Calcium antagonists. Clinical use in the treatment of angina

Vasospastic angina: Past, present, and future

Vasospastic angina (VSA) is characterized by episodes of rest angina that are responsive to short-acting nitrates and are attributable to coronary artery vasospasm. The condition is underdiagnosed as the provocation test is rarely performed. VSA, the most important component of non-obstructive coronary artery disease, can present with angina, be asymptomatic, or can even present with fatal arrhythmias and cardiac arrest. Although most patients with VSA respond well to vasodilating medications, prognosis does not improve as expected in most patients, suggesting the existence elusive prognostic factors and pathogenesis that warrant further exploration. Moreover, patients with either severe or refractory VSA barely respond to conventional treatment and may develop life-threatening arrhythmias or suffer sudden cardiac death during ischemic attacks, which are associated with immune-inflammatory responses and have been shown to achieve remission following glucocorticoid and immunoglobulin treatments. Our recent work revealed that inflammation plays a key role in the initiation and development of coronary spasms, and that inflammatory cytokines have predictive value for diagnosis. In contrast to the existing literature, this review both summarizes the theoretical and clinical aspects of VSA, and also discusses the relationship between inflammation, especially myocarditis and VSA, in order to provide novel insights into the etiology, diagnosis, and treatment of VSA.

How to Improve Effectiveness and Adherence to Antihypertensive Drug Therapy: Central Role of Dihydropyridinic Calcium Channel Blockers in Hypertension

Essential hypertension is a complex clinical condition, characterized by multiple and concomitant abnormal activation of different regulatory and contra-regulatory pathophysiological mechanisms, leading to sustained increase of blood pressure (BP) levels. Asymptomatic rise of BP may, indeed, promote development and progression of hypertension-related organ damage, which in turn, increases the risk of major cardiovascular and cerebrovascular events. A progressive and independent relationship has been demonstrated between high BP levels and increased cardiovascular risk, even in the high-to-normal range. Conversely, evidence from randomized controlled clinical trials have independently shown that lowering BP to the recommended targets reduces individual cardiovascular risk, thus improving event-free survival and reducing the incidence of hypertension-related cardiovascular events. Despite these benefits, overall rates of BP control remain poor, worldwide. Currently available guidelines support a substantial equivalence amongst various antihypertensive drug classes. However, several studies have also reported clinically relevant differences among antihypertensive drugs, in terms of both BP lowering efficacy and tolerability/safety profile. These differences should be taken into account not only when adopting first-line antihypertensive therapy, but also when titrating or modulating combination therapies, with the aim of achieving effective and sustained BP control. This review will briefly describe evidence supporting the use of dihydropyridinic calcium channel blockers for the clinical management of hypertension, with a particular focus on barnidipine. Indeed, this drug has been demonstrated to be effective, safe and well tolerated in lowering BP levels and in reducing hypertension-related organ damage, thus showing a potential key role for improving the clinical management of hypertension.

Calcium channel blockers and hypertension

Effective treatment of high blood pressure (BP) represents a key strategy for reducing the burden of hypertension-related cardiovascular and renal diseases. In spite of these well-established concepts, hypertension remains poorly controlled worldwide. In order to improve BP control in patients with hypertension, several interventions have been proposed, among which (1) preferred use of more effective, sustained, and well-tolerated antihypertensive drug aimed to ensure adherence to prescribed medications and (2) extensive use of rational, integrated, and synergistic combination therapies, even as first-line strategy, aimed to achieve the recommended BP targets. Within the possible antihypertensive drug classes currently available for the clinical management of hypertension, both in monotherapy and in combination therapy, drugs inhibiting the renin-angiotensin system and calcium channel blockers (CCBs) have demonstrated to be effective and safe in lowering BP levels and achieving the recommended BP targets with a good tolerability profile. In particular, CCBs have been one of the most widely used classes of antihypertensive agents in the last 20 years, based on their effectiveness in reducing BP levels, good tolerability, and abundant evidence on reducing cardiovascular and renal consequences of hypertension. This article provides an updated overview of the evidence supporting the use of CCBs-based antihypertensive regimen, both in monotherapy and in combination therapies with different classes of antihypertensive drugs.

