Treatment of stable angina of effort with verapamil: a double-blind, placebo-controlled randomized crossover study

Advances in stroke pharmacology

Stroke occurs when a cerebral blood vessel is blocked or ruptured, and it is the major cause of death and adult disability worldwide. Various pharmacological agents have been developed for the treatment of stroke either through interrupting the molecular pathways leading to neuronal death or enhancing neuronal survival and regeneration. Except for rtPA, few of these agents have succeeded in clinical trials. Recently, with the understanding of the pathophysiological process of stroke, there is a resurrection of research on developing neuroprotective agents for stroke treatment, and novel molecular targets for neuroprotection and neurorestoration have been discovered to predict or offer clinical benefits. Here we review the latest major progress of pharmacological studies in stroke, especially in ischemic stroke; summarize emerging potential therapeutic mechanisms; and highlight recent clinical trials. The aim of this review is to provide a panorama of pharmacological interventions for stroke and bridge basic and translational research to guide the clinical management of stroke therapy.

Stroke neuroprotection revisited: Intra-arterial verapamil is profoundly neuroprotective in experimental acute ischemic stroke

While clinical trials have now solidified the role of thrombectomy in emergent large vessel occlusive stroke, additional therapies are needed to optimize patient outcome. Using our previously described experimental ischemic stroke model for evaluating adjunctive intra-arterial drug therapy after vessel recanalization, we studied the potential neuroprotective effects of verapamil. A calcium channel blocker, verapamil is often infused intra-arterially by neurointerventionalists to treat cerebral vasospasm. Such a direct route of administration allows for both focused targeting of stroke-impacted brain tissue and minimizes potential systemic side effects. Intra-arterial administration of verapamil at a flow rate of 2.5 µl/min and injection volume of 10 µl immediately after middle cerebral artery recanalization in C57/Bl6 mice was shown to be profoundly neuroprotective as compared to intra-arterial vehicle-treated stroke controls. Specifically, we noted a significant (P ≤ 0.05) decrease in infarct volume, astrogliosis, and cellular apoptosis as well as a significant increase in neuronal survival and functional outcome over seven days. Furthermore, intra-arterial administration of verapamil was well tolerated with no hemorrhage, systemic side effects, or increased mortality. Thus, verapamil administered intra-arterially immediately following recanalization in experimental ischemic stroke is both safe and neuroprotective and merits further study as a potential therapeutic adjunct to thrombectomy.

Rationale for the use of calcium antagonists in the treatment of silent myocardial ischemia

Silent myocardial ischemia, whether it occurs at rest or during exercise, is associated with an unfavorable prognosis and may lead to sudden cardiac death. Agents used to treat silent myocardial ischemia have included nitrates, beta-blockers, and calcium antagonists (CAs). Despite treatment with traditional anti-ischemic agents, studies have shown that up to 40% of patients who receive what is considered to be clinically optimal antianginal therapy continue to have daily episodes of silent myocardial ischemia. The use of nitrates and beta-blockers is sometimes confounded by issues of tolerance and tolerability. Although the CAs have been found to be effective in decreasing the duration and frequency of episodes of silent ischemia, in general beta-blockers produce a greater reduction in these variables. Thus a need for effective and tolerable anti-ischemic agents persists. A new class of CAs, the tetralol derivatives, may show promise in this regard. The first of this new class, mibefradil, is characterized by selective blockade of T-type calcium-ion channels and has been shown in a few studies to reduce the frequency and duration of asymptomatic ischemic episodes in patients with stable exertional angina pectoris. Large-scale clinical trials are necessary before the efficacy and tolerability of this new CA can be compared fully with those of the beta-blockers and currently available CAs.

Effects of various doses of intracoronary verapamil on coronary resistance vessels in humans

To investigate the vasodilatory effect of various doses of intracoronary verapamil on coronary resistance vessels, we studied 13 patients with normal angiograms. A coronary Doppler guide wire was inserted into the left anterior descending coronary artery, and coronary blood flow velocity (CBFV) was measured. Verapamil was injected into the left coronary artery at doses of 0.1 mg, 0.5 mg, 1.0 mg, and 2.0 mg at 10-min intervals. Nitroglycerin was also injected into the same artery to avoid changes in cross-sectional area. As a measure of coronary vascular resistance, coronary vascular resistance index (CVRI) was calculated as the quotient of mean aortic pressure/CBFV. An injection of verapamil produced a dose-dependent increase in CBFV: 79 +/- 38% with 0.1 mg, 131 +/- 56% with 0.5 mg, 143 +/- 46% with 1.0 mg, and 128 +/- 47% with 2.0 mg of verapamil. The percent peak decreases in CVRI were dose dependent: -42 +/- 13% with 0.1 mg, -50 +/- 17% with 0.5 mg, -62 +/- 14% with 1.0 mg, and -60 +/- 9% with 2.0 mg of verapamil. Thus, intracoronary verapamil produces a dose-dependent dilation of coronary resistance vessels, and the optimal effect is produced with an injection of verapamil at a dose of 1.0 mg into the left coronary artery. At this dose, verapamil did not affect atrioventricular conduction.

