Antihypertensive effect of cardiovascular Ca2+-antagonist in hypertensive patients in the absence and presence of beta-adrenergic blockade

Lack of a pharmacokinetic interaction between nifedipine and the beta-adrenoceptor blockers metoprolol and atenolol

Nifedipine, metoprolol and atenolol were administered orally to young, healthy volunteers. Each drug was given alone and nifedipine was also given with both beta-adrenoceptor blockers. Each drug was given for 3 days immediately before the study days. Plasma and urine drug concentrations were measured and the relevant pharmacokinetic parameters calculated. No pharmacokinetic interaction between nifedipine and the beta-adrenoceptor blockers was revealed.

Calcium entry blockers for the treatment of severe hypertension and hypertensive crisis

Calcium entry blockers (diltiazem, nifedipine, and verapamil) are currently indicated for the treatment of patients with vasospastic and chronic stable angina pectoris. The calcium entry blocking actions of these drugs cause potent peripheral vasodilatory and antihypertensive effects in human subjects. The drugs have proved beneficial in the treatment of patients with severe hypertension and hypertensive emergencies. Single oral, sublingual, and intravenous doses of these drugs have been shown to rapidly and smoothly reduce blood pressure in adults and children, without significant untoward effects. The absolute reduction in blood pressure with treatment appears to be inversely correlated with the pretreatment blood pressure level, and few episodes of hypotension have been reported. Combinations of calcium entry blockers with other antihypertensive regimens have also proved effective. Some patients experience a mild increase in heart rate with nifedipine, an effect that appears to be inversely related to age. Side effects are minimal and not life-threatening. Continuous hemodynamic monitoring of patients does not seem necessary in most cases. The role of calcium entry blockade in the treatment of hypertensive emergencies still needs to be established in relation to other available approved drug regimens for this condition.

Calcium-channel blockade with nifedipine and angiotensin converting-enzyme inhibition with captopril in the therapy of patients with severe primary hypertension

Nifedipine (10 mg qid) and captopril (25 mg qid) were tested alone and in combination in 14 patients suffering from severe primary hypertension. Each study period was of 1 week's duration. Circulatory response was evaluated through hourly pressure and pulse rate readings. The fall in pressure after oral nifedipine was maximal within 1 hr or less and was generally accompanied by palpitation and increase in pulse rate; with a six hourly dosing regimen the tendency of blood pressure to recover after each dose was interrupted by the next dose, so that values remained significantly reduced throughout the 24 hr, although pressure fluctuations were evident. Promptness of the antihypertensive action of captopril was similar, but the magnitude and the duration of the fall in pressure were less pronounced. When the converting-enzyme inhibitor was combined with the calcium-channel blocker, pressure fluctuations were not abolished, but the antihypertensive response was definitely enhanced, so that normal blood pressure was maintained for several hours during the day. Additional positive effects of captopril were mitigation of the heart rate reaction and prevention of the ankle pitting or edema elicited by nifedipine. A balance in arteriolar and venular dilatation promoted by captopril is the suggested mechanism for these effects. With the two-drug combination the function of the left ventricle was not reduced and possibly improved; blood urea nitrogen and serum electrolyte and creatinine concentration were not affected. Plasma renin activity increased with captopril and reverted toward baseline with the addition of nifedipine, suggesting an interference of the calcium-channel blocker with the release of renin.

Hemodynamic and clinical findings after combined therapy with metoprolol and nifedipine in acute myocardial infarction

In a double-blind trial, 30 patients with suspected acute myocardial infarction with onset of symptoms within the previous 24 h were randomized to treatment with 10 mg nifedipine/placebo orally 4 times a day during hospitalization. All patients were given 15 mg metoprolol intravenously 20 min after the initial administration of nifedipine/placebo, and thereafter, 50 mg 4 times a day. The combined therapy resulted only in moderate changes in systolic blood pressure and heart rate compared with metoprolol alone. Three of the 15 patients in the nifedipine group versus 2 of the 15 in the placebo group were withdrawn because of hypotension and/or bradycardia. None was withdrawn because of congestive heart failure or A-V block. It is concluded that the combination of nifedipine and metoprolol seems to be a relatively well-tolerated combination in acute myocardial infarction.

Antihypertensive and renal effects of nicardipine

Both the acute blood pressure lowering and renal effects of the calcium antagonist nicardipine and those after 1 week's treatment were investigated in 10 normotensive volunteers and in 10 patients with mild to moderate essential hypertension. After 1 week of placebo, nicardipine was administered orally for 1 week (20 mg three times daily), Investigations, done on the first and last day of nicardipine treatment were compared with those on the last day of placebo. During water loading, nicardipine increased urinary volume and urinary excretion of sodium significantly after 1 week nicardipine treatment. In the normotensive group the natriuretic effect was caused by a decrease of fractional proximal and distal reabsorption of sodium. In the hypertensive group the natriuresis was achieved mainly by an increase of the rate of glomerular filtration (GFR) and also by a slight distal effect. Our results show that nicardipine had natriuretic effects. There were trends suggesting that the renal effects may differ between patients with essential hypertension and normotensive volunteers, but the findings might also be related to differences in age between the groups.

Antihypertensive therapy with diltiazem and comparison with hydrochlorothiazide

Fourteen hypertensive patients with a mean sitting systolic and diastolic blood pressure (BP) of 153 +/- 16/100 +/- 4 mm Hg were treated successively with hydrochlorothiazide and diltiazem for 8 weeks each. The BP response and changes in heart rate, left ventricular size and function, and plasma catecholamine concentrations and renin activity were monitored. The 2 drugs had comparable antihypertensive effects, with mean decreases of 14, 9 and 11 mm Hg for the sitting, standing and supine diastolic BP, respectively, during hydrochlorothiazide treatment and mean decreases of 16, 18 and 12 mm Hg during diltiazem treatment. Heart rate was unchanged, although plasma norepinephrine concentrations increased significantly during diltiazem treatment. Plasma renin activity increased slightly, from 0.6 to 0.9 ng/ml/hour during diltiazem treatment, but the change was not significant (p less than 0.10). Left ventricular ejection fraction and end-diastolic volume were not affected by either agent. In conclusion, diltiazem is an effective antihypertensive agent, which because of its benign side effect profile, may be useful as a step 1 agent.