Calcium channel blockers: spectrum of side effects and drug interactions

Calcium antagonists are a chemically heterogenous group of agents with potent cardiovascular effects which are beneficial in the treatment of angina pectoris, arterial hypertension and cardiac arrhythmias. The main side effects for the group are dose-dependent and the result of the main action or actions of the calcium antagonists, i.e. vasodilatation, negative inotropic effects and antiarrhythmic effects. Pronounced hypotension is reported for the main calcium antagonist drugs; verapamil, diltiazem and nifedipine. While conduction disturbances and bradycardia are seen more often after verapamil and diltiazem, tachycardia, headache and flush are more frequent after nifedipine. Constipation is relatively frequent after verapamil while nifedipine is reported to induce diarrhea in som patients. Idiosyncratic side effects are rare but have been reported from the skin, mouth, musculoskeletal system, the liver and the central nervous system. These side effects include urticarial rashes, gingival hyperplasia, arthralgia, hepathotoxicity and transistory mental confusion or akathisia. Verapamil, diltiazem and possibly also nifedipine have been reported to increase serum digoxin concentrations but the clinical relevance of these drug interactions are not clear. Furthermore, verapamil and diltiazem may potentiate the effects of beta-adrenergic blocking drugs and verapamil may also potentiate the effects of neuromuscular blocking drugs. It is concluded that side effects after calcium antagonist drugs are mostly trivial and transient although they may sometimes be relatively common. Clinically relevant drug interactions are few. Judged from the point of efficacy and safety, calcium antagonists will have a major place in the future pharmacotherapy of several cardiovascular disorders.

Identification and characterization of potential impurities of amlodipine maleate

Six impurities ranging from 0.43 to 1.42% in amlodipine maleate were detected by a simple isocratic reverse-phase high performance liquid chromatography (HPLC). LC-MS was performed to identify the mass of the impurities. Based on the spectral data (IR, NMR and MS), the structures of these impurities were characterized as 3-ethyl 5-methyl 4-(2-chlorophenyl)-2-[2-(1,3-dioxo-2,3-dihydro-1H-2-isoindolyl)ethoxymethyl]-6-methyl-1,4-dihydro-3,5-pyridinedicarboxylate (impurity I); 5-ethyl 3-methyl 4-(2-chlorophenyl)-2-methyl-6-[2-(2-methylcarbamoylphenyl-carboxamido)ethoxymethyl]-1,4-dihydro-3,5-pyridinedicarboxylate (impurity II); besylate salt of 3-ethyl 5-methyl 2-(2-aminoethoxymethyl)-4-(2-chlorophenyl)-6-methyl-3,5-pyridinedicarboxylate (impurity III); dimethyl 2-(2-aminoethoxymethyl)-4-(2-chlorophenyl)-6-methyl-1,4-dihydro-3,5-pyridinecarboxylate (impurity IV); 3-ethyl 5-methyl 2-(2-aminoethoxymethyl)-4-(4-chlorophenyl)-6-methyl-1,4-dihydro-3,5-pyridinedicarboxylate (impurity V); diethyl 2-(2-aminoethoxymethyl)-4-(2-chlorophenyl)-6-methyl-1,4-dihydro-3,5-pyridinedicarboxylate (impurity VI).

Synthesis, structural elucidation and pharmacological properties of some 5-acetyl-3,4-dihydro-6-methyl-4-(substituted phenyl)-2(1H) -pyrimidinones

In this study, the synthesis of some new 5-acetyl-3,4-dihydro-6-methyl-4-(substituted phenyl)-2(1H)-pyrimidinones has been reported. The compounds were prepared by the Biginelli reaction of acetylacetone with aromatic aldehydes and urea. The structures of the compounds were characterized by UV, IR, 1H NMR, 13C NRM, mass spectra and elementary analysis. The calcium antagonistic activity of these compounds was tested in vitro on rat ileum precontracted with 4 x 10(-3) M barium chloride.

Novel calcium antagonists with both calcium overload inhibition and antioxidant activity. 1. 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-(aminopropyl)thiazolidinones

A series of 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-(aminopropyl)thiazolidinones was synthesized in order to explore novel calcium antagonists with potent antiischemic activity. These compounds were designed to have, in addition to Ca2+ antagonistic activity, both Ca2+ overload prevention and antioxidant activity in one molecule. These three kinds of activity were evaluated by using a K+-depolarized rat aorta, a veratridine-induced Ca2+ overload model of rat cardiomyocytes, and a soybean lipoxygenase-induced lipid peroxidation model of rabbit low-density lipoprotein, respectively. In particular, 2-(3, 5-di-tert-butyl-4-hydroxyphenyl)-3-[3-[N-methyl-N-[2-[3, 4-(methylenedioxy)phenoxy]ethyl]amino]propyl]-1,3-thiazolidin-4-on e (7o) was found to be highly potent and possessed a well-balanced combination of these actions in vitro.

