Polygenic Hypercholesterolemia Medication

Updated: Jan 20, 2017
  • Author: Catherine Anastasopoulou, MD, PhD, FACE; Chief Editor: George T Griffing, MD  more...
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Medication

Medication Summary

The statin (HMG-CoA reductase inhibitor) class of drugs has revolutionized the treatment of hypercholesterolemia. Statins are highly efficacious and very well tolerated. [3] Thus, other drugs are often not needed for low-density lipoprotein cholesterol (LDL-C) reduction. See the charts below on clinical endpoints related to statins.

Angiographic and clinical endpoint trials with sta Angiographic and clinical endpoint trials with statins.
Major coronary heart disease (CHD) clinical endpoi Major coronary heart disease (CHD) clinical endpoint studies of primary prevention and stable CHD with statins versus placebo. *not statistically significant. + atorvastatin 10 mg is the comparator rather than placebo. ++ LDL-C in the atorvastatin 80 mg group/LDL-C in the atorvastatin 10 mg group.

Newer drugs being studied for control of hypercholesterolemia include PCSK9 (proprotein convertase subtilisin kexin 9) inhibitors, probucol, neomycin, and thyromimetics-eprotirome.

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Antilipemic agent, HMG-COA Reductase Inhibitors

Class Summary

Studies have shown the efficacy of statin drugs in reducing coronary heart disease (CHD) events, CHD death, and total mortality rates. Efficacy for LDL-C lowering at approved doses of statins is listed in Medical Care. Primary prevention implies the use of statins in an asymptomatic population, which may include some people with clinically occult disease. Secondary prevention implies the use of statins in patients with clinically apparent disease.

The Scandinavian Simvastatin Survival Study (4S) was the first study to show significant reduction (compared with placebo) in the all-cause mortality rate (30%), in CHD events (34%), and in the CHD mortality rate (42%). In addition, subjects with CHD (secondary prevention) who were treated for moderate hypercholesterolemia (eg, treatment with simvastatin, mean dose 27 mg/d) maintained total cholesterol levels of less than or equal to 201 mg/dL for 5.4 years, which was the median follow-up period.

The West of Scotland Coronary Prevention Study (WOSCOPS) studied high-risk male subjects who had no history of CHD events (primary prevention). Pravastatin was administered at a dose of 40 mg/d for 4.9 years. Cardiovascular events were reduced by 31%, and the treatment caused a borderline statistically significant reduction of 31% in the total mortality rate compared with placebo.

The Cholesterol and Recurrent Events (CARE) study of subjects with CHD and cholesterol concentrations within the reference range (mean LDL-C level of 138 mg/dL) examined the effects of pravastatin at a dose of 40 mg/d. Compared with placebo, the CHD events were reduced by 24% at 5 years, with no significant change in total mortality.

The Air Force/Texas Coronary Atherosclerosis Prevention Study (AFCAPS/TexCAPS) enrolled more than 6000 subjects with average LDL-C concentrations and below-average high-density lipoprotein cholesterol (HDL-C) values. Lovastatin was administered at a dose of 20-40 mg/d for approximately 5 years, resulting in a 37% reduction in first major acute coronary events compared with placebo therapy.

The Long-Term Intervention with Pravastatin in Ischaemic Disease (LIPID) study used pravastatin at a dose of 40 mg/d for an average of 6.2 years in subjects with CHD; the CHD mortality rate decreased by 24%, and the total mortality rate decreased by 22% compared with placebo treatment.

The Atorvastatin versus Revascularization Treatment (AVERT) Study compared 80 mg atorvastatin daily with standard therapy and angioplasty in subjects with CHD. Although event rates at 18 months were the same between both groups, the time until the first CHD event was longer, with aggressive LDL-C lowering. Angioplasty alone has not been proven to prevent events, so this is not necessarily tantamount to a no-therapy comparison trial.

The Myocardial Ischemia Reduction with Aggressive Cholesterol Lowering (MIRACL) trial showed borderline significant reduction in coronary events in subjects treated with atorvastatin (80 mg/d) who presented with an acute coronary syndrome, although significant abnormalities revealed via liver function test were common. The major positive finding from this study was a 61% reduction in stroke in the atorvastatin-treated group.

In the Pravastatin in Elderly Individuals at Risk of Vascular Disease (PROSPER) study that compared pravastatin 40 mg/d versus placebo in subjects aged 70-82 years with a history of CHD or risk factors for CHD, active therapy reduced cardiovascular events by 15%.

