Comparative tolerability of the HMG-CoA reductase inhibitors

Risk-benefit of HMG-CoA reductase inhibitors in the treatment of HIV protease inhibitor-related hyperlipidaemia

HIV protease inhibitors decrease mortality and improve quality of life in patients with HIV infection. However, these drugs have been associated with serum lipid elevations, which may pose an increased risk of cardiovascular disease and pancreatitis. Treatment of protease inhibitor-related hyperlipidaemia (PIH) is complicated by drug interactions, which significantly increase concentrations of most 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase inhibitors (statins). Although pravastatin and atorvastatin effectively lower cholesterol and triglyceride concentrations in HIV-infected patients, a significant number of patients did not achieve their National Cholesterol Education Program low density lipoprotein concentration goals. Nonetheless, due to the increased risk of rhabdomyolysis with elevated statin concentrations, atorvastatin should be considered a second-line agent. The limited available PIH data supports the fact that pravastatin and atorvastatin are well-tolerated in HIV-infected individuals. More data are needed on the appropriate starting doses, maximum safe doses, role of combination statin-fibrate therapy, documentation of coronary heart disease benefit and incidence of myotoxicity and hepatotoxicity. Pravastatin has an acceptable risk-benefit ratio in PIH, while theoretical toxicity concerns exist with atorvastatin.

Statins: balancing benefits, efficacy and safety

Coronary heart disease (CHD) is the leading cause of death in the US. The risk of CHD is substantially increased in people with elevated levels of low-density lipoprotein cholesterol (LDL-C). The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) are the most effective drug class for lowering LDL-C. Long-term prospective studies have shown that statin therapy significantly reduces the risk of CHD morbidity and mortality in patients without or with evidence of established CHD (primary and secondary prevention, respectively). In 1988, treatment guidelines were first issued by the National Cholesterol Education Program Adult Treatment Panel I (NCEP-ATP I), then revised in 1993 (ATP II), to provide recommendations for the prevention and management of high cholesterol in adults. Despite these guidelines, recent national surveys have shown that effective therapies are being under-utilised and they often fail to achieve LDL-C goals established by NCEP-ATP II. The reasons appear to be multifactorial but include issues related to efficacy, safety, the potential for adverse drug reactions, failure to prescribe appropriate medication or dose and noncompliance with therapy. In the first major update of NCEP guidelines in almost a decade, the current ATP III recommendations have placed an increased number of Americans in the high-risk category, inviting even more aggressive therapy and escalating the challenge of reaching NCEP goals. New statins that may have even greater efficacy and less potential for drug interactions may help address some concerns associated with the failure to achieve treatment goals.

COX-2 selective inhibitors: analysis of the renal effects

COX-2 selective inhibitors provide analgesia and blunt inflammation while also sparing the gastrointestinal tract from classic NSAID toxicity. Therapeutic effects are thought to result from inhibition of the inflammatory COX-2 isoform. Organ sparing is considered the result of preservation of homeostatic COX-1 enzyme function. Similar roles of the COX isoforms in the kidney would reduce NSAID-associated nephrotoxicity. However, human kidney tissue expresses COX-2 enzyme, suggesting a role for this isoform in maintenance of physiological renal processes. Available clinical data on the renal effects of COX-2 selective inhibitors in humans also demonstrate nephrotoxic potential.

HMG-CoA reductase inhibitors and the malignant cell: the statin family of drugs as triggers of tumor-specific apoptosis

The statin family of drugs target HMG-CoA reductase, the rate-limiting enzyme of the mevalonate pathway, and have been used successfully in the treatment of hypercholesterolemia for the past 15 years. Experimental evidence suggests this key biochemical pathway holds an important role in the carcinogenic process. Moreover, statin administration in vivo can provide an oncoprotective effect. Indeed, in vitro studies have shown the statins can trigger cells of certain tumor types, such as acute myelogenous leukemia, to undergo apoptosis in a sensitive and specific manner. Mechanistic studies show bcl-2 expression is down-regulated in transformed cells undergoing apoptosis in response to statin exposure. In addition, the apoptotic response is in part due to the depletion of the downstream product geranylgeranyl pyrophosphate, but not farnesyl pyrophosphate or other products of the mevalonate pathway including cholesterol. Clinically, preliminary phase I clinical trials have shown the achievable plasma concentration corresponds to the dose range that can trigger apoptosis of tumor types in vitro. Moreover, little toxicity was evident in vivo even at high concentrations. Clearly, additional clinical trials are warranted to further assess the safety and efficacy of statins as novel and immediately available anti-cancer agents. In this article, the experimental evidence supporting a role for the statin family of drugs to this new application will be reviewed.

