Pharmacokinetics and pharmacodynamics of pravastatin alone and with cholestyramine in hypercholesterolemia

Microfluidic technology and simulation models in studying pharmacokinetics during pregnancy

Introduction: Preterm birth rates and maternal and neonatal mortality remain concerning global health issues, necessitating improved strategies for testing therapeutic compounds during pregnancy. Current 2D or 3D cell models and animal models often fail to provide data that can effectively translate into clinical trials, leading to pregnant women being excluded from drug development considerations and clinical studies. To address this limitation, we explored the utility of in silico simulation modeling and microfluidic-based organ-on-a-chip platforms to assess potential interventional agents. Methods: We developed a multi-organ feto-maternal interface on-chip (FMi-PLA-OOC) utilizing microfluidic channels to maintain intercellular interactions among seven different cell types (fetal membrane-decidua-placenta). This platform enabled the investigation of drug pharmacokinetics in vitro. Pravastatin, a model drug known for its efficacy in reducing oxidative stress and inflammation during pregnancy and currently in clinical trials, was used to test its transfer rate across both feto-maternal interfaces. The data obtained from FMi-PLA-OOC were compared with existing data from in vivo animal models and ex vivo placenta perfusion models. Additionally, we employed mechanistically based simulation software (Gastroplus®) to predict pravastatin pharmacokinetics in pregnant subjects based on validated nonpregnant drug data. Results: Pravastatin transfer across the FMi-PLA-OOC and predicted pharmacokinetics in the in silico models were found to be similar, approximately 18%. In contrast, animal models showed supraphysiologic drug accumulation in the amniotic fluid, reaching approximately 33%. Discussion: The results from this study suggest that the FMi-PLA-OOC and in silico models can serve as alternative methods for studying drug pharmacokinetics during pregnancy, providing valuable insights into drug transport and metabolism across the placenta and fetal membranes. These advanced platforms offer promising opportunities for safe, reliable, and faster testing of therapeutic compounds, potentially reducing the number of pregnant women referred to as "therapeutic orphans" due to the lack of consideration in drug development and clinical trials. By bridging the gap between preclinical studies and clinical trials, these approaches hold great promise in improving maternal and neonatal health outcomes.

Real-life management of drug-drug interactions between antiretrovirals and statins

BACKGROUND

PIs cause drug-drug interactions (DDIs) with most statins due to inhibition of drug-metabolizing enzymes and/or the hepatic uptake transporter OATP1B1, which may alter the pharmacodynamic (PD) effect of statins.

OBJECTIVES

To assess the management of DDIs between antiretrovirals (ARVs) and statins in people living with HIV (PLWH) considering statin plasma concentrations, compliance with dosing recommendations and achievement of lipid targets.

METHODS

PLWH of the Swiss HIV Cohort Study were eligible if they received a statin concomitantly with ARVs. HDL, total cholesterol (TC) and statin plasma concentration were measured during follow-up visits. Individual non-HDL and TC target values were set using the Framingham score and the 2018 European AIDS Clinical Society recommendations.

RESULTS

Data were analysed for rosuvastatin (n = 99), atorvastatin (n = 92), pravastatin (n = 46) and pitavastatin (n = 21). Rosuvastatin and atorvastatin underdosing frequently led to suboptimal PD response. Insufficient lipid control was observed with PIs despite high atorvastatin concentrations, likely explained by inhibition of OATP1B1 resulting in less statin uptake in the liver. Target lipid values were more often achieved with unboosted integrase inhibitors due to both their favourable DDI profiles and neutral effect on lipids. Insufficient lipid control was common with pravastatin and pitavastatin regardless of co-administered ARVs and despite using maximal recommended statin doses. The latter suggests lower efficacy compared with rosuvastatin or atorvastatin.

CONCLUSIONS

Suboptimal management of DDIs with statin underdosing was observed in 29% of prescriptions. Integrase inhibitor-based regimens and/or treatment with rosuvastatin or atorvastatin should be favoured in patients with refractory dyslipidaemia.

An updated review of pharmacokinetic drug interactions and pharmacogenetics of statins

INTRODUCTION

Hydroxymethylglutaryl-coenzyme A reductase inhibitors (statins) lower cholesterol synthesis in patients with hypercholesterolemia. Increased statin exposure is an important risk factor for skeletal muscle toxicity. Potent inhibitors of cytochrome P450 (CYP) 3A4 significantly increase plasma concentrations of the active forms of simvastatin, lovastatin, and atorvastatin. Fluvastatin is metabolized by CYP2C9, whereas pravastatin, rosuvastatin, and pitavastatin are unaffected by inhibition by either CYP. Statins also have different affinities for membrane transporters involved in processes such as intestinal absorption, hepatic absorption, biliary excretion, and renal excretion.

AREAS COVERED

In this review, the pharmacokinetic aspects of drug-drug interactions with statins and genetic polymorphisms of CYPs and drug transporters involved in the pharmacokinetics of statins are discussed.

EXPERT OPINION

Understanding the mechanisms underlying statin interactions can help minimize drug interactions and reduce the adverse side effects caused by statins. Since recent studies have shown the involvement of drug transporters such as OATP and BCRP as well as CYPs in statin pharmacokinetics, further clinical studies focusing on the drug transporters are necessary. The establishment of biomarkers based on novel mechanisms, such as the leakage of microRNAs into the peripheral blood associated with the muscle toxicity, is important for the early detection of statin side effects.

Long-Acting Injectable Statins-Is It Time for a Paradigm Shift?

In recent years, advances in pharmaceutical processing technologies have resulted in development of medicines that provide therapeutic pharmacokinetic exposure for a period ranging from weeks to months following a single parenteral administration. Benefits for adherence, dose and patient satisfaction have been witnessed across a range of indications from contraception to schizophrenia, with a range of long-acting medicines also in development for infectious diseases such as HIV. Existing drugs that have successfully been formulated as long-acting injectable formulations have long pharmacokinetic half-lives, low target plasma exposures, and low aqueous solubility. Of the statins that are clinically used currently, atorvastatin, rosuvastatin, and pitavastatin may have compatibility with this approach. The case for development of long-acting injectable statins is set out within this manuscript for this important class of life-saving drugs. An overview of some of the potential development and implementation challenges is also presented.

Medication Exposure in Highly Adherent Psychiatry Patients

Medication exposure is dependent upon many factors, the single most important being if the patient took the prescribed medication as indicated. To assess medication exposure for psychotropic and other medication classes, we enrolled 115 highly adherent psychiatry patients prescribed five or more medications. In these patients, we measured 21 psychotropic and 38 nonpsychotropic medications comprising a 59 medication multiplex assay panel. Strict enrollment criteria and reconciliation of the electronic health record medication list prior to study initiation produced a patient cohort that was adherent with 91% of their prescribed medications as determined by comparing medications detected empirically in blood to the electronic health record medication list. In addition, 13% of detected medications were not in the electronic health record medication list. We found that only 53% of detected medications were within the literature-derived reference range with 41% below and 6% above the reference range specific to each medication. When psychotropic medications were analyzed near trough-level, only sertraline was found to be within the literature-derived reference range for all patients tested. Concentrations of the remaining medications indicated extensive exposure below the reference range. This is the first study to empirically and comprehensively assess medication exposure obtained in comorbid polypharmacy patients, minimizing the important behavioral factor of adherence in the study of medication exposure. These data indicate that low medication exposure is extensive and must be considered when therapeutic issues arise, including the lack of response to medication therapy.

Medication adherence, medical record accuracy, and medication exposure in real-world patients using comprehensive medication monitoring

Background

Poor adherence to medication regimens and medical record inconsistencies result in incomplete knowledge of medication therapy in polypharmacy patients. By quantitatively identifying medications in the blood of patients and reconciling detected medications with the medical record, we have defined the severity of this knowledge gap and created a path toward optimizing medication therapy.