The Medical Research Council/British Heart Foundation Heart Protection Study (HPS) assessed the effects of simvastatin (40 mg/d) versus placebo in approximately 20,000 subjects with vascular disease or at high risk for CHD with total cholesterol levels greater than 135 mg/dL, including approximately 6000 subjects with diabetes mellitus. CHD endpoints were reduced by approximately 24% and were effective in multiple subgroups, including subjects with diabetes. The mortality rate was reduced by approximately 15%.

The Anglo-Scandinavian Cardiac Outcomes Trial (ASCOT) used 10 mg of atorvastatin versus placebo in approximately 10,000 subjects with hypertension. CHD event rates were reduced approximately 36%. However, most subgroups, including subjects with diabetes mellitus or metabolic syndrome, did not return positive results, perhaps because of the short duration (3.3 y) of the study.

The Reversal of Atherosclerosis with Aggressive Lipid Lowering (REVERSAL) trial compared treatment with atorvastatin (80 mg) with treatment with pravastatin (40 mg) in subjects with CHD. After 18 months, the atorvastatin treatment group had a slight decrease in atheroma volume based on intravascular ultrasonography evaluations, and the pravastatin group had a slightly increased atheroma volume.

The Pravastatin or Atorvastatin Evaluation and Infection Therapy (PROVE-IT) study also compared atorvastatin therapy (80 mg/d) with pravastatin therapy (40 mg/d) in subjects who had been hospitalized for acute coronary syndromes. The baseline LDL-C level was approximately 106 mg/dL. After a mean follow-up of 2 years, the intensively treated group had LDL-C levels of approximately 62 mg/dL, compared with approximately 95 mg/dL in the pravastatin group. Cardiovascular events were reduced by 16%.

Unfortunately, the study had a dropout rate of approximately one third. The number of patients needed to treat was 26, but the number needed to cause transaminase values to exceed 3 times the upper limit of normal was only 46 patients. In this scenario, 26 patients would have to be treated to prevent one clinical event, and 46 patients would have to be treated to see one case of transaminases >3 X ULN (and possibly end up stopping therapy). Interestingly, subjects pretreated with statins or those with baseline LDL-C levels of less than 125 mg/dL did not show a benefit from high-dose atorvastatin therapy compared with pravastatin therapy (40 mg).

A pooled analysis of 5 statin trials revealed that intensive-dose therapy was associated with a greater risk of diabetes when compared with moderate dosing.

The Treating to New Targets (TNT) study assessed the effect of therapy with atorvastatin 80 mg/d versus atorvastatin 10 mg/d in patients with stable CHD for a period of 4.9 years. The mean on-treatment LDL-C level was 77 mg/dL in the former group and 101 mg/dL in the latter group. The relative risk of cardiovascular events was reduced by 22%. Mortality was higher but not significantly statistically different in the high-dose atorvastatin group, although persistent transaminase elevations were 6 times higher in this group.

The statins lower LDL-C by inhibiting HMG-CoA reductase, the enzyme that regulates the rate-limiting step in cholesterol synthesis. The amount of the intermediate (i.e., mevalonate) is lowered, and, subsequently, cholesterol levels are reduced in hepatic cells. This, in turn, results in up-regulation of LDL receptors and increased hepatic uptake of LDL from the circulation.

Atorvastatin (Lipitor)

Atorvastatin is highly efficacious at high doses, resulting in as much as a 60% reduction in LDL-C. It inhibits HMG-CoA reductase, which, in turn, inhibits cholesterol synthesis and increases cholesterol metabolism. The half-lives of atorvastatin and its active metabolites are longer than those of all other statins (ie, approximately 17 h for native drug, approximately 48 h for active metabolites, compared with 3-4 h for other drugs).

Atorvastatin was used for primary prevention (10-mg dose) in the ASCOT trial of subjects with hypertension and at the 80-mg dose in the AVERT, MIRACL, REVERSAL, PROVE-IT, and TNT trials.

Fluvastatin (Lescol XL)

Fluvastatin is the least potent of statin drugs. The Lescol Intervention Prevention Study showed that in subjects with CHD monitored after a first percutaneous intervention, fluvastatin at 80 mg/d reduced CHD events compared with placebo. It is a synthetically prepared HMG-CoA reductase inhibitor with some similarities to lovastatin, simvastatin, and pravastatin. However, it is structurally distinct and has a different biopharmaceutical profile (eg, no active metabolites, extensive protein binding, minimal CSF penetration). Fluvastatin has been shown to reduce CHD events after revascularization.

