Anti-ischemic effects and long-term survival during ranolazine monotherapy in patients with chronic severe angina

Evaluation of a novel anti-ischemic agent in acute coronary syndromes: design and rationale for the Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST-elevation acute coronary syndromes (MERLIN)-TIMI 36 trial

BACKGROUND

Despite advances in antithrombotic therapies and invasive technology, the risk of recurrent ischemic complications in patients with non-ST-elevation acute coronary syndromes (NSTE-ACSs) remains substantial. Ranolazine is a novel agent that inhibits the late sodium current thereby reducing cellular sodium and calcium overload and has been shown to reduce ischemia in patients with chronic stable angina.

STUDY DESIGN

MERLIN-TIMI 36 is a phase III, randomized, double-blind, parallel-group, placebo-controlled, multinational clinical trial to evaluate the efficacy and safety of ranolazine during long-term treatment of patients with NSTE-ACS receiving standard therapy (N = 6500). Eligible patients are randomized 1:1 to ranolazine or matched placebo, initiated as 200 mg intravenously over 1 hour, followed by an 80-mg/h infusion (40 mg/h for patients with severe renal insufficiency) for up to 96 hours and oral ranolazine ER 1000 mg BID or matched placebo until the end of study. The primary end point is the time to first occurrence of any element of the composite of cardiovascular death, myocardial infarction, or recurrent ischemia. Secondary end points include ischemia on Holter monitoring, hospitalization for new or worsening heart failure, quality of life measures, and exercise performance. The evaluation of long-term safety will include death from any cause and symptomatic documented arrhythmia. Recruitment began in October 2004. The trial will continue until 730 major cardiovascular events and 310 deaths are recorded with expected completion in 24 to 28 months.

CONCLUSIONS

MERLIN-TIMI 36 will evaluate the role of ranolazine in the acute and chronic management of patients presenting with NSTE-ACS.

Angina pectoris: evaluation in the office

Angina pectoris is a clinical manifestation of myocardial ischemia. Complete evaluation consists of a review of risk factors, a careful history, and, typically, a provocative test. Stress testing can be performed with exercise(treadmill, bicycle, or arm ergometry) or pharmacologic agents that increase cardiac work (dobutamine) or dilate the coronary vessels (adenosine or dipyridamole). Patients who have high-risk features found by clinical history or by stress testing should be referred for coronary angiography and possible revascularization. Comprehensive management of patients who have angina (with or without revascularization) includes smoking cessation,diet and weight control, vasculoprotective drugs (aspirin, statins, and possibly ACE inhibitors), and antianginal medications (nitrates, D-blockers, and calcium channel blockers). These strategies have led to an important reduction in morbidity and mortality over the past 2 decades, and the focus on implementing guidelines for patients who are currently undertreated is expected to improve outcomes further.

Improved left ventricular function and reduced necrosis after myocardial ischemia/reperfusion in rabbits treated with ranolazine, an inhibitor of the late sodium channel

Ranolazine is an inhibitor of the late sodium current and, via this mechanism, decreases sodium-dependent intracellular calcium overload during ischemia and reperfusion. Ranolazine reduces angina, but there is little information on its effects in acute myocardial infarction. The aim of this study was to test the effects of ranolazine on left ventricular (LV) function and myocardial infarct size after ischemia/reperfusion in rabbits. Ten minutes before coronary artery occlusion (CAO), anesthetized rabbits were assigned to vehicle (n=15) or ranolazine (2 mg/kg i.v. bolus plus 60 microg/kg/min i.v. infusion; n=15). Hearts received 60 min of CAO and 3 h of reperfusion. CAO caused LV dysfunction associated with necrosis. However, at the end of reperfusion, rabbits treated with ranolazine had better global LV ejection fraction (0.42+/-0.02 versus 0.33+/-0.02; p<0.007) and stroke volume (1.05+/-0.08 versus 0.78+/-0.07 ml; p<0.01) compared with vehicle. The fraction of the LV wall that was akinetic or dyskinetic was significantly less in the ranolazine group at 0.23+/-0.03 versus 0.34+/-0.03 in vehicle-treated group; p<0.02. The ischemic risk region was similar in both groups; however, infarct size was significantly smaller in the treated group (44+/-5 versus 57+/-4% vehicle; p<0.04). There were no significant differences among groups in heart rate, arterial pressure, LV end-diastolic pressure, or maximum-positive or -negative first time derivative of LV pressure (dP/dt). In conclusion, the results of this study show that ranolazine provides protection during acute myocardial infarction in this rabbit model of ischemia/reperfusion. Ranolazine treatment led to better ejection fraction, stroke volume and less wall motion abnormality after reperfusion, and less myocardial necrosis.

