Calcium antagonist protects the myocardium from reperfusion injury by interfering with mechanisms directly related to reperfusion: an experimental study with the ultrashort-acting calcium antagonist clevidipine

Hypertensive emergencies: an update

PURPOSE OF REVIEW

Systemic hypertension (HTN) is a common medical condition affecting over 1 billion people worldwide. One to two percent of patients with HTN develop acute elevations of blood pressure (hypertensive crises) that require medical treatment. However, only patients with true hypertensive emergencies require the immediate and controlled reduction of blood pressure with an intravenous antihypertensive agent.

RECENT FINDINGS

Although the mortality from hypertensive emergencies has decreased, the prevalence and demographics of this disorder have not changed over the last 4 decades. Clinical experience and reported data suggest that patients with hypertensive urgencies are frequently inappropriately treated with intravenous antihypertensive agents, whereas patients with true hypertensive emergencies are overtreated with significant complications.

SUMMARY

Despite published guidelines, most patients with hypertensive crises are poorly managed with potentially severe outcomes.

Clevidipine for severe hypertension in patients with renal dysfunction: a VELOCITY trial analysis

Introduction. Acute and severe hypertension is common, especially in patients with renal dysfunction (RD). Clevidipine is a rapidly acting (t½∼1 min) intravenous (IV) dihydropyridine calcium-channel blocker metabolized by blood and tissue esterases and may be useful in patients with RD. The purpose of this analysis was to assess the safety and efficacy of clevidipine in patients with RD. Methods. VELOCITY, a multicenter open-label study of severe hypertension, enrolled 126 patients with persistent systolic blood pressure (SBP) >180 mmHg. Investigators pre-specified a SBP initial target range (ITR) for each patient to be achieved within 30 min. Blood pressure monitoring was by cuff. Clevidipine was infused via peripheral IV at 2 mg/h for at least 3 min, then doubled every 3 min as needed to a maximum of 32 mg/h (non-weightbased treat-to-target protocol). Per protocol, clevidipine was continued for at least 18 h (96 h maximum). RD was diagnosed and reported as an end-organ injury by the investigator and was defined as requiring dialysis or an initial creatinine >2.0 mg/dl. Primary endpoints were the percentage of patients within the ITR by 30 min and the percentage below the ITR after 3 min of clevidipine infusion. Results. Of the 24 patients with moderate to severe RD, most (13/24) were dialysis dependent. Forty-six percent were male, with mean age 51 >14 years; 63% were black and 96% had a hypertension history. Median time to achieve the ITR was 8.5 min. Almost 90% of patients reached the ITR in 30 min without evidence of overshoot and were maintained on clevidipine through 18 h. Most patients (88%) transitioned to oral antihypertensive therapy within 6 h of clevidipine termination. Conclusions. This report is the first demonstrating that clevidipine is safe and effective in RD complicated by severe hypertension. Prolonged infusion maintained blood pressure within a target range and allowed successful transition to oral therapy.

Clevidipine for the treatment of severe hypertension in adults

BACKGROUND

Intravenous antihypertensive agents are used when immediate control of blood pressure (BP) is required, including during the perioperative cardiac surgery period. Controlling postoperative BP is challenging because of the need to adequately reduce BP while maintaining appropriate end-organ perfusion. Clevidipine is an intravenous, ultra-short-acting, third-generation dihydropyridine calcium channel antagonist with selectivity for arteriolar vasodilatation. It is approved by the US Food and Drug Administration for the treatment of severe hypertension.

OBJECTIVE

This paper reviews the clinical pharmacology, pharmacokinetic and pharmacodynamic properties, tolerability, and clinical efficacy of clevidipine.

METHODS

To minimize selection bias, each author conducted an independent search for English-language publications indexed on MEDLINE and International Pharmaceutical Abstracts through January 2010 using the term clevidipine. All identified prospective, randomized and nonrandomized Phase III trials were included in the review.