Lovastatin (Mevacor, Altoprev)

Lovastatin was the first statin approved by the FDA. It has been shown to retard atherosclerosis in angiographic and carotid ultrasound trials and to reduce clinical events in primary prevention (AFCAPS/TexCAPS). It is a prodrug hydrolyzed in vivo to mevinolinic acid, one of several active metabolites. Once hydrolyzed, it competes with HMG-CoA for HMG-CoA reductase, a hepatic microsomal enzyme, thus reducing the quantity of mevalonic acid, a precursor of cholesterol. Cholesterol can also be taken up by the liver from LDL by endocytosis. The diminishing de novo synthesis of cholesterol leads to increased clearance of circulating LDL. In the AFCAPS/TexCAPS study, 20-40 mg lovastatin daily reduced the incidence of CHD events in a relatively low-risk primary prevention population. Lovastatin is available as IR (Mevacor and generic) and SR (Altocor) dosage forms.

Pravastatin (Pravachol)

Pravastatin reduces CHD events when used in primary prevention in patients with marked LDL-C elevations (WOSCOPS). It also reduces CHD events and mortality rates in patients with CHD and moderate increases in LDL-C (LIPID study). Pravastatin reduces CHD events in patients with cholesterol levels within reference range and known CHD (CARE study), and it reduces cardiovascular events in elderly persons (PROSPER).

Simvastatin (Zocor)

Simvastatin was the first drug shown to reduce total mortality rate by reducing LDL-C concentrations in patients with CHD with marked LDL-C elevations at baseline (4S). It markedly affects mortality rates and CHD events in patients with CHD and marked hypercholesterolemia (4S). It also reduces CHD events by more than 40% in similar patients with type 2 diabetes mellitus. Simvastatin has also been shown to reduce CHD events in patients with a wide variety of cholesterol concentrations (>135 mg/dL) at baseline, ie, in the HPS. Adverse effects, including LFT abnormalities and myalgia, were minimal at this dose.

Rosuvastatin (Crestor)

Rosuvastatin is an HMG-CoA reductase inhibitor that decreases cholesterol synthesis and increases cholesterol metabolism. It reduces total cholesterol, LDL-C, and triglyceride levels and increases the HDL-C level. Rosuvastatin is used adjunctively with diet and exercise to treat hypercholesterolemia. It is the most efficacious of the statins. It may raise HDL-C at higher doses than equally effective doses of atorvastatin. It is not metabolized by the cytochrome P450 system. A dose of 40 mg is associated with hematuria and proteinuria, which is of unknown clinical significance. No clinical outcome studies have been completed as yet.

Pitavastatin (Livalo)

Pitavastatin is an HMG-CoA reductase inhibitor (statin) indicated for primary or mixed hyperlipidemia. In clinical trials, 2 mg/d reduced total cholesterol and LDL cholesterol similar to atorvastatin 10 mg/d and simvastatin 20 mg/d.

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Antilipemic agent, 2-Azetidinone

Class Summary

These drugs inhibit dietary cholesterol absorption. Ezetimibe (Zetia) is the only medication in this class with Food and Drug Administration (FDA) approval. It selectively inhibits cholesterol absorption in the intestine by binding to the Niemann-Pick C1-like 1 (NPC1L1) protein. Alone or with a statin, ezetimibe lowers LDL-C levels by 12-19%. In individuals who hyperabsorb cholesterol, LDL-C reduction of as much as 40% has been documented.

There have been many studies to evaluate the efficacy of Ezetimibe.

The latest study being IMPROVE-IT (IMProved Reduction of Outcomes: Vytorin Efficacy International Trial), which was a large randomized controlled trial that included 18,144 patients with acute coronary syndrome who were randomized to receive Vytorin [ezetimibe 10 mg/simvastatin 40 mg] or simvastatin 40 mg and were monitored for up to 9 years. Of patients receiving Vytorin, 32.7% experienced a primary endpoint event (which was death from cardiovascular disease, nonfatal myocardial infarction, unstable angina requiring hospitalization, or coronary revascularization occurring at least 30 days after randomization) compared to 34.7% of the patients receiving 40 mg simvastatin (hazard ratio of 0.936; p value 0.016). No statistical difference in the rate of cardiovascular mortality or rate of death from any other cause was observed between the two groups. There was a reduction in LDL cholesterol by 24% with the use of additional ezetimibe in the regimen. The rate of hemorrhagic stroke was slightly higher in Vytorin group (59%) as compared to simvastatin alone (43%) [hazard ratio 1.38 (0.93-2.04), p value- 0.11]. Also, the study found greater benefit for patients >75 years of age and those with diabetes mellitus, however, the sample size was considered to be small for statistical power significance. Thus, it is considered a landmark study as it is the first clinical trial showing benefit of adding non-statin therapy to statin therapy for cardiovascular benefit.