Hemodynamic and antiischemic effects of intravenous elgodipine, a new dihydropyridine calcium channel blocker, in patients with chronic stable angina

Elgodipine is a new second-generation dihydropyridine calcium antagonist. Its hemodynamic and antiischemic properties were evaluated in a single-blind, placebo-controlled trial in 22 males with chronic stable angina. Coronary artery disease was angiographically confirmed. Measurements were performed with a Swan-Ganz thermodilution catheter during a 30-minute period of rest and before the end of a 4-minute bicycle exercise test at maximum individual workload, both with placebo (IV infusion of 5 ml saline over 30 minutes) and elgodipine (10 micrograms/kg/2 min bolus IV, then IV infusion of 1 micrograms/kg/min for 28 minutes. Elgodipine caused very similar hemodynamic changes at rest and during exercise. Its major hemodynamic modification was the marked decrease in systemic vascular resistance, which was accompanied by an increase in cardiac index and stroke volume. Mean arterial blood pressure was slightly reduced, whereas the opposite small increase in heart rate meant that the double product remained unchanged. Contrary to resting conditions, pulmonary capillary wedge pressure, pulmonary artery pressures, pulmonary vascular resistance, and mean right atrial pressure remained normal or increased to a lesser extent during exercise after elgodipine. After elgodipine ischemic ST depression during exercise was diminished, and 11 of 16 assessable patients remained free from angina pectoris. We conclude that elgodipine is an efficacious antianginal drug. Its major mechanism of action is lowering of systemic vascular resistance. Thus elgodipine improves systolic cardiac function in patients with chronic stable angina and may delay the onset of ischemic diastolic dysfunction during exercise, as indicated by a normal left ventricular end-diastolic pressure (LVEDP). The data also suggest an improvement in coronary blood flow during exercise.

Efficacy of conventional and sustained-release verapamil in stable angina pectoris

The efficacy of sustained-release (s.r.) verapamil and conventional verapamil were compared in a double blind, crossover study in 20 patients (age 53 +/- SD6 years) who had stable effort angina and had used betablockers and long acting nitrates for at least two weeks. All patients received s.r. verapamil 200 mg b.i.d. and conventional verapamil 120 mg t.i.d. in a randomised order for two weeks. A symptom limited bicycle exercise test was performed at the end of the patients' previous medication period with betablocker plus long acting nitrate and at the end of both verapamil treatments in the morning before drug administration and three hours thereafter. All the patients improved subjectively during both verapamil regimens according to NYHA classification and they had fewer anginal attacks. The time to onset of ST-segment depression during exercise remained shorter during beta-blockade and long acting nitrates than during both verapamil regimens (P less than 0.05). During the peak action three hours after drug administration conventional verapamil was most effective at comparable workloads (P less than 0.05), whereas the exercise time was slightly prolonged with s.r. verapamil before drug administration.

Effects of calcium antagonists on the erythrocyte membrane

The effects of dihydropyridine compounds nimodipine, nicardipine and NB818 (isopropyl methyl-6-carbamoyloxymethyl-4-(2,3-dichlorophenyl)-1,4-dihydro-2-methyl- 3,5- pyridine-dicarboxylate) on erythrocyte membranes have been studied. These compounds showed protective effects against hypotonic haemolysis, but not against heat-induced haemolysis. An increase in deformability of erythrocytes by these calcium antagonists was observed using a capillary tube centrifugal method. The erythrocytes showed slight stomatocytosis after 30 min of incubation with calcium antagonists, but did not show significant changes in mean corpuscular volume and ATP levels.

