Vascular selective calcium entry blockers in the treatment of cardiovascular disorders: focus on felodipine

Felodipine Determination by a CdTe Quantum Dot-Based Fluorescent Probe

In this work, a CdTe quantum dot-based fluorescent probe was synthesized to determine felodipine (FEL). The synthesis conditions, structure, and interaction conditions with FEL of CdTe quantum dots were analysed by fluorescence spectrophotometry, Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), UV–visible spectroscopy, and TEM. The CdTe QD concentration was 2.0 × 10⁻⁴ mol/L. The amount of quantum dots controlled in the experiment was 0.8 mL. The controlled feeding ratio of N (Cd²⁺):N (Te²⁻):N (TGA) was 2:1:4, the heating temperature was 140 °C, the heating time was 60 min, and the pH of the QD precursor was adjusted to 11 for subsequent experiments. The UV–visible spectrum showed that the emission wavelength of CdTe quantum dots at 545 nm was the strongest and symmetric. The particle size of the synthesized quantum dots was approximately 5 nm. In the interaction of CdTe quantum dots with FEL, the FEL dosage was 1.0 mL, the optimal pH value of Tris-HCl buffer was 8.2, the amount of buffer was 1.5 mL, and the reaction time was 20 min. The standard curve of FEL was determined under the optimal synthesis conditions of CdTe quantum dots and reaction of CdTe quantum dots with FEL. The linear equation was Y = 3.9448x + 50.068, the correlation coefficient R2 was 0.9986, and the linear range was 5 × 10⁻⁶–1.1 × 10⁻⁴ mol/L. A CdTe quantum dot-based fluorescent probe was successfully constructed and could be used to determine the FEL tablet content.

Micellar-Emphasised simultaneous determination of ivabradine hydrochloride and felodipine using synchronous spectrofluorimetry

Sensitive and green micellar spectrofluorimetric approach was applied for the simultaneous estimation of ivabradine hydrochloride (IVB) and felodipine (FLD) in ng/mL concentration range. The approach depended on measuring the first derivative synchronous peak amplitude (¹ D) of both drugs at ∆λ= 60 nm in tween-80 micellar system. The method was rectilinear alongside the concentration range (0.02-0.4) μg/mL and (0.05-1.0) μg/mL at 269.5 nm and 378.5 nm for of IVB and FLD, respectively. The proposed method was validated by following ICH guidelines. The method was successfully applied without interference for laboratory-prepared synthetic mixtures, single pharmaceutical preparation and within spiked biological fluids with acceptable percent recoveries. Comparing the performance of the suggested method with the comparison methods, showed no discrepancy. The method ecofriendly properties were evaluated by 3 different tools confirming an excellent green method.

Enhanced Oral Bioavailability of Felodipine from Solid Lipid Nanoparticles Prepared Through Effervescent Dispersion Technique

Felodipine (FLD), a dihydropyridine calcium channel blocker with excellent antihypertensive effect, is poorly soluble and undergoes extensive hepatic metabolism, which lead to poor oral bioavailability (about 15%) and limit its clinic application. The goal of this study was to develop solid lipid nanoparticles (SLNs) loading FLD to improve the oral bioavailability. The FLD loaded solid lipid nanoparticles (FLD-SLNs) were prepared by the effervescent dispersion technique developed by our laboratory, which might have some advantages over traditional methods. The FLD-SLNs showed desired particle characteristics with particle size (198.15 ± 1.82 nm), poly dispersity index (0.26 ± 0.02), zeta-potential (- 25.53 ± 0.60 mV), entrapment efficiency (95.65 ± 0.70%), drug loading (2.33 ± 0.10%), and a spherical appearance. Pharmacokinetic results showed that the FLD-SLNs presented 3.17-fold increase in area under the curve (AUC_(0-t)) compared with free FLD after oral administration in beagle dogs, which indicated that SLNs prepared using the effervescent dispersion technique can improve the bioavailability of lipophilic drugs like felodipine by enhancement of absorption and reduction first-pass metabolism.

Dry Gel Containing Optimized Felodipine-Loaded Transferosomes: a Promising Transdermal Delivery System to Enhance Drug Bioavailability

