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Biomedical subjects

Michael H Davidson

Publications and source records attributed to Michael H Davidson.

At least 55 records · Page 3Linked to original sources
PubMed2005

Simvastatin plus ezetimibe: combination therapy for the management of dyslipidaemia.

Hyperlipidaemia is a pivotal risk factor for the development of atherosclerotic disease. A large number of studies have demonstrated that the treatment of abnormalities in lipoprotein levels reduces the risk for myocardial infarction, peripheral vascular disease, carotid artery disease, stroke, and cardiovascular mortality. Despite the development of multiple drug classes to treat dyslipidaemias and the promulgation of clearly defined guidelines for the management of lipid disorders, dyslipidaemia tends to be undertreated in the majority of patients at risk for cardiovascular disease. A part of the reluctance to treat different lipoprotein fractions to goal levels is attributable to physician- and patient-related concerns over the increasing toxicity of available therapies, as their dosages are increased. The risks of hepatotoxicity, myalgia, and rhabdomyolysis are fairly well characterised in patients receiving statins, fibrates and niacin. Another issue affecting treatment success rates is the fact that many patients with complex dyslipidaemias are inadequately responsive to single-agent therapy. As the epidemics of obesity, metabolic syndrome and diabetes mellitus continue to worsen, physicians will encounter severe, mixed dyslipidaemias more frequently. Many of these patients will require combinations of drugs to address the various metabolic derangements causing changes in multiple lipoprotein fractions. Although the need for combination therapy is well-established in the management of disorders, such as hypertension and diabetes, it is less often used for the treatment of dyslipidaemias. The development of safe, cost-effective, and efficacious combination dyslipidaemic therapy is an important goal in cardiovascular medicine. Simvastatin plus ezetimibe has recently been combined as a fixed dose therapy, which offers clinicians the opportunity to simultaneously inhibit two key pathways in cholesterol metabolism: hepatic cholesterol biosynthesis and the absorption of cholesterol at the level of the proximal jejunum. This dual mechanism of inhibition substantially increases the capacity to decrease serum levels of atherogenic low-density lipoproteins and increase high-density lipoprotein, compared with that observed when either drug is used alone. This combination increases the likelihood of therapeutic success in patients with dyslipidaemia.

Azetidines↗
PubMed2005

Cholesterol absorption blockade with ezetimibe.

The reduction of circulating atherogenic lipoproteins through lifestyle modification and pharmacologic intervention is an important therapeutic goal in patients at risk for acute cardiovascular events. A large number of clinical trials have demonstrated that the reduction of low-density lipoprotein cholesterol (LDL-C) is associated with significant decreases in the incidence of all cause mortality, stroke, fatal and nonfatal myocardial infarction, and the need for revascularization with coronary artery bypass grafting and percutaneous transluminal coronary angioplasty. Therapy with 3-hydroxy-3-methylglutaryl coenzyme A (HMG CoA) reductase inhibitors (i.e., statins) are the agents of choice for treating a variety of dyslipidemias, particularly when LDL-C levels are elevated. The statins are highly efficacious; however, not all patients are able to tolerate the higher doses of these medications due to adverse side-effects such as hepatoxicity and myotoxicity. Moreover, many patients cannot achieve their various lipoprotein targets at even the highest doses of these medications. Ezetimibe is a novel cholesterol absorption inhibitor that blocks the translocation of dietary and biliary cholesterol from the gastrointestinal lumen into the intracellular space of jejunal enterocytes. Ezetimibe undergoes enterohepatic recirculation with minimal systemic exposure and not does not adversely impact the pharmacokinetic profile of statins. Ezetimibe significantly reduces serum LDL-C. It is safe when used as monotherapy or when used in combination with statins. Ezetimibe is indicated in the management of hyperlipidemia, familial hypercholesterolemia, and sitosterolemia and significantly increases the percentage of patients able to reach their lipid-lowering goals.

Anticholesteremic Agents↗
PubMed2004

Evidence for altered positional specificity of LCAT in vivo: studies with docosahexaenoic acid feeding in humans.