The role of calcium antagonists in the treatment of myocardial ischemia

Calcium antagonists are often prescribed for treatment of ischemic heart disease. Therapeutic activity is achieved by reducing myocardial oxygen requirements and by increasing blood supply in ischemic heart disease associated with coronary artery spasms. The efficacy of calcium antagonists depends on the type and clinical presentation of ischemic heart disease: (1) in vasospastic angina (variant angina, short episodes of angina at rest), first-line therapy with calcium antagonists will reduce the number of ischemic episodes and improve long-term prognosis. (2) In effort angina the efficacy of calcium antagonists is comparable with that of beta blockers. (3) In unstable angina the use of calcium antagonists is controversial. Large-scale studies with nifedipine showed no benefit when it was given alone but an additive effect in patients pretreated with beta blockers. In contrast, diltiazem and verapamil appear to have comparable efficacy to beta blockers in patients with unstable angina. (4) After myocardial infarction the results of treatment with calcium antagonists have been disappointing. Nifedipine and verapamil did not reduce mortality or the incidence of reinfarction. In one study diltiazem significantly reduced the rate of reinfarction in patients who had had a non-Q wave infarction, but in a recent large-scale multicenter trial it had no effect on mortality and cardiac events in patients with evidence of both Q- and non-Q wave infarctions. Other secondary preventative measures against reinfarction, such as the use of beta-blockers and aspirin, appear to be more effective than calcium antagonists. The most frequently prescribed calcium antagonists, verapamil, diltiazem, and nifedipine, each of which represents a different chemical class, have in general similar efficacy in vasospastic and effort angina. Their different pharmacologic profile, such as the slowing of heart rate with verapamil or diltiazem and a more marked vasodilatation with nifedipine and other dihydropyridines, may become clinically relevant in individual patients. The new dihydropyridine derivatives have a pharmacologic profile comparable to that of nifedipine but some of these compounds, especially amlodipine, have more favorable pharmacokinetics, such as a prolonged elimination half-life. These agents may offer the advantage of a more practical dosage regimen for long-term treatment in patients with ischemic heart disease.

Comparison of the antianginal efficacy of four calcium antagonists and propranolol in stable angina pectoris

The antianginal effects of propranolol 160 mg/day, diltiazem 240 mg/day, nicardipine 80 mg/day, nifedipine 40 to 80 mg/day and verapamil 320 mg/day were compared in 12 patients with chronic stable angina pectoris using a symptom-limited exercise test. Compared to placebo propranolol and calcium antagonists similarly reduced (p less than 0.001) the frequency of antianginal attacks and nitroglycerin consumption, and increased exercise tolerance and time to greater than or equal to 1 mm S-T segment depression. After propranolol the pressure-rate product at submaximal and maximal exercise was significantly decreased. The calcium antagonists produced a significant reduction in the submaximal pressure-rate product, but no significant change in the peak pressure-rate product. Maximum ST depression was significantly lower after propranolol and was unchanged after the calcium antagonists. None of the drugs caused significant adverse effects. The results indicate that in patients with stable effort angina pectoris, diltiazem, nicardipine, nifedipine and verapamil were as effective as propranolol in improving exercise tolerance and time to ischaemia, and they did not alter the peak pressure-rate product. Different antianginal mechanisms may be operative for the various calcium antagonists.

A comparison of nine calcium ion antagonists and propranolol: exercise tolerance, heart rate and ST-segment changes in patients with chronic stable angina pectoris

The effects of nine calcium ion antagonists on exercise tolerance, heart rate and ST-segment changes were compared with those of propranolol in two hundred and eighty patients with established chronic stable angina pectoris. These patients participated in clinical trials for anti-anginal efficacy against placebo, using identical methods and similar protocols, but the comparison reported here was retrospective. The trials were all fixed dose, and the dose was determined by previous upward titration to arrive at an average maximal tolerance level. All the drugs except prenylamine increased the exercise tolerance significantly when compared with placebo. Maximal ST-segment depression on exercise was reduced during treatment with propranolol while treatment with the calcium ion antagonists had no significant effect. The time to the development of 1 mm ST-segment depression was prolonged by all the drugs. Nifedipine, PY-108-068 and nicardipine increased the resting heart rate whereas verapamil, diltiazem, gallopamil, KB-944, prenylamine and tiapamil produced a slight reduction. Propranolol produced a highly significant reduction in the resting and maximal heart rates and the rate-pressure product, whereas gallopamil increased the rate-pressure product by +8% and prenylamine reduced it by -10%. At the doses used, diltiazem, gallopamil and verapamil produced a greater increase in exercise tolerance than did propranolol, while the other drugs were inferior. None of the calcium ion antagonists matched the increase in the time taken to develop 1 mm ST-segment depression with propranolol, although the results with verapamil and gallopamil were close. The calcium ion antagonists are effective antianginal agents which produce their effects by mechanisms which are very different to the beta-adrenoreceptor blocking agents.