Methods and findings

We validated a liquid chromatography-tandem mass spectrometry assay to detect and/or quantify 38 medications across a broad range of chronic diseases to obtain a comprehensive survey of patient adherence, medical record accuracy, and exposure variability in two patient populations. In a retrospectively tested 821-patient cohort representing U.S. adults, we found that 46% of medications assessed were detected in patients as prescribed in the medical record. Of the remaining medications, 23% were detected, but not listed in the medical record while 30% were prescribed to patients, but not detected in blood. To determine how often each detected medication fell within literature-derived reference ranges when taken as prescribed, we prospectively enrolled a cohort of 151 treatment-regimen adherent patients. In this cohort, we found that 53% of medications that were taken as prescribed, as determined using patient self-reporting, were not within the blood reference range. Of the medications not in range, 83% were below and 17% above the lower and upper range limits, respectively. Only 32% of out-of-range medications could be attributed to short oral half-lives, leaving extensive exposure variability to result from patient behavior, undefined drug interactions, genetics, and other characteristics that can affect medication exposure.

Conclusions

This is the first study to assess compliance, medical record accuracy, and exposure as determinants of real-world treatment and response. Variation in medication detection and exposure is greater than previously demonstrated, illustrating the scope of current therapy issues and opening avenues that warrant further investigation to optimize medication therapy.

Biochemistry of Statins

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Elevated blood lipids may be a major risk factor for CVD. Due to consistent and robust association of higher low-density lipoprotein (LDL)-cholesterol levels with CVD across experimental and epidemiologic studies, therapeutic strategies to decrease risk have focused on LDL-cholesterol reduction as the primary goal. Current medication options for lipid-lowering therapy include statins, bile acid sequestrants, a cholesterol-absorption inhibitor, fibrates, nicotinic acid, and omega-3 fatty acids, which all have various mechanisms of action and pharmacokinetic properties. The most widely prescribed lipid-lowering agents are the HMG-CoA reductase inhibitors, or statins. Since their introduction in the 1980s, statins have emerged as the one of the best-selling medication classes to date, with numerous trials demonstrating powerful efficacy in preventing cardiovascular outcomes (Kapur and Musunuru, 2008 [1]). The statins are commonly used in the treatment of hypercholesterolemia and mixed hyperlipidemia. This chapter focuses on the biochemistry of statins including their structures, pharmacokinetics, and mechanism of actions as well as the potential adverse reactions linked to their clinical uses.

Association between SLCO1B1 521 T＞C and 388 A＞G Polymorphisms and Statins Effectiveness: A Meta-Analysis

AIM

Previous studies on the association between the SLCO1B1 521 T＞C and 388 A＞G polymorphisms and statin effectiveness have been inconsistent. We performed this meta-analysis to provide a more comprehensive estimation of this issue.

METHODS

Multiple electronic literatues databases were searched on March 5th 2014. A quality assessment was performed using the Methodological Index for Non-Randomized Studies (MINORS) criteria. A meta-analysis, sub-group analysis, sensitivity analysis (RevMan 5.2), publication bias measuring and meta-regression analysis were conducted utilizing the Stata software program (version 12.0).

RESULTS

A total of 13 studies were included in the final meta-analysis, which included 7,079 participants. Overall, there was no statistically significant association in the four genetic models of hypolipidemic effect. For the 521 T＞C polymorphism, significant associations were found for the long-term effectiveness of lowering the low-density lipoprotein cholesterol (LDL-C) and in non-Asian populations in the dominant model [(CC＋TC vs. TT: mean difference (MD)=1.44, 95% CI: 0.25-2.64,p=0.02) and (CC＋TC vs. TT: MD=1.38, 95% CI: 0.28-2.49, p=0.01)], the recessive model [(CC vs. TT＋TC: MD=3.31, 95% CI: 0.09-6.54, p=0.04) and (CC vs. TT＋TC: MD=2.83, 95% CI: 0.26-5.41, p=0.03)], and the homozygote comparison [(CC vs. TT: MD=3.68, 95% CI: 0.42-6.94,p=0.03) and (CC vs. TT: MD=3.33, 95% CI: 0.67-5.99, p=0.01)], respectively. There were no significant differences for the other analyses of the 521 T＞C polymorphism or all the analyses of the 388 A＞G polymorphism.

CONCLUSIONS

The overall results suggest that the SLCO1B1 521 T＞C and 388 A＞G polymorphisms do not affect the lipid-lowering effectiveness of statins. However, allele C of the SLCO1B1 521 T＞C polymorphism leads to an attenuated effect on lowering the LDL-C in non-Asian populations and the long-term effectiveness of statin treatment.

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.

Pravastatin improves renal ischemia-reperfusion injury by inhibiting the mevalonate pathway

Statins are known to lessen the severity of renal ischemia-reperfusion injury. The present study was undertaken to define the mechanism of renoprotective actions of statins using a mouse kidney injury model. Treatment of mice with pravastatin, a widely used statin, improved renal function after renal ischemia-reperfusion without lowering the plasma cholesterol level. Administration of pravastatin with mevalonate, a product of HMG-CoA reductase, eliminated renal protection suggesting an effect of pravastatin on mevalonate or its metabolism. In hypercholestrolemic apolipoprotein E knockout mice with reduced HMG-CoA reductase activity; the degree of injury was less severe than in control mice, however, there was no protective action of pravastatin on renal injury in the knockout mice. Treatment with a farnesyltransferase inhibitor (L-744832) mimicked pravastatin's protective effect but co-administration with the statin provided no additional protection. Both pravastatin and L-744832 inhibited the injury-induced increase in plasma IL-6 concentration to a similar extent. Our results suggest the protective effect of pravastatin on renal ischemia-reperfusion injury is mediated by inhibition of the mevalonate-isoprenoid pathway independent of its lipid lowering action.

The Role of Statin Drugs in the Management of the Peripheral Vascular Patient

The impact of statin therapy on established vascular conditions and recurrent disease is most relevant for long-term care. Patients receiving statin therapy have been shown to experience less recurrent stenosis following carotid endarterectomy and stent angioplasty, reduced cardiac events following cardiac and noncardiac vascular surgery, and reduction in aneurysm development. In patients with peripheral arterial disease, claudication distance is increased, as well as patency rates following infrainguinal arterial bypass grafting. Of note, statins drugs may also prove beneficial in the prevention of certain cancers, Alzheimer's disease, and osteoporosis (all diseases frequently seen concurrently in the patient with peripheral arterial disease). As such, it is becoming all the more necessary that vascular surgeons remain informed about clinical research initiatives related to statin use and lipid management in general. The following is a review of lipid metabolism as it applies to statins as well as a review of the beneficial effects of statins.

SLCO1B1 521T-->C functional genetic polymorphism and lipid-lowering efficacy of multiple-dose pravastatin in Chinese coronary heart disease patients

AIMS

Pravastatin is a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, which is widely used both in primary and secondary prevention of coronary heart disease (CHD). Pravastatin is not subject to metabolism by cytochrome P450s, but it is actively transported from blood into target tissues (e.g. hepatocytes in the liver) by the organic anion transporting polypeptide 1B1 (OATP1B1), encoded by SLCO1B1. The aim of the present study was to evaluate the impact of SLCO1B1 521T-->C (Val174Ala) functional genetic polymorphism on the lipid-lowering efficacy of multiple-dose pravastatin in Chinese patients with CHD.

METHODS

Forty-five hospitalized patients with CHD prospectively received pravastatin as a single-agent therapy (20 mg day(-1) p.o.) for 30 days. Serum triglycerides, total cholesterol, low-density lipoprotein-cholesterol and high-density lipoprotein-cholesterol concentrations were determined before and after pravastatin treatment.

RESULTS

Pravastatin treatment significantly decreased plasma lipids in all patients (P < 0.001). Importantly, we showed an attenuated pravastatin pharmacodynamic effect on total cholesterol in patients with 521TC heterozygote genotype (from 5.52 +/- 0.51 mmol l(-1) to 4.70 +/- 0.35 mmol l(-1), % change -14.5 +/- 6.6%, N = 9) compared with 521TT homozygote genotype (from 5.47 +/- 1.15 mmol l(-1) to 4.21 +/- 0.89 mmol l(-1), % change -22.4 +/- 10.3%, N = 36) (mean +/- SD, P = 0.03, two-tailed test with alpha set at 5%). SLCO1B1 521T-->C functional polymorphism did not significantly influence pravastatin pharmacodynamics on other plasma lipids (P > 0.05).

CONCLUSIONS

The 521T-->C polymorphism of SLCO1B1 appears to modulate significantly the total cholesterol-lowering efficacy of pravastatin in Chinese patients with CHD. Further studies are warranted to determine the extent to which SLCO1B1 genetic variation may contribute to resistance to pravastatin in Asian patients treated with standard doses of pravastatin.