RESULTS

Seven Phase III trials were identified in which clevidipine was compared with baseline, placebo, or other intravenous antihypertensive agents in the settings of severe hypertension (1 study), preoperative cardiac surgery (1), perioperative cardiac surgery (1), and postoperative cardiac surgery (4). In a multicenter, randomized, double-blind, placebo-controlled study of the efficacy of clevidipine in treating preoperative hypertension, the mean reduction from baseline in mean arterial pressure was 31.2% with clevidipine and 11.2% with placebo (P < 0.001). In a randomized, open-label, prospective study involving separate comparisons of clevidipine with nitroglycerin, sodium nitroprusside, and nicardipine, the median total AUC for digression in systolic BP from the predetermined target range differed significantly between clevidipine and nitroglycerin (4.14 vs 8.87 mm Hg . min/h; respectively, P < 0.001) and between clevidipine and sodium nitroprusside (4.37 vs 10.5 mm Hg . min/h; P = 0.003), but not between clevidipine and nicardipine (1.76 and 1.69 mm Hg . min/h). Another study found no significant difference in efficacy in controlling BP during the 3-hour study period between clevidipine and sodium nitroprusside (AUC for mean [SD] arterial pressure, 106 [25] and 101 [28] mm Hg . min/h, respectively). Adverse events in these studies included atrial fibrillation (13.0%-36.1% clevidipine vs 12.0% placebo), nausea (5.0%-21.0% vs 12.0%, respectively), fever (19.0% vs 13.7%), insomnia (12.0% vs 6.1%), and acute renal failure (9.0% vs 2.0%). In the studies reviewed, only 1 case of chest discomfort in the setting of severe hypertension was considered a serious adverse event related to clevidipine therapy.

CONCLUSION

In the Phase III trials reviewed, clevidipine was effective in controlling BP in the settings of perioperative cardiac surgery and severe hypertension and was associated with minimal adverse effects.

Perioperative hypertension: a review of current and emerging therapeutic agents

Perioperative hypertension is a common problem encountered by anesthesiologists, surgeons, internists, and intensivists. Surprisingly, no randomized, placebo-controlled studies exist that show that the treatment of perioperative hypertension reduces morbidity or mortality. Nevertheless, perioperative hypertension requires careful management. While sodium nitroprusside and nitroglycerin are commonly used to treat these conditions, these agents are less than ideal. Intravenous beta blockers and calcium channel blockers have particular appeal in this setting.

Clevidipine Butyrate Injectable Emulsion

Each month, subscribers to The Formulary Monograph Service receive 5 to 6 well-documented monographs on drugs that are newly released or are in late phase 3 trials. The monographs are targeted to Pharmacy & Therapeutics Committees. Subscribers also receive monthly 1-page summary monographs on agents that are useful for agendas and pharmacy/nursing inservices. A comprehensive target drug utilization evaluation (DUE) is also provided each month. With a subscription, the monographs are sent in print and are also available online. Monographs can be customized to meet the needs of a facility. Subscribers to the The Formulary Monograph Service also receive access to a pharmacy bulletin board, The Formulary Information Exchange (The F.I.X). All topics pertinent to clinical and hospital pharmacy are discussed on The F.I.X.

Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. For more information about The Formulary Monograph Service or The F.I.X., call The Formulary at 800-322-4349. The November 2008 monograph topics are on romiplostim, rivaroxaban, golimumab, dronedarone, and degarelix. The DUE is on romiplostim.