Calcium channel blockers and cardiac surgery

Calcium channel blockers have an important role in the pharmacotherapy of cardiovascular disorders. These agents act by inhibiting the slow inward current into excitable cells, exert direct negative inotropic, chronotropic, and dromotropic activity, and are potent vasodilators. These direct effects are modified by reflex autonomic stimulation and by pathologic states. Serious adverse effects of the calcium channel blockers are most frequently observed in patients with ventricular dysfunction, conduction system disease, or concomitant beta blockade. Calcium channel blockers are indicated in the treatment of angina pectoris, supraventricular arrhythmias, and hypertension. The use of these agents in patients with hypertrophic cardiomyopathy, congestive heart failure, and pulmonary hypertension is investigational. The calcium channel blockers are gaining increased importance in the management of patients undergoing cardiac surgery. Verapamil is indicated for the treatment of post-cardiac-surgical atrial flutter and fibrillation; however, the calcium antagonists are not effective as prophylaxis against postoperative supraventricular arrhythmias. Laboratory studies have shown that drug interactions exist between calcium channel blockers and inhalational anesthetics and nondepolarizing neuromuscular blocking agents; clinical studies have demonstrated that these interactions are rarely significant. Perioperative coronary spasm can be effectively treated with the calcium channel blockers. The timing of calcium antagonist withdrawal prior to surgery is controversial, but continuation of therapy until surgery is usually safe. The clinical significance of platelet function inhibition by the calcium antagonists is unknown. Protection of ischemic myocardium by calcium channel blockers has been demonstrated. Important interactions between the calcium antagonists, hypothermia, and the ionic constituents of cardioplegia require further study before the role of these agents as adjuncts to clinical cardioplegia is defined. Expanded indications and the introduction of new calcium channel blockers will result in increased use of these agents in the future.

Efficacy of sustained-release verapamil in chronic stable angina pectoris

The effectiveness of a sustained-release preparation of verapamil (verapamil-SR) was compared with the regular formulation of verapamil and with placebo in 12 patients with chronic stable angina pectoris. All patients completed an 8-week, double-blind, double-crossover, randomized protocol with 2-week treatment periods of verapamil-SR, 240 mg twice daily; regular-formulation verapamil, 120 mg 4 times daily; and 2 placebo therapies. The frequency of weekly anginal episodes was reduced from 7.6 +/- 10.0 with placebo to 3.1 +/- 4.2 after the regular formulation of verapamil (p = 0.09) and from 6.4 +/- 7.6 with placebo to 2.8 +/- 4.8 after verapamil-SR (p = 0.06). Treadmill time increased from 384 +/- 144 seconds during the first placebo phase to 468 +/- 138 seconds after the regular formulation of verapamil (p less than 0.01) and from 354 +/- 102 seconds during the second placebo phase to 462 +/- 138 seconds after verapamil-SR (p less than 0.01). Time to the onset of angina was similarly prolonged by formulations of verapamil. There were no significant adverse effects after 1 year in any patient taking verapamil-SR, 240 mg twice daily. Thus, a twice-a-day verapamil-SR dose regimen is safe and is as effective for treatment of angina of effort as the regular formulation given 4 times a day.

Comparative effects of prolonged therapy with four calcium ion antagonists (diltiazem, nicardipine, tiapamil and verapamil) in patients with chronic stable angina pectoris

The comparative effects of prolonged chronic therapy with diltiazem, nicardipine, tiapamil and verapamil on exercise tolerance, ST-segment changes and heart rate were examined in 63 patients with established chronic stable angina pectoris. Multistage computer-assisted symptom-limited treadmill exercise tests were performed after 2 weeks of placebo ("baseline") and then after 4 months of open-label chronic drug therapy. Diltiazem improved the exercise duration by 95% (p less than 0.001), nicardipine by 45% (p less than 0.001), tiapamil by 69% and verapamil by 79% (p less than 0.001). Maximal ST-segment depression was not altered by any of the drugs, but time to the development of 1 mm ST-segment depression was significantly improved in all cases. Diltiazem and verapamil reduced the heart rate at rest significantly by 6 and 8 beats/minute, respectively, whereas nicardipine increased it by 10 beats/minute (p less than 0.02), and tiapamil did not produce any significant change. Maximal heart rate at the peak of exercise was increased by 14% with nicardipine (p less than 0.001) and 6% with verapamil (p less than 0.05), whereas diltiazem and tiapamil did not produce any appreciable effect. The rate-pressure product at the peak of exercise remained unaltered with diltiazem, tiapamil and verapamil, but with nicardipine it increased significantly to 222 +/- 10 units from a baseline of 175 +/- 6 units with placebo.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of nifedipine alone with propranolol alone for stable angina pectoris including hemodynamics at rest and during exercise