The hemodynamic effects of intravenous verapamil in patients on chronic propranolol therapy

Concern exists regarding the negative inotropic and chronotropic effects of verapamil given to patients receiving chronic propranolol therapy. In order to evaluate the safety of combined therapy, the hemodynamic effects of verapamil were investigated in a group of 19 patients on chronic propranolol therapy undergoing cardiac catheterization. Hemodynamic measurements and left ventriculography were performed prior to and 30 minutes after initiation of intravenous administration of verapamil. Verapamil doses varied from 0.025 mg/kg to 0.1 mg/kg intravenous bolus injection followed by an infusion of 0.005 mg/kg/min. Following verapamil administration, systolic, diastolic, and arterial mean pressures and systemic vascular resistance decreased significantly. There was no significant change in left ventricular end-diastolic pressure, mean pulmonary capillary wedge pressure, cardiac index, arteriovenous oxygen difference, heart rate, mean velocity of circumferential fiber shortening (VCF), end-diastolic volume index, end-systolic volume index, stroke volume index, and ejection fraction (EF). Stroke work index decreased significantly. Lack of improvement in cardiac index, VCF, and EF and decrease in stroke work index in spite of constant filling pressure and decreased afterload suggest the additive negative inotropic action of verapamil. The depressant action of propranolol itself was not determined by this study. In spite of the negative inotropic effect of verapamil, it can be administered acutely to patients who have been on propranolol therapy with relative safety if the propranolol has not already produced severe left ventricular dysfunction, relative hypotension, bradyarrhythmia, or conduction abnormalities.

Nifedipine--a calcium channel blocker--in asthmatic patients. Interaction with terbutaline

Seven asthmatic patients were studied in a single-blind randomized, crossover study after oral administration of 20 mg nifedipine or placebo. Four increasing doses of i.v. terbutaline were then given with 30 min interval. The study was concluded with inhalation of five terbutaline puffs. FEV1 measurements 30 min after intake of nifedipine did not show any difference compared to placebo. During the terbutaline treatment, however, there was a more pronounced bronchodilation after nifedipine than after placebo (P less than 0.05). Terbutaline-induced skeletal muscle tremor was similar after nifedipine and placebo pretreatments. After nifedipine intake there was a decrease of diastolic blood pressure and a reflexogenic tachycardia. Thus, this study showed a small potentiation of the beta 2-adrenoceptor mediated bronchodilation, which is of importance when treating patients with simultaneous asthma and hypertension or angina pectoris.

Systemic and regional hemodynamics in normotensive and spontaneously hypertensive rats after slow-channel calcium blocker nitrendipine

To determine the effects of the recently synthesized slow channel calcium blocker nitrendipine on systemic and regional hemodynamics, mean arterial pressure, heart rate, cardiac index and organ blood flow distribution were measured with the combined radioactive reference sample and microsphere techniques before and one hour after its oral administration (1 mg or 10 mg/kg). Twenty-week-old normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) conscious male rats were studied. At the 10 mg dose, nitrendipine exerted a hypotensive effect within 15 minutes, and this effect persisted throughout the study. After one hour, mean arterial pressure fell by 14 percent of pretreatment levels in WKY controls; it fell by 25 percent in SHR (p less than 0.001). This action was mediated by a fall in total peripheral resistance index (p less than 0.01) that was nonuniformly distributed to the organ circulations since blood flow was maintained or increased to brain, heart, kidneys, lungs, and adrenals, but decreased to skin. No change in cardiac index was observed.

Possible treatment of pre-eclampsia with calcium channel blocking agents

A review of the pathophysiology and treatment of pre-eclampsia indicates that vasospasm and vascular hyperreactivity are important elements in the disease process and its control. Five requirements for a therapeutic agent in pre-eclampsia are identified: control of generalized vasospasm, hypertension, and eclamptic convulsions, maintenance of placental perfusion, and lack of adverse effects on the fetus/neonate. Calcium channel blocking agents are well known arteriolar vasodilators and inhibitors of coronary artery vasospasm, and appear to possess qualities relevant to these therapeutic requirements for pre-eclampsia. It is proposed that calcium channel blocking agents may be effective agents in the management of pre-eclampsia.

Effects of diltiazem on cardiovascular responses during exercise in systemic hypertension and comparison with propranolol

Sixteen patients with uncomplicated systemic hypertension were treated with placebo, diltiazem (180 mg/day) and propranolol (60 mg/day) for 1 month each. Each patient performed multistage symptom-limited treadmill exercise tests during each period of administration. There was no significant difference in maximal exercise duration between placebo, diltiazem and propranolol. Diltiazem significantly decreased both systolic and diastolic blood pressure (BP) and heart rate at rest, during submaximal exercise at the same work load and maximal exercise. Propranolol produced similar changes in systemic BP and heart rate at rest and during exercise. However, the reductions in systolic BP, heart rate and pressure-rate product with diltiazem during exercise were smaller than those with propranolol at small doses, suggesting that diltiazem in its usual therapeutic dose was almost devoid of beta-blocking activity. Thus, diltiazem may be of benefit to hypertensive patients because it reduces systemic BP even during exercise. It is particularly useful when systemic hypertension occurs in association with coronary artery disease because of its effects of coronary artery dilatation and heart rate reduction.

Age and cardiovascular response adaptation. Determinants of an antihypertensive treatment concept primarily based on beta-blockers and calcium entry blockers

The patient's age has great impact on the development of hypertension, its duration, and severity. In patients with essential hypertension, sympathetic cardiovascular control changes from an early phase with increased beta-adrenoceptor-mediated responses, e.g., cardiac output and renin, into a later phase where these responses are blunted and alpha-adrenoceptor-mediated vasoconstriction prevails, associated with higher intracellular free sodium and calcium concentration. This pathophysiological view of essential hypertension has its corollary in the pharmacotherapeutic approach. Younger patients, who often have high renin levels, respond better to monotherapy with a beta-blocker or with a converting-enzyme inhibitor. Older patients, who often have low renin levels, respond less well to beta-blockers but particularly well to calcium entry blockers as an alternative to diuretics. Therefore, beta-blockers and calcium entry blockers form new cornerstones for antihypertensive treatment and strategy, with the potential of cardioprotection.

