Pharmacokinetics of cerivastatin in renal impairment are predicted by low serum albumin concentration rather than by low creatinine clearance

Impact of kidney dysfunction on hepatic and intestinal drug transporters

Emerging information suggests that pathology of the kidney may not only affect expression and function of membrane transporters in the organ, but also in the gastrointestinal tract and the liver. Transporter dysfunction may cause effects on handling of drug as well as endogenous compounds with subsequent clinical consequences. A literature search was conducted on Ovid and PubMed databases to select relevant in vitro, animal and human studies that have reported expression, protein abundance and function of the gastrointestinal and liver localized ABC transporters and SLC carriers in kidney dysfunction or uremia states. The altered function of drug transporters in the liver and intestines in kidney failure subjects may provide compensatory activity in handling endogenous compounds (e.g. uremic toxins), which is expected to affect drug pharmacokinetics and local drug actions.

Design, conduct, analysis, and interpretation of clinical studies in patients with impaired kidney function

Chronic kidney disease has been shown to alter the pharmacokinetics of drugs that are eliminated not only via the renal pathway but also by metabolism or nonrenal transport. Guidance documents from regulatory agencies on the pharmacokinetics of drugs in patients with impaired kidney function provide a framework for facilitating study design, conduct, data analysis, and the generation of dosing recommendations. Design considerations include establishment of appropriate enrollment criteria, selection of appropriate matched control group(s), and staging of impaired kidney function by estimated glomerular filtration rate or creatinine clearance. When studies in hemodialysis patients are conducted, optimizing the timing of characterization of the pharmacokinetics profile based on the schedule of hemodialysis sessions will allow for a robust assessment in these patients. In addition to traditional noncompartmental approaches, the use of pharmacometric approaches can integrate data from multiple clinical studies and provide a quantitative rationale for dose selection in patients with impaired kidney function. This article addresses the challenges and opportunities associated with the design, conduct, analysis, and interpretation of clinical studies to allow for their future facilitation and for the establishment of safe and efficacious dosing in patients with impaired kidney function.

Current understanding of drug disposition in kidney disease

Patients with chronic kidney disease (CKD) represent 13% of the American population. CKD has been shown to significantly alter drug disposition of nonrenally eliminated drugs. Indeed, modifications in the expression and function of intestinal and hepatic drug metabolism enzymes and uptake and efflux transporters have been reported. Uremic toxins, inflammatory cytokines, and parathyroid hormone have been implicated as causes. These changes can have an important clinical impact on drug disposition and lead to unintended toxicity if they are administered without dose adjustment in patients with impaired kidney function. This review summarizes recent preclinical and clinical studies and presents the current understanding of the effect of CKD on drug absorption, distribution, metabolism, and excretion.

Emerging evidence of the impact of kidney disease on drug metabolism and transport

Several lines of emerging evidence indicate that kidney disease differentially affects uptake and efflux transporters and metabolic enzymes in the liver and gastrointestinal (GI) tract, and uremic toxins have been implicated as the cause. In patients with kidney disease, even drugs that are eliminated by nonrenal transport and metabolism could lead to important unintended consequences if they are administered without dose adjustment for reduced renal function. This is particularly so in the case of drugs with narrow therapeutic windows and may translate into clinically significant variations in exposure and response.