The ENHANCE (Ezetimibe and Simvastatin in Hypercholesterolemia Enhances Atherosclerosis Regression) trial, was undertaken to demonstrate that progression of atherosclerosis reflected by changes in carotid intima-media thickness (CIMT) would be reduced if ezetimibe was added to 80 mg of simvastatin in patients with heterozygous familial hypercholesterolemia. At the end of the 24-month study, however, no significant difference in CIMT was found between patients using ezetimibe in combination with simvastatin and those using simvastatin alone, despite greater reductions in LDL-C and C-reactive protein levels in the ezetimibe/simvastatin combination group.

Prominent investigators weighed in, stating that if ezetimibe could not improve CIMT, then it had no role in cholesterol management. It should be noted, however, that the cholesterol levels in the study subjects had been aggressively managed for many years, and they did not have increased CIMT at baseline. The study sought to show increased regression and decreased progression in subjects receiving both simvastatin and ezetimibe, compared with simvastatin alone. But regression cannot occur in subjects whose CIMT is normal, and therefore no difference in regression between the 2 treatment groups would have been possible at the end of the study.

In order to demonstrate reduced progression, the CIMT in the simvastatin-only arm would have had to increase. In fact, no progression occurred in this group. Therefore, the simvastatin-ezetimibe subjects could not have benefited from decreased progression because no progression occurred in the simvastatin-only subjects.

The SEAS (Simvastatin and Ezetimibe in Aortic Stenosis) trial, was meant to demonstrate that intensive LDL-C lowering through administration of a daily dose of 40 mg of simvastatin plus 10 mg of ezetimibe would reduce the incidence of major cardiovascular events and also reduce the number of events related to aortic stenosis. As expected, cardiovascular endpoints were clinically and statistically lower in patients using the combination therapy than they were in in placebo-treated patients. However, events related to aortic stenosis were not reduced in the combination group. In addition, the investigators made an unexpected finding, that the incidence of cancer was significantly greater in the ezetimibe/simvastatin group than it was in the patients using placebo (11.1% vs 7.5% [P = 0.01]).

An expert statistician, Richard Peto, with special expertise in analyzing cancer data was invited to analyze the SEAS findings. He was also given access to data from 2 much larger, ongoing clinical trials at that time—SHARP (Study of Heart and Renal Protection) and IMPROVE-IT—with a total of 20,617 randomized patients. SHARP was designed to compare results from the use of simvastatin 20 mg plus ezetimibe to those from placebo, and IMPROVE-IT was designed to compare the results from the administration of simvastatin 40 mg plus ezetimibe to simvastatin 40 mg.

In the combined data from the SHARP and IMPROVE-IT trials, more cancer deaths and fewer cases of cancer were found in the patients assigned to ezetimibe; neither difference was statistically significant. Several features of the data suggested lack of credibility: cancer incidence and death were not prespecified endpoints in SEAS; no excess of cancers at any particular site (more than 15 different sites were involved) were observed; and longer duration of follow-up did not result in an increased trend in cancer incidence or death. The final conclusion by Peto et al was that the available data from the SHARP, IMPROVE-IT, and SEAS trials did not "provide credible evidence of any adverse effect of ezetimibe on rates of cancer." A more definitive answer will be possible when the SHARP and IMPROVE-IT trials are analyzed after a longer follow-up period.

In a study by Zieve et al, the addition of ezetimibe (10 mg) to atorvastatin (10 mg) resulted in significantly more improvement in most serum lipid levels, including better attainment of prespecified LDL-C levels, than did doubling and then quadrupling the atorvastatin dose (to 20mg and then 40 mg), in patients aged 65 years or older with hyperlipidemia and a high risk for coronary heart disease. The study included 1,053 patients; lipid levels were followed over a 12-week period.

