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

Clinical pharmacology of calcium antagonists. Satellite symposium on calcium antagonists

A new class of agents has been made available for the treatment of hypertension. These calcium antagonists have rapid bioavailability and dramatic antihypertensive effects through reduction of total peripheral resistance and the vascular resistance of the major target organs of the body. These changes are usually associated with unchanged cardiac output, preserved organ blood flows, maintained organ function, and preserved reflex responses without fluid retention in long-term treatment. These drugs do not stimulate plasma renin activity and aldosterone levels. Thus they fulfill many of the major criteria for an ideal antihypertensive agent.

Pharmacokinetic interaction between nifedipine and propranolol

In 8 healthy volunteers, single-dose nifedipine pharmacokinetics were compared with and without the coadministration of propranolol. An elevation of the mean Cmax was found, from 73.9 +/- 14.1 when nifedipine was taken alone, to 115.7 +/- 12.1 (SE) ng/ml (P less than 0.02) when the agent was combined with propranolol. The AUC0----infinity increased as well, from 287.1 +/- 33.5 to 363.0 +/- 54.3 (SE) (micrograms.hr)/l (P less than 0.01), indicating an increase in bioavailability. Propranolol treatment did not significantly affect the nifedipine half-life (alpha or beta phase) or the estimated volume of distribution, whereas systemic clearance tended to decrease in 6 of the subjects. The most likely explanation for increased bioavailability of nifedipine when coadministered with propranolol is by a reduction of the hepatic "first-pass" clearance, as a result of changes in hepatic blood flow.

Drug treatment of hypertension

There are several first choices for the treatment of mild and moderate hypertension. The selection of a drug may be influenced by concomitant pathology, with positive indications for particular drugs, e.g. coexistent angina, indicating use of a beta-receptor blocking drug or calcium antagonist; fluid retention indicating a diuretic; or contraindication e.g. asthma, and beta-adrenoceptor blocking drugs. beta-Adrenoceptor blocking drugs have the advantage of a long history and of possibly being cardioprotective following myocardial infarction, but they have not yet been established as primary preventive agents in hypertensive patients. The alpha-receptor blocking drugs have the advantage of favourably affecting lipid profile and blood pressure. Therefore, there may be advantages in the use of combined alpha- and beta-blockade. The diuretics, which have the advantage of being inexpensive, are widely used but long term metabolic effects, particularly hypokalaemia, cause concern. This is correctable by co-administration of a potassium sparing diuretic and often preventable by using low doses of the diuretic. Diet may be important as hypokalaemia appears to be less of a problem where potassium intake is high. Experience with calcium antagonists is widening but the use of converting enzyme inhibitors is more limited, and some physicians are less ready to use them as first choice in mild hypertension at present. Drugs like methyldopa, clonidine, the adrenergic neurone inhibitory drugs are now used more as reserve agents. More severe cases of hypertension may require drugs from 2 of the 3 major groups: beta-blocking drugs, vasodilators and diuretics. In some cases, drugs from each of these 3 groups will be required.

Calcium modulators: future agents, future uses

The calcium modulators have been a significant therapeutic advancement for the treatment of angina. Structural analogs of verapamil and nifedipine have been synthesized, as have structurally unique compounds. As the role of calcium in body processes is further elucidated, the efficacy of the calcium modulators is being evaluated for numerous disorders. It is anticipated that the newly synthesized compounds will have specificity toward particular body processes, thus providing efficacy with minimal side effects.

Captopril and nifedipine in combination for moderate to severe essential hypertension

The effects of the addition of a calcium entry antagonist, nifedipine (20-mg tablet twice a day), to an angiotensin converting enzyme inhibitor, captopril (25 mg three times a day), and the addition of captopril to nifedipine were observed in two separate studies in patients with essential hypertension. After 4 weeks of captopril therapy alone, mean arterial pressure fell by 12 mm Hg, and with the addition of nifedipine to captopril for a further month, blood pressure fell by an additional 10 mm Hg. In a separate group of patients treated with the same doses, mean arterial pressure fell by 17 mm Hg with nifedipine treatment alone; when captopril was added to the nifedipine therapy for an additional month, mean arterial pressure fell by a further 11 mm Hg. These blood pressures were measured 2 hours after the last dose; however, there was less of a fall in blood pressure when it was measured 12 hours after the last dose. This study confirms that captopril and nifedipine have a marked additive effect on blood pressure in whichever order they are given, but it shows that the combination is relatively short-acting.