Inhibition of sodium-dependent calcium overload to treat myocardial ischemia

Because intracellular sodium and calcium overload play a key role in both mechanical and electrical dysfunction during myocardial ischemia, inhibition of the late sodium current would be expected to decrease the intracellular sodium and calcium overloads and thereby reduce their undesirable effects. Ranolazine selectively inhibits late sodium current relative to peak sodium current, and attenuates the abnormalities of ventricular repolarization and contractility associated with ischemia. This is the currently proposed mechanism (hypothesis) of action of the effects of ranolazine during myocardial ischemia.

Ranolazine: a new approach to management of patients with angina

OBJECTIVE

To review the pharmacology, pharmacokinetics, and clinical efficacy of ranolazine for the treatment of chronic stable angina.

DATA SOURCES

MEDLINE was searched (1966-February 2006) using the English-language key terms ranolazine and chronic stable angina. Additional studies were identified from the bibliographies of the reviewed literature.

STUDY SELECTION AND DATA EXTRACTION

Studies evaluating ranolazine, alone or in combination with other agents, were incorporated in this review.

DATA SYNTHESIS

Ranolazine is a metabolic modulator designed to improve cardiac energy availability and cardiac metabolism. It is believed to be a partial fatty acid oxidation inhibitor. Ranolazine has been shown to improve exercise duration and time to anginal attacks without significantly affecting heart rate or blood pressure. Adverse effects of ranolazine are reported to be dose related. The elimination half-life of ranolazine is estimated to be between 1.4 and 1.9 hours for the immediate-release and 7 hours for sustained-release preparations.

CONCLUSIONS

Ranolazine has a unique mechanism of action that is different from that of conventional agents. It has been studied as monotherapy or in combination with other commonly prescribed agents. It appears that ranolazine has a promising safety data profile and does not affect hemodynamic parameters. At this point, although ranolazine should not be used in place of conventional therapy, it appears that ranolazine may be considered in the management of symptomatic patients when standard antianginal medications are not tolerated or are ineffective.

Metabolic modulation of myocardial ischemia

The metabolic pathways of the heart during normoxia and ischemia have been well studied. High plasma fatty acid concentrations and the myocardial accumulation of long-chain fatty acyl metabolites during ischemia correlate with increased morbidity and mortality. However, enhanced glucose use can maintain cell homeostasis, diminish ischemic injury, and be clinically beneficial. Metabolic modulators represent a new class of drugs with the potential to treat myocardial ischemia. They are ideal as adjunctive anti-ischemic therapy because they lack the hemodynamic consequences of traditional therapy and treat the underlying metabolic dysfunction that leads to contractile failure and arrhythmias. Clinical studies have demonstrated their efficacy in acute and chronic settings. It is anticipated that there will be greater utilization of this new class of agents in the near future.

Evolving treatment strategies for chronic refractory angina

Chronic refractory angina is a term used to describe patients who, despite optimal medical therapy, have both angina and objective evidence of ischaemia. It is estimated that 5-15% of the 12 million patients with chronic angina in the US meet the criteria for having refractory angina. This review focuses on the following evolving pharmacological therapies for chronic refractory angina: L-arginine, ivabradine, ranolazine, nicorandil and trimetazidine. Evolving devices and invasive procedures including enhanced external counterpulsation, spinal cord stimulation, and transmyocardial revascularisation are also briefly discussed.