The effects of nifedipine and verapamil on antigen-induced bronchoconstriction in dogs

The effects of calcium channel blockers, nifedipine and verapamil (i.v. and aerosol), were investigated in beagle dogs natively allergic to Ascaris suum antigen. Control exposures to an aerosol of Ascaris antigen provoked significant bronchopulmonary changes, i.e., increases in pulmonary resistance (RL) and decreases in dynamic lung compliance (CDYN). Pretreatment with either nifedipine or verapamil (200 micrograms/kg, i.v.) provided significant inhibition in the RL responses to Ascaris antigen (P less than 0.015) while neither agent significantly affected CDYN changes. When administered as an aerosol, verapamil (1.0%; 10 breaths) significantly inhibited both the RL and CDYN responses to Ascaris antigen (P less than 0.05), whereas a similar concentration of nifedipine was without effect. Resting basal levels of RL and CDYN were unaffected by either the i.v. route or by aerosols of either nifedipine or verapamil. These results suggest that calcium channel blockers may have beneficial effects against allergen-provoked bronchoconstriction; however, differences appear to exist in the choice of agent, route of administration and site of action.

Role of nifedipine in treatment of hypertension

The efficacy of nifedipine in the treatment of hypertension was assessed in 15 patients whose hypertension continued while being treated with atenolol 100 mg and bendrofluazide 5 mg daily. Nifedipine was added in doses of 10, 20, and 30 mg three times daily in a placebo controlled, double blind trial. One patient was withdrawn from the trial because of severe postural hypotension with the highest dose. Erect and supine blood pressure in the remaining 14 patients were significantly reduced by all doses of nifedipine. The drug was well tolerated but plasma potassium fell by 0.3 mmol(mEq)/1 during treatment (p less than 0.05). Nifedipine is thus effective in the treatment of hypertension but should probably be used in combination with a potassium sparing diuretic.

[Calcium antagonists in the therapy of hypertension]

Calcium antagonists (nifedipine, verapamil, diltiazem) are potent vascular smooth muscle relaxants. Experimental and clinical investigations provide growing evidence that they are effective in acute and (sub)chronic therapy of arterial hypertension by lowering peripheral vascular resistance and improvement of altered hemodynamics--independent from pathogenesis of hypertension. Due to its prompt and profound hypotensive action, sublingual or oral nifedipine has been used successfully in hypertensive crises. The hypotensive effect usually correlated closely with the severity of hypertension and is nearly absent in normotensive controls. Since the blood pressure drop may occasionally results in absolute or relative hypotension, the initial dose should be as low as possible. The activation of the adrenergic and renin angiotension systems seen after nifedipine administration is less pronounced after chronic administration of the drug and is nearly absent after verapamil and diltiazem. Plasma aldosterone concentrations remain constant or are slightly decreased. In contrast to classic vasodilators, the long-term administration of calcium antagonists usually does not result in tachycardia (nifedipine), but slight sinus bradycardia (verapamil, diltiazem). Peripheral edema may occasionally occur after nifedipine. A tolerance has been observed during long-term treatment of hypertension. Combining these drugs (verapamil, diltiazem) with betablockers is not recommended due to the negative inotropic and bathmotropic effects. Simultaneous administration of nifedipine and beta-blockers enhances the hypotensive action, but favours the development of peripheral edema and in rare cases (especially in severe coronary heart disease) results in a dramatic drop in blood pressure and/or congestive heart failure. Further clinical evaluation and long-term trials of calcium antagonists as antihypertensive agents will be needed before definite conclusions can be drawn.

Calcium antagonists. Clinical use in the treatment of systemic hypertension

Increased peripheral vascular resistance is the cause of elevated systemic blood pressure in most patients with long standing hypertension. The desired haemodynamic effect in antihypertensive therapy is dilation of the constricted arterioles by a drug that acts directly on the vascular smooth muscle while not affecting the heart or the venous return. Hydralazine, diazoxide and minoxidil act directly on vascular smooth muscle to produce vasodilatation and have been used with variable degrees of success in the long term treatment of hypertension. Their cellular mechanism of dilation is not understood fully, but the ability to chelate certain trace metals required for smooth muscle contraction has been proposed as a possible mechanism of action for these drugs. The calcium antagonists (calcium entry blocking drugs) are a distinct group of compounds that interfere with the normal transmembrane flux of extracellular calcium ions on which vascular tissue depends for contraction or impulse generation. Thus, calcium anti-agonists can reduce the contractile activity of the heart, and promote coronary and systemic vasodilatation. These effects provide the clinical rationale for the use of calcium antagonists in the management of ischaemic heart disease and hypertrophic cardiomyopathy. Since systemic vasodilatation can be expected to reduce elevated arterial blood pressure, interest has focused recently on calcium antagonists in the medical management of systemic hypertension. All the calcium antagonists are able, in low concentrations, to relax the smooth muscle vasculature from coronary, cerebral, mesenteric, and renal arteries. The effects on the myocardium, cardiac impulse tissue, and vascular smooth muscle are different in magnitude, however, depending on the individual agent that is used. Clinical experience in the treatment of hypertension with this class of agents is confined to verapamil, nifedipine, and diltiazem. In this article, the scientific rationale for using calcium antagonists in the treatment of arterial hypertension is explored and the clinical experiences with the different calcium antagonists used in hypertension are reviewed.

A comparative study of the pharmacodynamic effects of nimodipine and nifedipine in the isolated spontaneously beating rabbit heart

Myocardial effects of the calcium antagonistic drugs nimodipine and nifedipine were comparatively studied in retrogradely perfused rabbit hearts at stepwise increasing drug concentrations in the perfusion liquid within the range of 1-60 ng ml-1. Pharmacodynamic steady states developed slowly within about 25 min. at each concentration level. Nimodipine produced in comparison with nifedipine a progressive and very marked negative chronotropic effect and caused simultaneously a very pronounced increase in the QT-interval. The potency of nimodipine with regard to these effects were about 10 times that of nifedipine. The PQ-interval was only increased significantly at the two highest concentrations of nimodipine. Both drugs caused a pronounced inhibition of myocardial contractility as judged from the decrease in contraction amplitude and rate of contraction. Myocardial efficiency expressed as the ratio of contraction-rate to oxygen consumption decreased progressively and highly significantly with increasing drug concentrations. The relative potency between nimodipine and nifedipine with regard to the negative inotropic effects was only about 1.7. Increasing exposure to nimodipine produced a progressive decrease of the mean coronary flow-rate, whereas nifedipine initially caused an increase followed by a terminal decrease to the initial flow-rate level.