Ezetimibe (Zetia)

It is FDA approved for the treatment of heterozygous familial and nonfamilial hyperlipidemia, homozygous familial hypercholesterolemia, and homozygous sitosterolemia. It may be administered as monotherapy or in combination with HMG-CoA reductase inhibitors. No clinical endpoint trials have been completed yet. The combination therapy lowers LDL-C levels 45-60%. Its effect on CHD events compared with a statin alone is unknown.

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Nicotinic Acid

Class Summary

Nicotinic acid/niacin is the most effective agent for raising HDL-C levels. It lowers triglycerides as effectively as fibrates do and is more reliable for lowering LDL-C.

Niacin has several features that make it the most difficult lipid agent to prescribe:

Niacin at doses greater than 2 grams or in time-release formulations can cause significant hepatotoxicity. Immediate-release niacin is the least likely to cause hepatic injury, and time-release niacin is the most likely to cause it. Extended-release niacin has an intermediate risk, and if the FDA maximum approved dose for Niaspan, 2000 mg/day, is not exceeded, the risk of serious hepatic injury is minimal.

Niacin inhibits urate metabolism and can precipitate an acute gouty attack. Patients with a history of gout whose uric acid levels have been normalized with allopurinol have minimal, if any, risk.

Niacin may increase insulin resistance but is not contraindicated in the treatment of patients with diabetes.

Patient tolerability limits niacin's use, the most common side effect being flushing, sometimes accompanied by pruritus and/or rash. Several techniques can lessen or, in some cases, prevent these symptoms, which are prostaglandin-mediated. Time itself will usually decrease symptoms; therefore, to enhance tachyphylaxis and, more importantly, to decrease the risk of hepatotoxicity, niacin should always be started at a low dose and gradually increased ("start low, go slow").

Many patients who will be treated with niacin are already on prophylactic aspirin, 81 mg/day. Aspirin taken 30-60 minutes before niacin may lessen symptoms, but 325 mg is often necessary. Taking niacin with a small, low-fat snack slows absorption and thereby decreases symptoms. Activities that might cause vasodilation (hot food or beverages, spicy food, hot showers) should be avoided. Benadryl is sometimes effective in decreasing a severe reaction.

Niacin is used primarily to treat hypertriglyceridemia, but it also has a beneficial impact on HDL-C and LDL-C levels, and it is the only lipid medication that lowers lipoprotein (a). Niacin has been shown to retard progression of atherosclerosis and reduce CHD events when used in conjunction with a bile acid sequestrant or lovastatin.

The ARBITER 6–HALTS (Arterial Biology for the Investigation of the Treatment Effects of Reducing Cholesterol 6–HDL and LDL Treatment Strategies) Trial compared the effects of 2 lipid-lowering combination therapies on CIMT. In a prospective, randomized, parallel-group, open-label study, patients received either extended-release niacin (2 g/d target dose) or ezetimibe (10 mg/d) in addition to their long-term statin therapy. All participants (n=363) had been treated with statin monotherapy at a consistent dose. Inclusion required that lipid panels were obtained within 3 months before enrollment showing an LDL cholesterol level of less than 100 mg/dL (2.6 mmol/L), as well as an HDL cholesterol level of less than 50 mg/dL (men) or 55 mg/dL (women) (1.3 or 1.4 mmol/L, respectively). The mean common CIMT change from baseline after 14 months was the study’s primary end point.

Following a prespecified interim analysis conducted after 208 patients (mean age 65 y, 80% men) had completed the trial, the trial was terminated early on the basis of efficacy. The results are described for these 208 patients. In the niacin group, HDL cholesterol level were increased by 18.4% to 50 mg/dL (P <0.001). Niacin also significantly reduced LDL cholesterol and triglyceride levels. The ezetimibe group showed a 19.2% decrease in LDL cholesterol, 66 mg/dL (1.7 mmol/L) (P <0.001). Ezetimibe did not increase HDL cholesterol (HDL levels were actually reduced), but it did reduce triglycerides. Niacin was more effective than ezetimibe in changing mean CIMT over 14 months (P = 0.003), leading to a significant reduction of mean (P = 0.001) and maximal CIMT (P ≤0.001 for all comparisons).

Completed trials with clinical endpoints (eg, AIM-HIGH, ACCORD, and HPS2-THRIVE clinical trials) have shown that the addition of decreased triglycerides and/or increased HDL-C levels in statin-treated patients does not result in further reduction in risk of CV events. Consistent with this conclusion, the FDA has determined that the benefits of niacin ER tablets for coadministration with statins no longer outweighs the risks, and the approval for this indication should be withdrawn. Additionally, the combination products that include simvastatin or lovastatin plus long-acting niacin (ie, Advicor, Simcor) were withdrawn from the US market at the beginning of 2016 and are no longer available.