Selection of optimal therapy for chronic stable angina

Patients with chronic stable angina (CSA) seek a medical opinion for relief of their symptoms and because of fear of having a heart attack. The underlying lesion responsible for CSA is often a severe narrowing of one or more coronary arteries. In addition, the coronary arteries of patients with CSA contain many more nonobstructive lesions, which progress at variable rates, and are prone to rupture and may manifest as acute coronary syndromes (myocardial infarction , unstable angina , or sudden ischemic death). Most patients with CSA can be managed with medical treatment. For angina relief, optimum doses of one of the antianginal drugs (beta blockers , long-acting organic nitrates, or calcium channel blockers ) should be used. If the patient remains symptomatic, combination treatment of BBs plus nitrates or BBs plus dihydropyridine CCBs, or nondihydropyridine CCBs plus nitrates should be tried. Triple therapy has not been shown to be more effective than treatment with two agents. To reduce the incidence of MI, UA, and sudden ischemic death, treatment strategies should include smoking cessation, daily aspirin, daily exercise, and pharmacologic therapy for dyslipidemias, and for elevated blood pressure. Patients who remain symptomatic despite medical therapy and those not willing to take or unable to tolerate antianginal drugs should be considered for percutaneous or surgical coronary revascularization. Patients who do not respond to medical therapy and are not candidates for a revascularization procedure may be considered for additional treatment with trimetazidine or nicorandil (these drugs are not available in the United States or approved by the US Food and Drug Administration, but are available in some other countries). Ranolazine also looks promising but is not yet available for clinical use. As a last resort, enhanced external counterpulsation, spinal cord stimulation, sympathectomy, or direct transmyocardial revascularization should be considered for symptom relief.

Clinical Pharmacokinetics of Ranolazine

Ranolazine is a compound that is approved by the US FDA for the treatment of chronic angina pectoris in combination with amlodipine, beta-adrenoceptor antagonists or nitrates, in patients who have not achieved an adequate response with other anti-anginals. The anti-anginal effect of ranolazine does not depend on changes in heart rate or blood pressure. It acts through different pharmacological mechanisms where inhibition of the late inward sodium current (reducing calcium overload and thereby left ventricular diastolic tension) is one plausible mechanism of reduced oxygen consumption. Initial studies used an oral solution or an immediate-release (IR) capsule, but subsequently an extended-release (ER) formulation was developed to allow for twice-daily administration with maintained efficacy. Following administration of an oral solution or IR capsule, peak plasma concentrations (C(max)) are observed within 1 hour. After administration of radiolabelled ranolazine, 73% of the dose was excreted in urine, and unchanged ranolazine accounted for <5% of radioactivity in both urine and faeces. The absolute bioavailability ranges from 35% to 50%. Food has no effect on rate or extent of absorption from the ER formulation. Ranolazine protein binding is about 61-64% over the therapeutic concentration range. Volume of distribution at steady state ranges from 85 to 180 L. Ranolazine is extensively metabolised by cytochrome P450 (CYP) 3A enzymes and, to a lesser extent, by CYP2D6, with approximately 5% excreted renally unchanged. Elimination half-life of ranolazine is 1.4-1.9 hours but is apparently prolonged, on average, to 7 hours for the ER formulation as a result of extended absorption (flip-flop kinetics). Elimination occurs through parallel linear and saturable elimination pathways, where the saturable pathway is related to CYP2D6, which is partly inhibited by ranolazine. Oral plasma clearance diminishes with dose from, on average, 45 L/h at 500 mg twice daily to 33 L/h at 1000 mg twice daily. The departure from dose proportionality for this dose range is modest, with increases in steady-state C(max) and area under plasma concentration-time curve (AUC) from 0 to 12 hours of 2.5- and 2.7-fold, respectively. Ranolazine pharmacokinetics are unaffected by sex, congestive heart failure and diabetes mellitus. AUC increases up to 2-fold with advancing degree of renal impairment. Ranolazine is a weak inhibitor of CYP3A, and increases AUC and C(max) for simvastatin, its metabolites and HMG-CoA reductase inhibitor activity <2-fold. Digoxin AUC is increased 40-60% by ranolazine through P-glycoprotein inhibition. Ranolazine AUC is increased by CYP3A inhibitors ranging from 1.5-fold for diltiazem 180 mg once daily to 3.9-fold for ketoconazole 200 mg twice daily. Verapamil increases ranolazine exposure approximately 2-fold. CYP2D6 inhibition has a negligible effect on ranolazine exposure.