Calcineurin inhibitors and post-transplant hyperlipidaemias

Cardiovascular disease is now the leading cause of death in transplant recipients. This is due, in part, to the vulnerability of these patients to a complicated set of conditions including hypertension, diabetes mellitus, and post-transplant hyperlipidaemia (PTHL). PTHL is characterised by persistent elevations in total serum cholesterol, low density lipoprotein cholesterol and triglyceride levels. The causes of PTHL are complex and not fully understood, however several classes of immunosuppressants including the corticosteroids, rapamycins and calcineurin inhibitors, appear to play a role. PTHL has been observed in most studies in which patients received calcineurin inhibitor-based regimens, and has been observed with both tacrolimus and cyclosporin. Comparing these calcineurin inhibitors with regard to the relative incidence or severity of PTHL occurring during treatment is difficult because of the use of higher doses of corticosteroids in cyclosporin-based regimens, as compared with tacrolimus-based regimens. However, current expert opinion suggests that the discrepancies in the relative incidence and severity of PTHL are largely accounted for by this difference in corticosteroid dose. At this point in time, evidence for potential differences is scant and inconclusive. Further study is needed, not only to investigate differences in lipid profile, but also of the relative effects of these immunosuppressants on long term graft function as well as on cardiovascular morbidity and mortality. PTHL can be successfully managed with a combination of dietary management, reduction and, if appropriate, withdrawal of corticosteroids, and the administration of lipid-lowering drugs. With this combination of therapeutic options, the threats to long term health posed by PTHL may be effectively addressed.

Cyclosporin: an updated review of the pharmacokinetic properties, clinical efficacy and tolerability of a microemulsion-based formulation (neoral)1 in organ transplantation

Cyclosporin is a lipophilic cyclic polypeptide immunosuppressant that interferes with the activity of T cells chiefly via calcineurin inhibition. The original oil-based oral formulation of this drug (Sandimmun)l was characterised by high intra- and interpatient pharmacokinetic variability, with poor bioavailability in many patients; a novel microemulsion formulation (Neoral)1 was therefore developed to circumvent these problems. Studies show increases, attributable chiefly to improved absorption in patients who absorb the drug only poorly from the original formulation, in mean systemic exposure to cyclosporin with the microemulsion, with no clinically significant differences in tolerability or drug interaction profiles. Cyclosporin microemulsion is at least as effective as the oil-based formulation in renal, liver and heart transplant recipients, with trends towards decreased incidence of acute rejection with the microemulsion formulation in some (statistically significant in a few) trials. Cyclosporin microemulsion and tacrolimus appear to have similar efficacy in preventing acute rejection episodes in most renal, pancreas-kidney, liver and heart transplant recipients. However, there are indications of superior efficacy for tacrolimus in some trials, particularly in the prevention of severe acute rejection and in Black transplant recipients. Current 12-month data also indicate equivalent efficacy of sirolimus in renal transplantation. Conversion from the oil-based to microemulsion formulation in stable renal, liver and heart transplant recipients is achievable with no change in acute rejection rates. The addition of an anti-interleukin-2 receptor monoclonal antibody and/or mycophenolate mofetil to cyclosporin microemulsion plus corticosteroids decreases rates of acute rejection; corticosteroid withdrawal without increased acute rejection rates was also achieved on the addition of these agents in some trials. Pharmacoeconomic analyses have shown savings in direct healthcare costs in kidney or liver transplantation when cyclosporin microemulsion is used in preference to the oil-based formulation, although studies incorporating indirect costs or expressing costs in terms of therapeutic outcomes are currently unavailable.

CONCLUSIONS

The introduction of cyclosporin microemulsion has consolidated the place of the drug as a mainstay of therapy in all types of solid organ transplantation; research into optimisation of outcomes through more effective therapeutic monitoring in patients receiving this formulation is ongoing. Several novel immunosuppressants have been introduced in recent years: further clinical and pharmacoeconomic research will be needed to clarify the relative positioning of these agents, particularly with respect to specific patient groups. Other new drugs (basiliximab/daclizumab and mycophenolate mofetil) offer particular advantages when used in combination with cyclosporin.

Possible association of QTc interval prolongation with co-administration of quetiapine and lovastatin

BACKGROUND

QTc interval prolongation can occur as a result of treatment with both conventional and novel antipsychotic medications and is of clinical concern because of its association with the potentially fatal ventricular arrhythmia, torsade de pointes.

METHODS

One case is described in which a patient with schizophrenia, who was being treated for dyslipidemia, developed a prolonged QTc interval while taking quetiapine and lovastatin.

RESULTS

QTc returned to baseline when the lovastatin dose was reduced.