The percentage of saturated cholesteryl esters (CEs) synthesized by human LCAT is several times higher than expected from the sn-2 acyl composition of plasma phosphatidylcholine (PC), whereas the synthesis of 20:4 CE and 22:6 CE is much lower than expected. To explain these discrepancies, we proposed that LCAT transfers some saturated fatty acids from the sn-1 position of PC species that contain 20:4 or 22:6 at sn-2. The present studies provide in vivo evidence for this hypothesis. We determined the composition and synthesis of CE species in plasma of volunteers before and after a 6 week dietary supplementation with docosahexaenoic acid (22:6; DHA). In addition to an increase in the DHA content of all plasma lipids, there was a significant (+12%; P <0.005) increase of 16:0 CE, although there was no increase in 16:0 at sn-2 of PC. The increase of DHA in CE was much lower than its increase at sn-2 of PC. Ex vivo synthesis of CE species in plasma showed a significant (+24%; P <0.005) increase in the synthesis of 16:0 CE after DHA supplementation, which correlated positively with the increase of 22:6, but not of 16:0, at sn-2 of PC. These results show that the positional specificity of human LCAT is altered when the concentration of 16:0-22:6 PC is increased by DHA supplementation.

Docosahexaenoic Acids↗
PubMed2004

Emerging therapeutic strategies for the management of dyslipidemia in patients with the metabolic syndrome.

The benefits of lipid-lowering therapy in significantly reducing cardiovascular events has been established in many at-risk populations. However, patients with the metabolic syndrome (MS) pose a challenge for clinical management. A high degree of residual risk exists in patients with the MS or diabetes mellitus, and this is of growing importance because of the increasing prevalence of obesity and its associated comorbidities in the world. As the MS has emerged as a major risk factor for both cardiovascular disease and diabetes, targeting treatment to achieve aggressive goals becomes paramount. This article reviews emerging therapeutic strategies for the management of dyslipidemia in patients with the MS.

Adult↗
PubMed2004

Biologic therapies for dyslipidemia.

Biologic therapies involve the utilization of proteins, DNA, antibodies, or other substances derived or synthesized from living tissue for therapeutic effects. There are several biologic therapies in clinical development for the prevention and treatment of atherosclerosis. The most advanced in human trials are apolipoprotein mimetics, which include apolipoprotein A-1 Milano and phospholipid complexes. Infusions of these apolipoprotein mimetics have been demonstrated to reduce atherosclerotic development in both animal models and humans. Autoimmunization to create neutralizing antibodies to cholesteryl ester transfer protein is also in human trials. Gene therapies to reduce low-density lipoproteins and increase high-density lipoproteins are on the horizon, but the ability to safely prolong gene expression in humans will require the development of novel vectors.

Apolipoprotein A-I↗
PubMed2004

Therapeutic interventions targeted at the augmentation of reverse cholesterol transport.

PURPOSE OF REVIEW: Serum high-density lipoproteins (HDLs) and reverse cholesterol transport (RCT) are important therapeutic targets in the management of atherosclerotic disease. This review summarizes the pathway of RCT and the currently available means by which investigators are attempting to modulate HDL levels and increase rates of RCT. RECENT FINDINGS: Low levels of HDL are commonly encountered in patients with atherosclerotic disease. HDLs mediate a substantial number of antiatherogenic effects along blood vessel walls. One of the most important of these antiatherogenic mechanisms is RCT, a series of reactions by which HDL is able to facilitate the net translocation of cholesterol from peripheral cells to the liver for excretion. There is scientific evidence supporting the concept of RCT in both animals and humans. To facilitate RCT, it is important that therapeutic effort be made to raise serum levels of HDL. Statins, fibrates, niacin, thiazolidinediones, and various combinations of these drugs all raise HDL levels. However, in many high-risk patients with established atherosclerotic disease, the elevations in HDL achieved with these medications are frequently inadequate. Newer agents designed to raise HDL and promote RCT are currently being developed, including infusible bioengineered HDL, edible HDL composed of D-amino acids, and agents capable of inhibiting cholesterol ester transfer protein, among others. SUMMARY: Established therapies for raising HDL can be effective either as monotherapy or when used in combination. Newer strategies are being developed to exploit more specifically the capacity of HDL to drive RCT and either prevent or reverse the course of atherosclerotic disease.

Apolipoprotein A-I↗
PubMed2004

Combination therapy in the management of complex dyslipidemias.

PURPOSE OF REVIEW: Patients with dyslipidemias continue to be undertreated in both the primary and secondary prevention settings. Many patients have therapeutic needs that exceed simple reductions in low-density lipoprotein levels using statins. This review discusses the need for comprehensive management of all abnormalities in a given patient's lipoprotein profile and for the use of combinations of anti-lipidemic medications, when indicated. RECENT FINDINGS: The majority of high-risk patients with manifestations of atherosclerotic disease or who have a coronary artery disease risk equivalent are not meeting their various lipoprotein targets. There is considerable reluctance to titrate statins and to use combinations of anti-lipidemic medications in patients not reaching their various lipoprotein targets. Combinations of anti-lipidemic medications can be specifically tailored to address abnormalities in multiple lipoprotein fractions. Recent clinical trials clearly demonstrate that combination therapy is well tolerated and facilitates lipoprotein goal attainment. SUMMARY: Therapeutic approaches that incorporate the use of multiple anti-lipidemic medications should be more widely adopted in order to increase the number of patients able to meet their lipoprotein goals and to produce more substantially reduced risks for acute cardiovascular events.