The AIM-HIGH (Atherothrombosis Intervention in Metabolic Syndrome with Low HDL/High Triglycerides and Impact on Global Health Outcomes) trial was aimed to determine whether there is incremental clinical benefit of niacin in reducing cardiovascular events in patients who have attained optimal on-treatment levels of LDL-C with a statin. During a 3-year follow-up in 3,414 patients with established CV disease and low high-density lipoprotein cholesterol (HDL-C) levels, combined niacin + low-density lipoprotein cholesterol (LDL-C)–lowering therapy did not reduce CV events compared with LDL-C–lowering therapy alone. The study was terminated prematurely due to lack of suggested benefit. Baseline lipoprotein tertiles did not predict differential benefit or harm with ER niacin added to aggressive LDL-C–lowering therapy, but a small subgroup of subjects with baseline dyslipidemia showed possible benefit.

HPS2-THRIVE (Heart Protection Study 2: Treatment of HDL to Reduce the Incidence of Vascular Events) was designed to assess the effects of adding extended-release niacin in combination with laropiprant to effective statin-based LDL cholesterol–lowering treatment in 25,673 high-risk patients with prior vascular disease. Laropiprant is an antagonist of the prostaglandin D2 receptor DP1 that has been shown to improve adherence to niacin therapy by reducing flushing in up to two thirds of patients. It did not significantly reduce the risk of major vascular events, either overall or in any particular subgroup of patients. However, the study identified significant hazards, which included new-onset diabetes, increased hospitalization related to diabetes in persons with established diabetes, myopathy, serious bleeding events, and increased rate of infections.

Niacin (Niaspan, Niacor, Slo-Niacin)

The immediate-release dosage (IR) form is less hepatotoxic than the sustained-release (SR) form but not as well tolerated by patients because of prostaglandin-mediated flushing, itching, or rash. IR niacin started at low doses and gradually increased over several weeks allows some patients to accommodate to these adverse effects. Higher doses (4-6 g/d) can be used more safely than SR niacin. Niacor and Nicolar are prescription formulations of IR niacin that, while more expensive than over-the-counter brands, may make it less likely that patient will switch brands. Changing the formulation of niacin while on high doses may increase the risk of hepatotoxicity.

The SR dosage form is more hepatotoxic than IR niacin; therefore, strongly advise against switching formulations or brands during treatment. Over-the-counter and prescription SR niacin are available. Over-the-counter brands cost less, but if using this option, recommend only reliable manufacturers. Slo-Niacin is an over-the-counter formulation available in 250-, 500-, and 750-mg tablets. Sundown also is a manufacturer of over-the-counter SR niacin. Prescription SR niacin, Niaspan, is available in 375-, 500-, and 1000-mg tablets.

Niaspan with nocturnal dosing may be more tolerable than the other preparations. Niacin has no real utility in treating pure hypercholesterolemia because of the availability of statins. It is questionable whether adding it to statins to increase a low serum HDL-C reduces CHD risk beyond that observed with a statin alone.

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Antilipemic agent, fibric acids

Class Summary

Older fibrates (eg, clofibrate, gemfibrozil) are used primarily for triglyceride lowering. The Helsinki Heart Study, published in 1987, showed a decrease in CHD events in patients with elevated non–HDL-C concentrations when used in primary prevention. With the advent of statins, fibrates have largely fallen out of favor when pure LDL-C lowering is needed. However, fenofibrate is more efficacious for LDL-C lowering than earlier fibrates. Ongoing studies may help determine if fenofibrate is useful in patients with mixed dyslipidemia, particularly subjects with type 2 diabetes mellitus. The Diabetes Atherosclerosis Intervention Study showed that such subjects with CHD have stabilization of angiographic findings when treated with fenofibrate compared with placebo. This trial was inadequately powered to assess an effect on CHD events. Currently, fenofibrate should probably be relegated to second-line therapy for LDL-C reduction in patients intolerant of statins.