Use of calcium channel antagonists for cardiovascular disease

Until recently, only three calcium channel antagonists--verapamil, diltiazem and nifedipine--were available for managing cardiovascular disorders such as hypertension and ischemic heart disease. In the past few years, however, several dihydropyridine calcium channel antagonists, including nicardipine, isradipine, felodipine, nimodipine, and amlodipine, have been marketed. Others are currently awaiting FDA approval. In addition, bepridil, which belongs to a new class of calcium channel antagonists, has recently been marketed for refractory angina pectoris. Clinical uses of calcium channel antagonists have been expanded since the 1970s to include management of cardiovascular disorders such as supraventricular arrhythmias, CHF secondary to diastolic dysfunction, and myocardial reinfarction in selected patients. Calcium channel antagonists are also being investigated for prevention of atherosclerosis. Calcium channel antagonists are a heterogeneous group of pharmacologic agents. Differences in tissue selectivity are largely responsible for the variations in hemodynamic and electrophysiologic properties of these agents. Thus, their clinical uses and side effect profiles differ. These differences must be taken into consideration in the selection of the most appropriate agent for a specific indication. Potential advantages of some of the newer dihydropyridine calcium channel antagonists include less frequent dosing (amlodipine and isradipine) and little or no negative inotropic effect (nicardipine, felodipine, amlodipine, isradipine) compared with the prototype calcium channel antagonists. Additional clinical experience with these newer agents is required, however, before their role in the management of cardiovascular disorders can be fully delineated. The availability of sustained-release formulations of verapamil, diltiazem, nifedipine, felodipine, and nicardipine, as well as the recent marketing of calcium channel antagonists with relatively long half-lives (amlodipine and isradipine), makes once- or twice-daily dosing possible with most calcium channel blockers. However, selection of a particular agent will depend on several factors, including clinical efficacy, side effect profile, cost, and patient characteristics such as concomitant disease states and baseline hemodynamic status.

Synthesis and calcium antagonistic activity of some new 2-thioxo-1,2,3,4-tetrahydropyrimidine derivatives

A series of 1,2,3,4-tetrahydro-6-methyl-4-(substituted phenyl)-2-thioxo-5-pyrimidinecarboxylic acid methyl esters were synthesized by condensing thiourea with methyl acetoacetate and nonsubstituted or differently substituted benzaldehydes in absol. ethanol using HCl as a catalyst according to the Biginelli reaction. The structures of the compounds were confirmed by elemental and spectroscopic analysis. -The compounds were evaluated for their calcium antagonistic activity on the basis of their potency in inhibiting [3H] PN 200-110 binding on microsomes obtained from rat skeletal muscle.

Amlodipine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in cardiovascular disease

Amlodipine, a basic dihydropyridine derivative, inhibits the calcium influx through 'slow' channels in peripheral vascular and coronary smooth muscle cells, thus producing marked vasodilation in peripheral and coronary vascular beds. Short to medium term clinical trials indicate that amlodipine is effective as both an antianginal agent in patients with stable angina pectoris and an antihypertensive agent in patients with mild to moderate hypertension. In small comparative studies amlodipine was at least as effective as 'standard' agents, including atenolol, verapamil, hydrochlorothiazide or captopril in hypertension, and diltiazem or nadolol in angina pectoris. Amlodipine is well tolerated, and does not appear to cause some of the undesirable effects often associated with other cardiovascular agents (e.g. adverse changes in serum lipid patterns, cardiac conduction disturbances, postural hypotension). The most common adverse effects associated with amlodipine therapy--oedema and flushing--are related to the vasodilatory action of the drug, and are generally mild to moderate in severity. Thus, amlodipine seems to provide a useful alternative to other agents currently available for the treatment of essential hypertension and chronic stable angina pectoris, with certain pharmacodynamic and tolerability properties that should be advantageous in many patients.

Verapamil. An updated review of its pharmacodynamic and pharmacokinetic properties, and therapeutic use in hypertension

