Calcium channel antagonists in the treatment of coronary artery disease: fundamental pharmacological properties relevant to clinical use

Novel Polyhydroquinoline-Hydrazide-Linked Schiff's Base Derivatives: Multistep Synthesis, Antimicrobial, and Calcium-Channel-Blocking Activities

Polyhydroquinoline (PHQ) are the unsymmetrical Hantzsch derivatives of 1,4-dihydropyridines with several biological applications. In this work, twenty-five (3-27) new Schiff's base derivatives of polyhydroquinoline hydrazide were synthesized in excellent to good yields by a multi-component reaction. The structures of the synthesized products (1-27) were deduced with the help of spectroscopic techniques, such as 1H-, 13C -NMR, and HR-ESI-MS. The synthesized products (1-27) were tested for their antibacterial and in vitro calcium -channel-blocking (CCB) potentials using the agar-well diffusion method, and isolated rat aortic ring preparations, respectively. Among the series, sixteen compounds were found to inhibit the growth of Escherichia coli and Enterococcus faecalis. Among them, compound 17 was observed to be the most potent one at a dose 2 µg/mL, with an 18 mm zone of inhibition against both bacteria when it was compared with the standard drug amoxicillin. Eight compounds showed CCB activity of variable potency; in particular, compound 27 was more potent, with an EC50 value of 0.7 (0.3-1.1) µg/mL, indicating their CCB effect.

A pathophysiological compass to personalize antianginal drug treatment

Myocardial ischaemia results from coronary macrovascular or microvascular dysfunction compromising the supply of oxygen and nutrients to the myocardium. The underlying pathophysiological processes are manifold and encompass atherosclerosis of epicardial coronary arteries, vasospasm of large or small vessels and microvascular dysfunction - the clinical relevance of which is increasingly being appreciated. Myocardial ischaemia can have a broad spectrum of clinical manifestations, together denoted as chronic coronary syndromes. The most common antianginal medications relieve symptoms by eliciting coronary vasodilatation and modulating the determinants of myocardial oxygen consumption, that is, heart rate, myocardial wall stress and ventricular contractility. In addition, cardiac substrate metabolism can be altered to alleviate ischaemia by modulating the efficiency of myocardial oxygen use. Although a universal agreement exists on the prognostic importance of lifestyle interventions and event prevention with aspirin and statin therapy, the optimal antianginal treatment for patients with chronic coronary syndromes is less well defined. The 2019 guidelines of the ESC recommend a personalized approach, in which antianginal medications are tailored towards an individual patient's comorbidities and haemodynamic profile. Although no antianginal medication improves survival, their efficacy for reducing symptoms profoundly depends on the underlying mechanism of the angina. In this Review, we provide clinicians with a rationale for when to use which compound or combination of drugs on the basis of the pathophysiology of the angina and the mode of action of antianginal medications.

Differential effects on out-of-hospital cardiac arrest of dihydropyridines: real-world data from population-based cohorts across two European countries

AIMS

Various drugs increase the risk of out-of-hospital cardiac arrest (OHCA) in the general population by impacting cardiac ion channels, thereby causing ventricular tachycardia/fibrillation (VT/VF). Dihydropyridines block L-type calcium channels, but their association with OHCA risk is unknown. We aimed to study whether nifedipine and/or amlodipine, often-used dihydropyridines, are associated with increased OHCA risk, and how these drugs impact on cardiac electrophysiology.

METHODS AND RESULTS

We conducted a case-control study with VT/VF-documented OHCA cases with presumed cardiac cause from ongoing population-based OHCA registries in the Netherlands and Denmark, and age/sex/index date-matched non-OHCA controls (Netherlands: PHARMO Database Network, Denmark: Danish Civil Registration System). We included 2503 OHCA cases, 10 543 non-OHCA controls in Netherlands, and 8101 OHCA cases, 40 505 non-OHCA controls in Denmark. To examine drug effects on cardiac electrophysiology, we performed single-cell patch-clamp studies in human-induced pluripotent stem cell-derived cardiomyocytes. Use of high-dose nifedipine (≥60 mg/day), but not low-dose nifedipine (<60 mg/day) or amlodipine (any-dose), was associated with higher OHCA risk than non-use of dihydropyridines [Netherlands: adjusted odds ratios (ORadj) 1.45 (95% confidence interval 1.02-2.07), Denmark: 1.96 (1.18-3.25)] or use of amlodipine [Netherlands: 2.31 (1.54-3.47), Denmark: 2.20 (1.32-3.67)]. Out-of-hospital cardiac arrest risk of (high-dose) nifedipine use was not further increased in patients using nitrates, or with a history of ischaemic heart disease. Nifedipine and amlodipine blocked L-type calcium channels at similar concentrations, but, at clinically used concentrations, nifedipine caused more L-type calcium current block, resulting in more action potential shortening.

CONCLUSION

High-dose nifedipine, but not low-dose nifedipine or any-dose amlodipine, is associated with increased OHCA risk in the general population. Careful titration of nifedipine dose should be considered.

An Overview of the Potential Use of Ethno-Medicinal Plants Targeting the Renin-Angiotensin System in the Treatment of Hypertension

The development of risk factors associated with cardiovascular disorders present a major public health challenge in both developed countries and countries with emerging economies. Hypertension and associated complications including stroke and myocardial infarction have reached pandemic levels. Current management strategies of hypertension predominantly include the utilization of pharmaceutical drugs which are often associated with undesirable side effects. Moreover, the drugs are often too expensive for populations from resource-limited Southern African rural, and some urban, communities. As a result, most patients rely on ethno-medicinal plants for the treatment of a variety of diseases including cardiovascular and metabolic disorders. The effectiveness of these plants in managing several cardiovascular diseases has been attributed to the presence of bioactive phytochemical constituents. In this review, the treatment options that target the renin-angiotensin system (RAS) in the management of hypertension were summarized, with special emphasis on ethno-medicinal plants and their influence on the ACE1 RAS pathway. The dearth of knowledge regarding the effect of ethno-medicinal plants on the ACE2 pathway was also highlighted.