Pharmacokinetics and response to pravastatin in paediatric patients with familial hypercholesterolaemia and in paediatric cardiac transplant recipients in relation to polymorphisms of the SLCO1B1 and ABCB1 genes

AIMS

Our aim was to investigate associations between the single nucleotide polymorphisms (SNPs) in the SLCO1B1 (encoding OATP1B1) and ABCB1 (encoding P-glycoprotein) genes with the pharmacokinetics and efficacy of pravastatin in children with heterozygous familial hypercholesterolaemia (HeFH) and in paediatric cardiac transplant recipients.

METHODS

Twenty children with HeFH (aged 4.9-15.6 years) and 12 cardiac transplant recipients (aged 4.4-18.7 years and receiving triple immunosuppressive medication) who had participated in previous pharmacokinetic and pharmacodynamic studies with pravastatin were genotyped for the -11187G > A and 521T > C SNPs in the SLCO1B1 gene and for the 2677G > T/A and 3435C > T SNPs in the ABCB1 gene.

RESULTS

Two HeFH patients with the -11187GA genotype had a 81% lower peak plasma pravastatin concentration (Cmax) (difference in means -13.9 ng ml(-1), 95% CI -21.1, -6.7; P < 0.001) and a 74% smaller area under the plasma concentration-time curve (AUC0, infinity) (-25.3 ng ml(-1) h, 95% CI -35.6, -15.0; P < 0.0001) and significantly greater increase in high density lipoprotein (HDL) cholesterol after 2 months treatment with pravastatin than patients with the reference genotype. No significant differences were seen in the pharmacokinetics or effects of pravastatin between HeFH patients with the SLCO1B1 521TC and 521TT genotypes. The cardiac transplant recipients with the SLCO1B1 521TC genotype (n = 3) had a 46% lower Cmax (-67.7 ng ml(-1), 95% CI -135.7, 0.3; P = 0.055) and 62% lower AUC(0,24 h) (-228.5 ng ml(-1) h, 95% CI -402.7, -54.3; P = 0.016) and a shorter half-life (t1/2) (0.9 +/- 0.1 vs. 1.3 +/- 0.4 h, P = 0.015) of pravastatin than those with the reference genotype. Decreases in total and low-density lipoprotein cholesterol by pravastatin were significantly smaller, and the increase in HDL-cholesterol was greater in the transplant recipients with the 521TC genotype compared with patients with the 521TT reference genotype.

CONCLUSIONS

In children with HeFH and in paediatric cardiac transplant recipients receiving immunosuppressive medication, the -11187G > A and SLCO1B1 521T > C SNPs were associated with decreased plasma concentrations of pravastatin. These differences are opposite to those seen previously in healthy adults. The mechanisms underlying these phenomena are unclear and warrant further study.

Endocrinology and Dialysis: Management of Lipid Abnormalities Associated with End-Stage Renal Disease

The management of lipid abnormalities in patients with end-stage renal disease (ESRD) remains controversial. Large, well-designed studies investigating the effects of dyslipidemia on cardiovascular (CV) morbidity and mortality and the role of cholesterol lowering drugs in reducing mortality in ESRD patients are lacking. While it seems reasonable to suspect that dyslipidemia and its treatment in ESRD patients will affect CV morbidity and mortality similar to that in the general population, recent studies have suggested that this may not be the case. Furthermore, the pharmacokinetics of lipid lowering drugs are altered in patients with ESRD and must be considered when treating this group of patients. This article reviews the major classes of drugs used to treat dyslipidemia, emphasizing their role in patients with ESRD.

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.

Prescription des statines en cas d’insuffisance rénale

BACKGROUND

Chronic kidney disease (CKD) is extremely common in adults, although often undiagnosed and thus untreated. Cardiovascular disease is the leading cause of death among patients with CKD and reducing its risk in this population is an important priority. Dyslipidemia is almost always present when proteinuria is above 3 gr/24 hours. Roughly two thirds of all patients with end-stage renal failure and kidney transplants suffer from dyslipidemia and should receive lipid-lowering therapy, as suggested by recent Afssaps (French drug agency) and NKF-K/DOQI (National Kidney Foundation-Kidney Disease Outcomes Quality Initiative) guidelines. We reviewed recent studies on efficacy, tolerability and prescription recommendations of statins in CKD and renal transplant patients.

METHODS

We searched Medline, the international medical database, to conduct a systematic review of the literature on the efficacy and tolerability of statins in CKD and renal transplant patients and on specific recommendations for dosage adjustments in this population.

RESULTS

The efficacy of statins in decreasing total cholesterol and LDL-cholesterol levels in dialysis and renal transplant patients is similar to that in the general population. On the other hand, large-scale randomized clinical trials among CKD (4D) and renal transplant (ALERT) patients do not demonstrate that statins significantly decrease rates of cardiovascular disease. They have a beneficial effect on proteinuria and lower the rate of kidney function deterioration in patients with dyslipidemia. Early introduction of a statin in transplant patients did not lead to improved kidney function or prevent loss of the graft. Although most statins are not excreted by the kidneys, the dosage of some must be adapted in CKD patients because of pharmacokinetic modifications induced by renal impairment.

CONCLUSION

Statins at appropriately adapted doses have the same efficacy in CKD patients as in subjects with normal kidney function, and tolerance is not a problem. Their effectiveness in cardiovascular prevention in this population has not been demonstrated to date. Results about statin-induced kidney protection are encouraging but further and more specific studies are needed.

Statins' dosage in patients with renal failure and cyclosporine drug-drug interactions in transplant recipient patients

Dyslipidemia is frequent in patients with renal failure and in transplant recipient patients. This lead to a wide use of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) in patients with impaired renal function or in patients treated with cyclosporine as post-transplantation immunosuppressive therapy. As a result, it is crucial for those patients' physicians to be aware of how to handle these drugs when renal function is impaired and/or when cyclosporine is co-administered. Most statins have an extensive hepatic elimination and the renal route is usually a minor elimination pathway. However, pharmacokinetic alterations have been described for some of these drugs in patients with renal insufficiency. Cyclosporine is a widely used immunosuppresive therapy in solid organ transplant patients and drug-drug interactions are likely to occur when statins and cyclosporine are administered together. Those interactions may theoretically result in increased statins and/or cyclosporine serum levels with potential muscle and/or renal toxicity. As a result, caution is warranted if concurrent administration is performed. In this review, we synthesized the data from the literature on (1) the pharmacokinetics and dosage adjustment of atorvastatin, fluvastatin, pravastatin, rosuvastatin, and simvastatin in patients with renal failure and (2) the potential drug-drug interactions between these drugs and cyclosporine in transplant recipient patients.

Pharmacokinetic properties of pravastatin in Mexicans: An open-label study in healthy adult volunteers

BACKGROUND

The pharmacokinetic properties of pravastatin, particularlyAUC and Cmax, are variable by population. A description of the pharmacokinetic properties of pravastatin in Mexican mestizos was not found in a search of MEDLINE/PubMed (key terms: pravastatin, Mexican, and pharmacokinetics; years: 1966-2005). Because Mexicans and Japanese have common ancestors (Mongoloid group), they also have a common gene pool. This gene pool was modified by genetic "bottlenecks" that occurred when these populations migrated to the Americas and when the Mexican population mixed with the Spanish population during the 16th and 17th centuries. Previous studies in Japanese subjects showed 5 main mutations on the hepatic drug transporter OATP-C, resulting in higher Cmax and AUC values compared with whites. In the Japanese population, the rates of expression of the (*) 1b and (*) 15 alleles were 46% and 15%, respectively.

OBJECTIVE

The aim of this study was to evaluate the pharmacokinetic propertiesof pravastatin in healthy Mexican mestizo volunteers and to compare them with those in white and Japanese populations described in the literature.

METHODS

This open-label, uncontrolled pilot study of the pharmacokineticproperties of pravastatin was conducted at the Division of Pharmacology, Center for Research and Advanced Studies, Mexico City, Mexico. Healthy, adult, Mexican volunteers received a single dose of pravastatin 10 mg PO (tablet). High-performance liquid chromatography was used to determine plasma pravastatin concentrations between 15 minutes and 12 hours after dosing.