Although verapamil is a well-established treatment for angina, cardiac arrhythmias and cardiomyopathies, this review reflects current interest in calcium antagonists as anti-hypertensive agents by focusing on the role of verapamil in hypertension. Verapamil is a phenylalkylamine derivative which antagonises calcium influx through the slow channels of vascular smooth muscle and cardiac cell membranes. By reducing intracellular free calcium concentrations, verapamil causes coronary and peripheral vasodilation and depresses myocardial contractility and electrical activity in the atrioventricular and sinoatrial nodes. Verapamil is well suited for the management of essential hypertension since it produces generalised systemic vasodilation resulting in a marked reduction in systemic vascular resistance and, consequently, blood pressure. Evidence from clinical studies supports the role of oral verapamil as an effective and well-tolerated first-line treatment for the management of patients with mild to moderate essential hypertension. Clinical studies have shown that verapamil is more effective the higher the pretreatment blood pressure and some authors have found a more pronounced antihypertensive effect in older patients or in patients with low plasma renin activity. Sustained release verapamil formulations are available for oral administration which, as a single daily dose, are as effective in lowering blood pressure over 24 hours as equivalent doses of conventional verapamil formulations given 3 times daily. As a first-line antihypertensive agent, oral verapamil is equivalent to several other calcium antagonists, beta-blockers, diuretics, angiotensin-converting enzyme (ACE) inhibitors and other vasodilators, and is not associated with many of the common adverse effects of these treatments. Verapamil may be preferred as an alternative first-line antihypertensive treatment to diuretics in elderly patients because it has similar efficacy in these patients without causing the adverse effects commonly linked with diuretic treatment. Furthermore, because verapamil does not cause bronchoconstriction, it may be used in preference to beta-blockers in patients with asthma or chronic obstructive airway disease. Reflex tachycardia, orthostatic hypotension or development of tolerance is not evident following verapamil administration. As a second- or third-line treatment for patients refractory to established antihypertensive regimens, verapamil produces marked blood pressure reductions when combined with diuretics and/or ACE inhibitors, beta-blockers and vasodilators such as prazosin.(ABSTRACT TRUNCATED AT 400 WORDS)

The efficacy of nifedipine and acebutolol in coronary artery disease assessed by radionuclide ventriculography

The efficacy of a fixed combination of 10 mg nifedipine and 100 mg acebutolol was tested in 21 patients with angiographically proven coronary artery disease (CAD). Ejection fraction (EF), emptying and filling rate (VS and VD), and end-systolic volume (ESV) were assessed by means of radionuclide ventriculography at rest and during exercise prior to as well as 1 hour and 5 hours following oral drug application. Whereas exercise-induced worsening of cardiac function had been documented in all the patients prior to medication, EF and ESV improved significantly after drug administration.

Beta-adrenoceptor antagonists plus nifedipine in the treatment of chronic stable angina pectoris

The antianginal effects of beta-adrenoceptor antagonists are achieved by a reduction in myocardial oxygen demand. This is a rational approach to treatment in patients whose angina is caused by a fixed stenosis. However, dynamic coronary vasospasm is an important factor in patients with chronic stable angina. Nifedipine increases myocardial oxygen supply by reducing coronary vascular tone and is a logical approach to treatment in these patients. For monotherapy of angina, nifedipine is less effective than the beta-adrenoceptor antagonists, but the combination has additive effects in reducing the frequency of anginal episodes and improving exercise tolerance. Plasma concentrations of nifedipine are closely related to clinical efficacy, and the variable first-pass metabolism of the drug leads to wide interindividual differences in peak concentrations and duration of action. Increasing the size of individual doses of nifedipine carries a risk of enhanced side effects due to high peak plasma concentrations. Optimal treatment may be more appropriately achieved in some patients by a slow release formulation, but with an increased frequency of administration.

Effects of some calcium channel blockers on isolated human penile erectile tissues

The effects of the calcium channel blockers (CCBs) verapamil, nifedipine and diltiazem on contractile activation of isolated human penile erectile tissues were investigated. Specimens of the corpus spongiosum (CS) and corpora cavernosa (CC) were obtained from men with a history of normal penile erection undergoing cystourethrectomy because of bladder malignancy. Preparations were mounted in organ baths and isometric tension was recorded. Deprivation of extracellular calcium abolished electrically induced contractions in both CS and CC preparations within 15 min.; norepinephrine (NE)-induced contractions were reduced by 90% (CS) and 83% (CC) after 30 min. All the CCBs reduced electrically induced contractions concentration-dependently, nifedipine being the most potent agent. Contractions induced by exogenous NE were depressed by about 50%, whereas high K+ (124 mM) induced responses were abolished. It is concluded that contraction in penile erectile tissues is mediated mainly by neuronally released NE stimulating postjunctional alpha-adrenoceptors. The contraction is highly dependent on extracellular calcium and can partly be inhibited by CCBs. It cannot be excluded that some CCBs injected intracavernosally may be useful for diagnosis and even treatment of erectile dysfunction. However, calcium channel blockade may not be as effective as a therapeutic principle as blockade of alpha-adrenoceptors.