Ranolazine

Ranolazine (Ranexa), a piperazine derivative, is a new antianginal agent approved for the treatment of chronic stable angina pectoris for use as combination therapy when angina is not adequately controlled with other antianginal agents. While the exact mechanism of action of ranolazine is not known, its antianginal and anti-ischaemic effects do not appear to depend upon changes in blood pressure or heart rate. An extended-release (ER) oral formulation of ranolazine has been developed to facilitate twice-daily administration whilst maintaining therapeutically effective plasma concentrations. In patients with chronic stable angina, ranolazine ER monotherapy was shown to improve exercise duration at trough plasma drug concentration in a dose-dependent manner compared with placebo. The drug was effective as adjunctive therapy in patients with chronic stable angina whose condition was not controlled adequately with conventional antianginal therapy. In randomised clinical trials, ranolazine ER was well tolerated, with no overt effects on cardiovascular haemodynamics or conduction, apart from a modest increase in corrected QT (QTc) interval (but no torsades de pointes). Importantly, the efficacy and tolerability of ranolazine ER were not affected by comorbid conditions, including old age, heart failure (HF) or diabetes mellitus. Comparative trials of ranolazine ER with other antianginal agents and trials examining its effects on long-term morbidity and mortality in patients with ischaemic heart disease are required to determine with greater certainty the place of the drug in current antianginal therapy. Nevertheless, ranolazine ER may well prove to be a useful alternative and adjunct to conventional haemodynamic antianginal therapy in the treatment of chronic stable angina.

Analytical and semipreparative resolution of ranolazine enantiomers by liquid chromatography using polysaccharide chiral stationary phases

Novel HPLC methods were developed for the analytical and semipreparative resolution of new antianginal drug ranolazine enantiomers. Good baseline enantioseparation was achieved using cellulose tris (3,5-dimethylphenylcarbamate) (CDMPC) chiral stationary phases (CSPs) under both normal-phase and polar organic modes. The validation of the analytical methods including linearity, LODs, recovery, and precision, and the semipreparative resolution of ranolazine racemate were carried out using methanol as mobile phase without any basic and acidic additives under polar organic mode, using CDMPC CSPs. At analytical scale, the elution times of both enantiomers were less than 7.5 min at 20 degrees C and 1.0 mL/min, with the separation factor (a) 1.88 and the resolution factor (R(s)) 2.95. At semipreparative scale, about 14.3 mg/h enantiomers could be isolated and elution times of both enantiomers were less than 13 min at 2.0 mL/min. To increase the throughput, the technique of overlapping injections was used. The first eluted enantiomer was isolated with a purity of 99.6% enantiomer excess (e.e.) and > 99.0% yield. The second enantiomer was isolated with a purity of 98.8% e.e. and > 99.0% yield. In addition, optical rotation and circular dichroism spectroscopy of both ranolazine enantiomers isolated were also investigated.