RESULTS

Twenty-four subjects (15 women, 9 men; mean age, 30.6 years)participated in the study. The mean (SD) Cmax was 9.5 (2.4) ng/mL; Tmax, 0.8 (0.3) hours; AUC0-∞ 35.7 (19.7) ng/mL - h; t1/2, 2.7 (1.1) hours; and mean residence time, 3.1 (1.1) hours. One volunteer (4%) had an AUC value that differed substantially from the rest of the study population, producing a bimodal distribution of the pharmacokinetic parameters. No adverse events were observed or reported during the trial.

CONCLUSIONS

In this small pilot study of the pharmacokinetic properties of pravastatin in Mexican mestizos, AUC was not statistically significantly different from previous studies, either in a white or Japanese population. However, we did not find the high values reported for Cmax in some Japanese subjects carrying recently reported mutations on the pravastatin transporter.

Optimal lipid modification: the rationale for combination therapy

BACKGROUND

An emphasis on more aggressive lipid-lowering, particularly of low-density lipoprotein cholesterol, to improve patient outcomes has led to an increased use of combination lipid-lowering drugs. This strategy, while potentially beneficial, has triggered concerns regarding fears of adverse effects, harmful drug interactions, and patient nonadherence.

OBJECTIVE

To present key data regarding combination lipid-altering therapy including use, rationale, major trials, benefits, potential adverse effects, compliance issues, and limitations.

METHOD

Literature was obtained from MEDLINE (1966 - June 2005) and references from selected articles.

RESULTS

A substantial body of evidence from epidemiological data and clinical trials indicates that aggressive lipid modification, especially low-density lipoprotein reduction, is associated with reduced cardiovascular events. Numerous studies utilizing various combinations of cholesterol-lowering agents including statin/fibrate, statin/niacin, statin/bile acid resin, and statin/ezetimibe have demonstrated significant changes in the lipid profile with acceptable safety. Long-term trials of combination therapy evaluating clinical outcomes or surrogate markers of cardiovascular disease, while limited, are promising.

CONCLUSION

Combining lipid-altering agents results in additional improvements in lipoproteins and has the potential to further reduce cardiovascular events beyond that of monotherapy.

Efficacy and safety of rosuvastatin alone and in combination with cholestyramine in patients with severe hypercholesterolemia: A randomized, open-label, multicenter trial

BACKGROUND

Patients with severe hypercholesterolemia may need greater cholesterol reductions than can be achieved with statin therapy alone.

OBJECTIVE

The primary objective of this trial was to compare the efficacy of a combination of rosuvastatin plus cholestyramine with that of rosuvastatin alone for reducing low-density lipoprotein cholesterol (LDL-C) levels after 6 weeks of treatment.

METHODS

In this open-label, multicenter, randomized, parallel-group, comparator trial, adult patients with severe hypercholesterolemia (LDL-C level, 190-400 mg/dL) received rosuvastatin 40 mg/d for 6 weeks after a 6-week dietary lead-in period and were then randomized to 6 weeks of treatment with rosuvastatin 80 mg/d alone or rosuvastatin 80 mg/d plus cholestyramine 16 g/d (8 g BID with meals).

RESULTS

Of 153 eligible patients, 147 (83 men, 64 women; mean [SD] age, 54.5 [13.7] years; mean [SD] bodyweight, 81.3 [14.4] kg) received randomized treatment, and 144 had post baseline measurements and were included in the analysis. The mean (SD) reduction in LDL-C was 522% (13.0%) after treatment with rosuvastatin 40 mg, and the least squares mean (SE) reductions in LDL-C were 56.4% (1.8%) and 60.5% (1.8%) after treatment with rosuvastatin 80 mg alone (n = 69) and rosuvastatin 80 mg plus cholestyramine (n = 75), respectively. No significant differences between treatments were found for these or other lipid measurements. Incremental LDL-C reductions >30% were obtained in 29% (22/75) of patients receiving combination therapy and 4% (3/69) of patients receiving rosuvastatin alone. The combination therapy was less well tolerated, primarily due to gastrointestinal symptoms; otherwise, the treatments were generally well tolerated.

CONCLUSION

In this group of patients with severe hypercholesterolemia, the combination of rosuvastatin 80 mg with cholestyramine 16 g/d did not provide a significantly greater efficacy benefit than rosuvastatin alone.

Steady-State Pharmacokinetics of Pravastatin in Children with Familial Hypercholesterolaemia

OBJECTIVE

To determine pharmacokinetic data for pravastatin in children, since current data are insufficient in this age group.

SUBJECTS AND METHODS

A 2-week, multiple-dose, steady-state pharmacokinetic study was carried out with pravastatin 20mg daily in 24 children with familial hypercholesterolaemia (aged 8-16 years; 12 prepubertal, 12 pubertal). A plasma concentration-time curve was performed on day 14. Pharmacokinetic curves for each individual were constructed using nonparametric methods, yielding area under the plasma concentration-time curve (AUC), maximum plasma concentration (C(max)) and half-life (t((1/2))). Clearance values and volumes of distribution were calculated from these parameters. Cholesterol lowering was observed on day 14 and 6 weeks after the start of pravastatin.

RESULTS

The C(max) in prepubertal (group A) children (52.1 +/- 27.0 mug/L [mean +/- SD]) differed, although not significantly (p = 0.09, unpaired two-tailed t-test), from the C(max) in adolescents (group B) [31.7 +/- 29.2 mug/L]. There was a moderate negative correlation between C(max) and age (Spearman correlation r = -0.42; p = 0.04). The AUC in prepubertal children (91.3 +/- 39.7 mug . h/L) did not differ significantly from the AUC in adolescents (69.3 +/- 57.0 mug . h/L). The t((1/2)) was the same for the two groups: 2.5 +/- 1.1h. Clearance values (CL/f) varied widely between the two groups (group A: 4.3 +/- 1.8 L/min; group B: 11.0 +/- 11.9 L/min; p = 0.08). A moderate positive correlation was found between clearance and age (Spearman correlation r = 0.36; p = 0.09). A large variation was found in the volumes of distribution within the two groups (group A: 31.2 mL/kg [SD 26.7], group B:37.0 mL/kg [SD 29.6]; p = 0.12). A very weak positive correlation was found between age and volume of distribution (Spearman correlation r = 0.11; p = 0.61). A 27% low-density lipoprotein-cholesterol reduction from baseline was achieved at day 14.

CONCLUSIONS

Body surface area and gender did not influence the pharmacokinetics of pravastatin in children aged 8-16 years. On the basis of our findings there are no reasons to use pravastatin at a dosage according to bodyweight or to use different dosage regimens from those in adults. However, for prepubertal children half the advised starting dose for adults may be sufficient.

Effect of Colesevelam HCl on Single-Dose Fenofibrate Pharmacokinetics

OBJECTIVE

The primary aim of this study was to determine whether there is an effect of colesevelam HCl (WelChol; Sankyo Pharma Inc., Parsippany, NJ, USA) on fenofibric acid (active metabolite of fenofibrate, TriCor, Abbott Laboratories, North Chicago, IL, USA) pharmacokinetics following single-dose fenofibrate when colesevelam HCl and fenofibrate are administered concomitantly, or when colesevelam HCl is administered 4 hours following fenofibrate therapy.

METHODS

Thirty healthy volunteers were enrolled in a randomised, open-label, three-way crossover, drug interaction study. Subjects received one of three treatments at each of three dose administration periods: (i) treatment A -- fenofibrate 160 mg plus colesevelam HCl 3750 mg (6 x 625 mg tablets) administered with breakfast; (ii) treatment B -- fenofibrate 160 mg administered with breakfast, followed 4 hours later by colesevelam HCl 3750 mg (6 x 625 mg tablets) administered with lunch; or (iii) treatment C -- fenofibrate 160 mg administered with breakfast. Treatments were separated by a 10-day washout period. Blood samples were collected at predetermined time intervals, both before and after drug administration. Plasma concentrations of fenofibrate and fenofibric acid were measured using a validated liquid chromatography/mass spectroscopy/mass spectroscopy method.