Algorithms↗
PubMed2004

Effect of contrast enhancement on measurement of carotid artery intimal medial thickness.

Previous studies have used standard B-mode ultrasound to quantify the aggregate mean intimal medial thickness (IMT) of the near and far wall of the common carotid artery (CCA). Many investigators have had difficulty in accurately evaluating the near wall IMT secondary to difficulty in discerning the vessel lumen and intima. The purpose of this study is to determine the effect of contrast enhanced ultrasound on IMT measurement when compared with non-enhanced images. Twenty-six patients who had standard carotid ultrasounds completed over a 6-month period were evaluated, with 24 imaged by the same sonographer. Five to six measurements of the near and far walls were obtained over a 1 cm distance, beginning and ending 0.5 cm and 1.5 cm proximal to the carotid bifurcation. The measurements were made with and without the contrast agent Optison (perflutren protein type-A microspheres), which was given as an i.v. bolus (0.5-0.7 cc). Of those imaged by the same sonographer, 40 carotid arteries were examined and a total of 867 measurements were obtained. A total of 10% of the carotid ultrasounds were restudied approximately 1 month after the initial interpretation to assess observer accuracy. The near wall CCA mean (SD) IMT was 0.075 (0.019) cm for left with contrast versus 0.067 (0.023) cm for left without contrast and 0.089 (0.024) cm for right with versus 0.071 (0.022) cm for right without, p < or = 0.0001 both sides. For the far wall of the CCA, the mean (SD) IMT comparison was 0.075 (0.021) cm for left with versus 0.070 (0.016) cm for left without, p = 0.005, and 0.070 (0.023) cm for right with versus 0.070 (0.016) cm for right without, p = 0.68. In conclusion, contrast-enhanced IMT measurement showed a highly statistically significant difference in near carotid wall thickness determinations versus non-contrast values. The thicker measurement is in agreement with previously reported data showing that non-contrast images underestimated near wall common carotid IMT in histologic samples.

Aged↗
PubMed2004

Rosuvastatin safety: lessons from the FDA review and post-approval surveillance.

Rosuvastatin is the first statin approved by the regulatory authorities since the withdrawal of cerivastatin. Although highly efficacious, this new statin has generated considerable controversy regarding its safety. Rosuvastatin was approved for clinical use based on the largest pre-approval database for all statins prior to commercial use. In this database, rosuvastatin had a similar safety profile to other approved statins up to the highest approval dose of 40 mg. As with all statins, there is a marked increase in adverse effects when the dose is titrated from 40 to 80 mg, and rosuvastatin demonstrates a similar dose/toxicity relationship. In the pre-approval data trials on 80 mg, there was a 1.0% (n = 16) incidence of myopathy and 7 patients developed rhabdomyolysis. However the <or= 40 mg doses had a myopathy rate similar to other statins. In the post-marketing surveillance for rosuvastatin, there have been reports of rhabdomyolysis, but the incidence rate, when corrected for prescription utilisation, is similar to other statins following initial approval.

Acute Kidney Injury↗
PubMed2003

Comparison of the efficacy and safety of rosuvastatin versus atorvastatin, simvastatin, and pravastatin across doses (STELLAR* Trial).