Felodipine has a very low bioavailability due to first-pass metabolism. The aim of this study was to enhance its bioavailability by transdermal application. Felodipine-loaded transferosomes were prepared by thin-film hydration using different formulation variables. An optimized formula was designed using statistical experimental design. The independent variables were the used edge activator, its molar ratio to phosphatidylcholine, and presence or absence of cholesterol. The responses were entrapment efficiency of transferosomes, their size, polydispersity index, zeta potential, and percent drug released after 8 h. The optimized formula was subjected to differential scanning calorimetry studies and its stability on storage at 4°C for 6 months was estimated. This formula was improved by incorporation of different permeation enhancers where ex vivo drug flux through mice skin was estimated and the best improved formula was formulated in a gel and lyophilized. The prepared gel was subjected to in vivo study using Plendil® tablets as a reference. According to the calculated desirability, the optimized transferosome formula was that containing sodium deoxycholate as edge activator at 5:1 M ratio to phosphatidylcholine and no cholesterol. The thermograms of this formula indicated the incorporation of felodipine inside the prepared vesicles. None of the tested parameters differed significantly on storage. The lyophilized gel of labrasol-containing formula was chosen for in vivo study. The relative bioavailability of felodipine from the designed gel was 1.7. In conclusion, topically applied lyophilized gel containing felodipine-loaded transferosomes is a promising transdermal delivery system to enhance its bioavailability.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Exercise intolerance

Exercise intolerance is the primary symptom of chronic diastolic heart failure. It is part of the definition of heart failure and is intimately linked to its pathophysiology. Further, exercise intolerance affects the diagnosis and prognosis of heart failure. In addition, understanding the mechanisms of exercise intolerance can lead to developing and testing rational treatments for heart failure. This article focuses on the fundamental principles of exercise physiology and on the assessment, pathophysiology, and potential treatment of exercise intolerance in diastolic heart failure.

Diastolic Heart Failure in the Elderly

Most elderly patients, particularly women, who have heart failure have a normal ejection fraction. Patients who have this syndrome have severe symptoms of exercise intolerance, frequent hospitalizations, and increased mortality. The pathophysiology and treatment are not well defined. Control of systemic hypertension may be a key to prevention and treatment. Several large trials of specific agents are currently underway.

Diastolic heart failure in the elderly

Most elderly patients, particularly women, who have heart failure have a normal ejection fraction. Patients who have this syndrome have severe symptoms of exercise intolerance, frequent hospitalizations, and increased mortality. The pathophysiology and treatment are not well defined. Control of systemic hypertension may be a key to prevention and treatment. Several large trials of specific agents are currently underway.

Rho-kinase inhibition in the therapy of cardiovascular disease

Rho is a GTPase known to be a major mediator in the formation of stress fibers and focal adhesions, cell morphology, and smooth muscle contraction. Its role in smooth muscle contraction has led to exploration into the connection between Rho-mediated kinase activity and cardiovascular disease. The role of Rho-kinase in calcium sensitization for vascular smooth muscle contraction has recently been characterized. Inappropriate coronary artery vasoconstriction resulting from increased Rho-kinase in the vascular system is likely involved in the pathogenesis of exercise-induced myocardial ischemia, spontaneous coronary artery spasm, and hypertension. In clinical trials, Rho-kinase inhibitors such as fasudil and Y-27632 have demonstrated antiischemic, antivasospastic, and antihypertensive effects. These compounds have also exhibited the ability to blunt progression of cardiomyocyte hypertrophy and cardiac remodeling in heart failure. As such, Rho-kinase inhibition represents a potential novel therapeutic approach in cardiovascular disease.

Calcium antagonists

Calcium antagonists were introduced for the treatment of hypertension in the 1980s. Their use was subsequently expanded to additional disorders, such as angina pectoris, paroxysmal supraventricular tachycardias, hypertrophic cardiomyopathy, Raynaud phenomenon, pulmonary hypertension, diffuse esophageal spasms, and migraine. Calcium antagonists as a group are heterogeneous and include 3 main classes--phenylalkylamines, benzothiazepines, and dihydropyridines--that differ in their molecular structure, sites and modes of action, and effects on various other cardiovascular functions. Calcium antagonists lower blood pressure mainly through vasodilation and reduction of peripheral resistance. They maintain blood flow to vital organs, and are safe in patients with renal impairment. Unlike diuretics and beta-blockers, calcium antagonists do not impair glucose metabolism or lipid profile and may even attenuate the development of arteriosclerotic lesions. In long-term follow-up, patients treated with calcium antagonists had development of less overt diabetes mellitus than those who were treated with diuretics and beta-blockers. Moreover, calcium antagonists are able to reduce left ventricular mass and are effective in improving anginal pain. Recent prospective randomized studies attested to the beneficial effects of calcium antagonists in hypertensive patients. In comparison with placebo, calcium antagonist-based therapy reduced major cardiovascular events and cardiovascular death significantly in elderly hypertensive patients and in diabetic patients. In several comparative studies in hypertensive patients, treatment with calcium antagonists was equally effective as treatment with diuretics, beta-blockers, or angiotensin-converting enzyme inhibitors. From these studies, it seems that a calcium antagonist-based regimen is superior to other regimens in preventing stroke, equivalent in preventing ischemic heart disease, and inferior in preventing congestive heart failure. Calcium antagonists are also safe and effective as first-line or add-on therapy in diabetic hypertensive patients. Heart rate-lowering calcium antagonists (verapamil, diltiazem) may have an edge over the dihydropyridines in post-myocardial infarction patients and in diabetic nephropathy. Thus, calcium antagonists may be safely used in the management of hypertension and angina pectoris.