Effect of hepatic impairment on the multiple-dose pharmacokinetics of ranolazine sustained-release tablets

The effect of hepatic impairment on the pharmacokinetics of a sustained-release formulation of ranolazine and 3 major metabolites was investigated in an open-label, parallel-group study. Ranolazine (875-mg loading dose followed by 500 mg every 12 hours for a total of 4 maintenance doses) was administered to subjects with mild (n = 8) or moderate (n = 8) hepatic impairment and a matched control group of healthy volunteers (n = 16). Moderate, but not mild, hepatic impairment significantly increased ranolazine steady-state area under the concentration-time curve (AUC0-12) by 76% (P < .001) and maximum plasma concentration C(max) by 51% (P < .01). The AUC0-12 ratio (metabolite/ranolazine) decreased for all metabolites in parallel with the degree of hepatic impairment. AUC0-infinity for the CYP3A substrate midazolam administered as a single dose was significantly correlated with ranolazine AUC0-12 at steady state (r2 = .33, P < .001). Over the time interval studied, ranolazine was well tolerated in healthy subjects and hepatically impaired subjects.

Efficacy and safety of fasudil in patients with stable angina: a double-blind, placebo-controlled, phase 2 trial

OBJECTIVES

This study sought to evaluate the efficacy and safety of fasudil, an orally available rho kinase inhibitor, in patients with stable angina.

BACKGROUND

Several small, non-placebo-controlled trials suggest that fasudil reduces myocardial ischemia in patients with stable or vasospastic angina.

METHODS

In a multicenter, double-blind, placebo-controlled, randomized trial, the efficacy and safety of fasudil were evaluated in stable angina patients. Of the 206 patients screened, 84 patients with reproducible exercise times were randomized 1:1 to fasudil or placebo. Nitroglycerin as needed and a beta- or calcium-channel blocker were allowed. Fasudil or matching placebo was force-titrated from 20 mg three times daily to 80 mg twice daily with 20 mg twice-daily increments every two weeks. Symptom-limited exercise testing was performed after two, four, six, and eight weeks of treatment.

RESULTS

At peak, exercise duration was significantly improved at all visits in both groups, although exercise duration was numerically greater in patients receiving fasudil versus those receiving placebo. Time to > or =1 mm ST-segment depression was increased with fasudil at both peak and trough compared with placebo (172.1 s vs. 44.0 s, p = 0.001, and 92.8 s vs. 26.4 s, p = 0.02, respectively). Fasudil improved Seattle Angina Questionnaire scores. No significant differences in Canadian Cardiovascular Society class, time to angina, or frequency of angina or nitroglycerin use were noted between groups. Fasudil did not affect heart rate or blood pressure, and was well tolerated.

CONCLUSIONS

Fasudil up to 80 mg three times daily significantly increased the ischemic threshold of angina patients during exercise with a trend toward increased exercise duration. Further investigation of fasudil doses >80 mg three times daily is indicated.

An increase in late sodium current potentiates the proarrhythmic activities of low-risk QT-prolonging drugs in female rabbit hearts

Assessment of the proarrhythmic risk associated with drugs that prolong the QT interval is difficult. We hypothesized that the proarrhythmic activities of drugs with very low to moderate risk of causing torsades de pointes would be well differentiated when the late sodium current (I(NaL)) was greater than normal. The effects of selected QT-prolonging drugs on electrical activity of female rabbit isolated hearts were determined in the absence and presence of sea anemone toxin (ATX-II; an enhancer of I(NaL)). I(NaL) recorded from ventricular myocytes isolated from female rabbit hearts was slightly increased by 1 and 3 nM ATX-II (n = 13, P < 0.01). ATX-II (1 nM) prolonged the duration of the monophasic action potential (MAPD(90)) the isolated heart by of 19 +/- 3% (P < 0.001, n = 31) and shifted the concentration-response relationships for cisapride (1-30 nM), ziprasidone (0.01-3 microM), quinidine (0.1-1 microM), and moxifloxacin (0.01-1 microM) to prolong MAPD to the left by 2- to 12-fold. In contrast, the increases in MAPD(90) caused by 1 nM ATX-II and pentobarbital were only additive, and the increases in MAPD(90) caused by ATX-II and ranolazine [(+/-)-N-(2,6-dimethylphenyl)-(4[2-hydroxy-3-(2-methoxyphenoxy)propyl]-1-piperazine] were less than additive. Episodes of arrhythmic activity were commonly observed, and beat-to-beat variability of action potential duration was increased, during exposure of hearts to cisapride, ziprasidone, quinidine, and moxifloxacin but not during exposure of hearts to ranolazine or pentobarbital, in the presence of ATX-II. Thus, in the female rabbit heart, ATX-II potentiated the effects of QT-prolonging drugs to increase MAPD(90) and unmasked the proarrhythmic activities of these drugs at clinically relevant drug concentrations.