The publication of the Veterans Affairs HDL Intervention Trial is notable. This trial consisted of male subjects with CHD, relatively low LDL-C concentrations (mean of 112 mg/dL), and low HDL-C concentrations (mean of 32 mg/dL). Coronary events were reduced 22% with gemfibrozil treatment compared with placebo treatment. This effect was thought to be due to an increase (6%) in HDL-C levels; however, the almost 30% decrease in triglyceride levels in subjects treated with gemfibrozil may also have played a role in risk reduction.

Fenofibrate (Tricor, Lofibra, Antara, Fenoglide, Fibricor, Trilipix, Lipofen)

Fenofibrate lowers LDL-C better than older fibrate drugs. It is currently used primarily for triglyceride reduction and in mixed dyslipidemias. It induces lipoprotein lipase and decreases hepatic production of apolipoprotein CIII (an inhibitor of LPL) via PPAR alpha activity, which enhances plasma catabolism and clearance of triglyceride-rich particles. Fatty acid oxidation is enhanced by fenofibrate activation of acyl-CoA synthetase and other enzymes. Inhibition of acetyl-CoA carboxylase and fatty acid synthetase activity by fenofibrate further decreases the synthesis of triglycerides. The result is a marked reduction in plasma triglyceride and VLDL levels and an increase in HDL-C levels. The Diabetes Atherosclerosis Intervention Study associated it with decreased progression of coronary atherosclerosis in subjects with type 2 diabetes mellitus.

Gemfibrozil (Lopid)

Gemfibrozil is used primarily to lower serum triglyceride levels. Statin clinical endpoint trials have largely made its use for pure cholesterol lowering obsolete. The Veterans Affairs HDL Intervention Trial suggests that gemfibrozil (and probably other fibrates) may be used in patients with CHD, low LDL-C, and low HDL-C. Its mechanism of action is unknown but probably is similar to fenofibrate. It may inhibit lipolysis and secretion of VLDL and decrease hepatic fatty acid uptake.

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Bile acid sequestrants

Class Summary

These agents are also called resins. Bile acid sequestrants are used primarily as additional therapy in patients with familial hypercholesterolemia who experience inadequate LDL-C lowering with statins. These agents are also useful in pediatric hypercholesterolemia. Several studies show that LDL-C lowering with resins retards the progression of atherosclerosis. The Lipid Research Clinics Coronary Primary Prevention Trial showed that cholestyramine therapy could reduce the risk for CHD events.

Interference with anionic drug absorption and patient compliance are major problems with this class of drugs. They inhibit absorption of many drugs; major ones including statins, estrogen products including OCP, steroids, sulphonylureas, thyroid hormones, multivitamins including Vitamin D, warfarin, diuretics. This should be kept in mind while prescribing these drugs. Resins may be used as an adjunct in primary hypercholesterolemia. These drugs form a nonabsorbable complex with bile acids in the intestine, which, in turn, inhibits enterohepatic reuptake of intestinal bile salts

Cholestyramine (Questran, Questran Light, Prevalite)

Cholestyramine is FDA approved for the treatment of primary hypercholesterolemia. It is flavored to improve palatability. The light version is sweetened with aspartame and is more palatable to some patients.

Colesevelam (WelChol)

Colesevelam is a new high-capacity bile acid sequestrant. It is better tolerated than older agents (eg, cholestyramine and colestipol), and drug interactions are less of a problem. It can lower LDL-C levels by 15-18% as monotherapy. It is useful in patients who cannot tolerate statins, have contraindications for statin therapy, or request nonsystemic therapy. It can also be used in combination with a statin for additive LDL-C lowering. Colesevelam has no effect on serum triglyceride levels and a modest beneficial effect on HDL-C. It has also been shown to improve HbA1c in type 2 diabetes patients with diet and exercise. Thus, it may be preferred in this patient population, if intolerant to statins.

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Antilipemic agent, PCSK9 Inhibitors

Class Summary

Proprotein convertase subtilisin/kexin type 9 (PCSK 9) inhibitors are newly approved lipid lowering agents. They are monoclonal antibodies to PCSK-9 which in vivo act to prevent degradation of LDL receptors (LDL-R). LDL-R are present on the surface of hepatocytes and their main function in uptake of LDL particles and their degradation. The LDL-R again return to the surface of hepatocytes to repeat the process. PCSK 9 binds to LDL-R and promote its degradation. [36]  PCSK 9 inhibitors by acting on this pathway can cause dramatic decrease in LDL cholesterol.