Beta-Blockers, Calcium Channel Blockers, and Mortality in Stable Coronary Artery Disease

PURPOSE OF REVIEW

To examine the current clinical evidence behind the use of calcium channel blockers (CCB) and beta-blockers (BB) for the treatment of patients with stable coronary artery disease (SCAD) and their effect on mortality.

RECENT FINDINGS

Current evidence suggests that BB use as a first line antianginal medication is associated with lower 5-year all-cause mortality only in patients who had MI within a year. This could be driven due to their effects reducing the sympathetic neuro-hormonal activation of more acutely ill patients. The use of CCB as an antianginal therapy, although proven effective in multiple trials both as monotherapy and combined with other agents, has not shown mortality benefit. Both BB and CCB are effective antianginals, and the selection among them depends on the patient clinical presentation and comorbidities. BB are the only ones that have shown survival benefit in SCAD, particularly the first year post-MI.

Phytotherapy of Hypertension: An Updated Overview

BACKGROUND

Cardiovascular disorders are the leading cause of morbidity and mortality throughout the globe. Hypertension is the main risk factor that contributes to the development of many diseases. The use of herbal therapies, medicinal plants and their derivatives for the remedy and management of hypertension is well-recognized and popular among a wide part of the world population.

METHODS

The aim of the current review was to collect, treat, and critically analyze the published research studies relative to experimental and clinical investigations which have studied the blood pressure lowering abilities of medicinal plant derivatives in the last decade. This review was organized into three principal axes; the first axis was attributed to the in vivo and in vitro experimental studies; the second treated the clinical trials; while, the last one is devoted to analyze the mechanisms of action underlying the therapeutic antihypertensive effectiveness of phytochemicals.

RESULTS

Different types of extracts and isolated molecules obtained from a large variety of species demonstrated their efficiency in improving the increase of blood pressure either experimentally or clinically. Medicinal species such as garlic (Allium sativum), celery (Apium graveolens), Black Cumin (Nigella sativa) and Ginseng (Panax) are among the most common and therapeutically used plant derivatives for controlling hypertension while Asteraceae, Apiaceae and Rosaceae are among the botanical families which were frequently studied in the last decade. Isolated compounds such as allicin and apigenin have received more interest in this field. Recent evidence from clinical trials suggests that a wide variety of herbal preparations and plant extracts or natural isolated compounds have a favorable therapeutic impact on blood flow. Interestingly, phytochemicals can either act directly on blood vessels via a vasorelaxant effect involving a variety of signaling cascades or indirectly through inhibiting or stimulating diversity of systems such as angiotensin-converting enzyme (ACE), renin-angiotensin system (RAS) or the diuretic activity. Hence, based on the findings of the present review medicinal plant derivatives could be used as preventive and curative agents in the case of cardiovascular disorders, particularly hypertension and could play a promoting function for the discovery of new antihypertensive agents.

CONCLUSION

The analysis of the published data shows that a great effort remains to be done to investigate the medicinal plants cited as antihypertensive through published ethnopharmacological surveys. The analysis of the literature in this field shows the lack of standardization at the level of experimental study methods as well as the need to study purified molecules. Moreover, the mechanistic studies when they exist remain in the whole partial. On the other hand, few advanced clinical studies have been conducted. Finally, the determination of the efficacy/safety ratio remains absent in almost all studies.

The Search for Disease-Modifying Therapies in Pulmonary Hypertension

Pulmonary hypertension (PH) and its severe subtype pulmonary arterial hypertension (PAH) encompass a set of multifactorial diseases defined by sustained elevation of pulmonary arterial pressure and pulmonary vascular resistance leading to right ventricular failure and subsequent death. Pulmonary hypertension is characterized by vascular remodeling in association with smooth muscle cell proliferation of the arterioles, medial thickening, and plexiform lesion formation. Despite our recent advances in understanding its pathogenesis and related therapeutic discoveries, PH still remains a progressive disease without a cure. Nevertheless, development of drugs that specifically target molecular pathways involved in disease pathogenesis has led to improvement in life quality and clinical outcomes in patients with PAH. There are presently more than 12 Food and Drug Administration-approved vasodilator drugs in the United States for the treatment of PAH; however, mortality with contemporary therapies remains high. More recently, there have been exuberant efforts to develop new pharmacologic therapies that target the fundamental origins of PH and thus could represent disease-modifying opportunities. This review aims to summarize recent developments on key signaling pathways and molecular targets that drive PH disease progression, with emphasis on new therapeutic options under development.

Pathophysiological Mechanisms and Correlates of Therapeutic Pharmacological Interventions in Essential Arterial Hypertension

Treating arterial hypertension (HT) remains a hard task. The hypertensive patient is often a subject with several comorbidities and metabolic abnormalities. Clinicians everyday have to choose the right drug for the single patient among the different classes of antihypertensives. Apart from lowering blood pressure, a main therapeutic target should be that of counteracting all the possible pathophysiological mechanisms involved in HT itself and in existing/potential comorbidities. All the ancillary positive and negative effects of the administered drugs should be considered: in particular, since hypertensive patients are often glucose intolerant/diabetic, carrier of serum lipids disorder, have already developed atherosclerotic diseases and endothelial dysfunction, they should not be treated with drugs negatively interfering with these conditions but with molecules that, if possible, improve them. The main pathophysiological mechanisms and correlates of therapeutic pharmacological interventions in essential HT are reviewed here.