Effects of ranolazine on exercise tolerance and HbA1c in patients with chronic angina and diabetes

AIMS

The anti-anginal efficacy and safety of ranolazine in diabetic and non-diabetic patients included in the Combination Assessment of Ranolazine In Stable Angina (CARISA) trial (JAMA 2004;291:309) were studied. Glycaemic control was also assessed in CARISA and its long-term open-label extension study.

METHODS AND RESULTS

Patients with chronic angina enrolled in CARISA (189 with diabetes, 634 without diabetes) on background atenolol, diltiazem, or amlodipine therapy were randomized to placebo, ranolazine 750 or 1000 mg twice daily for 12 weeks, during which exercise tolerance, angina frequency, nitroglycerin usage, glucose, HbA(1c), and lipids were measured. Patients completing the randomized study could enroll in an ongoing open-label extension study and were evaluated every 3 months. Ranolazine produced similar improvements in exercise parameters, nitroglycerin use, and angina frequency in diabetic and non-diabetic patients. Adverse events were similar between groups. Fasting glucose and lipids remained unaltered in diabetic patients after 12 weeks of therapy. In a post hoc analysis, ranolazine 750 and 1000 mg reduced HbA(1c) vs. placebo by 0.48+/-0.18% (P=0.008) and 0.70+/-0.18% (P=0.0002), respectively; the HbA(1c) levels appeared to remain unchanged over time during long-term therapy.

CONCLUSION

Anti-anginal efficacy and safety of ranolazine for angina were similar between diabetic and non-diabetic patients. Ranolazine significantly improved glycaemic control in diabetic patients.

Ranolazine*

Ranolazine is a novel new antianginal agent currently under investigation as monotherapy and adjunct therapy for the treatment of chronic stable angina. While the mechanism of action of ranolazine is not completely understood, it is believed to involve a reduction in fatty acid oxidation, ultimately leading to a shift in myocardial energy production from fatty acid oxidation to glucose oxidation. Since the oxidation of glucose requires less oxygen than the oxidation of fatty acids, ranolazine can help maintain myocardial function in times of ischemia. In addition, ranolazine has minimal effect on blood pressure and heart rate. Ranolazine, by inhibiting cellular ionic channels, prolongs the corrected QT interval. However, ranolazine has not yet been associated with any incidences of ventricular arrhythmia. The clinical data with ranolazine focuses on its use in chronic stable angina, where it has been shown to increase exercise tolerance and decrease angina compared with placebo, as well as in combination with beta-blockers and calcium channel blockers. The use of ranolazine for other cardiac conditions and the effect of ranolazine on morbidity and mortality remains to be determined. Ongoing clinical trials will help further establish the role of ranolazine in the treatment of cardiovascular disorders.

Ranolazine, a new antianginal drug

The increasing and unmet social and economic burden of ischemic heart disease calls for new antianginal therapies. Ranolazine, a new antianginal agent, has a different mode of action from existing therapies, which act by decreasing indices of cardiac work. Ranolazine mainly affects the late sodium current across the membrane of cardiomyocytes, inducing a cascade of electrophysiologic and metabolic effects with the potential to reduce the cardiac ischemic burden without significantly changing blood pressure and heart rate. In clinical trials, ranolazine has been demonstrated to exert antianginal and anti-ischemic effects in chronic angina. It improves exercise performance, and decreases angina frequency and nitroglycerin use. Ranolazine is well tolerated at therapeutic doses. Larger studies are needed to explore the effects on hard end-points of morbidity and mortality.