The effects of nifedipine (60 to 90 mg/day) and propranolol (240 mg/day) on symptoms, angina threshold and cardiac function were compared in a placebo-controlled, double-blind, crossover study. Five-week treatment periods with nifedipine and propranolol were compared with 2 weeks of placebo treatment in 21 men with chronic stable angina pectoris, 13 of whom had symptoms both at rest and on exertion. Compared with placebo, New York Heart Association functional class improved in patients equally with nifedipine (p = 0.001) and propranolol (p = 0.006). Frequency of chest pain decreased with nifedipine (p = 0.001) and propranolol (p = 0.01), and nitroglycerin consumption similarly decreased with both treatments. Nifedipine significantly delayed the onset of chest pain (p = 0.01) and 1 mm of ST-segment depression (p = 0.002) during bicycle exercise; smaller increases with propranolol were not statistically significant. A preferential clinical response to nifedipine (9 patients) or propranolol (6 patients) was unrelated to the presence or absence of pain at rest or to any baseline hemodynamic finding. Nifedipine and propranolol were equally effective in relieving exertional ischemia as shown by improvements in ejection fraction at identical workloads, from 0.48 +/- 0.11 to 0.58 +/- 0.12 (p less than 0.001) and 0.56 +/- 0.14 (p less than 0.001), respectively. Exercise wall motion, assessed by a semiquantitative wall motion score, also improved with both drugs. Propranolol treatment decreased exercise cardiac output by 14% (p = 0.01) through its effect on heart rate. In contrast, nifedipine treatment had no effect on cardiac output.(ABSTRACT TRUNCATED AT 250 WORDS)

Regular formulation and sustained-release verapamil therapy in normotension and in mild to moderate hypertension

Calcium entry blocker drugs have hypotensive effects that are mediated by both cardiac and noncardiac actions. Dihydropyridine calcium blockers, such as nifedipine and nicardipine, are potent vascular smooth muscle relaxants that lower blood pressure by decreasing peripheral arteriolar resistance. Reflex tachycardia, however, may blunt the magnitude of their hypotensive effect, especially in patients with increased baroreflex sensitivity. Nondihydropyridine calcium blocker drugs, such as verapamil and diltiazem, exert their hypotensive action by both cardiac and peripheral circulatory mechanisms. These drugs also act as arteriolar vasodilators. In addition, they slow the heart rate by decreasing the automaticity of sinoatrial pacemaker cells in the heart. The combined negative chronotropic and vasodilatory actions are especially useful in hypertensive patients with baroreflex sensitivity who are prone to fast heart rates, and in hypertensive patients with associated coronary artery disease. Coronary heart disease patients with or without coexisting hypertension usually show reduction in systolic blood pressure (SBP) and heart rate (HR) both at rest and during submaximal exercise on the treadmill or bicycle. A reduced double product (SBP X HR) with submaximal exertion results in a decrease in cardiac work and correlates with enhanced exercise capacity and delay in onset of angina during exercise testing. In some patients with both hypertensive and coronary heart diseases and ventricular dysrhythmias emerging during exercise, verapamil may confer antiarrhythmic as well as antihypertensive and antianginal benefits. At present, calcium blocker drugs, which have an elimination half-life of 3 to 6 hours, must be given 3 times a day for effective antihypertensive control.(ABSTRACT TRUNCATED AT 250 WORDS)

Efficacy and safety of sustained-release diltiazem in stable angina pectoris

The safety and efficacy of a sustained-release preparation of diltiazem (diltiazem-SR), with dose levels of 240 and 360 mg/day, were assessed in 18 patients with stable angina of effort. A double-blind, placebo-controlled, randomized, crossover protocol was used. Diltiazem-SR, when given twice daily, reduced the frequency of weekly anginal attacks from 9.3 +/- 10.4 with placebo to 3.7 +/- 4.7 with 240 mg/day and to 3.1 +/- 4.7 with 360 mg/day (both p less than 0.01 compared with placebo). Treadmill time was increased from 410 +/- 180 seconds during the placebo phase to 519 +/- 177 seconds during the 240-mg/day dose and to 506 +/- 182 seconds during the 360-mg/day dose of diltiazem-SR (both p less than 0.01 compared with placebo). The time to the onset of angina and ischemic ST-segment depression were similarly prolonged by both doses of diltiazem-SR. The beneficial effects of diltiazem-SR appeared partly due to a reduction in the heart rate during submaximal exercise. Diltiazem-SR is effective and safe for the treatment of angina of effort when given twice daily.

Nicardipine for stable angina pectoris

Nicardipine, 30 and 40 mg thrice daily, was administered to 66 patients with stable angina pectoris in a multicentre, randomised, double-blind, cross-over trial. With nicardipine therapy, duration of exercise and cumulative oxygen consumption increased, while times to onset of angina and 1 mm ST segment depression were prolonged. Anginal frequency and nitroglycerin consumption declined with use of nicardipine, but this did not reach statistical significance. Resting heart rate increased slightly and resting blood pressure decreased. Two patients on nicardipine and one on placebo sustained acute infarction. Otherwise, side effects were generally mild and transient.