Acute haemodynamic effects of a new calcium antagonist, nicardipine, in man. A comparison with nifedipine

1 The acute cardiovascular response to nicardipine was investigated using non invasive techniques in normal subjects. 2 In six subjects, i.v. nicardipine in an increasing dose (0.5-20 mg) was compared with saline, under double-blind conditions. A dose related increase in heart rate and fall in blood pressure were found. Pre-ejection period (PEP) and PEP/left ventricular ejection time (LVET) ratio of the systolic time intervals were shortened in a clearly dose related manner. Total electromechanical systole index (QS2 I) was decreased and LVET index prolonged. 3 In four subjects increasing oral doses (10-40 mg) of nicardipine, administered in a randomized double-blind placebo control design, demonstrated the same pattern, marked changes being found with the 40 mg dose. 4 Comparison with nifedipine in a double-blind-placebo controlled balanced trial in six subjects confirmed that 40 mg nicardipine and 20 mg nifedipine exhibited similar effects. Maximum response was reached between 0.5 and 1.5 h, and changes in some cardiovascular variables were still evident at 3 h.

Nifedipine in the treatment of difficult hypertensives

Nifedipine has been assessed as a possible alternative to other third line drugs in the management of patients with difficult to control hypertension. A group of 20 patients whose blood pressure was unsatisfactory on a 3 drug regimen had their third drug stopped and after a 2 week period nifedipine was added to their beta-blocker plus diuretic therapy. Eleven became normotensive on 30 mg nifedipine daily and a further 6 on 60 mg daily; giving on overall success rate of 85%. This result was achieved with a reduction in side effects and an absence of any haemodynamic or metabolic complications.

Antihypertensive effect of diltiazem in young or adult rats of genetically hypertensive strains

The antihypertensive effects of diltiazem were investigated in three different strains of genetically hypertensive rats, i.e. spontaneously hypertensive rats (SHR), stroke prone SHR (SHR-sp) and genetically hypertensive rats (GHR) compared to their respective controls, normotensive Wistar-Kyoto (NT-WKY) and New Zealand strain (NT-NZ). Either adult (3-6 months) or young (4 weeks), conscious rats were used. In adult SHR, SHR-sp and GHR, the percent decrease in blood pressure produced by diltiazem (10, 30 and 100 mg/kg orally (p.o.) or 0.1, 0.3, 1.0 and 3.0 mg/kg intravenously (i.v.)) was greater than in NT-WKY or NT-NZ, while no difference was detected in case of hydralazine (5 mg/kg p.o.). In contrast, the reactivity to diltiazem was not different between the young rats bred from the normotensive and hypertensive rats of both the Japanese and the New Zealand strains. It is concluded that diltiazem is a more effective antihypertensive agent in the hypertensive rats than in the normotensive rats. However, the increased reactivity to this compound in the adult hypertensive rats cannot be readily explained by the known pathogenetic factors leading to their hypertension.

The acute effects of nifedipine on calf and forefoot blood flow in patients with peripheral arterial insufficiency

The calcium-blocking agent nifedipine, which possesses vasodilating potency, was tested in 8 patients with peripheral arterial insufficiency. 10 mg sublingually significantly decreased systolic arm and ankle blood pressure. Neither blood flow nor local peripheral resistance in the calf and the forefoot at rest and the calf during postischemic reactive hyperemia changed significantly. During postischemic hyperemia in the forefoot, the drug significantly reduced peak blood flow and increased local peripheral resistance. The drug-induced reduction in forefoot peak blood flow was correlated to the fall in systolic arm and ankle blood pressure. It is suggested that nifedipine may shorten the claudication distance in patients with peripheral arterial insufficiency.

Hypotensive effects of diltiazem to normals and essential hypertensives

The hypotensive effect of acute and longterm, intravenous and oral administration of the calcium antagonist, diltiazem, was investigated in 8 normotensive volunteers and 55 patients with essential hypertension. Diltiazem i.v. infusion of 45 mg/h (0.5 mg/min, then 1.0 mg/min, each for 30 min rapidly decreased both blood pressure (BP) from 164 +/- 22/98 +/- 8 to 144 +/- 15/86 +/- 9 mmHg (mean +/- SD) and total peripheral resistance from 32.6 +/- 8.4 to 25.3 +/- 5.4 mmHg/l/min (p less than 0.001), and increased stroke volume from 58.2 +/- 9.5 to 64.2 +/- 8.6 ml/beat (p less than 0.05). It altered neither heart rate nor cardiac output in the hypertensives (n = 10). Oral diltiazem 60 mg rapidly decreased BP from 155 +/- 10/103 +/- 6 to 142 +/- 12/90 +/- 8 mmHg after 3 hours (p less than 0.01/p less than 0.001) in hypertensives (n = 8), but not in normotensives (n = 8). Diltiazem 90 mg p.o. decreased BP from 157 +/- 15/102 +/- 9 to 129 +/- 13/83 +/- 8 mmHg (p less than 0.01) in hypertensives (n = 15), and reduced the heart rate from 71 +/- 8 to 65 +/- 8 beats/min (p less than 0.01). The drug did not change plasma renin activity either in normotensives or hypertensives. The fall in diastolic BP was correlated with the plasma diltiazem concentration (r = 0.910, n = 6, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Exaggerated hypotensive responses to calcium antagonists in spontaneously hypertensive rats

The hypotensive effects of intravenous injection and infusion of diltiazem, l- and d-verapamil were investigated in conscious and anaesthetized rats with spontaneous hypertension (SHR) and normal blood pressure (NT-WKY). The inhibitory actions of these calcium-influx blockers on the pressor responses to angiotensin II (AII) and noradrenaline (NA) were also examined in anaesthetized SHR and NT-WKY. The intravenous injections of these three drugs (0.03, 0.1, 0.3, 1.0 mg/kg) lowered mean arterial pressure (MAP) in a dose related manner in conscious NT-WKY and SHR. The small dose of the blockers administered by intravenous infusion (0.02 mg/kg per min) also decreased MAP in both groups. The potency of the antihypertensive action was in the order l-verapamil greater than d-verapamil = diltiazem. The fall in blood pressure expressed as percentage of the initial MAP produced by the compounds was significantly enhanced in SHR compared to NT-WKY. The pressor responses to AII (0.03, 0.1, 0.3, 1.0 micrograms/kg i.v.) were suppressed by the intravenous infusion of 20 micrograms/kg per min with l-verapamil but not with d-verapamil, diltiazem and vehicle in NT-WKY, while no calcium blocker significantly diminished the vasopressor action of AII in SHR. The pressor effects of NA (0.3, 1.0, 3.0, 10.0 micrograms/kg i.v.) were inhibited by the same doses of l-verapamil and diltiazem but not with d-verapamil and vehicle in NT-WKY. Diltiazem reduced the response to NA in SHR but the other compounds (l- and d-verapamil) did not alter the pressor response to NA in SHR. The pressor responses to arginine vasopressin (3, 10, 30 and 100 mU/kg i.v.) were not altered by diltiazem infusion in either SHR or NT-WKY. It is concluded that these compounds are different in the potency of their hypotensive action and also the inhibition of the pressor responses to AII and NA. Calcium entry blockers are more effective antihypertensive agents in SHR than in NT-WKY. It appears that their inhibitory effects on the responses to AII and NA do not explain the exaggerated hypotensive responses in SHR.