RESULTS

Area under the concentration-time curve (AUC) from time zero to the timepoint of the lowest quantifiable concentration (AUCt), AUC from time zero to infinity (AUCinfinity) and maximum plasma concentration (Cmax) for fenofibric acid were 92.1%, 93.9% and 79.8%, respectively, of control values when colesevelam HCl and fenofibrate were coadministered with breakfast; and 91.9%, 93.9% and 99.1%, respectively, when fenofibrate was administered followed 4 hours later by administration of colesevelam HCl. The 90% confidence intervals for the ratios of geometric means for AUCt, AUCinfinity and Cmax comparing the three treatments were contained within the 80-125% equivalence range, with the exception of Cmax for treatment A. Coadministration of fenofibrate with colesevelam HCl resulted in an approximate 20% reduction in Cmax of the active metabolite (fenofibric acid). There were no significant differences in the time to Cmax, elimination rate constant or elimination half-life between any of the treatment groups.

CONCLUSIONS

Colesevelam HCl had no significant effect on fenofibrate bioavailability when administered either concomitantly with fenofibrate or 4 hours after fenofibrate.

Pharmacokinetic-pharmacodynamic drug interactions with HMG-CoA reductase inhibitors

The HMG-CoA reductase inhibitors (statins) are effective in both the primary and secondary prevention of ischaemic heart disease. As a group, these drugs are well tolerated apart from two uncommon but potentially serious adverse effects: elevation of liver enzymes and skeletal muscle abnormalities, which range from benign myalgias to life-threatening rhabdomyolysis. Adverse effects with statins are frequently associated with drug interactions because of their long-term use in older patients who are likely to be exposed to polypharmacy. The recent withdrawal of cerivastatin as a result of deaths from rhabdomyolysis illustrates the clinical importance of such interactions. Drug interactions involving the statins may have either a pharmacodynamic or pharmacokinetic basis, or both. As these drugs are highly extracted by the liver, displacement interactions are of limited importance. The cytochrome P450 (CYP) enzyme system plays an important part in the metabolism of the statins, leading to clinically relevant interactions with other agents, particularly cyclosporin, erythromycin, itraconazole, ketoconazole and HIV protease inhibitors, that are also metabolised by this enzyme system. An additional complicating feature is that individual statins are metabolised to differing degrees, in some cases producing active metabolites. The CYP3A family metabolises lovastatin, simvastatin, atorvastatin and cerivastatin, whereas CYP2C9 metabolises fluvastatin. Cerivastatin is also metabolised by CYP2C8. Pravastatin is not significantly metabolised by the CYP system. In addition, the statins are substrates for P-glycoprotein, a drug transporter present in the small intestine that may influence their oral bioavailability. In clinical practice, the risk of a serious interaction causing myopathy is enhanced when statin metabolism is markedly inhibited. Thus, rhabdomyolysis has occurred following the coadministration of cyclosporin, a potent CYP3A4 and P-glycoprotein inhibitor, and lovastatin. Itraconazole has been shown to increase exposure to simvastatin and its active metabolite by at least 10-fold. Pharmacodynamically, there is an increased risk of myopathy when statins are coprescribed with fibrates or nicotinic acid. This occurs relatively infrequently, but is particularly associated with the combination of cerivastatin and gemfibrozil. Statins may also alter the concentrations of other drugs, such as warfarin or digoxin, leading to alterations in effect or a requirement for clinical monitoring. Knowledge of the pharmacokinetic properties of the statins should allow the avoidance of the majority of drug interactions. If concurrent therapy with known inhibitors of statin metabolism is necessary, the patient should be monitored for signs and symptoms of myopathy or rhabdomyolysis and the statin should be discontinued if necessary.

Effect of colesevelam on lovastatin pharmacokinetics

OBJECTIVE

To assess potential interactions of colesevelam hydrochloride and lovastatin in healthy volunteers when lovastatin alone was administered with dinner, both lovastatin and colesevelam were administered with dinner, and colesevelam was administered with dinner and lovastatin was administered 4 hours later with a snack.

METHODS

A single-center, open-label, 3-period, crossover drug interaction study was performed with 22 healthy volunteers. Blood samples were collected at specified intervals before and after dosing, and plasma concentrations of lovastatin and lovastatin hydroxyacid were measured using a liquid chromatography/mass spectroscopy/mass spectroscopy method.

RESULTS

Maximal concentration (Cmax), AUC from time 0 to the last time point measured (AUC0-t), and AUC0-infinity values for lovastatin were 102%, 94%, and 104%, and for lovastatin hydroxyacid were 102%, 91%, and 92%, respectively, of control values when colesevelam and lovastatin were coadministered with dinner. Administration of colesevelam with dinner and lovastatin 4 hours later with a snack resulted in a decreased Cmax and AUC0-t for lovastatin (63% and 37%, respectively; p < 0.05) and an increased Cmax and AUC0-t for lovastatin hydroxyacid (61% and 50%, respectively; p < 0.05), both compared with lovastatin alone administered with dinner.

CONCLUSIONS

Colesevelam had no significant effect on lovastatin pharmacokinetics when coadministered with lovastatin at dinner. A split-dosing regimen resulted in alterations in pharmacokinetic parameters for lovastatin and lovastatin hydroxyacid that are likely due to known differences in the pharmacokinetics of lovastatin when administered to patients with meals or in a fasting state.

Combination lipid-altering therapy: an emerging treatment paradigm for the 21st century

For the care of an expanding segment of the US population with multiple coronary risk factors, combination lipid-altering therapy is emerging as a treatment imperative. The most recent National Cholesterol Education Program's consensus guidelines emphasize long-term global coronary heart disease (CHD) risk status, designate patients with CHD risk equivalents (eg, diabetes, peripheral arterial disease, 20% or more 10-year absolute CHD risk) for aggressive lipid-altering therapy, and deem the metabolic syndrome (eg, obesity, insulin resistance, hypertension, elevated triglycerides, low levels of high-density lipoprotein cholesterol, small dense low-density lipoprotein particles) as a secondary target for intervention. With the advancing age of the US population and the high prevalence of diabetes, the metabolic syndrome, and CHD, increasing numbers of patients will require a more balanced metabolic attack attainable only through combination lipid-altering regimens. Many of these patients, as well as persons at heightened risk for cardiovascular disease because of a range of heritable conditions (eg, familial hypercholesterolemia, familial combined hyperlipidemia), will undoubtedly require binary or ternary regimens involving statins in concert with niacin, fibric-acid derivatives, or bile acid resins. Such approaches enable the clinician to exploit the complementary effects of these agents, allowing them to be administered at low, optimally tolerable doses that are consistent with superior efficacy and a lower risk of adverse events as compared with escalating doses of monotherapy.

Antiinflammatory and antiarteriosclerotic actions of HMG-CoA reductase inhibitors in a rat model of chronic inhibition of nitric oxide synthesis

Recent studies suggest that some of the beneficial effects of 3-hydroxyl-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) may be due to their cholesterol-lowering independent effects on the blood vessels. Chronic inhibition of endothelial nitric oxide (NO) synthesis by oral administration of N(omega)-nitro-L-arginine methyl ester (L-NAME) to rats induces early vascular inflammation as well as subsequent arteriosclerosis. The aim of the study is to test whether treatment with statins attenuates such arteriosclerotic changes through their cholesterol-lowering independent effects. We investigated the effect of statins (pravastatin and cerivastatin) on the arteriosclerotic changes in the rat model. We found that treatment with statins did not affect serum lipid levels but markedly inhibited the L-NAME-induced vascular inflammation and arteriosclerosis. Treatment with statins augmented endothelial NO synthase activity in L-NAME-treated rats. We also found the L-NAME induced increase in Rho membrane translocation in hearts and its prevention by statins. Such vasculoprotective effects of statins were suppressed by the higher dose of L-NAME. In summary, in this study, we found that statins such as pravastatin and cerivastatin inhibited vascular inflammation and arteriosclerosis through their lipid-lowering independent actions in this model. Such antiarteriosclerotic effects may involve the increase in endothelial NO synthase activity and the inhibition of Rho activity.

Cardiovascular drug-drug interactions

The drug-drug interactions discussed in this article have either documented or suspected clinical relevance for patients with cardiovascular disease and the clinician involved in the care of these patients. Oftentimes, drug-drug interactions are difficult, if not impossible, to predict because of the high degree of interpatient variability in drug disposition. Certain drug-drug interactions, however, may be avoided through knowledge and sound clinical judgment. Every clinician should maintain a working knowledge of reported drug-drug interactions and an understanding of basic pharmacokinetic and pharmacodynamic principles to help predict and minimize the incidence and severity of drug-drug interactions.