Aggressive blood pressure control and stroke prevention: role of calcium channel blockers

Cerebrovascular disease is a major cause of morbidity and mortality worldwide and its prevalence is expected to increase as a result of projected demographic trends. Stroke is one of the leading causes of disability and death of over 30 million people each year worldwide. Hypertension is the most important modifiable risk factor for stroke. Recent data indicate that treatment with antihypertensive drugs reduces the incidence of all strokes in men (by 34%), women (by 38%), the elderly (by 36%), including those older than 80 years (by 34%), younger persons, those with systolic and diastolic hypertension, persons with isolated systolic hypertension, and those with a history of stroke or transient ischemic attack (by 28%). Furthermore, several large, prospective, randomized, clinical outcome trials have shown that calcium channel blockers (CCBs) are effective and safe antihypertensive drugs compared with placebo and reduce the cardiovascular morbidity and mortality of treated patients. Moreover, when CCBs were compared with conventional antihypertensive drugs they demonstrated similar blood pressure-lowering effects and similar reductions in cardiovascular morbidity and mortality, with the exception of a higher incidence of heart failure and fatal myocardial infarction in some studies. Considering all the evidence available today, however, these drugs should be considered safe for the treatment of the uncomplicated hypertensive patient in combination with other drugs. They can also be used as first-line therapy for older, stroke-prone hypertensive patients. The aim of this review is to summarize the role of CCBs in the prevention of stroke.

Pharmacological management of renal colic in the older patient

Renal colic affects up to 12% of the population. Initial management of most patients is expectant. Acute symptom management of renal colic is best accomplished with a combination of parenteral opioids and NSAIDs. The elderly patient with a kidney stone should be screened for contraindications to NSAID therapy, such as renal failure or previous peptic ulcer disease. Use of parenteral opioids is often necessary during the acute setting, and downward-adjusted doses and monitoring are necessary to prevent associated confusion and respiratory depression. Novel therapy with desmopressin may also be effective for symptom control at the initial presentation, without the adverse effects of opioids or NSAIDs. However, use of desmopressin in the elderly must be undertaken cautiously, given the potential adverse effects of this agent. Many small, distal ureteral stones are treated initially with watchful waiting for the first 2-4 weeks after presentation. The patient should have effective, non-parenteral analgesics for use at home. Included in these agents are oral or suppository NSAIDs and oral opioids. Medical expulsion therapy with alpha-adrenoceptor antagonists or calcium channel antagonists is efficacious. alpha-Adrenoceptor antagonists such as the alpha(1A/)(1)(D)-selective tamsulosin are well tolerated in the elderly and increase the rate of spontaneous stone passage by approximately 50% for small distal stones. These agents also appear to decrease the severity of renal colic. Corticosteroids and calcium channel antagonists are also effective but their use in the elderly is not recommended as first-line therapy.

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.

Calcium Antagonists

Calcium antagonists comprise 2 main subclasses, dihydropyridines and nondihydropyridines, and have been studied extensively in hypertensive patients. Early meta-analyses suggested that short-acting calcium antagonists were associated with higher mortality rates resulting from cardiovascular events and other etiologies. Recent meta-analyses failed to show any substantive difference between long acting calcium antagonists and other antihypertensive drug classes with regard to cardiovascular outcomes in those with low to moderate cardiovascular risk or kidney disease progression among those with stage 2 or 3 nonproteinuric kidney diseases. The data from calcium antagonist trials are consistent in that they decrease stroke incidence but fail to protect against new-onset heart failure. In people with proteinuric kidney disease, that is > 300 mg protein/gram creatinine, use of dihydropyridine calcium antagonists to lower blood pressure without the use of agents that block the renin angiotensin aldosterone system does not provide optimal slowing of nephropathy progression. This relates directly to lack of antiproteinuric effects with this subclass and not seen with nondihydropyridine agents that reduce proteinuria to a greater degree than dihydropyridines. Thus, calcium antagonists are safe and as efficacious as other antihypertensive agents to reduce cardiovascular risk. They should be avoided in people with systolic dysfunction but may be used for blood pressure lowering in people with preserved systolic function. Dihydropyridine calcium antagonists should only be used in conjunction with angiotensin-converting enzyme inhibitors or angiotensin receptor blockers in proteinuric kidney disease because they will not optimally slow kidney function loss in their absence.

Mibefradil (Ro 40-5967): the first selective T-type Ca2+ channel blocker

Mibefradil is a novel Ca2+ antagonist acting on both L- and T-type Ca2+ channels, with a ten-fold selectivity for T-type Ca2+ channels. It belongs to a chemical class different from other Ca2+ antagonists (tetralol derivative), and binds to a new receptor site on the L-type Ca2+ channel, where it does not affect dihydropyridine (DHP) binding but appears to overlap the verapamil and fantofarone sites. In vitro and in vivo studies indicate that mibefradil has a high selectivity for the coronary vasculature over the peripheral vasculature and the myocardium. It has no relevant negative inotropic effects in various animal models, in normotensive patients, and patients with hypertension or angina pectoris. Instead, treatment with mibefradil slightly decreases heart rate and improves cardiac function. Clinical studies confirm that mibefradil is an effective antihypertensive and anti-ischaemic drug, which may be beneficial in the treatment of heart failure. Its excellent pharmacological and safety profile combined with high bioavailability makes it a promising new drug. Many of the unique pharmacological properties of mibefradil may derive from its selective block of T-type Ca2+ channels.