Current medical management of chronic stable angina

Severe atherosclerotic narrowing of one or more coronary arteries is responsible for myocardial ischemia and angina pectoris in most patients with stable angina. The coronary arteries of patients with stable angina also contain many more non-obstructive plaques, which are prone to rupture resulting in acute coronary syndrome (unstable angina, myocardial infarction, sudden ischemic death). Therefore, the medical management must use strategies which not only relieve symptoms and prolong angina free walking but also reduce the incidence of adverse clinical outcomes. Whether any of the approved antianginal drugs, nitrates, beta-blockers, and calcium channel blockers reduce the incidence of adverse clinical outcomes in patients with stable angina has not been studied to date. Published data shows that percutaneous coronary revascularization procedures and coronary bypass surgery are effective in relieving angina but these procedures do not reduce mortality or the incidence of myocardial infarction compared to anti-anginal drug therapy. From the available data, an initial trial of medical treatment with anti-anginal drugs and strategies to reduce adverse clinical outcomes (smoking cessation, daily aspirin, treatment of dyslipidemias and hypertension) is indicated in most patients with stable angina pectoris. The initial choice of drug will depend on the presence or absence of comorbid conditions. Patients who do not respond to medical therapy or do not wish to take anti-anginal drugs and whose life style is limited because of anginal symptoms should be offered percutaneous revascularization procedures with or without stent placement or coronary bypass surgery. New drug-coated stents hold promise but long-term data and large-scale trials assessing the continued long-term improvement in symptoms and reduction of adverse outcomes is needed before offering such devices to all patients with stable angina. Newer medical therapies such as metabolic modulators and sinus rate lowering drugs also hold promise but need further evaluation. Patients who have refractory angina despite optimal medical therapy and are not candidates for revascularization procedures may be candidates for some new techniques of enhanced external Counterpulsation, Spinal Cord Stimulation, sympathectomy or direct transmyocardial revascularization. The usefulness of these techniques, however, needs to be confirmed in large randomized trials.

Comparative efficacy of ranolazine versus atenolol for chronic angina pectoris

We investigated whether ranolazine therapy improves exercise-induced angina pectoris and myocardial ischemia compared with placebo or with standard doses of atenolol in patients who had chronic angina and evaluated the effects on hemodynamics at rest and during exercise. In this trial, 158 patients who had symptom-limited exercise discontinued beta-blocker therapy and were randomized into a double-blind, 3-period, crossover study of 400 mg of immediate-release ranolazine 3 times daily, 100 mg/day of atenolol, or placebo, each administered for 1 week. Exercise tests were administered at the end of each treatment period. Therapy with ranolazine or atenolol produced statistically significant improvement in all 3 exercise end points compared with placebo. Compared with atenolol therapy, ranolazine therapy resulted in significantly longer total exercise duration and was statistically indistinguishable from atenolol for time to onset of angina and ST-segment depression. Except for a modest increase in systolic blood pressure at peak exercise during ranolazine therapy, hemodynamic measurements did not differ significantly during ranolazine and placebo therapies. In contrast, atenolol significantly decreased blood pressure, heart rate, and rate-pressure product at rest and during exercise compared with placebo or ranolazine. In conclusion, ranolazine therapy prolonged exercise duration and decreased exercise-induced ischemia and angina with quantitative effects equal to or greater than those with atenolol. Unlike atenolol, the anti-ischemic and antianginal effects of ranolazine occurred without decreases in blood pressure, heart rate, or rate-pressure product.