Short- and long-term treatment of stable effort angina with nicardipine, a new calcium channel blocker: a double-blind, placebo-controlled, randomised, repeated cross-over study

This study evaluated 1 year the efficacy of therapy with nicardipine in patients with chronic stable angina pectoris. Twenty-five male patients were entered. After a placebo run-in phase, the patients received nicardipine 30 mg, nicardipine 40 mg, and placebo, three times daily given in random, double-blind manner for 8 weeks. A double-blind, cross-over study comparing nicardipine with placebo was then undertaken. After 5 months of open treatment with nicardipine 90 or 120 mg day-1, patients received either placebo or nicardipine for 3 weeks, each followed by the alternative treatment for an additional 3 weeks and further open-label treatment with nicardipine for another 3-5 months. There were no significant changes in the PR, QRS or QT intervals, or in the QRS pattern during the short-term and long-term studies. There were no significant differences in mean heart rate after nicardipine compared with baseline. During treatment with nicardipine 120 mg day-1, patients reported significantly fewer anginal attacks compared with placebo, and nitroglycerin consumption also decreased. Nicardipine increased treadmill time, time to onset of angina, and time to one mm ST segment depression. These effects were maintained after 6 months of continued nicardipine therapy. Adverse effects were minor and well tolerated and included headache, dizziness, gastrointestinal upset, flushing paraesthesia and pedal oedema. Abrupt withdrawal of nicardipine at the end of the study resulted in a rapid return of the original symptoms but without further deterioration from the baseline measurements. Nicardipine was effective in the treatment of stable effort angina pectoris; this benefit was maintained for the entire year of treatment.

The efficacy and safety of high-dose verapamil and diltiazem in the long-term treatment of stable exertional angina

The efficacy and safety of high-dose verapamil (480 mg/day) and diltiazem therapy (360 mg/day) were compared in separate cohorts of 26 and 20 patients, respectively. All patients had stable exertional angina and underwent an initial 6-week double-blind, placebo-controlled, randomized phase followed by a 12-month open-label period. Angina attacks were reduced by verapamil (6.3 +/- 7.5 to 2.5 +/- 4.1 attacks per week, p less than 0.001) and by diltiazem (9.2 +/- 7.5 to 3.0 +/- 3.1 attacks per week, p less than 0.001), while treadmill time increased with both verapamil (372 +/- 132 to 444 +/- 108 s, p less than 0.001) and diltiazem (412 +/- 175 to 536 +/- 164 s, p less than 0.001) during the short-term study. Both agents continued to show similar salutory effects at the end of one year. The beneficial effects of both drugs appeared to be related in part to a reduction of the rate-pressure product during submaximal exercise (12% by verapamil, 7% by diltiazem, both p less than 0.05). Adverse effects were few and consisted primarily of mild constipation in six patients taking verapamil, and pedal edema and transient flushing in 2 patients each using diltiazem. Thus, high-dose verapamil and diltiazem have similar beneficial effects and are safe for the long-term treatment of effort-related angina pectoris.

Verapamil: full spectrum calcium channel blocking agent: an overview

Oral verapamil approved for use in all forms of angina, with its additional heart rate-controlling properties has undergone extensive clinical investigation and use since its initial development and has been demonstrated to be safe, well-tolerated and effective over a broad range of cardiovascular disorders. Further potential therapeutic indications for verapamil use remain to be assessed. Additional research with this exciting drug is ongoing.

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)

Efficacy and safety of incremental doses of diltiazem for the treatment of stable angina pectoris

The safety and efficacy of incremental doses of diltiazem in treating angina pectoris were assessed in 20 patients with functional class II to III exertional angina. During an initial single-blind dose titration phase, dilitiazem produced a dose-related improvement in anginal frequency and exercise capacity. Weekly anginal attacks were reduced to 7.5 +/- 8.9, 5.6 +/- 7.8 and 4.9 +/- 7.3 on diltiazem, 120, 240 and 360 mg per day, respectively, as compared with 11.9 +/- 8.7 on placebo (all p less than 0.001). Treadmill time was significantly enhanced by high dose (360 mg per day) as compared with moderate dose (240 mg per day) diltiazem: 473 +/- 149 versus 424 +/- 146 seconds (p less than 0.05). Time to ischemic ST segment depression was similarly changed: 344 +/- 132 versus 298 +/- 142 seconds (p less than 0.05) by high dose as compared with moderate dose diltiazem. During a subsequent double-blind phase, high dose diltiazem significantly reduced weekly anginal frequency when compared with placebo: 3.1 +/- 3.0 versus 9.3 +/- 7.1 (p less than 0.001); and increased treadmill exercise time: 508 +/- 158 versus 418 +/- 172 seconds on placebo (p less than 0.05). Subjective and objective benefits of high dose diltiazem were sustained during a follow-up period of 6 months without major drug side effects.