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.

Different antioxidative potencies of dihydropyridine calcium channel modulators in various models

There is evidence that dihydropyridine calcium antagonists (DHP) play a beneficial role during the development of atherosclerosis. Since antioxidative properties of this substance class may be important, we investigated the antioxidative potency of the DHP prototype calcium channel antagonist nifedipine, the long acting calcium channel antagonist lacidipine, the DHP calcium channel agonist Bay K 8644 and the bulky DHP derivate Bay O 5572 (negligible effects on L-type calcium channels) in three different models. Additionally, we examined the potential correlation between lipophilic and antioxidative properties. In an in vitro model, Bay K 8644 was significantly more effective in scavenging superoxide anions (hypoxanthine/xanthine-oxidase-assay) than lacidipine, Bay O 5572 or nifedipine (micro- to millimolar concentration range). Addition of artificial membrane preparations (dimyristoylphosphatidylcholine) to mimic a physiological environment resulted in an enhanced antioxidative effect, with lacidipine being the most effective DHP to quench radicals (low micromolar concentration range). Thirdly, in a more physiological model of hyperglycemia (30 mmol/l) induced release of reactive oxygen species (ROS) from native endothelial cells of porcine coronary arteries, we showed that nifedipine was a significantly more potent antioxidant (therapeutical nanomolar concentration range) than the other DHP. Calculation of the lipophilicity of the four substances (lacidipine>Bay O 5572>Bay K 8644>nifedipine) showed a positive correlation between the antioxidative potency and the lipophilicity in the model with the artificial membranes but not in the other models. We conclude that it seems necessary to access antioxidative properties of substances in physiological models in which we could demonstrate that nifedipine exhibits ROS-quenching properties in a therapeutic concentration range.

The role of existing and newer calcium channel blockers in the treatment of hypertension

Calcium channel blockers (CCBs), which include both dihydropyridines such as nifedipine and amlodipine and non-dihydropyridines (verapamil and diltiazem), are among the most widely prescribed agents for the management of essential hypertension. Several large outcome risk trials and comprehensive meta-analyses have found that CCBs reduce the cardiovascular morbidity and mortality associated with uncontrolled hypertension, including stroke. CCBs, however, appear less effective than angiotensin-converting enzyme inhibitors and diuretics for preventing heart failure and myocardial infarction. CCBs are among the agents listed as potential first-line therapy, either alone or in combination with other agents in hypertension management guidelines. Furthermore, CCBs are suitable for add-on therapy in combination with diuretics, angiotensin-converting enzyme inhibitors, and angiotensin-II receptor blockers. CCBs may be partially suitable for patients with comorbid Raynaud's syndrome, isolated systolic hypertension (dihydropyridine), or angina pectoris (non-dihydropyridine). The newer inherently long-acting dihydropyridine agents (e.g., lacidipine, lercanidipine), which are not currently available in the United States, appear to have comparable efficacy to older agents of the dihydropyridine class but may have an improved tolerability profile, especially with regard to peripheral edema.

Hirudin (desulfated, 54–65) contracts canine coronary arteries: Extracellular calcium influx mediates hirudin-induced contractions

OBJECTIVE

Although the anticoagulatory properties of hirudin are well known, its direct vasoactive effects have not been investigated extensively. Hirudin stimulates nitric oxide and prostacyclin production in noncoronary vascular beds, but its actions on coronary arteries are unknown.

MATERIALS AND METHODS

Five-millimeter segments of canine left circumflex coronary arteries were obtained for organ chamber experiments. Some segments were denuded of endothelium before study. Segments were exposed to hirudin (10(-10)-10(-6) mol/L) following precontraction with prostaglandin F(2alpha) with or without pretreatment with indomethacin or calcium channel blockers (verapamil and nifedipine).

RESULTS

Hirudin stimulated endothelium-independent contraction in coronary arterial segments. Maximum tension (hirudin 10(-6) mol/L) above precontraction baseline was 33.6 +/- 9.0% (n = 10, P < 0.05) for endothelium-intact and 31.8 +/- 11.5% (n = 8, P < 0.05) for endothelium-denuded arterial segments. Differences between endothelium-intact and endothelium-denuded segments were not significant. Contractile responses to hirudin were unaffected by the presence of indomethacin. Pretreatment with either verapamil or nifedipine (10(-4) mol/L) for 1 h attenuated these contractions. The maximal increase in tension above baseline (hirudin 10(-6) mol/L) for verapamil and nifedipine was only 6.2 +/- 12.4 and 3.8 +/- 7.0% (n = 6, P < 0.05 versus endothelium-intact control), respectively.

CONCLUSIONS

Hirudin stimulates endothelium-independent contractions of canine coronary arteries in vitro. Pretreatment with calcium channel blockers attenuates this response, suggesting that extracellular influx of calcium has an important mechanistic role in hirudin-mediated coronary artery constriction.

Calcium channel blockers: an update

This paper reviews the current literature pertaining to calcium channel blockers, including their classification, properties, and therapeutic indications, in light of several recent trials that have addressed their safety. Calcium channel blockers are a structurally and functionally heterogeneous group of medications that are used widely to control blood pressure and manage symptoms of angina. They are classified as dihydropyridines or nondihydropyridines. As a class, they are well tolerated and are associated with few side effects. The question of whether they may precipitate cardiovascular events has been largely settled by recent trials, such as the Antihypertensive and Lipid-Lowering Treatment to Prevent Heart Attack Trial (ALLHAT), the International Verapamil Slow-Release/Trandolapril Study (INVEST), and the Controlled Onset Verapamil Investigation of Cardiovascular Endpoints (CONVINCE) study, in which no such association was found. Even so, the use of these agents has been linked with an increased risk of heart failure. Thus, long-acting calcium channel blockers may be safely used in the management of hypertension and angina. However, as a class, they are not as protective as other antihypertensive agents against heart failure.