Nicardipine. A review of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy, in the treatment of angina pectoris, hypertension and related cardiovascular disorders

Nicardipine is an antagonist of calcium influx through the slow channel of the cell membrane and has been shown to be an effective and relatively well-tolerated treatment for stable effort angina and rest angina due to coronary artery spasm, and mild to moderate hypertension. Although its exact mechanism of action in these disease states has not been precisely defined, the potent coronary and peripheral arterial dilator properties of nicardipine, with concomitant improvements in oxygen supply/demand and reductions in systemic vascular resistance, are of major importance. Clinical studies have shown that nicardipine appears to be effective in the treatment of chronic stable exercise-induced angina pectoris and possibly in angina at rest due to coronary artery spasm. In the treatment of stable angina, nicardipine has proved to be equally as effective as nifedipine. However, haemodynamic and clinical studies indicate that nicardipine may have a further advantage of not depressing cardiac conduction or left ventricular function, even in patients with compromised cardiac pumping ability. Nicardipine also appears to be useful as initial monotherapy or in combination with other antihypertensive drugs when used in the treatment of mild to moderate hypertension, and may have some advantages over other vasodilators in this regard in that it may not be as frequently associated with fluid retention or weight gain as other similar drugs. In the treatment of hypertension nicardipine has been shown to be as effective as drugs such as hydrochlorothiazide, cyclopenthiazide, propranolol and verapamil in short term studies although confirmation of its long term usefulness in well-designed clinical trials is still required. Similarly, although the use of nicardipine in other disorders such as congestive heart failure and cerebrovascular disease has provided encouraging preliminary results, more studies are needed to clarify its place in their treatment. Side effects appear to be dose related and more frequent within the first few weeks of therapy. Most of these effects are minor and transient in nature and include headache, flushing and peripheral oedema. Thus, there is no doubt that nicardipine provides a suitable alternative to other drugs available for the treatment of angina and hypertension. However, further well-designed comparative clinical trials are needed to clarify its relative place in the long term management of these disorders.

Arterial and venous effects of verapamil in normal volunteers

1. The effects of verapamil (120 mg orally) and a placebo on arterial pressure, heart rate, PR interval, arterial flows and diameters of the brachial and carotid arteries (pulsed Doppler technique), forearm vascular resistance, and venous diameter and compliance (cutaneous microstrain gauge and plethysmography) have been compared over a 10-hr period in six healthy volunteers during a double-blind and cross-over study. 2. Verapamil reduced diastolic blood pressure by approximately 10 mm Hg, did not affect heart rate and increased PR interval by approximately 15%. 3. Verapamil significantly increased brachial and carotid arterial blood flows by 56% (P less than 0.01) and 16% (P less than 0.05), respectively, but the diameters of these vessels were not significantly modified (+7 and +4%, respectively, NS). Forearm vascular resistance decreased by 40% (P less than 0.01), indicating that verapamil preferentially dilates small arteries. All these effects peaked at 2 h after drug intake and lasted for 6 h. 4. Verapamil increased hand dorsal vein diameter and flow by 95% (P less than 0.05) and 80% (P less than 0.05), respectively, from 2 to 4 h after drug intake but venous compliance, assessed by the venous diameter/venous flow ratio, was not significantly modified (from 0.71 to 0.69, NS), thus indicating that veins are not directly affected by this drug.

Resting angina with fixed coronary artery stenosis: nocturnal decline in ischemic threshold

Atrial pacing was performed in 16 patients with angina at rest and significant coronary artery stenosis (greater than 70%) over 2 consecutive days in the morning (10 A.M. to 1 P.M.), in the afternoon (4 to 7 P.M.), and at night (12 midnight to 3 A.M.) to assess possible circadian variations of their ischemic threshold. Overall, the incidence of resting angina was highest at night. All pacing results were positive (greater than or equal to 1.0 mm ST segment shift) and tended to be reproducible in nine patients, whereas some or all were negative in seven. Among all positive results, ischemic thresholds at night were significantly lower than those in the morning and in the afternoon (125 +/- 3 vs 138 +/- 3 and 139 +/- 2 beats/min, mean +/- SEM; p less than .005). In nine patients, 19 pacing tests produced ST segment elevation, of which 13 were performed at night (68%). We conclude that patients with resting angina and severe coronary stenosis often exhibit a nocturnal decline in their ischemic threshold, which seems to facilitate development of transmural ischemia during atrial pacing.

Evaluation of a coronary lysing system: results of a preclinical safety and efficacy study

The purpose of this study was to evaluate the efficacy and safety of a recently developed transluminal lysing system in the removal of coronary stenotic lesions from a human cadaver heart and in the cannulation of coronaries in the anesthetized dog. The left coronary arteries of three dogs were cannulated on separate occasions, with coronary arteriography and translation of the transluminal lysing system cutter to the distal segments of the coronary vessels performed each time. Proximal and distal coronary pressures were recorded from the guiding catheter and the transluminal lysing system cutter, demonstrating no significant pressure differential and minimal damping. Pathological examination of the dog coronaries after sacrifice demonstrated minor intimal irregularities with no significant thrombosis or vessel perforation. A significant portion of the occlusive stenotic lesions were removed from coronary vessels of a human cadaver heart with subsequent reestablishment of angiographic dye flow to the distal coronary vessels without evidence of debris loss from the transluminal lysing system cutter or the appearance of occlusions in the distal vessels. We conclude that the transluminal lysing system can be introduced into the coronary artery of a living dog on repeated occasions without causing significant coronary damage, coronary occlusive thrombosis, myocardial destruction, morbidity, or mortality; furthermore, occlusive stenotic lesions can be removed from cadaver coronary vessels by the transluminal lysing system with the establishment of angiography patency.