CONCLUSIONS

QTc prolongation associated with antipsychotic medication occurs in a dose-dependent manner. We therefore hypothesize that the addition of lovastatin caused an increase in plasma quetiapine levels through competitive inhibition of the cytochrome P(450) (CYP) isoenzyme 3A4. Our case highlights the potential for a drug interaction between quetiapine and lovastatin leading to QTc prolongation during the management of dysipidemia in patients with schizophrenia.

Safety and efficacy of simvastatin in hypercholesterolemic patients undergoing chronic renal dialysis

Dyslipidemia is universal but hypercholesterolemia per se is present in around 50% of dialysis patients. Although dietary therapy is of benefit in some, the majority require drug therapy. We compared the efficacy and safety of simvastatin plus an optimized lipid-lowering dialysis diet with placebo plus diet in a randomized, double-blind trial stratified for dialysis modality. Patients treated with hemodialysis (HD) or continuous ambulatory peritoneal dialysis (CAPD) for at least 9 months and with serum non-high-density lipoprotein (HDL) cholesterol greater than 135 mg/dL, low-density lipoprotein (LDL) greater than 116 mg/dL, and triglyceride less than 600 mg/dL after a 6-week dietary treatment phase and an 8-week diet plus placebo run-in phase, were enrolled in the 24-week double-blind treatment phase. Fifty-seven patients (16 men, 41 women, median age 63 years, range 22-75 yr) were randomized 2:1 to diet plus 5 mg/day simvastatin (n = 38: 22 HD, 16 CAPD) or diet plus placebo (n = 19: 12 HD, 7 CAPD) for 24 weeks. Dose was doubled bimonthly (maximum 20 mg/day) if non-HDL cholesterol was greater than 135 mg/dL. Forty-two patients (73.7%) completed the trial. Comparing baseline and 24 weeks, simvastatin (median 10 mg/day) was significantly more effective than placebo in reducing serum non-HDL cholesterol concentrations. For HD, the median percentage changes for total cholesterol (TC) (simvastatin versus placebo) were -21.4% and -12.1% (P = 0.011), respectively; for LDL cholesterol, -33.0% and -8.8% (P = 0.023); for non-HDL cholesterol, -25.2% and -14.0% (P = 0.008); and for TC:HDL, -17.65% and -1.67% (P = 0.008). For CAPD, changes for TC were -22.1% and -1.5% (P = 0.003), respectively; for LDL, -36.4% and 0.0% (P = 0.001); for non-HDL cholesterol, -24.9% and -3.6% (P = 0.002); and for TC:HDL ratio, -21.49% and +9.74% (P = 0.045). Changes with CAPD in apolipoprotein (Apo) A1 were -4.7% and +4.0% (P = 0.031); and for ApoB, -19.9% and +2.6%, respectively (P = 0.031). There were no significant changes in ApoA1 or ApoB with HD. Compared with placebo, triglyceride levels fell 10.2% with HD and 6.2% with CAPD. HDL cholesterol was unchanged with HD but rose 8.5% with CAPD. These trends, however, did not reach statistical significance (P > 0.05). There was no effect on Lp (a). The incidence of clinical and laboratory adverse experiences were not increased in the simvastatin-treated patients compared with placebo. Simvastatin appears to be a safe and effective treatment for the reduction of serum non-HDL cholesterol levels in both HD and, particularly, CAPD patients.

A general assessment of the safety of HMG CoA reductase inhibitors (statins)

Few principles in medicine today are as well accepted as the benefits of using statins to reduce cardiovascular risk factors and to prevent cardiovascular disease. The recent withdrawal of a statin (cerivastatin) has lead to a re-examination of all statins, and an attempt to better assess the risk-benefit ratio of this class of drugs. Although the benefits of statin treatment are well known from a myriad of clinical trials, the safety of these compounds has not been an issue since lovastatin was first introduced in 1987. This report provides a brief review of statin safety, and reiterates the excellent profile of this class of drugs.

Use of statins in CNS disorders

It is well established that 3-hydroxy-3-methyglutaryl coenzyme A (HMG-CoA) reductase inhibitors ("statins") reduce cholesterol levels and prevent coronary heart disease (CHD). Although a causal relation between elevated cholesterol levels and stroke has not been well defined, a number of large secondary prevention studies and meta-analyses have shown that statin therapy reduces stroke in patients with CHD and hypercholesterolemia. In addition to the vascular effects of statins (stabilization of atherosclerotic plaques, decreased carotid intimal-medial thickness), there are increasing data to suggest that these agents have additional properties that are potentially neuroprotective. These include endothelial protection via actions on the nitric oxide synthase system, as well as antioxidant, anti-inflammatory and anti-platelet effects. These actions of statins might have potential uses in other neurological disorders such as Alzheimer's disease and certain types of brain tumors.