Modulation of L-type Ca2+ channels in neonatal rat heart by a novel Ca2+ channel agonist

L-type Ca2+ channels are essential in triggering the intracellular Ca2+ release and contraction in heart cells. In this study, we used patch clamp technique to compare the effect of two pure enantiomers of L-type Ca2+ channel agonists: (+)-CGP 48506 and the dihydropyridine (+)-SDZ-202 791 in cardiomyocytes from rats 2-5 days old. The predominant Ca2+ current activated by standard step pulses in these myocytes was L-type Ca2+ current. The dihydropyridine antagonist (+)-PN200-110 (5 microM) blocked over 90% of Ca2+ currents in most cells tested. CGP 48506 lead to a maximum of 200% increase in currents. The threshold concentration for the CGP effect was at 1 microM and the maximum was reached at 20 microM. SDZ-202 791 had effects in nanomolar concentrations and a maximum effect at about 2 microM. The maximal effect of (+)-SDZ-202 791 was a 400% increase in the amplitude of Ca2+ currents and was accompanied by a 10-15 mV leftward shift in the voltage dependence of activation. CGP 48506 increased the currents equally at all voltages tested. Both compounds slowed the deactivation of tail currents and lead to the appearance of slowly activating and slowly deactivating current components. However, SDZ-202 791 had larger effects on deactivation and CGP 48506 had larger effect on the rate of Ca2+ current activation. The effect of SDZ-202 791 was fully additive to that of CGP 48506 even after maximum concentrations of CGP. This observation suggests that the two Ca2+ channel agonists may act at two different sites on the L-type Ca2+ channel. We suggest that CGP 48506 would be a potential cardiotonic agent without the deleterious proarrhythmic effects attributable to the dihydropyridine agonists.

Topical nifedipine with lidocaine ointment vs. active control for treatment of chronic anal fissure: results of a prospective, randomized, double-blind study

PURPOSE

Chronic anal fissure may be treated by chemical or surgical sphincterotomy. The aim of this study was to test the efficacy of local application of nifedipine and lidocaine ointment in healing chronic anal fissure.

METHODS

The study was performed according to a prospective, randomized, double-blind design. One hundred ten patients who gave informed consent were recruited. They received a clinical examination, a questionnaire to evaluate symptoms and pain, anorectal manometry, and anoscopy. Healing of anal fissure at Day 42 of therapy was defined as the primary efficacy variable of the study. Patients treated with nifedipine (n = 55) used topical 0.3 percent nifedipine and 1.5 percent lidocaine ointment every 12 hours for 6 weeks. The control group (n = 55) received topical 1.5 percent lidocaine and 1 percent hydrocortisone acetate ointment during therapy. Anal pressures were measured by recording resting and maximal voluntary contraction pressures at baseline and at Day 21. Long-term outcomes were determined after a median follow-up of 18 months.

RESULTS

Healing of chronic anal fissure was achieved after 6 weeks of therapy in 94.5 percent of the nifedipine-treated patients (P < 0.001) as opposed to 16.4 percent of the controls. Mean anal resting pressure decreased from a mean value +/- standard deviation of 47.2 +/- 14.6 to 42 +/- 12.4 mmHg in the nifedipine group. This represents a mean reduction of 11 percent (P = 0.002). Changes of maximal voluntary contraction in nifedipine-treated patients were not significant. No changes in mean anal resting pressure and maximal voluntary contraction were observed in the control group. We did not observe any systemic side effect in patients treated with nifedipine. After the blinding was removed, recurrence of the fissure was observed in 3 of 52 patients in the nifedipine group within 1 year of treatment, and 2 of these patients healed with an additional course of topical nifedipine and lidocaine ointment.

CONCLUSIONS

Our study clearly demonstrates that the therapeutic use of topical nifedipine and lidocaine ointment should be extended to the conservative treatment of chronic anal fissure.

Evidence-based evaluation of calcium channel blockers for hypertension: equality of mortality and cardiovascular risk relative to conventional therapy

OBJECTIVES; We present a meta-analysis based on three recent, substantial, randomized outcome trials and several smaller trials that compared calcium channel blockers (CCBs) with conventional therapy (diuretics or beta-blockers) or with angiotensin-converting enzyme (ACE) inhibitors.

BACKGROUND

There is continuing uncertainty about the safety and efficacy of CCBs in the treatment of hypertension. Previous meta-analyses conflict and suggest that CCBs increase myocardial infarction (MI) or protect from stroke.

METHODS

Standard procedures for meta-analysis were used to analyze three major trials on 21,611 patients and another three lesser studies to a total of 24,322 patients.

RESULTS

Calcium channel blockers have a strikingly similar risk of total and cardiovascular mortality and of major cardiovascular events to conventional therapy. Calcium channel blockers give a lower risk of nonfatal stroke (-25%, p = 0.001) and a higher risk of total MI (18%, p = 0.013), chiefly nonfatal (18%). After performing the Bonferroni correction for multiplicity, these p values become 0.004 and 0.052, respectively. When compared with ACE inhibitors in 1,318 diabetic patients, CCBs had a substantially higher risk of nonfatal (relative risk [RR] = 2.259) and total MI (RR = 2.204, confidence interval 1.501 to 3.238; p = 0.001 or 0.004 with Bonferroni correction). Total and cardiovascular mortality rates are similar. To confirm the hypothesis that ACE inhibitors are superior to CCBs in diabetic patients requires more trial data, especially with renal end points.

