomized to receive six weeks of either a combination of 10 mg of ezetimibe plus 160 mg of fenofibrate (combination) or 10 mg of atorvastatin monotherapy (atorvastatin). The primary endpoint was the percentage reduction of low-density lipoprotein cholesterol (LDL-C).

Results

LDL-C decreased by 34.6% with the combination therapy versus 36.7% with atorvastatin monotherapy. The difference between the two groups was not statistically significant (p = 0.46). Both study interventions provided similar improvements in total cholesterol (-25.1% with combination versus -24.6% with atorvastatin, p = 0.806) and high-density lipoproteins (+10.0% with combination versus +8.9% with atorvastatin, p = 0.778). Combination therapy showed a trend towards a greater reduction in triglycerides (-25.4% with combination versus -14.5% with atorvastatin, p = 0.079), although there was no significant difference between the two study interventions in terms of the improvement in the TC:HDL ratio (-29.0% with combination versus -28.7% with atorvastatin, p = 0.904).

Conclusions

The combination of ezetimibe plus fenofibrate appeared to produce nearly identical alterations in serum lipoprotein levels when compared to monotherapy with 10 mg of atorvastatin. Daily treatment with the combination of ezetimibe plus fenofibrate is an acceptable alternative to atorvastatin for the treatment of dyslipidemia in patients who are intolerant of statins.

Transporters as drug targets: discovery and development of NPC1L1 inhibitors

The potent cholesterol absorption inhibitor ezetimibe was developed as a first-in-class drug for treating hypercholesterolemia even before its molecular target, Niemann-Pick C1-like 1 (NPC1L1), had been identified. The NPC1L1 protein mediates sterol transport across the enterocyte brush border membrane and is essential for intestinal cholesterol absorption, a major pathway controlling whole-body cholesterol homeostasis. An elucidation of the mechanism underlying NPC1L1-dependent cholesterol absorption would greatly facilitate the discovery and development of new cholesterol-lowering agents for treating hypercholesterolemia and other cholesterol-related metabolic disorders.

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.

The efficacy and safety of ezetimibe and low-dose simvastatin as a primary treatment for dyslipidemia in renal transplant recipients

BACKGROUND/AIMS

The efficacy and safety of a combination of ezetimibe and low-dose statin as primary treatment for dyslipidemia in renal transplant patients were evaluated prospectively.

METHODS

The study enrolled 77 renal transplant recipients with dyslipidemia. They were given ezetimibe (10 mg) and simvastatin (10 mg) for 6 months as the initial treatment for dyslipidemia. Efficacy and safety were evaluated using lipid profiles, trough calcineurin inhibitor levels, allograft function, and adverse effects. The effects on proteinuria and high sensitivity C-reactive protein (hsCRP) levels were also evaluated.

RESULTS

Ezetimibe and low-dose simvastatin significantly decreased the levels of total cholesterol (34.6%), triglyceride (16.0%), and low-density lipoprotein cholesterol (LDL-C) (47.6%), and 82.5% of the patients reached the target LDL-C level of <100 mg/dL. No significant change in the trough calcineurin inhibitor levels or allograft function occurred, and no serious adverse effects were observed. Fourteen patients (18.2%) discontinued treatment; eight patients (11.7%) developed muscle pain or weakness without an increase in creatinine kinase levels, and two patients (2.6%) developed elevated liver transaminase levels. The proteinuria and hsCRP levels did not change significantly.

CONCLUSIONS

Ezetimibe and low-dose statin treatment is safe and effective as a primary treatment for dyslipidemia in renal transplant patients.

New options in the treatment of lipid disorders in HIV-infected patients

Since the introduction of HAART, there was a remarkably change in the natural history of HIV disease, leading to a notable extension of life expectancy, although prolonged metabolic imbalances could significantly act on the longterm prognosis and outcome of HIV-infected persons, and there is an increasing concern about the cardiovascular risk in this population. Current recommendations suggest that HIV-infected perons undergo evaluation and treatment on the basis of the Third National Cholesterol Education Program Expert Panel on Detection, Evaluation and Treatment of High Blood Cholesterol in Adults (NCEP ATP III) guidelines for dyslipidemia, with particular attention to potential drug interactions with antiretroviral agents and maintenance of virologic control of HIV infection. While a hypolipidemic diet and physical activity may certainly improve dyslipidemia, pharmacological treatment becomes indispensable when serum lipid are excessively high for a long time or the patient has a high cardiovascular risk, since the suspension or change of an effective antiretroviral therapy is not recommended. Moreover, the choice of a hypolipidemic drug is often a reason of concern, since expected drug-drug interactions (especially with antiretroviral agents), toxicity, intolerance, effects on concurrent HIV-related disease and decrease patient adherence to multiple pharmacological regimens must be carefully evaluated. Often the lipid goals of patients in this group are not achieved by the therapy recommended in the current lipid guidelines and in this article we describe other possibilities to treat lipid disorders in HIV-infected persons, like rosuvastatin, ezetimibe and fish oil.