Colesevelam: a new bile acid sequestrant

Coronary heart disease is the most prevalent form of cardiovascular disease in the United States. Hyperlipidemia--specifically, increased total and low-density lipoprotein cholesterol levels--positively correlates with the development of coronary heart disease. Colesevelam, a nonabsorbed, water-insoluble polymer, is a new bile acid sequestrant that is effective in lowering total and low-density lipoprotein cholesterol levels. In several short-term, placebo-controlled studies, colesevelam has decreased total cholesterol levels by approximately 6 to 10% and low-density lipoprotein cholesterol levels by approximately 9 to 20%. When given in combination with atorvastatin, lovastatin, or simvastatin, low-density lipoprotein cholesterol levels were decreased more than with colesevelam alone. Its unique hydrogel formulation may also minimize the potential for gastrointestinal adverse effects, which are common with other bile acid sequestrants. There have been few published studies available concerning this drug; no long-term studies and few large-scale studies have been published.

Clinical pharmacokinetics of pravastatin: mechanisms of pharmacokinetic events

Pravastatin, one of the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins) widely used in the management of hypercholesterolaemia, has unique pharmacokinetic characteristics among the members of this class. Many in vivo and in vitro human and animal studies suggest that active transport mechanisms are involved in the pharmacokinetics of pravastatin. The oral bioavailability of pravastatin is low because of incomplete absorption and a first-pass effect. The drug is rapidly absorbed from the upper part of the small intestine, probably via proton-coupled carrier-mediated transport, and then taken up by the liver by a sodium-independent bile acid transporter. About half of the pravastatin that reaches the liver via the portal vein is extracted by the liver, and this hepatic extraction is mainly attributed to biliary excretion which is performed by a primary active transport mechanism. The major metabolites are produced by chemical degradation in the stomach rather than by cytochrome P450-dependent metabolism in the liver. The intact drug and its metabolites are cleared through both hepatic and renal routes, and tubular secretion is a predominant mechanism in renal excretion. The dual routes of pravastatin elimination reduce the need for dosage adjustment if the function of either the liver or kidney is impaired, and also reduce the possibility of drug interactions compared with other statins. which are largely eliminated by metabolism. The lower protein binding than other statins weakens the tendency for displacement of highly protein-bound drugs. Although all statins show a hepatoselective disposition, the mechanism for pravastatin is different from that of the others. There is high uptake of pravastatin by the liver via an active transport mechanism, but not by other tissues because of its hydrophilicity, whereas the disposition characteristics of other statins result from high hepatic extraction because of high lipophilicity. These pharmacokinetic properties of pravastatin may be the result of the drug being given in the pharmacologically active open hydroxy acid form and the fact that its hydrophilicity is markedly higher than that of other statins. The nature of the pravastatin transporters, particularly in humans, remains unknown at present. Further mechanistic studies are required to establish the pharmacokinetic-pharmacodynamic relationships of pravastatin and to provide the optimal therapeutic efficacy for various types of patients with hypercholesterolaemia.

Cerivastatin: a review of its pharmacological properties and therapeutic efficacy in the management of hypercholesterolaemia

Cerivastatin is an HMG-CoA reductase inhibitor used for the treatment of patients with hypercholesterolaemia. The lipid-lowering efficacy of cerivastatin has been demonstrated in a number of large multicentre, randomised clinical trials. Earlier studies used cerivastatin at relatively low dosages of < or =0.3mg orally once daily, but more recent studies have focused on dosages of 0.4 or 0.8 mg/day currently recommended by the US Food and Drug Administration (FDA). Along with modest improvements in serum levels of triglycerides and high density lipoprotein (HDL)-cholesterol, cerivastatin 0.4 to 0.8 mg/day achieved marked reductions in serum levels of low density lipoprotein (LDL)-cholesterol (33.4 to 44.0%) and total cholesterol (23.0 to 30.8%). These ranges included results of a pivotal North American trial in almost 1000 patients with hypercholesterolaemia. In this 8-week study, US National Cholesterol Education Program (Adult Treatment Panel II) [NCEP] target levels for LDL-cholesterol were achieved in 84% of patients randomised to receive cerivastatin 0.8 mg/day, 73% of those treated with cerivastatin 0.4 mg/day and <10% of placebo recipients. Among patients with baseline serum LDL-cholesterol levels meeting NCEP guidelines for starting pharmacotherapy, 75% achieved target LDL-cholesterol levels with cerivastatin 0.8 mg/day. In 90% of all patients receiving cerivastatin 0.8 mg/day, LDL-cholesterol levels were reduced by 23.9 to 58.4% (6th to 95th percentile). Various subanalyses of clinical trials with cerivastatin indicate that the greatest lipid-lowering response can be expected in women and elderly patients. Cerivastatin is generally well tolerated and adverse events have usually been mild and transient. The overall incidence and nature of adverse events reported with cerivastatin in clinical trials was similar to that of placebo. The most frequent adverse events associated with cerivastatin were headache, GI disturbances, asthenia, pharyngitis and rhinitis. In the large pivotal trial, significant elevations in serum levels of creatine kinase and transaminases were reported in a small proportion of patients receiving cerivastatin but not in placebo recipients. As with other HMG-CoA reductase inhibitors, rare reports of myopathy and rhabdomyolysis have occurred with cerivastatin, although gemfibrozil or cyclosporin were administered concomitantly in most cases. Postmarketing surveillance studies in the US have been performed. In 3 mandated formulary switch conversion studies, cerivastatin was either equivalent or superior to other HMG-CoA reductase inhibitors, including atorvastatin, in reducing serum LDL-cholesterol levels or achieving NCEP target levels. Pharmacoeconomic data with cerivastatin are limited, but analyses conducted to date in the US and Italy suggest that cerivastatin compares favourably with other available HMG-CoA reductase inhibitors in terms of its cost per life-year gained.

CONCLUSION

Cerivastatin is a well tolerated and effective lipid-lowering agent for patients with hypercholesterolaemia. When given at dosages currently recommended by the FDA in the US, cerivastatin achieves marked reductions in serum levels of LDL-cholesterol, reaching NCEP target levels in the vast majority of patients. Thus, cerivastatin provides a useful (and potentially cost effective) alternative to other currently available HMG-CoA reductase inhibitors as a first-line agent for hypercholesterolaemia.

New insights into the pharmacodynamic and pharmacokinetic properties of statins

The beneficial effects of statins are assumed to result from their ability to reduce cholesterol biosynthesis. However, because mevalonic acid is the precursor not only of cholesterol, but also of many nonsteroidal isoprenoid compounds, inhibition of 3-hydroxy-3-methylglutaryl coenzyme A reductase may result in pleiotropic effects. It has been shown that several statins decrease smooth muscle cell migration and proliferation and that sera from fluvastatin-treated patients interfere with its proliferation. Cholesterol accumulation in macrophages can be inhibited by different statins, while both fluvastatin and simvastatin inhibit secretion of metalloproteinases by human monocyte-derived macrophages. The antiatherosclerotic effects of statins may be achieved by modifying hypercholesterolemia and the arterial wall environment as well. Although statins rarely have severe adverse effects, interactions with other drugs deserve attention. Simvastatin, lovastatin, cerivastatin, and atorvastatin are biotransformed in the liver primarily by cytochrome P450-3A4, and are susceptible to drug interactions when co-administered with potential inhibitors of this enzyme. Indeed, pharmacokinetic interactions (e.g., increased bioavailability), myositis, and rhabdomyolysis have been reported following concurrent use of simvastatin or lovastatin and cyclosporine A, mibefradil, or nefazodone. In contrast, fluvastatin (mainly metabolized by cytochrome P450-2C9) and pravastatin (eliminated by other metabolic routes) are less subject to this interaction. Nevertheless, a 5- to 23-fold increase in pravastatin bioavailability has been reported in the presence of cyclosporine A. In summary, statins may have direct effects on the arterial wall, which may contribute to their antiatherosclerotic actions. Furthermore, some statins may have lower adverse drug interaction potential than others, which is an important determinant of safety during long-term therapy.