Fatty acid oxidation inhibitors in the management of chronic complications of atherosclerosis

Ischemic heart disease is characterized by a modification of the normal energy balance of the heart. During and following an ischemic event, circulating fatty acids are elevated, resulting in the acceleration of fatty acid oxidation at the expense of glucose oxidation. Despite the reduction in glucose oxidation, the rate of glycolysis increases, leading to an uncoupling of glucose metabolism. This results in the accumulation of metabolic byproducts, which leads to a decrease in cardiac efficiency. A novel therapeutic strategy involves improving the efficiency of oxygen utilization by the ischemic heart by the modulation of energy metabolism. This can be achieved by a reduction in the levels of circulating fatty acids using beta-blockers, glucose-insulin-potassium infusions, and nicotinic acid. Alternatively, fatty acid oxidation can be directly inhibited using trimetazidine, ranolazine, or glucose oxidation directly activated using dichloroacetate, which significantly improves the efficiency of the heart.

Ischemic heart disease: metabolic approaches to management

The number of patients with coronary artery disease and its risk factors is increasing in Western nations. New treatments for these patients may soon include a class of agents known as the metabolic modulators. This group of agents consists of the partial fatty acid oxidation inhibitors trimetazidine and ranolazine, as well as dichloroacetate, which promotes carbohydrate utilization. Metabolic modulators also include the nutriceuticals L-carnitine and D-ribose. The available evidence regarding the benefits of each of these five agents is reviewed.

Current and future treatment strategies for refractory angina

Patients with refractory angina are not candidates for revascularization and have both class III or IV angina and objective evidence of ischemia despite optimal medical therapy. An estimated 300,000 to 900,000 patients in the United States have refractory angina, and 25,000 to 75,000 new cases are diagnosed each year. This review focuses on treatment strategies for refractory angina and includes the mechanism of action and clinical trial data for each strategy. The pharmacological agents that have been used are ranolazine, ivabradine, nicorandil, L-arginine, testosterone, and estrogen; currently, only L-arginine, testosterone, and estrogen are approved by the Food and Drug Administration. Results with the noninvasive treatments of enhanced external counterpulsation and transcutaneous electrical nerve stimulation are provided. Invasive treatment strategies including spinal cord stimulation, transmyocardial revascularization, percutaneous myocardial revascularization, and gene therapy are also reviewed.

Ranolazine: ion-channel-blocking actions and in vivo electrophysiological effects

Ranolazine is a novel anti-ischemic drug that prolongs the QT interval. To evaluate the potential mechanisms and consequences, we studied: (i) Ranolazine's effects on HERG and IsK currents in Xenopus oocytes with two-electrode voltage clamp; (ii) effects of ranolazine, compared to d-sotalol, on effective refractory period (ERP), QT interval and ventricular rhythm in a dog model of acquired long QT syndrome; and (iii) effects on selected native currents in canine atrial myocytes with whole-cell patch-clamp technique. Ranolazine inhibited HERG and IsK currents with different potencies. HERG was inhibited with an IC(50) of 106 micromol l(-1), whereas the IC(50) for IsK was 1.7 mmol l(-1). d-Sotalol caused reverse use-dependent ERP and QT interval prolongation, whereas ranolazine produced modest, nonsignificant increases that plateaued at submaximal doses. Neither drug affected QRS duration. d-Sotalol had clear proarrhythmic effects, with all d-sotalol-treated dogs developing torsades de pointes (TdP) ventricular tachyarrhythmias, of which they ultimately died. In contrast, ranolazine did not generate TdP. Effects on I(Kr) and I(Ks) were similar to those on HERG and IsK. Ranolazine blocked I(Ca) with an IC(50) of approximately 300 micromol l(-1). I(Na) was unaffected. We conclude that ranolazine inhibits I(Kr) by blocking HERG currents, inhibits I(Ca) at slightly larger concentrations, and has modest and self-limited effects on the QT interval. Unlike d-sotalol, ranolazine does not cause TdP in a dog model. The greater safety of ranolazine may be due to its ability to inhibit I(Ca) at concentrations only slightly larger than those that inhibit I(Kr), thus producing offsetting effects on repolarization.