Effects of renal failure on drug transport and metabolism

Renal failure not only alters the renal elimination, but also the non-renal disposition of drugs that are extensively metabolized by the liver. Although reduced metabolic enzyme activity in some cases can be responsible for the reduced drug clearance, alterations in the transporter systems may also be involved in the process. With the development of renal failure, the renal secretion of organic ions mediated by organic anion transporters (OATs) and organic cation transporters (OCTs) is decreased. 3-Carboxy-4-methyl-5-propyl-2-furanpropanoic acid (CMPF) and other organic anionic uremic toxins may directly inhibit the renal excretion of various drugs and endogenous organic acids by competitively inhibiting OATs. In addition, the expression of OAT1 and OCT2 was reduced in chronic renal failure (CRF) rats. Renal failure also impairs the liver uptake of drugs and organic anions, such as bromosulphophthalein (BSP), indocyanine green (ICG), and thyroxine, where organic anion transport polypeptides (OATPs) are the major transporters. Most previous studies have been done in animals or cell culture, very often in rat models, but these are presumed to reflect the presentation of advanced renal disease in humans as well. Recent studies demonstrate that the uremic toxins CMPF and indoxyl sulfate (IS) can directly inhibit rOatp2 and hOATP-C in hepatocytes. The protein content of the liver uptake transporters Oatp1, 2, and 4 were significantly decreased in CRF rats. Decreased activity of the intestinal efflux transporter, P-glycoprotein (P-gp), was also observed in CRF rats, with no significant change of protein content, suggesting that uremic toxins may suppress P-gp function. However, increased protein levels of multidrug resistance-associated protein (MRP) 2 in the kidney and MRP3 in the liver were found in CRF rats, suggesting an adaptive response that may serve as a protective mechanism. Increases in drug areas under the curve (AUCs) in subjects with advanced renal disease for drugs that are not renally excreted are consistent with uremic toxin effects on either intestinal or hepatic cell transporters, metabolizing enzymes, or both. In conclusion, alterations of drug transporters, as well as metabolic enzymes, in patients with renal failure can be responsible for reduced drug clearance.

EFFECTS OF UREMIC TOXINS ON HEPATIC UPTAKE AND METABOLISM OF ERYTHROMYCIN

Hepatic clearance of erythromycin (Ery) is significantly reduced in patients with end stage renal disease. Since Ery is primarily eliminated via excretion of unchanged drug in the bile, we suspect that this change could be due to the effect of uremic toxins on hepatic uptake and/or efflux transporters. Using rat hepatocytes and microsomes as model proof of concept systems, we examined six uremic toxins, 3-carboxy-4-methyl-5-propyl-2-furan-propanoic acid (CMPF), indoxyl sulfate (IS), hippuric acid (HA), indole acetic acid (IA), guanidinosuccinic acid (GSA), and indoxyl-beta-D-glucuronide (IG), for their effects on Ery uptake and metabolism. Ery and the metabolite N-demethyl-Ery were measured by liquid chromatography/tandem mass spectrometry. The uptake of Ery by rat hepatocytes was markedly inhibited by rifampin and digoxin, but not by quinidine, suggesting that Oatp2 plays a major role in the uptake of Ery. At 50 microM, CMPF significantly (p < 0.05) reduced hepatocyte accumulation of Ery and N-demethyl-Ery. At higher concentrations (>200 microM), CMPF appears to also inhibit the enzymatic metabolism of Ery. In contrast, IS did not significantly inhibit the hepatocyte uptake of Ery, even at the highest concentration (800 microM) tested, but reduced metabolite generation (p < 0.001). The other uremic toxins, HA, IA, IG, and GSA, did not affect either hepatic uptake or microsomal metabolism of Ery. CMPF, IS, and HA were shown not to inhibit differential P-glycoprotein transport of Ery in cellular systems. Our results suggest that CMPF can directly inhibit the uptake of Ery by inhibiting Oatp2, whereas IS is more likely to inhibit the enzymatic metabolism of Ery.

Statins and renal function

Renal disease is often associated with an increased risk of vascular events. Moreover, an accelerated form of atherosclerosis commonly occurs in these patients. The reasons for these associations are not clearly defined but include the widespread presence of several established risk factors (eg, dyslipidemia, hypertension, and diabetes). Other predictors of atherosclerotic disease may also be abnormally elevated (eg, homocysteine, fibrinogen, and lipoprotein a). In addition, there is evidence that impaired renal function per se predicts vascular risk. Despite this high-risk background, the potential benefit of treatment with statins has not been widely investigated in these patients. The present review considers the evidence (experimental and clinical) that statins exert beneficial effects in patients with different types of renal disease. This includes improved renal function, decreased microalbuminuria, and a fall in blood pressure. Statins may also improve renal allograft survival. The potential mechanisms mediating these effects are considered. The interactions between statins and several risk factors that may be present in patients with impaired renal function are also considered. There is an urgent need to define the role of statins in these high-risk patients. Which is the statin of choice? This question is relevant because impaired renal function can interfere with statin pharmacokinetics. Furthermore, other drugs administered to these patients may cause serious interactions with statins.