Treatment of acute severe hypertension: current and newer agents

Approximately 72 million people in the US experience hypertension. Worldwide, hypertension may affect as many as 1 billion people and be responsible for approximately 7.1 million deaths per year. It is estimated that approximately 1% of patients with hypertension will, at some point, develop a hypertensive crisis. Hypertensive crises are further defined as either hypertensive emergencies or urgencies, depending on the degree of blood pressure elevation and presence of end-organ damage. Immediate reduction in blood pressure is required only in patients with acute end-organ damage (i.e. hypertensive emergency) and requires treatment with a titratable, short-acting, intravenous antihypertensive agent, while severe hypertension without acute end-organ damage (i.e. hypertensive urgency) is usually treated with oral antihypertensive agents. The primary goal of intervention in a hypertensive crisis is to safely reduce blood pressure. The appropriate therapeutic approach of each patient will depend on their clinical presentation. Patients with hypertensive emergencies are best treated in an intensive care unit with titratable, intravenous, hypotensive agents. Rapid-acting intravenous antihypertensive agents are available, including labetalol, esmolol, fenoldopam, nicardipine and sodium nitroprusside. Newer agents, such as clevidipine and fenoldopam, may hold considerable advantages to other available agents in the management of hypertensive crises. Sodium nitroprusside is an extremely toxic drug and its use in the treatment of hypertensive emergencies should be avoided. Similarly, nifedipine, nitroglycerin and hydralazine should not to be considered first-line therapies in the management of hypertensive crises because these agents are associated with significant toxicities and/or adverse effects.

Perioperative hypertension management

Perioperative hypertension is commonly encountered in patients that undergo surgery. While attempts have been made to standardize the method to characterize the intraoperative hemodynamics, these methods still vary widely. In addition, there is a lack of consensus concerning treatment thresholds and appropriate therapeutic targets, making absolute recommendations about treatment difficult. Nevertheless, perioperative hypertension requires careful management. When treatment is necessary, therapy should be individualized for the patient. This paper reviews the pharmacologic agents and strategies commonly used in the management of perioperative hypertension.

Hypertensive crises: challenges and management

Hypertension affects > 65 million people in the United States and is one of the leading causes of death. One to two percent of patients with hypertension have acute elevations of BP that require urgent medical treatment. Depending on the degree of BP elevation and presence of end-organ damage, severe hypertension can be defined as either a hypertensive emergency or a hypertensive urgency. A hypertensive emergency is associated with acute end-organ damage and requires immediate treatment with a titratable short-acting IV antihypertensive agent. Severe hypertension without acute end-organ damage is referred to as a hypertensive urgency and is usually treated with oral antihypertensive agents. This article reviews definitions, current concepts, common misconceptions, and pitfalls in the diagnosis and management of patients with acutely elevated BP as well as special clinical situations in which BP must be controlled.

Current diagnosis and management of hypertensive emergency

The appropriate and timely evaluation and treatment of patients with severely elevated blood pressure is essential to avoid serious adverse outcomes. Most importantly, the distinction between a hypertensive emergency (crisis) and urgency needs to be made. A sudden elevation in systolic (SBP) and/or diastolic blood pressure (DBP) that is associated with acute end organ damage (cardiovascular, cerebrovascular, or renal) is defined as a hypertensive crisis or emergency. In contrast, acute elevation in SBP and/or DBP not associated with evidence of end organ damage is defined as hypertensive urgency. In patients with a hypertensive emergency, blood pressure control should be attained as expeditiously as possible with parenteral medications to prevent ongoing and potentially permanent end organ damage. In contrast, with hypertensive urgency, blood pressure control can be achieved with the use of oral medications within 24-48 hours. This paper reviews the management of hypertensive emergencies.

Pharmacodynamic, Pharmacokinetic and Clinical Effects of Clevidipine, an Ultrashort-Acting Calcium Antagonist for Rapid Blood Pressure Control