CONCLUSIONS

Mortality (total and cardiovascular) and major cardiovascular events with CCBs were apparently similar to those events seen with conventional first-line therapy (diuretics or beta-blockers). Stroke reduction more than balanced increased MI. In diabetics, CCBs may be less safe than ACE inhibitors.

The INSIGHT and NORDIL trials: Are calcium antagonists equivalent to established drug therapies for cardiovascular protection?

Calcium channel blockers have come into worldwide use for treating hypertension and other circulatory disorders. In recent years, results of several observational studies have suggested that these drugs may not be as safe or effective as other available therapies, such as diuretics and beta-blockers, in the prevention of cardiovascular events. The Nordic Diltiazem (NORDIL) and the International Nifedipine GITS Study: Intervention as a Goal in Hypertension Treatment (INSIGHT) studies were the first two randomized interventional trials in hypertensive patients that directly compared the effects of therapy based on calcium antagonists with those of diuretic and beta-blocker-based treatment on major cardiovascular endpoints. Both studies found that the effectiveness of calcium antagonist therapy was similar to that of diuretic and beta-blocker therapy for preventing the composite primary endpoint of fatal and nonfatal stroke, myocardial infarction, and other cardiovascular death. The two studies shared several nonsignificant trends for cause-specific events, including greater stroke prevention and lesser coronary event prevention in the calcium antagonist groups compared with the diuretic and beta-blocker groups. There is not yet sufficient evidence to prove whether cause-specific differences exist. Results of the NORDIL and INSIGHT studies support incorporating calcium antagonist-based therapy as an additional safe and effective approach for preventing blood pressure-related illness and death.

Current status of safety and efficacy of calcium channel blockers in cardiovascular diseases: a critical analysis based on 100 studies

Recently, serious concerns have been expressed about the long-term safety of the calcium channel blockers (CCBs) as a group. Safety and efficacy are, however, ultimately linked to each other; therefore both must be evaluated especially in the therapy of angina and hypertension, the main clinical indications for CCBs. The structural, functional, and pharmacokinetic heterogeneity of CCBs means that the efficacy and dangers of one subclass, such as the short-acting dihydropyridines (DHPs), in one situation, such as unstable angina, do not necessarily apply in other clinical situations. One hundred studies are reviewed according to their methods of data collection: case series, case control, cohort, randomized controlled trials (RCTs), and meta-analyses. Large, well-designed RCTs and the meta-analyses based on these trials remain the gold standard. Observational studies, though potentially less reliable sources of information because of selection bias, may nevertheless produce hypotheses that must then be tested in RCTs. Regarding safety, both observational studies and RCTs suggest that adverse effects of CCBs may be linked to short-acting agents, specifically short-acting nifedipine. Two good studies favor the safety of verapamil, even in short-acting form. Incomplete but increasing overall evidence favors the safety of longer-acting DHPs. Heart failure remains a class contraindication to the use of all CCBs, with some exceptions. Regarding efficacy, there are positive results of RCTs with CCBs in 2 specific clinical situations, namely, verapamil in postinfarct protection in the absence of pre-existing heart failure, and 2 outcome studies on hypertension with longer acting DHPs. These results cannot automatically be applied to other clinical situations and to other CCBs. For example, there is no evidence for the safety or efficacy of DHPs used without beta blockers in postinfarct patients. In diabetic hypertensives, 2 relatively large RCTs show that the blood pressure can be reduced by DHP-based therapy in diabetics, with a reduction in hard end points. To achieve current blood pressure goals, combination therapy is almost always necessary, and in diabetics there is strong evidence that 1 essential component should be an angiotensin converting enzyme inhibitor. The future aim with CCBs must be to obtain a large database gathered from RCTs, which will give the same certainty about efficacy and safety that already holds for use of the diuretics in hypertension, beta-blockers in postmyocardial infarction patients, and the angiotensin converting enzyme inhibitors in heart failure.

Treatment of 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 pectoris. The coronary arteries of patients with stable angina also contain many nonobstructive plaques, which are prone to fissures or rupture resulting in presentation of acute coronary syndromes (unstable angina, myocardial infarction, sudden ischemic death). In addition to symptomatic relief of symptoms and an increase in angina-free walking time with antianginal drugs or revascularization procedures, the recent emphasis of treatment has been to reduce adverse clinical outcomes (coronary death and myocardial infarction). The role of smoking cessation, aspirin, treatment of elevated lipids, and treatment of high blood pressure in all patients and of beta-blockers and angiotensin-converting enzyme inhibitors in patients with diminished systolic left ventricular systolic function in reducing adverse outcomes has been well established. What is unknown, however, is whether any anti-anginal drugs (beta-blockers, long-acting nitrates, calcium channel blockers) effect adverse outcomes in patients with stable angina pectoris. Recent trials evaluated the usefulness of suppression of ambulatory ischemia in patients with stable angina pectoris, but it remains to be established whether suppression of ambulatory myocardial ischemia with antianginal agents or revascularization therapy is superior to pharmacologic therapy targeting symptom relief. Patients who have refractory angina despite optimal medical treatment and are not candidates for revascularization procedures may be candidates for newer techniques of transmyocardial revascularization, enhanced external counterpulsation, spinal cord stimulation, or sympathectomy. The usefulness of these techniques, however, needs to be confirmed in large randomized clinical trials.