Antianginal effects of hydroxyfasudil, a Rho-kinase inhibitor, in a canine model of effort angina

1. The effects of Rho-kinase inhibitor, fasudil, and of a more specific Rho-kinase inhibitor, hydroxyfasudil, on pacing-induced myocardial ischaemia were determined in anaesthetized open-chest dogs. 2. The dogs were subjected to left anterior descending coronary artery (LAD) stenosis producing a sufficient ischaemia as measured by ST-segment depression on electrocardiograms only when the hearts were paced 60 beats min(-1) above the baseline. After a recovery (nonpacing) period, drugs or saline were infused intravenously over 30 min. The animals were again subjected to 5 min of pacing 25 min after the initiation of the treatment. 3. Hydroxyfasudil (0.1 and 0.3 mg kg(-1)) and fasudil (0.3 mg kg(-1)) suppressed the ST-segment depression. Hydroxyfasudil and fasudil also increased the regional blood flow of the LAD perfused endomyocardium region in the canine model of effort angina. 4. To determine the flow profile for hydroxyfasudil in dogs, blood flow in three vascular beds was measured. Hydroxyfasudil (0.3 mg kg(-1) for 30 min) significantly increased coronary blood flow and vertebral blood flow, without significantly changing the femoral blood flow. 5. Hydroxyfasudil had no inotropic or chronotropic effect on the isolated hearts of guinea-pigs. Hydroxyfasudil (2 mg kg(-1) for 20 min) did not affect the PR or QTc interval in anaesthetized dogs. 6. Inhibition of Rho-kinase appears to protect myocardium subjected to pacing-induced ischaemia through the increase in the regional myocardial blood flow. Hydroxyfasudil may be categorized as a novel type of anti-anginal drug, without any inotropic or chronotropic effects.

Diastolic dysfunction in the elderly. Genesis and diagnostic and therapeutic implications

Diastolic left ventricular function is altered substantially with advancing age in healthy persons, and diastolic dysfunction impacts most cardiovascular disorders in the elderly. Older, healthy persons have a delayed relaxation Doppler filling pattern and their early deceleration time is similar to, or modestly lengthened, compared with younger, healthy persons. Two abnormal Doppler filling patterns, the pseudo-normal and the restricted, are discerned more easily, and are more specific in the elderly than the young, because they are the opposite (reverse) of the normal elderly pattern. Most heart failure in the elderly occurs in the presence of preserved systolic function (presumed diastolic heart failure). Elderly patients with diastolic heart failure tend to be women with hypertrophied, hyperdynamic left ventricles, and chronic hypertension. Prognosis may be somewhat better than in systolic heart failure, but the difference diminishes when adjusted for gender and in the very elderly. The pathophysiology of this disorder is not well characterized, diagnostic criteria have not been standardized, and there are no large, multicenter, randomized trials to guide therapy. Further research in this area should be a high priority.

Heart failure with normal systolic function

Contrary to popular belief, population studies indicate that most elderly patients with heart failure have preserved left ventricular systolic function (i.e., presumed diastolic heart failure). Several normal aging changes may predispose older individuals to diastolic heart failure, including increased hypertrophy and stiffness of the left ventricle, increased vascular stiffness, and decreased cardiovascular reserve. Progress in diastolic heart failure has been hindered by a lack of standard case definition; absence of a readily available, reliable test to quantitate diastolic function; poor understanding of the pathophysiology of heart failure; and lack of data from randomized, controlled, multicenter trials. Typical patients are older women with chronic hypertension, left ventricular hypertrophy, chronic exercise intolerance, and occasional acute exacerbations (pulmonary edema). Although heart failure is a clinical, bedside diagnosis, echocardiography is helpful in differentiating diastolic from systolic heart failure and in ruling out other disorders. Although optimal pharmacologic therapy has not been clarified, control of blood pressure; exercise conditioning; and a multidisciplinary, case management approach seem beneficial.

Influence of felodipine on left ventricular hypertrophy and systolic function in orthotopic heart transplant recipients: possible interaction with cyclosporine medication

BACKGROUND

Concentric left ventricular (LV) hypertrophy develops early in orthotopic heart transplant (OHT) recipients. To compare the effects of a calcium channel blocker, felodipine, versus diuretics on LV hypertrophy and LV systolic function repeated magnetic resonance imaging studies were performed in OHT recipients. Cyclosporine levels and neurohormones were also measured to explore potential interactions with treatment.