Clinical value of calcium antagonists in treatment of cardiovascular disorders

All calcium antagonists have the ability to decrease the symptoms and signs in some patients with ischemic heart disease and help lower the blood pressure in hypertensive persons, but in clinical doses nifedipine does not exhibit antiarrhythmic properties, although these are an important part of the action of verapamil, diltiazem and some substances with a similar chemical structure. In certain disorders beta-adrenergic blocking drugs are useful adjuncts, and under some circumstances, particularly variant angina and supraventricular arrhythmias, specific calcium antagonists are the drugs of choice. More data are needed to define the role of calcium antagonists during cardiopulmonary bypass, in the protection of the ischemic myocardium, in the management of hypertrophic cardiomyopathy and in specific cases of primary pulmonary hypertension. When used with an appropriate sense of perspective and careful observation, calcium antagonists provide useful additional means of helping selected patients suffering from particular cardiovascular diseases.

Felodipine--a new vasodilator, in addition to beta-receptor blockade in hypertension

In a double-blind, cross-over trial, 10 men with primary hypertension, not adequately controlled with a beta-blocker alone, were also given felodipine or placebo for periods of one week. Placebo was administered single-blind for 2 weeks and 1 week, respectively, before randomization and between treatments. The dose of felodipine ranged from 6.25 mg to 25 mg. The addition of felodipine resulted in a pronounced (20%), statistically significant reduction in blood pressure (BP) and a small but significant increase in heart rate (HR). The effects were seen within 1-2 h and were maximal after 3-4 h. During steady state treatment the duration of BP reduction was at least 12 h. No orthostatic reaction was seen. There was a significant correlation between the plasma concentration of felodipine and change in BP. The most frequently reported side-effects were headache and ankle oedema, the latter probably being due to pronounced pre-capillary vasodilatation. There was no weight increase and thus no indication of general water retention. No clinically significant change in laboratory variables and no influence on the P-Q time were seen. Thus, felodipine in combination with a beta-blocker seems to be a useful addition to the treatment of hypertensive patients whose BP is not adequately controlled with a beta-blocker alone.

Acute antihypertensive effect and pharmacokinetics of a tablet preparation of nifedipine

A tablet formulation of nifedipine was given to 8 hospitalized hypertensive men, W.H.O. stage I or II, mean age 45 years. After an initial placebo test, nifedipine 20, 40 or 60 mg was given in random order at 72-h intervals, in a single administration crossover study. The placebo and the active drug were given at 8 a.m. Blood pressure and heart rate were measured twice by the same observer, every 20 min from 7 to 8 a.m., and then hourly until 8 p.m., first in recumbency and again after 1 min of standing upright. Plasma nifedipine was assayed in samples taken hourly from 8 a.m. to noon, every 2 h from noon to 8 p.m., and 24 and 48 h after drug administration. All 3 doses significantly lowered blood pressure; the fall during recumbency was significantly larger (-18%) and lasted longer (12 h) after 60 mg than after 20 mg (-11% and 7 h). All 3 doses caused a similar increase in heart rate (+29 to +38%), which reached its maximum after 2 h and lasted for 5 h. The maximum plasma concentration and the area under the plasma concentration--time curve were dose-dependent despite large inter-subject variation. Absorption, bioavailability and elimination were linear between the 20 and 60 mg doses. Plasma nifedipine levels were strongly correlated with the concomitant decrease in mean arterial blood pressure (r = 0.61, p less than 0.001). Four patients experienced mild side effects (headaches, flushes, drowsiness or weakness). This tablet form of nifedipine has a potent antihypertensive action which lasts longer than that of the capsule presentation.

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.

Acute effects of the calcium antagonist, nifedipine, on blood pressure, pulse rate, and the renin-angiotensin-aldosterone system in patients with essential hypertension

Ten milligrams nifedipine was administered orally to young and old persons with or without hypertension, and the acute effects of nifedipine on the renin-angiotensin-aldosterone system were studied one half to 3 hours later. Nifedipine reduced blood pressure and increased pulse rate in young and old persons with or without hypertension. Simultaneously, nifedipine produced a significant increase of plasma renin activity in young persons with or without hypertension but failed to do so in old persons with or without hypertension. As a result, angiotensin I and II increased significantly in young persons but not in old persons. Hydralazine elevated aldosterone concentration by stimulating the renin-angiotensin system but nifedipine failed to do so despite its effect on the renin-angiotensin system in young individuals. Since calcium is required to secrete aldosterone, it is suggested that nifedipine blocked aldosterone secretion by the agent's calcium antagonizing action.

Evaluation of the chronotropic property of captopril in hypertensive patients

Captopril was administered (50 mg orally) to 88 untreated hypertensive patients (70 with essential hypertension, eight with renal arterial disease, 10 with renal parenchymal disease) and to 25 hypertensive patients treated with sympatholytic or beta-blocking agent (20 with essential hypertension, five with renal arterial disease). In the former group, captopril caused a decrease in heart rate (HR) in 18 patients and an increase in only two. As a whole, captopril caused significant decreases in blood pressure without increase in HR. Significant negative correlation was observed between change in HR and plasma renin activity obtained before captopril administration (n = 79, r = -0.425, p less than 0.0001). Hypotensive and chronotropic effects of captopril were almost identical in untreated and treated patients. Hypotensive effects caused by captopril and nifedipine (20 mg orally) were almost identical. Nifedipine caused reflex tachycardia, while captopril caused slight bradycardia. Absence of compensatory tachycardia appears to be related to reduction of endogenous angiotensin II by captopril.U

Comparison of oral propranolol and verapamil for combined systemic hypertension and angina pectoris. A placebo-controlled double-blind randomized crossover trial

The relative efficacies of oral verapamil, a calcium-entry blocking drug, and propranolol, a beta-adrenergic blocking drug, were compared in 12 patients who had both stable angina pectoris and mild to moderate systemic hypertension, using a placebo-controlled, double-blind, randomized crossover protocol. Compared with placebo, both propranolol and verapamil decreased the frequency of anginal attacks and the number of nitroglycerin tablets consumed, and increased exercise duration and total work; there were no significant differences in the antianginal effect of the two drugs. Both verapamil and propranolol reduced the supine and standing systolic and diastolic blood pressure measured at rest; compared with propranolol, however, verapamil had greater effects on standing diastolic blood pressure (p less than 0.002). Resting heart rate was reduced from placebo baseline with large doses of both drugs; compared with verapamil, however, propranolol exerted greater effects on resting heart rate and rate-pressure product. Plasma renin activity was increased from placebo baseline with verapamil (p less than 0.05), but was reduced with propranolol (p less than 0.05); no significant change in plasma aldosterone was seen with either drug. Verapamil appears to be a safe and effective treatment alternative to propranolol for relieving anginal symptoms, improving exercise tolerance, and reducing elevated systemic blood pressure in patients with both angina pectoris and mild to moderate systemic hypertension.