In 2003, PCSK 9 mutation was found in 2 families with familial hypercholesterolemia (FH) who did not have the usual FH associated gene mutation. [37]  Further research showed that the mechanism of PCSK 9 in increasing LDL cholesterol level and inhibiting PCSK 9 would be a novel mechanism of LDL lowering therapy. [38]

In 2012, Alirocumab was found to lower LDL cholesterol in healthy volunteers as well as patients with familial and non-familial hypercholesterolemia. [36] Subsequently phase 3 trials with both Alirocumab and Evolocumab have shown significant decrease in LDL cholesterol levels.

In the US, two drugs have been approved by the FDA: Alirocumab in July 2015 and Evolocumab in August 2015. Bococizumab is another PCSK 9 inhibitor which is currently in phase 3 trials. Statins increase PCSK 9 levels and thus PCSK 9 inhibitors act synergistically with statins to lower LDL cholesterol levels. [38]

The ODYSSEY COMBO II trial randomly assigned patients at high cardiovascular risk and elevated LDL-C despite maximal doses of statin to alirocumab or ezetimibe with concomitant statin therapy. At week 24, the alirocumab group had 50.6% reduction in LDL-C compared with 20.7% in the ezetimibe group. [39]  In the GAUSS-2 trial, patients at high cardiovascular risk who were statin intolerant were randomly assigned to receive either evolocumab (140 mg every 2 weeks or 420 mg monthly) or ezetimibe. After 12 weeks, LDL-C lowering in the evolocumab groups ranged between 53% and 56% compared with 37%-39% for ezetimibe. [40] The Durable Effect of PCSK9 Antibody Compared with Placebo Study (DESCARTES), was a randomized, double-blind, placebo-controlled, phase 3 trial, which compared evolocumab with placebo in patients with hyperlipidemia who received the study drug for 52 weeks after a run-in period of 4 to 12 weeks of background lipid-lowering therapy showed 57% reduction in LDL cholesterol level. [41] Similar results have been seen in patients with familial hypercholesterolemia. 

A meta-analysis of 25 randomized control trials of Evolocumab and Alirocumab with about 12,200 subjects have shown 50% reduction in LDL- cholesterol with favorable increase in HDL cholesterol. [42]  Another meta-analysis of 24 randomized controlled trials with 10,159 subjects showed additional significant reduction in all cause mortality as well as secondary end point reduction in myocardial infarction, but not unstable angina. [43]  However, most of the trials were of shorter duration and thus long term effect of PCSK 9 inhibitors in cardiovascular mortality need to be ascertained. Two trials are expected to give us more insight into the cardiovascular benefits:  Further Cardiovascular Outcomes Research with PCSK9 Inhibition in Subjects with Elevated Risk (FOURIER) study, a 27,500-patient trial testing evolocumab against statin therapy for the reduction of the primary composite end point of cardiovascular death, MI, hospitalization for unstable angina, stroke, or coronary revascularization (results are expected in late 2017) and The ODYSSEY-Outcomes study which will include 18,000 ACS patients randomized to alirocumab or placebo on top of optimal medical therapy (results expected in early 2018). Studies on PCSK9 Inhibition and the Reduction of vascular Events (SPIRE-1 and SPIRE-2) trial results, using bococizumab will also be available in 2018.

Cost has been a major factor in widespread use of the drug- an estimated $15,000  every year as compared to many generic available statins. However, it is a promising drug in patients with polygenic hypercholesterolemia who require further reduction in LDL cholesterol and are on maximally tolerated statins.

 

Evolocumab (Repatha)

Evolocumab has been FDA approved for the treatment of heterozygous familial hypercholesterolemia or clinical atherosclerotic cardiovascular disease and for the treatment of homozygous familial hypercholesterolemia, adjunct to diet and maximally tolerated statin therapy. It is to be administered in adults who require additional lowering of low desnsity lipoprotein cholesterol. It can be given subcutaneously 140 mg every 2 weeks or 420 mg once monthly. Its effects on cardiovascular morbidity and mortality has not been determined.

Alirocumab (Praluent)

Alirocumab has been FDA approved for the treatment of primary hyperlipidemia, adjunct to diet and maximally tolerated statin therapy in adults with heterozygous familial hypercholesterolemia or clinical atherosclerotic cardiovascular disease, who require additional lowering of low desnsity lipoprotein cholesterol..The initial dose is 75 mg subcutaneous once every two weeks and may increase to 150 mg every two weeks if response is inadequate. The effect of alirocumab on cardiovascular morbidity and mortality has not been established.

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