Clevidipine is an ultrashort-acting vasoselective calcium antagonist under development for short-term intravenous control of blood pressure. Studies in animals, healthy volunteers and patients have demonstrated the vascular selectivity and rapid onset and offset of antihypertensive action of clevidipine, a synthetic 1,4-dihydropyridine that inhibits L-type calcium channels. Clevidipine has a high clearance (0.05 L/min/kg) and is rapidly hydrolyzed to inactive metabolites by esterases in arterial blood. Its half-life in patients undergoing cardiac surgery is less than one min. Unlike sodium nitroprusside, a drug commonly used for the short-term control of blood pressure, which dilates both arterioles and veins, clevidipine reduces blood pressure through a selective effect on arterioles. As documented in animals and in cardiac surgical patients, clevidipine reduces peripheral resistance without any undesirable effect on cardiac filling pressure. It increases stroke volume and cardiac output. In anesthetized patients undergoing cardiac surgery clevidipine, unlike sodium nitroprusside, does not increase heart rate. In addition of having a favorable hemodynamic profile, suitable for rapid control of blood pressure, clevidipine protects against ischemia/reperfusion injuries, which are not uncommon during major surgery. In anesthetized pigs, clevidipine reduced infarct size after 45 min-long myocardial ischemia by 40%. In rats, renal function and splanchnic blood flow were better maintained when blood pressure was reduced with clevidipine than with sodium nitroprusside. Clevidipine was well tolerated in Phases I and II of clinical trials that included more than 300 individuals/patients. Since there are no known compounds with similar pharmacodynamic and pharmacokinetic properties in clinical development, it is anticipated that clevidipine, a compound tailored to the needs of anesthesiologists, has the potential to become a drug of choice for controlling blood pressure during surgical procedures.

Failure to demonstrate myocardial protective effects of the ultra short-acting calcium antagonist clevidipine in a closed-chest reperfusion porcine model

Restoration of myocardial perfusion is essential in acute myocardial infarction for the salvaging of myocardial tissue. However, reperfusion per se can provoke myocardial necrosis within the jeopardized tissue. Yet, no intervention has been successfully applied to the clinical situation in this matter. Clevidipine, an ultra-short acting calcium antagonist, has, in open-chest animal models, shown to reduce the extent of reperfusion injury. In the present study we intended to reproduce those findings in a closed-chest porcine model with a clinically applicable set up. Pigs were subjected to balloon occlusion of the left anterior descending coronary artery (LAD) for 45 minutes. During 25 minutes, starting 1 minute prior to reperfusion, clevidipine, Intralipid, or saline was infused antegradely into the endangered myocardium. As no significant effects on infarct size were achieved, the model was modified. In a second phase, different anesthesias were evaluated addressing the same issue. Nonetheless no significant effects on infarct size were observed. Different techniques of occluding LAD, in an open-chest model, were investigated in a third phase, and revealed no significant differences between the techniques. However, when comparing all the closed- versus open-chest models, significant reduction in infarct size by the use of clevidipine was only obtained in the open-chest models. We could not demonstrate any significant myocardial protective effect with clevidipine in our porcine, closed-chest, acute infarct, and reperfusion model. However, in a modified open-chest model we obtained significant reduction in infarct size. Further studies are required to explain the discrepancies.

Involvement of Na+/H+ exchanger in hypoxia/re-oxygenation-induced neonatal rat cardiomyocyte apoptosis