Drug, meal and formulation interactions influencing drug absorption after oral administration. Clinical implications

Drug-drug, drug-formulation and drug-meal interactions are of clinical concern for orally administered drugs that possess a narrow therapeutic index. This review presents the current status of information regarding interactions which may influence the gastrointestinal (GI) absorption of orally administered drugs. Absorption interactions have been classified on the basis of rate-limiting processes. These processes are put in the context of drug and formulation physicochemical properties and oral input influences on variable GI physiology. Interaction categorisation makes use of a biopharmaceutical classification system based on drug aqueous solubility and membrane permeability and their contributions towards absorption variability. Overlaying this classification it is important to be aware of the effect that the magnitudes of drug dosage and volume of fluid administration can have on interactions involving a solubility rate limits. GI regional differences in membrane permeability are fundamental to the rational development of extended release dosage forms as well as to predicting interaction effects on absorption from immediate release dosage forms. The effect of meals on the regional-dependent intestinal elimination of drugs and their involvement in drug absorption interactions is also discussed. Although the clinical significance of such interactions is certainly dependent on the narrowness of the drug therapeutic index, clinical aspects of absorption delays and therapeutic failures resulting from various interactions are also important.

A pharmacokinetic evaluation of pravastatin in middle-aged and elderly volunteers

The pharmacokinetics of pravastatin, a serum-cholesterol-lowering drug, were studied in 20 middle-aged (46-59 years old, n = 8) and elderly subjects (60-81 years old, n = 12). Pravastatin serum levels were determined by HPLC and solid phase extraction. Cmax was 48.9 +/- 7.1 ng/ml (mean +/- SEM, n = 20), and the mean AUC0-4.5h was 104.4 ng x h/ml (n = 5) for a 20 mg daily oral dose. A great interindividual variability was found for Cmax, which varied from 6.2 ng/ml to 117.8 ng/ml on the 20 mg dose. As could be expected, Cmax and AUC0-4.5h were dose-related, but Tmax and t1/2 were not. In six cases, the elimination of the drug in serum could be described by a single phase but in four cases with two phases. No significant difference was found in Cmax between the middle-aged and the elderly or between males and females.

Pravastatin alone and in combination with low-dose cholestyramine in patients with primary hypercholesterolemia and coronary artery disease

This randomized, open-label study compared the cost efficiency of low-dose pravastatin combined with low-dose cholestyramine with high-dose pravastatin monotherapy in 59 patients with moderate hypercholesterolemia and coronary disease. Both regimes were effective in improving lipid profiles in these patients; however, low-dose combination therapy enhanced achievement in therapeutic goals and cost efficiency.

Pharmacodynamics and pharmacokinetics of the HMG-CoA reductase inhibitors. Similarities and differences

Hypercholesterolaemia plays a crucial role in the development of atherosclerotic diseases in general and coronary heart disease in particular. The risk of progression of the atherosclerotic process to coronary heart disease increases progressively with increasing levels of total serum cholesterol or low density lipoprotein (LDL) cholesterol at both the individual and the population level. The statins are reversible inhibitors of the microsomal enzyme HMG-CoA reductase, which converts HMG-CoA to mevalonate. This is an early rate-limiting step in cholesterol biosynthesis. Inhibition of HMG-CoA reductase by statins decreases intracellular cholesterol biosynthesis, which then leads to transcriptionally upregulated production of microsomal HMG-CoA reductase and cell surface LDL receptors. Subsequently, additional cholesterol is provided to the cell by de novo synthesis and by receptor-mediated uptake of LDL-cholesterol from the blood. This resets intracellular cholesterol homeostasis in extrahepatic tissues, but has little effect on the overall cholesterol balance. There are no simple methods to investigate the concentration-dependent inhibition of HMG-CoA reductase in human pharmacodynamic studies. The main clinical variable is plasma LDL-cholesterol, which takes 4 to 6 weeks to show a reduction after the start of statin treatment. Consequently, a dose-effect rather than a concentration-effect relationship is more appropriate to use in describing the pharmacodynamics. Fluvastatin, lovastatin, pravastatin and simvastatin have similar pharmacodynamic properties; all can reduce LDL-cholesterol by 20 to 35%, a reduction which has been shown to achieve decreases of 30 to 35% in major cardiovascular outcomes. Simvastatin has this effect at doses of about half those of the other 3 statins. The liver is the target organ for the statins, since it is the major site of cholesterol biosynthesis, lipoprotein production and LDL catabolism. However, cholesterol biosynthesis in extrahepatic tissues is necessary for normal cell function. The adverse effects of HMG-reductase inhibitors during long term treatment may depend in part upon the degree to which they act in extrahepatic tissues. Therefore, pharmacokinetic factors such as hepatic extraction and systemic exposure to active compound(s) may be clinically important when comparing the statins. Different degrees of liver selectivity have been claimed for the HMG-CoA reductase inhibitors. However, the literature contains confusing data concerning the degree of liver versus tissue selectivity. Human pharmacokinetic data are poor and incomplete, especially for lovastatin and simvastatin, and it is clear that any conclusion on tissue selectivity is dependent upon the choice of experimental model. However, the drugs do differ in some important aspects concerning the degree of metabolism and the number of active and inactive metabolites. The rather extensive metabolism by different cytochrome P450 isoforms also makes it difficult to characterise these drugs regarding tissue selectivity unless all metabolites are well characterised. The effective elimination half-lives of the hydroxy acid forms of the 4 statins are 0.7 to 3.0 hours. Protein binding is similar (> 90%) for fluvastatin, lovastatin and simvastatin, but it is only 50% for pravastatin. The best characterised statins from a clinical pharmacokinetic standpoint are fluvastatin and pravastatin. The major difference between these 2 compounds is the higher liver extraction of fluvastatin during the absorption phase compared with pravastatin (67 versus 45%, respectively, in the same dose range). Estimates of liver extraction in humans for lovastatin and simvastatin are poorly reported, which makes a direct comparison difficult.

Pravastatin. A reappraisal of its pharmacological properties and clinical effectiveness in the management of coronary heart disease

Pravastatin is an HMG-CoA reductase inhibitor which lowers plasma cholesterol levels by inhibiting de novo cholesterol synthesis. Pravastatin produces consistent dose-dependent reductions in both total and low density lipoprotein (LDL)-cholesterol levels in patients with primary hypercholesterolaemia. Favourable changes in other parameters such as total triglyceride and high density lipoprotein (HDL)-cholesterol levels are generally modest. Combination therapy with other antihyperlipidaemic agents such as cholestyramine further enhances the efficacy of pravastatin in patients with severe dyslipidaemias. Available data suggest that pravastatin is effective in elderly patients and in patients with hypercholesterolaemia secondary to diabetes mellitus or renal disease. The benefit of cholesterol-lowering in terms of patient outcomes is currently an area of considerable interest. Recently completed regression studies (PLAC I, PLAC II, KAPS and REGRESS) show that pravastatin slows progression of atherosclerosis and lowers the incidence of coronary events in patients with mild to moderately severe hypercholesterolaemia and known coronary heart disease. Large scale primary (WOSCOPS) and secondary (CARE) prevention studies, moreover, demonstrate that pravastatin has beneficial effects on coronary morbidity and mortality. In WOSCOPS, all-cause mortality was reduced by 22%. Pravastatin is generally well tolerated by most patients (including the elderly), as evidenced by data from studies of up to 5 years in duration. As with other HMG-CoA reductase inhibitors, myopathy occurs rarely (< 0.1% of patients treated with pravastatin): approximately 1 to 2% of patients may present with raised serum levels of hepatic transaminases. Thus, with its favourable effects on cardiovascular morbidity/mortality and total mortality, pravastatin should be considered a first-line agent in patients with elevated cholesterol levels, multiple risk factors or coronary heart disease who are at high risk of cardiovascular morbidity.