Nifedipine therapy in angina pectoris: evaluation of safety and side effects

Nifedipine, a calcium-channel blocker, differs in structure and mode of action not only from the nitrates and beta blockers but also from the other well-known calcium-channel blockers. These differences have important implications for the treatment of angina pectoris. Our clinical experience over a period of 6 years with all types of angina patients--mostly those with chronic stable angina but also those with Prinzmetal's and unstable angina-corroborates the efficacy reports published in the world literature. Although the safety profile of nifedipine has been generally regarded as favorable, a few reports of clinically significant adverse effects in specific patient groups have appeared in the literature. In order to provide a more comprehensive assessment of safety, the records of over 3000 patients treated with nifedipine in open and controlled multiple-dose studies were tabulated and analyzed. Of special concern were patients with clinically significant adverse experiences, patients with a concomitant diagnosis of congestive heart failure (CHF), patients who were being treated concurrently with beta blockers, and patients who had been taking nifedipine for more than 6 months. Results of this analysis confirm that nifedipine can be safely administered to a broad spectrum of angina patients, including those with a concomitant diagnosis of CHF and those receiving concurrent therapy with beta-blocking agents.

The relation of genetics to essential hypertension: a review

Essential hypertension is fundamentally a genetic disease which emerges because of environmental impact. The genetic factors involve intracellular abnormalities which affect calcium metabolism within smooth muscle cells and possibly within the heart and sympathetic nervous system. These abnormalities are influenced by one or more proteins of which calmodulin is a candidate. Sodium pump abnormalities may be primary but may be secondary feedback effects. Homeostasis keeps the blood pressure and cardiac function normal, but eventually becomes less effective. Such homeostasis is produced by negative feedback, but positive external factors also influence the eventual results. Gross homeostasis is provided by the baroreceptors, the renin-angiotensin-aldosterone system, etc. The malfunction of any one or any combination of these systems may produce or accelerate hypertension. Hyperplasia and hypertrophy of arteriolar smooth muscle play their role but also multiply the genetic cellular defects. It is possible that in the early history of man essential hypertension had an advantage which now has become obsolete because normotensive man's potential lifespan has been increased by modern civilization.

Reduced pressor effect of angiotensin II and of noradrenaline in normal man following the oral administration of the calcium-antagonist nifedipine

The pressor response to both angiotensin II (5, 10 and 20 ng kg-1 min-1) and to noradrenaline (50, 100 and 200 ng kg-1 min-1) was reduced (P less than 0.05 to less than 0.005) in six healthy male subjects following the administration of the calcium-antagonist nifedipine (10 mg p.o.). Nifedipine induced a rise in basal plasma noradrenaline concentrations but did not alter the plasma concentrations of adrenaline, dopamine, renin and aldosterone. A slight reduction in the angiotensin II induced rise of plasma aldosterone by nifedipine was observed after the administration of the largest dose of angiotensin II only (P less than 0.05). The reduced responsiveness towards pressor agents following oral nifedipine is in keeping with the known antihypertensive effect of calcium-antagonistic drugs and could provide a concept for the effectiveness of these drugs in hypertensive crisis.

Treatment of hypertension in dialysis and essential hypertension patients with nifedipine

The immediate antihypertensive effect of 10 mg nifedipine sublingually (nifedipine test), was measured in 19 chronic renal failure hypertensive patients on dialysis and 34 essential hypertensive patients with normal kidney function. The blood pressure decreased significantly in both groups. The minimal values were observed between 30 and 60 minutes after the sublingual administration of nifedipine. The blood pressure decreased from 178 +/- 3.3/104.0 +/- 3.9 to 136.0 +/- 4.7/87.5 +/- 5.1 mm Hg (p less than 0.001) in dialysis patients and from 176.8 +/- 4.5/107.1 +/- 2.4 to 133.0 +/- 3.0/81.7 +/- 2.2 mm Hg in essential hypertension patients (p less than 0.001). The decrease in blood pressure during the test had a significant positive correlation with the pre-test values. Thirteen hypertensive patients on dialysis and 20 essential hypertensive patients completed 2 weeks of daily oral nifedipine therapy, with a dose of 30 to 40 mg per day. The mean blood pressure at the end of the 2 weeks of treatment decreased from 179.5 +/- 4.5/108.5 +/- 5.3 mm Hg to 154.4 +/- 6.3/82.3 +/- 2.6 mm Hg (p less than 0.001) in dialysis patients, and from 176.8 +/- 5.8/110.3 +/- 2.9 to 151.3 +/- 5.3/93.5 +/- 2.6 mm Hg (p less than 0.001) in essential hypertension patients. The present results reveal that nifedipine has a powerful immediate as well as a long-term antihypertensive action in dialysis patients with high blood pressure. This effect is similar to that obtained in essential hypertensive patients.

Prevention of malignant hypertension in salt loaded "S" Dahl rats with the calcium antagonist nifedipine

Female "S" Dahl rats, fed an 8% NaCl diet from the 6th week of age developed malignant hypertension and heart hypertrophy in the course of 6 weeks on the salt regimen. Simultaneous treatment with nifedipine (300 ppm in diet additional to 8% NaCl) prevented the increase in blood pressure, reduced heart hypertrophy and mortality and improved the impaired renal function in "S" rats. The decrease in hematocrit in salt loaded "S" rats was prevented by nifedipine. The prophylactic effect of the calcium antagonist nifedipine is only partly due to the prevention of increase in systemic vascular resistance. In addition an improvement of failed intrarenal hemodynamics by nifedipine can be postulated. This enables the kidney of "S" rats to excrete the salt load without increasing blood pressure and plasma volume.