Although increased Na(+)/H(+) exchanger type-1 (NHE-1) activity has been implicated in the pathogenesis of myocardial infarction, the role of NHE-1 in induction of apoptosis, and the potential mechanisms involved have not been fully characterized. This study tested the hypothesis that NHE-1 activity is involved in hypoxia (H)/re-oxygenation (Re)-induced cardiomyocyte apoptosis by increasing mitochondrial Ca(2+) ([Ca(2+)]m). Primary cultured neonatal rat cardiomyocytes were subjected to 4.5 h of H followed by 12 h of Re. Relative to H alone, the level of X-rhod-1 acetoxymethyl (AM)-labeled [Ca(2+)]m was increased, and the frequency of cell death (propidium iodide (PI) staining) and apoptotic cells (terminal deoxynucleotidyl transferase (TdT)-mediated-UTP nick end labeling [TUNEL]), confirmed by Annexin-V, were augmented at the end of Re, along with appearance of cytosolic cytochrome c, activation of caspase-3, and increased ratio of Bax and Bcl-2. Addition of cariporide (20 micromol/l), a well-known NHE-1 inhibitor, to cultured cells before H significantly reduced [Ca(2+)]m, the number of PI and TUNEL positive cells relative to the levels at end of Re, but did not completely eliminate these changes compared to Sham control. There was a strong trend for attenuation in increased levels of [Ca(2+)]m, and the number of PI and TUNEL positive cells when same dose of cariporide was added only at Re, but the difference in these variables did not reach significance. In contrast, the levels of [Ca(2+)]m and the number of PI and TUNEL positive cells were significantly reduced to a level comparable to Sham control when cariporide (20 micromol/l) was administered before H and during Re, respectively, associated with a reduction in cytosolic cytochrome c, caspase-3 activity and ratio of Bax and Bcl-2. In conclusion, these data suggest that NHE-1 is involved in induction of cardiomyocyte apoptosis during both H and Re through a [Ca(2+)]m-dependent manner, thereby resulting in activation of cytochrome c-caspase-3 signaling pathways.

Calcium antagonist clevidipine reduces myocardial reperfusion injury by a mechanism related to bradykinin and nitric oxide

Certain calcium antagonists, in addition to their classic actions, can increase blood flow during ischemia via bradykinin- and nitric oxide (NO)-dependent mechanisms and protect the ischemic myocardium against reperfusion injury by enhancing NO bioavailability. The current study aimed to investigate the possible involvement of bradykinin and NO in the cardioprotective action of the short-acting calcium antagonist clevidipine during late ischemia and reperfusion. Anesthetized pigs were subjected to 45-min ligation of the left anterior descending coronary artery (LAD) followed by 4 h of reperfusion. Four groups were given vehicle, clevidipine, clevidipine in combination with the bradykinin B2 receptor antagonist HOE 140 or clevidipine in combination with HOE 140 and the NO donor S-nitroso-N-acetyl-D,L-penicillamine (SNAP) into the LAD during the last 10 min of ischemia and the first 5 min of reperfusion. There were no significant differences in hemodynamics among the groups before ischemia or during ischemia-reperfusion. The infarct size (IS) was 87% +/- 2% of the area at risk in the vehicle group. Clevidipine reduced the IS to 60% +/- 3% (p < 0.001 vs vehicle). When clevidipine was administered together with HOE 140, the protective effect of clevidipine was abolished (IS, 80% +/- 3%; p < 0.001 vs clevidipine), whereas addition of SNAP restored cardioprotection (IS, 62% +/- 5%; p < 0.001 vs vehicle). The increase in LAD blood flow by endothelium-dependent dilator substance P was significantly larger in the clevidipine group than in the other groups. The results suggest that the cardioprotective effect of clevidipine during late ischemia and early reperfusion is mediated via bradykinin- and NO-related mechanisms.

Time-dependent cardioprotection with calcium antagonism and experimental studies with clevidipine in ischemic-reperfused pig hearts: part II