The primary objective of this 6-week, parallel-group, open-label, randomized, multicenter trial was to compare rosuvastatin with atorvastatin, pravastatin, and simvastatin across dose ranges for reduction of low-density lipoprotein (LDL) cholesterol. Secondary objectives included comparing rosuvastatin with comparators for other lipid modifications and achievement of National Cholesterol Education Program Adult Treatment Panel III and Joint European Task Force LDL cholesterol goals. After a dietary lead-in period, 2,431 adults with hypercholesterolemia (LDL cholesterol > or =160 and <250 mg/dl; triglycerides <400 mg/dl) were randomized to treatment with rosuvastatin 10, 20, 40, or 80 mg; atorvastatin 10, 20, 40, or 80 mg; simvastatin 10, 20, 40, or 80 mg; or pravastatin 10, 20, or 40 mg. At 6 weeks, across-dose analyses showed that rosuvastatin 10 to 80 mg reduced LDL cholesterol by a mean of 8.2% more than atorvastatin 10 to 80 mg, 26% more than pravastatin 10 to 40 mg, and 12% to 18% more than simvastatin 10 to 80 mg (all p <0.001). Mean percent changes in high-density lipoprotein cholesterol in the rosuvastatin groups were +7.7% to +9.6% compared with +2.1% to +6.8% in all other groups. Across dose ranges, rosuvastatin reduced total cholesterol significantly more (p <0.001) than all comparators and triglycerides significantly more (p <0.001) than simvastatin and pravastatin. Adult Treatment Panel III LDL cholesterol goals were achieved by 82% to 89% of patients treated with rosuvastatin 10 to 40 mg compared with 69% to 85% of patients treated with atorvastatin 10 to 80 mg; the European LDL cholesterol goal of <3.0 mmol/L was achieved by 79% to 92% in rosuvastatin groups compared with 52% to 81% in atorvastatin groups. Drug tolerability was similar across treatments.

Adult↗
PubMed2003

Contemporary awareness and understanding of cholesterol as a risk factor: results of an American Heart Association national survey.

BACKGROUND: Public awareness and understanding of risk factors for atherosclerotic vascular disease are essential for successful primary and secondary prevention. The American Heart Association is committed to reducing cardiovascular disease. METHODS: A professional market survey company conducted a structured national telephone survey of English-speaking adults 40 years and older on behalf of the American Heart Association. Regional and sex quotas were imposed on the sample, and responses were weighted to match the 1999 census projections for region of the country, age, sex, and race. RESULTS: Interviews were completed with 1163 adults 40 years and older. A national probability sample of 1114 was created. Of the final sample, 28.5% were 65 years or older, 56.1% were women, and 86.5% were white. Although 91.2% of respondents stated that it was "important to them personally to have a healthy cholesterol level" (77.6% extremely or very important), 51% did not know their own level. Only 40.2% were aware of national guidelines for cholesterol management, and 53.1% either did not know or overestimated the correct desirable total cholesterol level for a healthy adult. When asked what sources of information they rely on the most, 66.8% identified physicians, while only 3.7% rely primarily on the Internet. CONCLUSIONS: Public understanding of cholesterol management is suboptimal. Physicians have a unique opportunity, on the basis of public attitudes and access, to improve cholesterol education.

Adult↗
PubMed2003

Risk for myopathy with statin therapy in high-risk patients.

Emerging data suggest that the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) offer important benefits for the large population of individuals at high risk for coronary heart disease. This population encompasses a sizable portion of individuals who are also at high risk for drug-drug interactions due to their need for multiple medications. In general, statins are associated with a very small risk for myopathy (which may progress to fatal or nonfatal rhabdomyolysis); however, the potential for drug-drug interactions is known to increase this risk in specific high-risk groups. The incidence of myopathy associated with statin therapy is dose related and is increased when statins are used in combination with agents that share common metabolic pathways. Of particular concern is the potential for interactions with other lipid-lowering agents such as fibrates and niacin (nicotinic acid), which may be used in patients with mixed lipidemia, and with immunosuppressive agents, such as cyclosporine, which are commonly used in patients after transplantation. Clinicians should be alert to the potential for drug-drug interactions to minimize the risk of myopathy during long-term statin therapy in patients at high risk for coronary heart disease.

Calcium Channel Blockers↗
PubMed2003

Lipid and apolipoprotein ratios: association with coronary artery disease and effects of rosuvastatin compared with atorvastatin, pravastatin, and simvastatin.

Plasma lipid and apolipoprotein ratios that include both an atherogenic and an antiatherogenic lipid component (eg, total cholesterol/high-density lipoprotein [HDL] cholesterol ratio, low-density lipoprotein [LDL] cholesterol/HDL cholesterol ratio, non-HDL cholesterol/HDL cholesterol ratio, and apolipoprotein [apo] B/apo A-I ratio) have been found to be strong predictors of coronary artery disease (CAD) risk. Three trials that compared the effects of rosuvastatin 10 mg versus atorvastatin 10 mg and 2 trials that compared the effects of rosuvastatin 10 mg versus simvastatin 20 mg and pravastatin 20 mg on lipid ratios in patients with hypercholesterolemia were prospectively designed for pooled analysis. At 12 weeks, in the 3-trial pooled analysis, rosuvastatin 10 mg (n = 389) showed significantly greater reductions in all 4 lipid ratios compared with atorvastatin 10 mg (n = 393) (p <0.001). The mean percent reduction from baseline in the LDL cholesterol/HDL cholesterol ratio was 51% in patients treated with rosuvastatin 10 mg versus 39% in patients treated with atorvastatin 10 mg. In the 2-trial pooled analysis, treatment with rosuvastatin 10 mg (n = 226) also resulted in significantly greater reductions in all 4 lipid ratios compared with both simvastatin 20 mg (n = 249) and pravastatin 20 mg (n = 252) (p <0.001). Mean percent reductions from baseline in the LDL cholesterol/HDL cholesterol ratio were 52%, 39%, and 30% for rosuvastatin 10 mg, simvastatin 20 mg, and pravastatin 20 mg, respectively, in these 2 trials.