Comparative effects of various calcium entry blockers and anti-asthmatic compounds on antigen-induced bronchoconstriction in rat and histamine release from rat mast cells

The effects of four calcium entry blockers (diltiazem, nifedipine, mesudipine and verapamil) were studied on antigen-induced bronchoconstriction in sensitized rats and histamine release from rat mast cells, in comparison with compounds frequently used in atopic patients (theophylline, isoproterenol, disodium cromoglycate, ketotifen and clemastine). The four Ca2+ entry blockers produced a dose-related inhibition of the IgE-dependent bronchoconstriction in rat whereas the other drugs exhibited a weak effect or even were inactive. 48/80-induced histamine release was antagonized by nifedipine, verapamil and ketotifen. On the contrary, diltiazem, mesudipine, theophylline, isoproterenol, disodium cromoglycate and clemastine were not able to interfere with this release process. These data may suggest an important role of both extra- and intracellular calcium in such phenomena.

A dose-ranging, placebo-controlled, double-blind trial of nisoldipine in effort angina: duration and extent of antianginal effects

Maximal treadmill exercise testing at 1, 3 and 8 hours was used to assess the onset, duration and antianginal efficacy of the dihydropyridine slow channel calcium-blocking agent, nisoldipine, in an oral dose range of 5, 10 and 20 mg. A double-blind, randomized, placebo-controlled design was used involving 12 patients with stable effort angina. Exercise tolerance was significantly increased 3 hours after each dose, when the maximal beneficial effect occurred. The improvement was observed as early as 1 hour after the 10 and 20 mg dose, and persisted for 8 hours after the 20 mg dose. At 3 hours, the onset of an exercise-induced ST segment depression of 0.1 mV or greater was increased by 62 (p less than 0.05), 75 (p less than 0.01) and 117 seconds (p less than 0.01) with the 5, 10 and 20 mg dose of nisoldipine, respectively, compared with placebo. Similarly, time to onset of angina was significantly increased. The sum of exercise-induced ST segment depression at peak exercise was significantly decreased (p less than 0.05) from 8.7 +/- 2.3 to 6.7 +/- 1.8 and 6.4 +/- 2.0 mm, respectively, after the 10 and 20 mg dose of nisoldipine. The rate-pressure product was significantly greater with nisoldipine than with placebo at the onset of ischemia and at peak exercise (22.8 +/- 1.1 versus 20 +/- 1.4 X 10(3) U for the 20 mg dose; p less than 0.01). Thus, nisoldipine is an effective antianginal agent with a rapid onset of action that improves exercise tolerance, increases angina threshold and persists for at least 8 hours after oral dosing.

Cardiovascular and pharmacokinetic consequences of combined administration of verapamil and propranolol in dogs

Verapamil and propranolol, alone and in combination, were given intravenously to anesthetized dogs to analyze the interaction between drug-induced cardiovascular effects and the resulting changes in pharmacokinetics. Dosing regimens were used that produced steady state plasma levels of both drugs, and the observed effects were clearly related to the plasma concentrations of the agents. When given alone, at stable "therapeutic" levels in plasma, verapamil or propranolol decreased spontaneous heart rate, increased atrioventricular conduction time, and had opposite effects on cardiac output. At the same doses, the combined infusion of the 2 drugs rapidly resulted in profound depression in cardiac function; in addition, plasma concentrations of both agents increased into ranges associated with cardiovascular toxicity. When verapamil doses were reduced, combined infusion with propranolol decreased atrioventricular conduction and cardiac output, but drug plasma concentrations (and associated effects) remained stable. When reduced doses of propranolol were added to infusion of verapamil, similar effects on cardiovascular function occurred, but plasma drug levels increased progressively throughout the remainder of the study period. In all combinations studied, beta blockade with propranolol decreased liver plasma flow and, therefore, the systemic clearance of verapamil. The in vitro effects of propranolol on verapamil metabolism were small, although significant, and not clinically relevant. These acute studies suggest that the hemodynamic effects resulting from verapamil and propranolol in combination may significantly diminish clearance of 1 or both drugs, thereby resulting in accumulation during continued administration, increased drug effects with increasing plasma concentrations, and potentially lethal drug toxicity.