The intracellular calcium level is increased during ischemia and early reperfusion. The aim of this study was to study the role of the calcium influx in the development of myocardial ischemic and reperfusion injury during the early and late phases of ischemia and during early reperfusion. An ultrashort-acting calcium antagonist, clevidipine, was used as a tool for this investigation. Pentobarbital-anesthetized pigs were subjected to 45 minutes of LAD occlusion followed by 240 minutes of reperfusion. In the first set of experiments, clevidipine (0.3 nmol/kg per minute) was infused over 5 minutes into the ischemic myocardium via a catheter in the LAD, starting at 5, 35, or 44 minutes following the onset of ischemia (n = 6 in each group). The area at risk and the infarct size were determined after 240 minutes of reperfusion by staining with Evans blue dye and triphenyl tetrazolium chloride (TTC), respectively. In a second set of experiments, two groups of animals (n = 6 in each) were subjected to the same periods of ischemia and reperfusion; one group received no infusion during ischemia, whereas the other group received vehicle infusion during a 5-minute period between 5 and 10 minutes of ischemia. In the first set of experiments, there were no significant differences between the groups with regard to hemodynamic variables. The area at risk expressed as a percentage of the left ventricle was of similar magnitude in all three clevidipine-treated groups (about 18%). The infarct size, expressed as a percentage of the area at risk, was significantly smaller in pigs given clevidipine after 5 minutes (58 +/- 17%; p < 0.01) and after 44 minutes (42 +/- 6%; p < 0.01) of ischemia than in pigs receiving clevidipine after 35 minutes of ischemia (85 +/- 4%). The difference in infarct size between pigs given clevidipine after 5 or 44 minutes of ischemia was not significant. In the second set of experiments, there was a similar area at risk and no significant difference in infarct size between the noninfusion group and the 5-minute vehicle infusion group, indicating that the LAD infusion per se did not affect infarct size. The present results demonstrate that blockade of calcium influx by the short-acting dihydropyridine calcium antagonist clevidipine during the early phase of ischemia and at the time of reperfusion, but not during a late phase of ischemia, limits infarct size induced by ischemia and reperfusion. This indicates that the pathophysiological importance of calcium influx varies according to the different phases of myocardial ischemia and reperfusion.

Time-dependent cardioprotection with calcium antagonism and experimental studies with clevidipine in ischemic-reperfused pig hearts: part I

Clevidipine is a new ultrashort-acting dihydropyridine calcium antagonist developed for blood pressure regulation during cardiac surgery. When given locally to the ischemic and reperfused myocardium, clevidipine exerts a cardioprotective effect that varies depending on the timing of administration during ischemia. The current study explored the pharmacokinetics of clevidipine when administered locally into the coronary circulation. Pentobarbital-anesthetized pigs were randomly divided into four groups, of which three were subjected to myocardial ischemia through ligation of the left anterior descending coronary artery (LAD) for 15, 35, or 45 minutes (n = 4 in each group). The fourth group (n = 4) was not subjected to LAD occlusion and acted as nonischemic controls. Clevidipine (0.3 nmol/kg per minute) was infused over a period of 5 minutes through a catheter distal to the LAD ligation in the ischemic pigs, or at the corresponding site of the nonligated LAD in the nonischemic pigs. Following release of the LAD ligation, or in the nonligated group following the drug infusion, the pigs were subjected to 60 minutes of reperfusion. Simultaneous blood samples were obtained for analysis of clevidipine from the femoral artery and the coronary vein during reperfusion and during drug infusion in the nonischemic pigs. Blood samples for estimating the in vitro hydrolysis rate both in whole blood and in plasma were also obtained. In nonischemic hearts, clevidipine reached a steady state level in the coronary venous blood of about 30 nM during the infusion. The concentration declined almost to the detection limit (1 nM) within 3 minutes of the end of infusion. The mean blood clearance of clevidipine was calculated to be 0.17 l/min per kilogram, and the estimated half-life was 0.5 minute. In animals subjected to different periods of ischemia, very low levels of clevidipine were detected in the coronary venous blood only during the first 2 minutes of reperfusion. There were no detectable levels in the arterial blood at any time. Blood concentration profiles of clevidipine did not differ with the length of myocardial ischemia. The in vitro half-life in pig blood was 13 minutes, and the corresponding half-life in plasma was 111 minutes. At a dose known to exert cardioprotection when given as an intracoronary injection, the systemic concentration of clevidipine does not reach pharmacologically active levels. Clevidipine has an ultrashort blood half-life, and ischemic duration of up to 45 minutes does not seem to change the cardiac metabolism of this drug. Thus, it represents a pharmacological tool well suited for the study of time windows in cardioprotection. Moreover, considering the possibility of exerting myocardioprotection without any systemic effects, it could be an interesting compound to test in a clinical setting.