Calcium- and calmodulin-dependent PMA-activation of the CD44 adhesion molecule

The ability of the CD44 adhesion molecule to interact with its ligand hyaluronic acid (HA) is tightly regulated. CD44-positive mouse LB lymphoma cells are unable to bind HA unless activated by the tumor promoter phorbol 12-myristate 13-acetate (PMA). PMA causes a dose-dependent increase in both CD44 expression level and HA-binding capacity, with the binding of HA observed only above a threshold amount of CD44 molecules. This induction of HA-binding as well as the increase in CD44 expression are prevented by cycloheximide, suggesting a requirement for new additional CD44 molecules on the cell surface and/or cooperating proteins. In the present study, we have investigated which of the signal transduction pathways activated by PMA leads to the increased CD44 expression with subsequent acquisition of HA-binding capacity. By comparing the influence of each inhibitory agent on PMA-activated LB lymphoma cells versus that on a constitutive HA-binder cell line derived from LB cells (designated HA9 cells), we could distinguish between an effect on the PMA-activation phase and a one on the HA-binding phase. Our data show that the PMA-induced HA-binding could not be blocked by agents inhibiting protein kinase C (PKC) (staurosporine, sphingosine, polymyxin B, quercetin) or genestein, an inhibitor of tyrosine protein kinases. However, this PMA response was strongly inhibited by calmodulin antagonists (chlorpromazine, trifluoperazine, W-7) and the calcium blocker verapamil. The calmodulin antagonists inhibited the PMA-induced increase in CD44 expression on LB cells, but had no influence on the ability of the constitutive HA-binder HA9 cell line to interact with HA, indicating an effect on the PMA induction phase rather than on the binding itself. Verapamil also blocked the PMA-induced increase in CD44 expression on LB cells, but in addition it slightly reduced the ability of the HA9 cells to bind HA without affecting their CD44 expression level. In conclusion, our data suggest that CD44 activation by PMA is calcium and calmodulin dependent, rather than mediated by protein kinase C.

Relaxing effects of cyclic GMP and cyclic AMP-enhancing agents on the long-lasting contraction to endothelin-1 in the porcine coronary artery

In the coronary circulation, endothelin-1 (ET-1) evokes spasms which are difficult to treat when the endothelial integrity is compromised. This study compares several classes of relaxing agents on already established contractions to ET-1 in an in vitro model using ring segments of the porcine left descending coronary artery (pLAD). All segments were precontracted with 10 nmol/L ET-1. The calcium channel blocker isradipine was 300 times more potent than verapamil, but was only a partial relaxant; the maximal relaxation obtained was 52 +/- 2% (n = 6). Atrial natriuretic peptide (ANP) was an equally potent relaxant of the ET-1 contraction; however, it too was an incomplete relaxant, maximal relaxation being < 60%. A 50% relaxation of the ET-1 contraction was obtained with 0.28 +/- 0.24 mumol/L ANP, n = 4 (IC50). Comparison of cyclic nucleotide analogues revealed a 30 times higher potency for 8-bromo-cyclic guanosine monophosphate (8-Br-cGMP)(IC50 44 +/- 11 mumol/L, n = 6) than for 8-bromo-cyclic adenosine monophosphate (8-Bi-cAMP) (IC50 1600 mumol/L, n = 6). The cyclic nucleotide phosphodiesterase (PDE) inhibitor milrinone, a PDE 3-inhibitor with an IC50 2.4 +/- 1.8 mumol/L, (n = 6) was 10 times more potent than rolipram (PDE 4-inhibitor), zaprinast (PDE 5-inhibitor) and vinpocentine (PDE 1-inhibitor). Withdrawal of these analogues and inhibitors from segments continuously exposed to 10 nmol/l ET-1 revealed that vinpocentine and 8-Br-cGMP were irreversible relaxants, in contrast to milrinone and 8-Br-cAMP. In conclusion, this study has demonstrated that cGMP-enhancing agents, such as the naturally occurring ANP, the calcium channel blocker isradipine, and the synthetic inhibitor of PDE 3, were the most effective relaxants of ET-1 evoked contractions in pLAD in vitro.

Diversity of calcium antagonists

Calcium antagonists (CAs) are widely used in the management of hypertension and chronic stable angina pectoris. Currently available CAs fall into three distinct structural classes--the dihydropyridines, the benzothiazepines, and the phenylalkylamines. The diversity of these agents, even among drugs within a structural group, is apparent in their pharmacology, physiologic effects, and therapeutic uses. Traditional CAs produce their effects through blockade of the L-type calcium channel. Recently, a new CA has been developed. Mibefradil, the first member of a new class of CAs, is a tetralol derivative. It is characterized by its selective blockade of T-type calcium channels. It differs from existing CAs and may offer important therapeutic advantages.

The clinical significance of neurohormonal activation

Progressive heart disease after the onset of left ventricular dysfunction has typically been attributed to hemodynamic factors. As left ventricular function declines, decreased cardiac output and tissue hypoperfusion lead to compensatory increases in afterload, preload, and heart rate. The purpose of these compensatory responses is to increase cardiac output and maintain tissue perfusion; however, they may also create hemodynamic stress for the failing heart. However, this does not explain the progression of heart failure despite hemodynamic maintenance with pharmacologic therapy. Activation of neurohormonal systems that are essential for homeostasis in the normal heart plays a key role in the progression of heart failure. In acute heart failure, these systems have beneficial effects, but in chronic heart failure their activation produces deleterious effects by increasing the load on the left ventricle and promoting structural remodeling, which may further impair left ventricular function. The issue of neurohormonal activation is an important one in cardiovascular medicine, not only for patients with heart failure but also for patients with hypertension and ischemic heart disease when left ventricular dysfunction is present. As neurohormonal activation may play a pathogenic role in the long-term outcome of patients, interventions that have favorable hemodynamic but unfavorable neurohormonal effects can actually exacerbate cardiac disease and may increase cardiovascular morbidity and mortality. As neurohormonal activation appears to parallel the severity of heart failure, whether assessed according to symptoms or prognosis, an understanding of neurohormonal activation and its interaction with hemodynamic factors is essential for optimizing pharmacologic therapy for cardiovascular disease.