Adult↗
PubMed2003

Effects of simvastatin, an HMG-CoA reductase inhibitor, in patients with hypertriglyceridemia.

BACKGROUND: Patients with elevated levels of serum triglycerides (TG) often have other associated lipid abnormalities (e.g., low levels of high-density lipoprotein cholesterol [HDL-C]) and are at increased risk of developing coronary heart disease. Although the therapeutic benefits of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) in hypercholesterolemic patients have been well established, less is known about the effects of statins in patient populations with hypertriglyceridemia. HYPOTHESIS: The purpose of this study was to evaluate the lipoprotein-altering efficacy of simvastatin in hypertriglyceridemic patients. METHODS: This was a multicenter, randomized, double-blind, placebo-controlled study. In all, 195 patients with fasting serum triglyceride levels between 300 and 900 mg/dl received once daily doses of placebo or simvastatin 20, 40, or 80 mg for 6 weeks. RESULTS: Compared with placebo, simvastatin treatment across all doses resulted in significant reductions (p < 0.05 - < 0.001) in serum levels of triglycerides (-20 to -31% decrease) and TG-rich lipoprotein particles. Significant (p < 0.001) reductions were also seen in low-density lipoprotein cholesterol (-25 to -35%) and non-HDL-C (-26 to -40%). Levels of HDL-C were increased (7-11%) in the simvastatin groups compared with placebo (p < 0.05 - < 0.001). CONCLUSION: The results of this study demonstrate the beneficial effects of simvastatin in patients with hypertriglyceridemia.

Adult↗
PubMed2003

Differential effects of simvastatin and atorvastatin on high-density lipoprotein cholesterol and apolipoprotein A-I are consistent across hypercholesterolemic patient subgroups.

BACKGROUND: In addition to lowering plasma levels of low-density lipoprotein cholesterol (LDL-C), statins also raise high-density lipoprotein cholesterol (HDL-C). HYPOTHESIS: Recent studies have shown that treatment with simvastatin results in larger increases in HDL-C than those seen with atorvastatin. The results of three clinical studies are analyzed, comparing the effects of simvastatin and atorvastatin on HDL-C and apolipoprotein A-I (apo A-I) in the total cohort and in several subgroups of hypercholesterolemic patients. The three studies were all multicenter, randomized clinical trials that included simvastatin (20-80 mg) and atorvastatin (10-80 mg) treatment arms. The subgroup analyses performed were gender; age (< 65 and > or = 65 years); baseline HDL-C (male: < 40 or > or = 40 mg/dl; female: < 45 or > or = 45 mg/dl), baseline LDL-C (< 160 or > or = 160 mg/dl), and baseline triglycerides (< 200 or > or = 200 mg/dl). RESULTS: Both drugs produced similar increases in HDL-C levels at low doses; however, at higher drug doses (40 and 80 mg), HDL-C showed a significantly greater increase with simvastatin than with atorvastatin (p < 0.05 to < 0.001). Therefore, while HDL-C remained consistently elevated across all doses of simvastatin, there appeared to be a pattern of decreasing HDL-C with an increasing dose of atorvastatin. A similar negative dose response pattern was also observed with apo A-I in atorvastatin-treated patients, suggesting a reduction in the number of circulating HDL particles at higher doses. Both drugs reduced LDL-C and triglycerides in a dose-dependent fashion, with atorvastatin showing slightly greater effects. The differential effects of atorvastatin and simvastatin on HDL-C and apo A-I were observed for both the whole study cohorts and all subgroups examined; thus, no consistent treatment-by-subgroup interactions were observed. CONCLUSION: The data presented show that, across different hypercholesterolemic patient subgroups, simvastatin increases HDL-C and apo A-I more than atorvastatin at higher doses, with evidence of a negative dose response effect on HDL-C and apo A-I with atorvastatin, but not simvastatin.

Apolipoprotein A-I↗