Evaluation of bepridil for the treatment of angina pectoris: evidence for preservation of left ventricular function

The efficacy of bepridil (400 mg once a day) was assessed in 15 patients with exertional angina pectoris. All 15 patients reported substantial clinical improvement during bepridil treatment compared with placebo treatment. Episodes of angina were 11.8 +/- 4.1 (mean +/- standard error of the mean)/week with placebo and 3.8 +/- 1.6 with bepridil (p less than 0.05); nitroglycerin use was 9.1 +/- 3.3 tablets/week with placebo and 3.5 +/- 1.7 with bepridil (p less than 0.05). Five of 15 patients receiving bepridil did not experience angina during treadmill exercise; in the remaining 10 patients, time to onset of angina during exercise was 5.7 +/- 0.9 minutes with bepridil as opposed to 4.5 +/- 0.8 minutes with placebo (p less than 0.05). Left ventricular (LV) performance at peak exercise as measured by first-pass radionuclide angiography revealed the ejection fraction to be 38 +/- 3% during placebo therapy and 47 +/- 4% during bepridil therapy (p less than 0.0025). End-diastolic LV volume was unchanged, but end-systolic volume was 136 +/- 11 and 117 +/- 13 ml (p less than 0.05) and stroke volume was 82 +/- 6 and 97 +/- 9 ml (p less than 0.05) during placebo and bepridil therapy, respectively. Heart rate at peak exercise was 136 +/- 3 beats/min with placebo and 128 +/- 3 beats/min with bepridil; however, blood pressure was unchanged. These studies demonstrate that bepridil results in significant clinical improvement and enhanced LV performance in patients with angina pectoris.

Comparative efficacy of 200, 300 and 400 mg of bepridil for chronic stable angina pectoris

A total of 178 patients participated in a 14-week, multicenter, double-blind, parallel study to evaluate the comparative efficacy and safety of single daily doses of 200, 300 and 400 mg of bepridil hydrochloride and placebo in the treatment of patients with chronic stable angina pectoris. The results showed that weekly angina attacks and nitroglycerin consumption were significantly reduced from baseline levels with all doses of bepridil (p less than 0.01), and the reductions were consistently greater than those in the placebo group. For the 400-mg dose the reductions in angina attacks and nitroglycerin consumption were significantly greater (p less than or equal to 0.05) than those in the placebo group at all but 1 evaluation point. Exercise tolerance improved significantly during bepridil administration (p less than or equal to 0.05), and a significant linear dose response was noted for total exercise time, total work and time to onset of angina. In addition, bepridil was significantly superior to placebo for these parameters at doses of 300 (p less than or equal to 0.05) and 400 mg (p less than or equal to 0.01). There were small reductions in heart rate (mean 3.7 beats/min) and prolongation of QT and QTc intervals (approximately 30 to 40 milliseconds) associated with bepridil treatment. Bepridil was well tolerated by patients in this study. When adverse effects occurred, they most frequently involved the gastrointestinal and central nervous systems. Of the patients receiving bepridil, 6% discontinued therapy because of adverse effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Dihydropyridine sensitive calcium channels in a smooth muscle cell line

The pharmacological properties of voltage sensitive calcium channels (VSCC) were examined in a rat aortic smooth muscle cell line (A10). The inorganic VSCC blockers Co2+ and Cd2+ blocked 45Ca2+ uptake into these cells in both 5 mM K+ and 50 mM K+ (depolarizing) conditions. The organic VSCC antagonists nitrendipine, nimodipine, D-600 and diltiazem also blocked 45Ca2+ uptake at low concentrations. The relative potencies of blockade were similar to those found in intact vascular smooth muscle. The VSCC "agonist" BAY K8644 enhanced 45Ca2+ uptake and this effect could be reversed by nitrendipine. These results indicate that A10 cells possess VSCC and that these VSCC behave similarly to those in authentic smooth muscle.

Effect of nicardipine in elderly hypertensive patients

The purpose of this study was to test tolerance and the antihypertensive effect of nicardipine, a new calcium antagonist, in 31 elderly patients aged 57-95 years. The study was conducted as a double-blind trial. The patients were allocated randomly to either active or placebo treatment. Sixteen patients were given 10-30 mg of nicardipine three times a day (mean dose, 69.4 mg per day); 15 other patients received a matching placebo. After 4 weeks, nicardipine lowered mean blood pressure, and the changes in systolic and diastolic blood pressure were significantly greater in the nicardipine group than in the placebo group. Nicardipine was tolerated very well, and orthostatic hypotension was never observed. There was no change in heart rate. Plasma renin activity (PRA) was measured in eight patients. There was no correlation between PRA and the antihypertensive effect of nicardipine. A pharmacokinetic study performed in 15 elderly patients showed a fast rate of absorption and also higher plasma levels than those observed in hypertensive adults (mean age, 54 years). This trial demonstrates the effectiveness of nicardipine in elderly hypertensive patients.