Clinical pharmacokinetics of 3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors

3-Hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase is the key enzyme of cholesterol synthesis. HMG-CoA reductase inhibitors are potent reversible inhibitors of this enzyme, which act by competing for the substrate HMG-CoA. This review is mainly devoted to the 4 main HMG-CoA reductase inhibitors used today: lovastatin, simvastatin, pravastatin and fluvastatin. Depending upon the dosage, these drugs are able to reduce plasma cholesterol levels by more than 40%. After absorption, each undergoes extensive hepatic first-pass metabolism. Up to 5 primary metabolites are formed, some of which are active inhibitors. The elimination half-lives vary from 0.5 to 3.5 hours and excretion is mainly via the faeces. A limited number of drug interactions has been reported. Increases in liver enzymes and muscle creatine kinase activity are among the most severe adverse effects. These powerful drugs should be reserved for patients with high plasma cholesterol levels and/or those with cardiovascular disease. New therapeutic approaches to atherosclerosis are currently under investigation. HMG-CoA reductase inhibitors are the cornerstone of this research.

Pravastatin modulates cholesteryl ester transfer from HDL to apoB-containing lipoproteins and lipoprotein subspecies profile in familial hypercholesterolemia

Familial hypercholesterolemia (FH) results from genetic defects in the LDL receptor, and is characterized by a marked elevation in plasma LDL and by qualitative abnormalities in LDL particles. Because LDL particles are major acceptors of cholesteryl esters (CEs) from HDL, significant changes occur in the flux of CE through the reverse cholesterol pathway. To evaluate the effects of an HMG-CoA reductase inhibitor, pravastatin, on CE transfer from HDL to apo B-containing lipoproteins and on plasma lipoprotein subspecies profile in subjects with heterozygous FH, we investigated the transfer of HDL-CE to LDL subfractions and changes in both concentration and chemical composition of the apo B- and the apo AI-containing lipoproteins. After pravastatin treatment (40 mg/d) for a 12-week period, plasma LDL concentrations (mean +/- SD, 745.4 +/- 51.9 mg/dL) were reduced by 36% in patients with FH (n = 6). By contrast, the qualitative features of the density profile of LDL subspecies in patients with FH, in whom the intermediate (d = 1.029 to 1.039 g/mL) and dense (d = 1.039 to 1.063 g/mL) subspecies were significantly increased relative to a control group, were not modified by pravastatin. In addition, no significant effect on the chemical composition of individual LDL subfractions was observed. Furthermore, plasma HDL concentrations were not modified, although the density distribution of HDL was normalized. Indeed, the HDL density peak was shifted towards the HDL2 subfraction (ratios of HDL2 to HDL3 were 0.7 and 1.1 before and after treatment, respectively). Evaluation of plasma CE transfer protein (CETP) mass was performed with an exogenous CE transfer assay. Under these conditions, no modification of plasma CETP protein mass was induced by pravastatin administration. However, the rate of CE transfer from HDL to LDL was reduced by 24% by pravastatin (61 +/- 17 micrograms CE.h-1.mL-1 plasma; P < .0005), although intermediate and dense LDL subfractions again accounted for the majority (71%) of the total CE transferred to LDL. Thus, pravastatin induced reduction of plasma CETP activity without change in the preferential targeting of the transfer of HDL-CE towards the denser LDL subfractions. In conclusion, pravastatin reduces the elevated flux of CE from HDL to apo B-containing lipoproteins in subjects with heterozygous FH as a result of a reduction in the LDL particle acceptor concentration.

Update on the treatment of hypercholesterolemia, with a focus on HMG-CoA reductase inhibitors and combination regimens

Numerous studies involving patients with hypercholesterolemia have demonstrated that reduction of lipid levels markedly reduces morbidity and mortality from cardiovascular disease. Diet alone may enable patients without established disease to attain target lipid levels, but pharmacotherapy generally is necessary for those with coronary artery disease. Choice of a suitable agent for monotherapy--a bile acid resin, niacin, or an HMG-CoA reductase inhibitor--may be determined by patient phenotype. For resistant cases, therapy combining an HMG-CoA reductase inhibitor with another agent generally is effective and well tolerated.

Gastrointestinal absorption of pravastatin in healthy subjects

The bioavailability of pravastatin, a hypocholesterolmic agent, may be enhanced by decreasing its exposure to stomach contents, where it may be converted nonenzymatically to a relatively inactive metabolite. The pharmacokinetics of pravastatin and its metabolite were determined after infusion of pravastatin directly into the stomach (locus for greatest bioavailability for the metabolite), duodenum (greatest bioavailability for pravastatin), jejunum, or ileum. An enterically coated formulation of pravastatin may increase its bioavailability.

Dyslipidemias and the secondary prevention of coronary heart disease

Dyslipidemias in patients with coronary heart disease confer a greater risk of ischemic cardiac events than comparable dyslipidemias in people free of disease. A major dyslipidemia can be diagnosed in more than 80% of patients with established premature coronary heart disease. These dyslipidemias constitute not only elevations of low-density lipoprotein cholesterol (hypercholesterolemia) but also indicate abnormalities in the metabolism of triglyceride-rich lipoproteins, high-density lipoproteins, and lipoprotein(a). Clinical trials have demonstrated that therapy to lower low-density lipoprotein levels can delay angiographic progression of coronary stenoses and reduce recurrent cardiac event rates. These clinical benefits from low-density lipoprotein cholesterol lowering may occur as early as 6 to 12 months after initiation of therapy. Intervention strategies for dyslipidemias are directed toward lowering the low-density lipoprotein cholesterol fraction to 90 to 100 mg/dl. This approach begins with dietary modification, weight loss, smoking cessation, and aerobic exercise. Patients with hypercholesterolemia refractory to nonpharmacologic intervention require lipid-lowering agents. The choice of lipid-lowering medications is influenced by concomitant abnormalities of lipoprotein metabolism, such as hypertriglyceridemia or hypoalphalipoproteinemia. Treatment of primary dyslipidemias other than hypercholesterolemia may be warranted in the presence of other cardiac risk factors; however, a broader spectrum of clinical trial data is needed to support or refute this contention.

Comparison of properties of four inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A reductase

Four inhibitors of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase have been approved for treatment of hypercholesterolemia. Three of these are fungal metabolites or derivatives thereof: lovastatin, simvastatin, and pravastatin. The fourth, fluvastatin, is totally synthetic. Its structure, containing a fluorophenyl-substituted indole ring, is distinct from that of the fungal metabolites. Lovastatin and simvastatin are administered as prodrugs, which undergo in vivo transformation to active inhibitory forms; fluvastatin and pravastatin are administered as active agents. The HMG-CoA reductase inhibitors are all effective in reducing plasma concentrations of low density lipoprotein. They have differing pharmacokinetic properties, which may be of importance in some patients. All of these drugs are very well tolerated, and there do not appear to be major differences in toxicity or adverse effects. When LDL reductions > 30% are needed, simvastatin is the most cost-effective HMG-CoA reductase inhibitor. However, these drugs are most commonly used in dosages that reduce LDL-C by 20-30%. For this degree of LDL reduction, fluvastatin is the most cost-effective HMG-CoA reductase inhibitor.

Drug treatment of dyslipoproteinemia

This article has focused on the appropriate indications for lipid-lowering drugs in adult patients with different lipoprotein disorders, which we have divided into primary hypercholesterolemia, combined hyperlipidemia,and hypertriglyceridemia. The mechanism of action, efficacy, and safety profile of the major drugs have been reviewed, and based on this information, we have presented our views on the appropriate drugs of first choice and appropriate second-choice agents for treatment of adult patients with different dyslipidemias. The rationale for the use of hypolipidemic drugs is strongest in patients with hyperlipidemia who concurrently have evidence for coronary or peripheral vascular disease, in whom the goal of secondary prevention is to retard further progression of atherosclerosis and potentially induce some regression, whereas in selected high-risk patients without evidence of atherosclerosis, the goals of therapy are to prevent the premature development of CAD or, in patients with severe hypertriglyceridemia, prevent the adverse sequelae of hepatomegaly, splenomegaly, and potentially pancreatitis. We have focused on the use of hypolipidemic drugs in adult patients, and the guidelines discussed are not appropriate for use in children with hyperlipidemia, in whom drug therapy should be undertaken selectively and in consultation with a lipid specialist. Many areas of controversy in the use of lipid-lowering drugs remain to be addressed by future studies; these include the use of lipid-lowering drugs in patients with secondary causes of hyperlipidemia (e.g., the nephrotic syndrome), the use of lipid-lowering drugs in women, and recommendations for drug therapy in older patients.