Safety of calcium antagonists in patients with congestive heart failure

Continuing high morbidity and mortality have spurred an ongoing search for new therapeutic agents for patients with congestive heart failure. Calcium antagonists (CAs) have been under active investigation in patients with heart failure since their introduction into clinical medicine, because their anti-ischemic and vasodilator properties were thought to be of potential benefit in this patient population. However, review of published clinical trials of CAs in patients with heart failure reveals that some of these drugs are associated with detrimental effects, including acute hemodynamic deterioration, increased symptoms of heart failure, and increased mortality. The adverse effects of short-acting CAs in patients with heart failure include negative inotropic effects and neurohormonal activation. Long-acting CAs, such as amlodipine and felodipine, had fewer negative inotropic effects, showed less evidence of neurohormonal activation, and were better tolerated in clinical trials. Amlodipine, in combination with an angiotensin-converting enzyme inhibitor, had a neutral effect in patients with ischemic heart failure and an unexplained benefit in a subgroup of patients with non-ischemic cardiomyopathy. Although the preliminary experience with long-acting dihydropyridine CAs in heart failure has been encouraging, safety concerns raised by past trials dictate that no CA can be recommended for the treatment of heart failure at this time.

Effects of amlodipine in patients with chronic heart failure

The role of calcium antagonists in patients with ischemic heart failure is currently unclear. We examined the effects of amlodipine on exercise capacity and central and regional hemodynamics in 32 patients with mild to moderate chronic heart failure in a single-center, double-blind, randomized placebo-controlled trial. All were taking at least 40 mg of furosemide daily with an angiotensin-converting enzyme inhibitor. Ischemic heart disease was the most common cause of heart failure, but no patient had symptom-limiting angina. Mean treadmill exercise capacity in patients taking amlodipine increased by 96 seconds (95% confidence interval -23 to 215) and 50 seconds (-34 to 135) in the placebo group; mean difference in change between treatments was 70 seconds (-90 to 233), p = 0.38. Active treatment with amlodipine did not affect self-paced corridor walking times. Similarly, there were no significant effects on cardiac output, oxygen uptake, heart rate, and mean arterial pressure at rest or during exercise. Calf and renal blood flow were also unchanged by treatment. The lack of significant effect demonstrated by these data suggests a limited role for amlodipine in patients with ischemic cardiomyopathy, although it may prove beneficial in those with nonischemic disease. More data are required before amlodipine can be recommended for all patients with chronic heart failure.

Cardiac effects of calcium antagonists in systemic hypertension

The calcium antagonists are a class of heterogeneous drugs, with a wide spectrum of direct and indirect cardiac effects that vary a great deal from one drug to another and depend upon formulation and duration of action. Calcium antagonists act by decreasing total peripheral resistance to lower arterial pressure. As a consequence, reflex tachycardia, increased cardiac output, and increased plasma catecholamine and plasma renin activity are commonly seen, particularly with the initial dose and with short-acting dihydropyridines. The abrupt vasodilation can paradoxically elicit angina and even acute myocardial infarction. These hemodynamic and neuroendocrine changes are less pronounced with the long-acting formulations. Most calcium antagonists diminish automaticity of the sinus node, slow conduction in the atrioventricular node, and have little, if any, effect on the automaticity of the myocytes. The dihydropyridines generally have less effect on automaticity and cardiac conduction than nondihydropyridines. The negative inotropic effect is most profound with nondihydropyridines and is greatly reduced or absent with newer dihydropyridines, such as isradipine, felodipine, amlodipine, and nisoldipine. Long-acting calcium antagonists generally improve myocardial oxygenation by unloading the heart, increasing coronary blood flow, and reducing myocardial oxygen consumption. Thus, calcium antagonists have a variety of beneficial effects in patients with hypertensive heart disease: they reduce left ventricular hypertrophy and its sequelae, such as ventricular dysrhythmias, impaired filling and contractility, and myocardial ischemia. Ongoing studies should provide a more conclusive answer regarding the efficacy and safety of calcium antagonists.

Portal hypotensive effects of tetrandrine and verapamil in portal hypertensive rats

The portal hypotensive effects of tetrandrine and verapamil (both calcium-channel blockers) were assessed in portal hypertensive rats. Portal hypertension was induced by partial portal vein ligation in Sprague-Dawley rats. Both tetrandrine (4, 8, 16 and 24 mg kg-1) and verapamil (0.5, 1.0, 1.5 and 2.0 mg kg-1) induced dose-dependent decreases of portal venous pressure and mean arterial pressure after intravenous infusion. for example, infusion of tetrandrine (16 mg kg-1) induced a maximum reduction of portal venous pressure and mean arterial pressure approximately 1 min after the start of infusion. Portal venous pressure decreased from baseline (12.5 mmHg) to 10.0 mmHg, and mean arterial pressure from baseline (90 mmHg) to 80 mmHg. Heart rate decreased from 250 to 240 beats min-1. At 24 mg kg-1, tetrandrine reduced portal venous pressure and mean arterial pressure to 20.3 +/- 2.4% and 28.4 +/- 1.4% of baseline, respectively. Our results show that both tetrandrine and verapamil induce portal pressure reduction in portal hypertensive animals.