Effects of treatment with nifedipine and metoprolol in essential hypertension

In a double-blind trial 26 patients with essential hypertension were treated with nifedipine or placebo for 8 weeks, following a 4-week run-in-placebo period in all patients. The daily dosage of nifedipine during this phase was 10 mg 3 times daily. Metoprolol was then added to the therapeutic regimen of both groups for a further 12 weeks. Both nifedipine and metoprolol used as mono-therapy caused statistically significant reductions of arterial pressure. The addition of metoprolol to nifedipine tended to reduce blood pressure further, but blood pressures were not significantly lower than during nifedipine mono-therapy. Side-effects were few and only two patients had to be withdrawn during active therapy, one for headaches during nifedipine therapy, and another for asthma during metoprolol treatment. Combined therapy with a beta-adrenoceptor blocking agent, such as metoprolol, and a calcium antagonist with vasodilation properties, such as nifedipine, offers a theoretically interesting approach in the treatment of hypertension, even though the practical outcome in the present study probably suffered from an inadequate dose of nifedipine during the period of combined therapy.

Acute and long-term hypotensive effects and plasma concentrations of nifedipine in patients with essential hypertension

The acute and long-term hypotensive effects of low doses of nifedipine, and the correlation between the fall in the blood pressure (BP) and the plasma nifedipine concentration, were investigated in patients with essential hypertension. The oral administration of nifedipine 5 mg rapidly decreased BP from 163 +/- 22/101 +/- 10 to 127 +/- 12/82 +/- 9 mmHg (mean +/- SD; p less than 0.001), and increased heart rate from 72 +/- 8 to 76 +/- 6 beats/min (p less than 0.05), plasma renin activity rose from 1.2 +/- 0.6 to 1.4 +/- 0.8 ng/ml/h (p less than 0.05), and plasma nifedipine concentration was 75.6 +/- 22.0 ng/ml 30 min after administration (n = 7). The nifedipine concentration was significantly correlated both with the fall in BP (r = 0.410, p less than 0.02, n = 31) and the rise in the heart rate (r = 0.412, p less than 0.02, n = 31). Treatment with nifedipine 5 mg t.d.s. alone or in combination either with propranolol 10 mg t.d.s., or thiazide 1 tablet daily, or propranolol and thiazide, controlled BP in 36 patients during the 22 week study period. During the long-term nifedipine therapy, the plasma nifedipine level was significantly correlated with the fall in systolic (r = 0.577, p less than 0.01, n = 20) and diastolic (r = 0.595, p less than 0.01, n = 20) BP. It was concluded that the plasma nifedipine concentration could be correlated with the fall in BP, and that low doses of nifedipine, either as monotherapy or in combination, were effective in the acute and long-term treatment of patients with essential hypertension.

Long-term therapy of arterial hypertension with nifedipine given alone or in combination with a beta-adrenoceptor blocking agent

The antihypertensive effect of nifedipine during long-term therapy was investigated in 5 patients receiving nifedipine as the sole drug and in 10 patients who had nifedipine in combination with a beta-adrenoceptor blocking drug. Nifedipine monotherapy was problematic because of side-effects and development of resistance to therapy after a few months. In patients who received the combined therapy significant and stable blood pressure reductions were maintained during the whole observation period (12-33 months). However, the occurrence of peripheral oedema in 4 of the patients necessitated the addition of a thiazide diuretic. It is concluded that nifedipine is not a first choice drug for the long-term treatment of arterial hypertension. When given in addition to a beta-blocker it is well tolerated and powerful but fluid retention may occur and if not counteracted by a diuretic it will limit the antihypertensive potential of the drug.

Nifedipine in the treatment of cardiovascular disease

Nifedipine, a calcium channel blocking agent, has been shown safe and effective in the treatment of various cardiac disorders. In Prinzmetal's variant angina, nifedipine relieves the acute spasm of a large coronary artery, and thereby reverses the sudden decrease in myocardial oxygen supply. In chronic stable angina, the efficacy of nifedipine stems from an interplay of direct and reflex effects. A decrease in systemic vascular resistance, and thus, myocardial oxygen demand, is considered the most important effect. Although this is partially offset by baroreceptor-mediated reflex increases in blood pressure and heart rate, the net effect is a decrease in myocardial oxygen consumption. The importance of nifedipine-induced increases in coronary blood flow in relieving stable angina remains controversial. Numerous clinical trials in patients with chronic angina have demonstrated that nifedipine increases exercise tolerance by lowering the heart rate-blood pressure product (an approximation of myocardial oxygen consumption). The maximal double product during exercise, however, does not increase, suggesting that the drug does not importantly improve myocardial oxygen supply. Nifedipine may also be of value in the therapy of unstable angina, acute myocardial infarction, and hypertension, as well as in the protection of the myocardium at risk during open heart surgery. However, definite recommendations on the use of the drug for these indications must await results of ongoing randomized studies. The effects of nifedipine are dose-related. Larger doses have been shown more effective than smaller doses, as long as an appropriate blood pressure is maintained. The side effects of nifedipine are mild and related to its vasodilating action.

Efficacy of sublingual nifedipine in the acute treatment of systemic hypertension

The effects of sublingual nifedipine, a calcium antagonist vasodilator, were assessed in 43 patients with moderate to severe hypertension in an emergency room setting. Following a no-response placebo treatment period, the patients with supine diastolic blood pressure of less than 110 mm Hg (group A, n equals 17) received 10 mg of sublingual nifedipine, and the patients with supine diastolic blood pressure of much greater than or equal to 110 mm Hg (group B, n equals 26) received a 20-mg sublingual dose. In group A, systolic blood pressure decreased from 172.4 plus or minus 18.6 mm Hg to 140.0 plus or minus 14.6 mm Hg; diastolic pressure from 108.8 plus or minus 3.3 mm Hg to 87.6 plus or minus 9.9 mm Hg (P less than 0.001)., In group B, systolic blood pressure decreased from 203.8 plus or minus 22.1 mm Hg to 160.0 plus or minus 23.6 mm Hg; diastolic pressure from 127.7 plus or minus 11.3 mm Hg to 96.7 plus or minus 14.1 mm Hg (P less than 0.001). Heart rate increased significantly only in the 20-mg dose group, from 76 plus or minus 2 to 89 plus or minus 6 beats/min (P less than 0.005). Th effects of sublingual nifedipine were seen in one to five minutes, and the maximal effect in 20 to 30 minutes, with return to placebo baseline in four to five hours. Adverse reactions were minimal in both treatment groups. Nifedipine is an effective and safe hypotensive drug in the rapid management of moderate to severe hypertension and seems to be an effective nonparenteral agent for treatment of hypertensive emergencies.