Hemodynamic effects of felodipine at rest and during exercise in exertional angina pectoris

To examine the antianginal effects of felodipine, a new calcium antagonist, 8 patients with coronary artery disease and exertional angina pectoris were studied. Hemodynamic measurements were made at rest, during submaximal exercise and during angina-limited exercise before and 30 minutes after oral administration of 0.1 mg/kg of felodipine. Angina pectoris was always prevented after the drug was given and the exercise intensity was increased until recurrence of angina (5 patients) or exhaustion (3 patients). Hemodynamic data were also recorded at this higher exercise capacity. At rest and during submaximal exercise, felodipine increased heart rate and decreased arterial blood pressure and systemic vascular resistance. The prevention of angina pectoris was accompanied by lower mean pulmonary capillary wedge pressure, systemic vascular resistance and ST-segment depression; the pressure-rate product was unchanged. The 20% greater exercise capacity after felodipine was attended by a 20% increase in maximal cardiac output, a 17% increase in maximal heart rate and a 13% increase in maximal pressure-rate product; the maximal arterial blood pressure and ST-segment abnormalities were unchanged and the systemic vascular resistance was lower. The relation between ST-segment depression and the pressure-rate product during exercise was favorably influenced by felodipine. Thus, felodipine is an active antianginal drug; its major mechanism of action is to lower the systemic vascular resistance. The data also suggest that it improves coronary blood flow during exercise.

Efficacy and safety of verapamil in patients with angina pectoris after 1 year of continuous, high-dose therapy

The long-term efficacy and safety of high-dose verapamil therapy (480 mg/day) was assessed in 26 patients with chronic stable angina pectoris during a 3-phase protocol: Phase 1--an initial, 6-week placebo-controlled, double-blind crossover assessment; Phase 2--an open label, 1-year follow-up; and Phase 3--a final drug withdrawal and rechallenge 10-week study. Three patients withdrew during Phase 2 (1 had hepatitis and 2 underwent coronary bypass surgery). Adverse effects during Phase 2 were mild, consisting of constipation (6 patients) and prolongation of the P-R interval (5 patients); however, no patient required alteration of the 480 mg/day dosage. At the end of Phase 2, 10 patients underwent the Phase 3 study, commencing with a 2-week period in which verapamil was either tapered gradually or abruptly discontinued. This was followed by an 8-week double-blind, placebo-controlled crossover rechallenge study with verapamil. The clinical and exercise responses to verapamil compared with placebo were similar during the Phase 3 protocol and the initial Phase 1 study (treadmill time increased by 55% and anginal attacks per week decreased by 63% during Phase 3, compared with a 28% increase and a 42% decrease, respectively, during Phase 1, p = not significant [NS]). Withdrawal of verapamil produced a similar return of anginal symptoms whether the drug was abruptly discontinued or its administration tapered. No patient had unstable angina pectoris or acute myocardial infarction. These investigations demonstrate that verapamil is safe and effective when evaluated after 1 year of continuous therapy using a dosage of 480 mg/day. There is no evidence of drug tachyphylaxis, nor does verapamil appear to cause an abrupt withdrawal syndrome in patients with chronic stable angina pectoris.

Electrophysiologic mechanism of exercise-induced sustained ventricular tachycardia

To elucidate electrophysiologic mechanism of exercise-induced ventricular tachycardia (VT), electrophysiologic studies were performed in 12 patients in whom sustained VT had developed during treadmill exercise testing. Six patients had arteriosclerotic coronary heart disease, 3 had cardiomyopathy, and 3 had no clinical evidence of organic heart disease. All patients had had documented episodes of sustained VT related to exertion and had experienced dizziness, syncope, or both. In addition, 3 patients had had nonfatal cardiac arrest. Electrophysiologic studies provoked paroxysms of sustained VT identical to those observed during treadmill exercise testing in 10 patients and provoked ventricular flutter/fibrillation in 1. Seven patients had VT suggestive of a reentrant mechanism, as the VT could be readily initiated with programmed ventricular extrastimulation or terminated by ventricular overdrive pacing, or both. Three patients had VT suggestive of catecholamine-sensitive automaticity. The VT could not be initiated with programmed electrical stimulation, but it could be provoked by intravenous isoproterenol infusion; furthermore, the VT could not be terminated with ventricular overdrive pacing, but it could be abolished by discontinuing isoproterenol infusion. Reproduction of VT in these 10 patients allowed serial pharmacologic testing in selecting an effective antiarrhythmic regimen. Thus (1) exercise-induced VT can be caused by either reentry or catecholamine-sensitive automaticity, and (2) electrophysiologic studies are of use in defining the underlying mechanism of exercise-induced sustained VT.