The CHORUS (Cerivastatin in Heart Outcomes in Renal Disease: Understanding Survival) protocol: a double-blind, placebo-controlled trial in patients with esrd

The 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor (statin)-mediated lowering of serum cholesterol has been associated with a significant reduction in cardiovascular morbidity and mortality. Recent studies suggest that additional non-lipid lowering effects (eg, endothelial stabilization, anti-inflammatory, antithrombogenic) may be important in modulating their effectiveness. Dyslipidemia is common in end-stage renal disease (ESRD), and hemodialysis patients have increased cardiovascular morbidity and mortality. Cerivastatin, a new statin with powerful low-density lipoprotein-cholesterol (LDL-C) lowering capabilities, possesses some unique non-LDL-C-mediated properties that may contribute to a reduction of coronary events in the patient with ESRD. The primary objective of this multicenter multinational study of 1,054 hemodialysis patients is to compare 2 years of treatment with cerivastatin (0.4 mg/d) versus placebo on the composite clinical event rate of myocardial infarction, sudden cardiac death, ischemic stroke, and the need for coronary arterial bypass graft (CABG) or percutaneous transluminal coronary angioplasty (PTCA) procedures in these patients. Changes in lipids, inflammatory proteins including heat stable C-reactive protein (hsCRP), interleukin-6 (IL-6), oncostatin-M, intracellular adhesion molecule-1 (ICAM-1) and monocyte-chemoattractant protein-1 (MCP-1), as well as markers of cardiac muscle pathology, such as troponin I and troponin T, will be assessed in a subset of patients. This study is the first of its kind to assess the effect of a statin on the reduction of cardiovascular morbidity and mortality in an incident hemodialysis population. It will determine whether treatment with cerivastatin can effectively reduce the significant cardiovascular morbidity and mortality.

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.

Clinical pharmacokinetics of cerivastatin

Cerivastatin sodium, a novel statin, is a synthetic, enantiomerically pure, pyridine derivative that effectively reduces serum cholesterol levels at microgram doses. Cerivastatin is readily and completely absorbed from the gastrointestinal tract, with plasma concentrations reaching a peak 2 to 3 hours postadministration followed by a monoexponential decay with an elimination half-life (t1/2beta) of 2 to 3 hours. Cerivastatin pharmacokinetics are linear: maximum plasma concentration (Cmax) and area under the concentration-time curve (AUC) are proportional to the dose over the range of 0.05 to 0.8 mg. No accumulation is observed on repeated administration. Cerivastatin interindividual variability is described by coefficients of variation of approximately 30 to 40% for its primary pharmacokinetic parameters AUC, Cmax and t1/2beta. The mean absolute oral bioavailability of cerivastatin is 60% because of presystemic first-pass effects. Its pharmacokinetics are not influenced by concomitant administration of food nor by the time of day at which the dose is given. Age, gender, ethnicity and concurrent disease also have no clinically significant effects. Cerivastatin is highly bound to plasma proteins (>99%). The volume of distribution at steady state of about 0.3 L/kg indicates that the drug penetrates only moderately into tissue; conversely, preclinical studies have shown a high affinity for liver tissue, the target site of action. Cerivastatin is exclusively cleared via metabolism. No unchanged drug is excreted. Cerivastatin is subject to 2 main oxidative biotransformation reactions: demethylation of the benzylic methyl ether moiety leading to the metabolite M-1 [catalysed by cytochrome P450 (CYP) 2C8 and CYP3A4] and stereoselective hydroxylation of one methyl group of the 6-isopropyl substituent leading to the metabolite M-23 (catalysed by CYP2C8). The product of the combined biotransformation reactions is a secondary minor metabolite, M-24, not detectable in plasma. All 3 metabolites are active inhibitors of hydroxymethylglutaryl-coenzyme A reductase with a similar potency to the parent drug. Approximately 70% of the administered dose is excreted as metabolites in the faeces, and 30% in the urine. Metabolism by 2 distinct CYP isoforms renders cerivastatin relatively resistant to interactions arising from inhibition of CYP. If one of the pathways is blocked, cerivastatin can be effectively metabolised by the alternative route. In addition, on the basis of in vitro investigations, there is no evidence for either cerivastatin or its metabolites having any inducing or inhibitory activity on CYP. The apparent lack of any clinically relevant interactions with a variety of drugs commonly used by patients in the target population supports this favourable drug-drug interaction profile.