METHODS

Twenty-two patients were randomized at baseline (2 months after OHT) to receive felodipine or diuretic treatment. Before and after 4 months of treatment (n = 19), LV dimensions and LV mass (Simpson's rule) were measured. The relationship between circumferential fiber shortening (two-shell cylindrical model) and end-systolic wall stress was used as a measure of load-independent LV contractility. Neurohormones were measured at the beginning and end of the treatment period, and cyclosporine levels and blood pressures were additionally measured during treatment.

RESULTS

At baseline, the felodipine and diuretic groups did not differ in LV mass, wall stress, and fiber shortening. During felodipine treatment LV mass decreased (p < 0.01) and tended to increase during diuretics treatment (p = 0.06). Afterload-corrected fiber shortening did not change during felodipine treatment, but decreased (p < 0.01) with diuretics. Changes in LV mass were positively correlated with cyclosporine levels (r = 0.70) in the diuretics group, but not in the felodipine group.

CONCLUSIONS

In OHT recipients during diuretic treatment, progression of LV hypertrophy occurs in relation to cyclosporine plasma levels and is accompanied by impairment of systolic contractile function. Felodipine induces regression of LV hypertrophy, while systolic contractile function is preserved. During felodipine treatment, regression of LV hypertrophy is unrelated to cyclosporine levels. Thus, felodipine seems to attenuate the hypertrophic effect of cyclosporine on transplanted hearts.

The pharmacology of ion channels: with particular reference to voltage-gated Ca2+ channels

Ion channels are molecular machines that serve as principal integrating and regulatory devices for the control of cellular excitability. They are also major targets for drug action. The basic aspects of ion channel structure and pharmacological control are reviewed and illustrated with specific reference to a major class of therapeutic agents and molecular tools--the clinically available Ca2+ channel antagonists.

Verapamil accelerates the transition to heart failure in obese, hypertensive, female SHHF/Mcc-fa(cp) rats

We sought to characterize the effects of the nonselective Ca2+ channel antagonist, verapamil, and the vascular-selective Ca2+ channel antagonist, felodipine, on obese, hypertensive, heart failure-prone, female SHHF/Mcc-fa(cp) rats. Rats were treated for < or = 2 months with verapamil (57 mg/kg/day) or felodipine (24 mg/kg/day). Blood pressures were determined at monthly intervals by the tail-cuff method. Heart weights and myosin isoforms were measured at the end of treatment. Direct cardiac effects of verapamil and felodipine were examined in electrically field stimulated, fura-2/AM-loaded cardiomyocytes. Both Ca2+ channel antagonists reduced systolic blood pressures. Verapamil, but not felodipine, increased heart weights and decreased expression of the myosin V1 isoform. In older animals, 75% of those treated with verapamil developed end-stage congestive heart failure. Age-matched control and felodipine-treated rats remained healthy. In isolated cardiomyocytes, 10(-9) M verapamil significantly reduced Ca2+ transient amplitudes but 10(-9) M felodipine did not. Both Ca2+ channel antagonists reduced blood pressures in obese, hypertensive, female SHHF rats. Verapamil, but not felodipine, produced heart failure in a large number of these animals. Differences between the in vivo effects of the two Ca2+ channel antagonists may be related to the differing effects on sarcolemmal Ca2+ influx.

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.

Use of calcium antagonists in patients with ischemic heart disease and systemic hypertension

Ischemic heart disease (IHD) and systemic hypertension commonly coexist in a large number of patients, and the presence of hypertension is a risk factor for worsening IHD. A monotherapy that would effectively treat both is thus an attractive idea, and calcium antagonists have been evaluated in this role. Calcium antagonists exert therapeutic effects through a combination of actions, including systemic and peripheral vasodilation, negative inotropy, and reduced nodal conduction. In randomized, double-blind clinical trials, verapamil compares favorably with propranolol in the alleviation of angina and hypertension. Both diltiazem and nifedipine, as well as long-acting diltiazem, are also effective in treating the combined condition. In addition, each of these drugs enhances exercise tolerance and favors compliance with calcium antagonist therapy. Recent questions regarding the safety of this class of drug have tempered the enthusiasm for their use as first-line therapy in cardiovascular disease. In particular, short-acting dihydropyridine derivatives, including nifedipine and isradipine, may increase cardiovascular morbidity and mortality because of reflex sympathetic stimulation. The results of appropriately controlled, prospective clinical trials will provide more definitive conclusions. For now, we must be cautious in the use of calcium antagonist monotherapy for combined IHD and hypertension.

Overview of the safety of felodipine based on clinical trials in patients with hypertension

All clinical studies of at least 1 week's duration with felodipine in patients with hypertension were included in a safety analysis. The major finding was that felodipine does not increase mortality or the incidence of major cardiovascular events and that the data indicate a favorable effect.