Clinical applications of slow channel blocking compounds

The slow-channel blockers constitute a structurally diverse group of drugs with varying mechanisms of action, propensities for site of greatest cardiovascular activity, and clinical efficacy. They share however the property of blocking the slow inward channel in heart muscle and of inhibiting calcium fluxes in smooth muscle. Their in vivo and in vitro actions must be distinguished. The overall actions represent a balance of direct and autonomically-mediated reflex actions interacting with the compounds' varying degrees of intrinsic non-competitive sympathetic antagonism. A knowledge of the pharmacodynamic differences between these drugs allows the physician to select the most appropriate agent for a given clinical situation. The central role of calcium in the cellular processes in the heart and the vascular system forms the basis for the utility of this class of drugs in a wide variety of cardiovascular disorders. Current intensive experimental and clinical investigations are likely to further define the roles of nifedipine, verapamil and diltiazem and their congeners in cardiovascular therapeutics. The prospect of development of newer compounds with greater selectivity of action is real. As pointed out by Braunwald (1982 a,b), with further clarification of the mechanisms of actions of these compounds and elucidation of the role of calcium fluxes throughout the body, more specific and potent agents may be developed. The apparent efficacy of the nifedipine congener nimodipine, in the treatment of cerebral vasospasm associated with subarachnoid hemorrhage (Allen et al., 1983) may simply be the first of a large number of 'specific' or targeted slow channel blockers. The development of such compounds may offer further therapeutic possibilities in the control of a variety of cardiocirculatory diseases.

Clinical relevance of verapamil plasma levels in stable angina pectoris

Plasma levels of verapamil and norverapamil were evaluated in 77 patients who received oral verapamiL for treatment of angina pectoris. There was a sixfold interpatient variation in verapamil plasma concentrations, but plasma concentrations were linearly related to doses of the drug (240 to 480 mg/day) in the same patient (r = 0.81). Plasma concentrations of norverapamil, the major active metabolite of verapamil, were similar to those of verapamil. Although verapamil produced a significant improvement in exercise tolerance in most patients, the increase in exercise time was not related to plasma levels of the drug; however, most patients with improvement had plasma levels exceeding 100 ng/ml. An increase in the dose of verapamil from 320 to 480 mg daily produced a substantial (71%) increase in plasma levels of the drug but no significant increase in exercise tolerance (4%). The average increase in the P-R interval with 480 mg of verapamil in these 77 patients was small (8%) (161 +/- 18 to 174 +/- 22 ms); on.y six patients had first-degree heart block. These minor effects on atrioventricular conduction were noted despite plasma verapamil concentrations in 76 patients that exceeded 100 ng/ml, a level that successfully converts supraventricular tachycardias after intravenous drug administration. We differences between the effects of oral and intravenous verapamil on atrioventricular conduction may be the result of stereoselective hepatic inactivation of verapamil's I-isomer. Determination of plasma levels of verapamil is of limited value in the management of patients with angina pectoris, but may be useful in the identification of nonresponders with plasma levels less than 100 ng/ml who may benefit from a further increment in drug dose.

Verapamil therapy for stable exertional angina pectoris

Clinical and exercise responses to therapy with the calcium-channel blocking agent verapamil were assessed in 26 patients with stable exertional angina pectoris using a double-blind, placebo-controlled, randomized crossover study design. Verapamil, 480 mg daily, reduced the frequency of angina attacks (5.6 +/- 7.3 to 2.2 +/- 3.0 attacks per week, p less than 0.001) and number of nitroglycerin tablets consumed (3.4 +/- 4.9 to 1.2 +/- 2.5 tablets per week, p less than 0.05), and increased exercise duration (6.4 +/- 2.1 to 7.5 to 1.8 minutes, p less than 0.001) (all data are mean +/- standard deviation). These changes were significantly better than those seen with placebo. These beneficial effects of verapamil were related to significant reduction in the heart rate-systolic blood pressure product during submaximal exercise. Adverse effects from verapamil were few and consisted primarily of constipation in 6 patients. A total of 193 patients had been entered in 6 independent clinical trials, which have compared verapamil with placebo for the treatment of stable exertional angina pectoris, using a similar study design. The combined evidence from all these studies indicates that verapamil is a highly effective and safe drug for the treatment of stable effort-related angina pectoris.