Circadian variation in variant angina

Thirteen hospitalized patients with variant angina were studied to assess circadian variation in disease activity. Over 48 hours, all angina attacks were noted, a continuous Holter electrocardiogram was recorded and 2 ergonovine tests were performed 12 hours apart, 1 at 4 AM and the other at 4 PM. Only 2 patients gave a clearcut history of more frequent nocturnal or early morning attacks. During the study period, 1.8 +/- 1.6 AM and 0.62 +/- 1.2 PM angina episodes per patient were reported (p less than 0.02), but a circadian pattern was apparent in only 4 patients. However, Holter analysis revealed 5.3 +/- 13.8 AM and 2.6 +/- 8.5 PM episodes of ST elevation per patient (p less than 0.05) and 8.1 +/- 13.9 AM and 3.2 +/- 8.5 PM episodes of ST elevation, ST depression or T-wave pseudonormalization (p less than 0.01). Ten of 11 patients with Holter abnormalities had more frequent AM than PM attacks (p less than 0.01). ST elevation developed during all 13 of the 4-AM and 12 of 13 of the 4-PM ergonovine tests. In 10 cases the ergonovine threshold at which the attack occurred was lower in the morning, in no case was it lower in the afternoon, and in 3 patients the morning and afternoon doses were identical (p less than 0.01). Thus, circadian variation in disease activity both for spontaneous and provoked attacks is present in most patients with variant angina, even though it is often not clinically apparent.

Improved exercise tolerance after propranolol, diltiazem or nifedipine in angina pectoris: comparison at 1, 3 and 8 hours and correlation with plasma drug concentration

Exercise tolerance 1, 3 and 8 hours after 80 mg of propranolol, 120 mg of diltiazem and 20 mg of nifedipine, and after 20 minutes of 0.6 mg of sublingual nitroglycerin were compared with placebo in 15 men who had chronic stable angina pectoris. Three hours after drug ingestion, the exercise time was prolonged by 72 +/- 26, 162 +/- 27 and 161 +/- 30 seconds (p less than 0.05) for propranolol, diltiazem and nifedipine, respectively, and by 123 +/- 35 seconds (p less than 0.001) 20 minutes after sublingual nitroglycerin compared with placebo. The onset of ST-segment depression greater than or equal to 0.1 mV was delayed by 120 +/- 34, 203 +/- 29 and 189 +/- 35 seconds (p less than 0.05) and by 79 +/- 23 seconds (p less than 0.05), respectively. After propranolol, the peak rate-pressure product decreased compared with placebo (15.1 +/- 1.1 U [10(-3)] vs 20.0 +/- 1.5 U, p less than 0.01). In contrast, the peak rate-pressure product was greater after diltiazem and nifedipine than after placebo (22.2 +/- 1.3 U [p less than 0.05] and 23.8 +/- 1.4 U [p less than 0.01]). The maximal increase in exercise tolerance was most marked for each drug at 3 hours, but was also significant at 1 hour for nifedipine and at 8 hours for diltiazem. At 3 hours, an increase in exercise time of more than 2 minutes was observed in 4 of 6 patients who had plasma propranolol concentrations greater than 40 ng/ml, 8 of 9 who had a plasma diltiazem concentration greater than 150 ng/ml, and in 7 of 7 who had a plasma nifedipine concentration greater than 90 ng/ml.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of verapamil and other calcium antagonists on chemotaxis of polymorphonuclear leukocytes

The calcium antagonists verapamil, D600, prenylamine, diltiazem and perhexiline inhibit chemotaxis and (stimulated) locomotion by rabbit polymorphonuclear leukocytes (PMN's). Inhibition occurs at relatively high concentrations (5.10(-5)-10(-3) M). Inhibition was most pronounced in the absence of extracellular Ca2+. In the presence of extracellular Ca2+ there was also inhibition of chemotaxis, but to a lesser degree than in the absence of Ca2+, thus extracellular Ca2+ partly reverses the inhibition of chemotaxis by calcium antagonists. The results suggest that the mechanism of action of these drugs in PMN chemotaxis differs from that in smooth muscle cell contraction, where much lower concentrations of these drugs are active. The data obtained suggest that calcium antagonists inhibit PMN chemotaxis and locomotion by interference with a Ca2+-dependent intracellular target.