Myocardial pharmacokinetics and pharmacodynamics of nifedipine in the isolated rabbit heart

The myocardial accumulation and disposition pharmacokinetics of the antianginal and antihypertensive calcium-antagonistic drug nifedipine were investigated in isolated, perfused and spontaneously beating rabbit hearts. The myocardium behaved pharmacokinetically as a two-compartment system with regard to the drug. The mean half-lives of the alpha-phase of distribution and of the beta-phase of disposition were about 1.2 and 6.5 min., respectively. Perfusion with a modified Krebs-Henseleit solution containing nifedipine in a concentration of 50 ng ml-1 caused by accumulation of about 1277 ng g-1 in the myocardium at steady state. Stepwise increased concentrations of nifedipine from 3 to 60 ng ml-1 in the liquid used in perfusions for 25 min. periods produced a pronounced progressive decrease in myocardial contractility to about 8%. The heart beating frequency simultaneously decreased gradually to about 76%. The mean coronary flow rate increased initially to 135% and then gradually decreased to 94%. These effects were accompanied by a decrease to about 0.27 in the ratio of the product of contraction amplitude and frequency to the oxygen consumption, a finding that was evaluated as an expression of reduced myocardial efficiency. No significant dromotropic effects were observed.

Antihypertensive and hormonal effects of single oral doses of captopril and nifedipine in essential hypertension

In a single-dose crossover study Captopril (SQ 14225), 1 mg/kg body weight, and Nifedipine (Bay a 1040) 20 mg were administered orally to 12 hospitalized patients with essential hypertension (Stage 1 or 2, W.H.O.). Both drugs significantly reduced blood pressure, but each dose acted differently: the mean maximum arterial pressure reduction was faster and greater with Nifedipine than with Captopril: -23 +/- 2% at 37 +/- 15 min and -17 +/- 1% at 86 +/- 25 min, respectively. Captopril inhibited angiotensin II and aldosterone production, but did not accelerate heart rate or stimulate vasopressin release. Nifedipine stimulated vasopressin release and increased heart rate, but the renin angiotensin aldosterone system was not significantly affected. The blood pressure reduction was related to the initial level of activation of the renin angiotensin system only for Captopril. The blood pressure reduction induced by one drug was not related to that produced by the other in the same patient.

Antiarrhythmic effect of the calcium antagonist tiapamil (Ro 11-1781) by intravenous administration in patients with coronary heart disease

Twenty coronary patients with a median age of 76 years were treated in the coronary care unit with tiapamil, a new Ca2+ antagonist, by intravenous infusion (until December, 1979, the generic name was dimeditiapramine). The following arrhythmias were identified: atrial fibrillation with ventricular rate greater than 95 beats/min (5 patients); supraventricular premature complexes (SVPC) (4 patients); and ventricular premature complexes (VPC), Lown grades 2-4 (15 patients). Electrocardiograms and hemodynamic parameters were continuously monitored prior to, during, and after the therapy. In patients with atrial fibrillation, sinus rhythm was not restored, but tiapamil decreased the ventricular rate by 54%. In patients with VPC, the median frequency of VPC decreased from 310.5 before tiapamil to 32.5 beats/h at the fourth hour of therapy (p less than 0.01). The median ectopic/sinus beat ratio decreased from 0.083 (pretreatment) to 0.008 at the fourth hour of infusion (p less than 0.10). In one of the patient with an insufficient decrease in the number of VPC, the VPOC changed from class 4a (pretreatment) to class 2 (during the therapy), returning to class 4a after the infusion was stopped. Tiapamil reduced the median systolic and diastolic blood pressures by 8.3 and 7.1%, respectively (p less than 0.05), the third hour. Hypotension and bradycardia were observed in 5/20 patients. The results show that tiapamil is effective against both supraventricular and ventricular arrhythmias, and thus its spectrum of action differs from that of other calcium antagonists.

Hemodynamic effects of a single oral dose of nifedipine following acute myocardial infarction

The hemodynamic effects of a single oral dose of 20 mg of nifedipine were studied in 21 stable patients after an acute myocardial infarction before withdrawal of Swan-Ganz and intra-arterial catheters. The drug appears safe, and no significant untoward effects were noted. Significant hemodynamic changes were present between 15 and 120 minutes after ingestion with a peak at 60 minutes. Mean arterial pressure decreased from 81+/-2.7 (SEM) to 71+/-2.3 mm Hg (P<0.001), and systemic vascular resistances decreased from 1438+/-88 to 1144+/-63 dynes/sec/cm5 (P<0.001). Cardiac index increased from 2.7+/-0.1 to 3.1+/-0.1 L/min/sq m (P<0.01) and heart rate from 79 +/- 3 to 82 +/- 4 (P<0.01). The pressure-rate product decreased from 10.3 X 10(3) to 9.5 X 10(3) (P<0.05), and pulmonary wedge pressure was unchanged from 12 mm Hg. The hemodynamic changes were similar whether patients were receiving propranolol or not. The afterload reducing effect was potentially most beneficial in the subgroup of patients with depressed left ventricular function where cardiac index increased by 20 percent.

Hemodynamics and coronary flow following diltiazem administration in anesthetized dogs and in humans

In this study, the systemic and coronary hemodynamic changes associated with the administration of diltiazem, a recent calcium antagonist, were evaluated in three different situations as follows: following a 200 microgram/kg intravenous bolus of the drug in 12 open-chest anesthetized dogs; following two successive intravenous infusions of diltiazem (15 microgram/kg/min and 30 microgram/kg/min), each for a period of ten minutes, in eight patients with angina pectoris investigated by coronary arteriography; and following a single oral dose of 120 mg of diltiazem in 17 patients undergoing hemodynamic monitoring in the coronary care unit after a recent myocardial infarction. Diltiazem was found to be a coronary vasodilator acting on the large coronary arteries and on collaterals. Its effects on myocardial oxygen requirements were variable; as a rule, the predominant effect was a drop in systemic vascular resistance or in heart rate. When systemic vascular resistance changed little, heart rate tended to decrease significantly; however, when systemic vascular resistance decreased notably, heart rate remained unchanged because of a relfex attempt to increase systemic blood pressure. Cardiac performance and left ventricular end-diastolic pressure were not affected and this lack of change in cardiac inotropism may confer and advantage to diltiazem over other calcium antagonistic drugs in patients with coronary heart disease.