Nicardipine in the treatment of Raynaud's phenomenon. Dissociation of platelet activation from vasospasm

A new calcium channel blocker, nicardipine, was studied for treatment of Raynaud's phenomenon in a double-blind, placebo-controlled, crossover trial during the winter months. Clinical response was assessed by a patient-kept diary of symptoms and finger systolic pressure that was measured at room temperature and during cold challenge. In vivo platelet activation was determined by measuring plasma levels of the platelet-specific proteins, beta-thromboglobulin and platelet factor 4. When treatment with placebo was compared with treatment with nicardipine, no significant differences were found in the number of Raynaud's attacks per day, the severity of attacks, change in character in Raynaud's phenomenon, use of hands in winter months, patient assessment of medication or objective measurements of finger systolic pressure, and critical closing temperature. There was a reduction of plasma levels of beta-thromboglobulin and platelet factor 4 in the overall study group while taking nicardipine compared with that during the placebo period (mean change 5.0 +/- 2.4 ng/ml, P = 0.054, and 1.4 +/- 0.6 ng/ml, P less than 0.01, respectively). These results demonstrate that while nicardipine was not effective in reducing the episodes of Raynaud's phenomenon, it did inhibit in vivo platelet activation. These findings suggest that platelet activation is not the primary event in the pathogenesis of acute vasospasm in Raynaud's phenomenon, since reduction of platelet activation by the drug did not change the severity of vasospasm.

Role of calcium antagonists in systemic hypertension

Despite the physiologic rationale of their use in hypertension, traditional vasodilators such as hydralazine and minoxidil are often relegated to the second and, more often, to the third and fourth steps of step-care programs. Although they are powerful blood pressure-lowering agents, they cause tachycardia, excessive renin stimulation and sodium retention, and cannot be used as the only antihypertensive agent. The characteristics of the antihypertensive action of calcium antagonists make them suitable for monotherapy. Indeed, all calcium antagonists, while effectively lowering blood pressure through vasodilation, either do not affect heart rate (verapamil and its analogs) or cause a moderate and transient heart rate increase (dihydropyridine compounds). Dihydropyridines also possess a natriuretic effect, probably due to inhibition of tubular sodium transport. The natriuretic effect is evident during the first 2 days of administration, but a small negative sodium balance persists for at least 1 week. There is no increase in body weight or fluid volumes with long-term administration of calcium antagonists with a marked acute natriuretic response, such as dihydropyridines, and those antagonists with a very moderate immediate natriuretic response, such as verapamil. All calcium antagonists, therefore, appear capable of preventing the sodium and water retention that vasodilatation would otherwise entail. More liberal step-care guidelines are now possible to find the agent most suitable for the individual patient. In these guidelines, calcium antagonists, as well as angiotensin converting enzyme inhibitors, are considered as possible first-choice agents along with diuretics and beta blockers.

Nicardipine in the treatment of essential hypertension controlled 6-month-study comparing nicardipine with propranolol at rest and during exercise

Thirty patients with mild to moderate essential hypertension entered a randomised double-blind parallel group study for 6 months to compare the effects of the new calcium channel blocker nicardipine 90 mg/day and propranolol 240 mg/day. Both drugs reduced systolic and diastolic blood pressures significantly in the supine and in standing positions. After 6 months of treatment, nicardipine had reduced the supine systolic and diastolic blood pressures by 16 and 17 mm Hg, respectively, and propranolol by 15 and 12 mm Hg. While propranolol treatment led to a marked decline in heart rate, nicardipine caused a small but statistically significant increase in heart rate throughout the study. Both drugs reduced blood pressure during maximal exercise, but propranolol had a greater effect. During exercise nicardipine did not affect the heart rate, whereas propranolol dramatically reduced it. Nicardipine did not produce any ECG changes at rest or during exercise. The side-effects for nicardipine were mild and were related to the vasodilatation induced by the drug. No abnormalities in routine blood chemical tests were found for either of the drugs. Nicardipine appears to be an effective single drug treatment for mild to moderate hypertension.

Nitrendipine vs. long-acting nifedipine in mild, moderate and severe hypertension

Long-acting nifedipine and nitrendipine, a nifedipine analogue, have been proposed for single-drug therapy of hypertension. In this study we compared the two preparations in three groups (10 subjects in each group) of mild (group 1), moderate (group 2), and severe (group 3) hypertensives. Drugs were administered for seven days (20 mg every 8 hr), according to a randomized, double-blind, crossover design. Blood pressure and heart rate readings were taken hourly, from 8 A.M. to 7 P.M., for the duration of the trial. In group 1, pressure was lowered to normal levels by both compounds and did not recover in the interval between one dose and the other, so that it remained normal throughout the day. In group 2, from an average of 170/109, values were reduced by the two preparations to 140/90 mm Hg within two hours, and then they tended to recover. This tendency was interrupted by the next dose. Because of this pattern, compared with the placebo period, pressure was substantially reduced during the twelve hours of the day; however, for a certain span it remained higher than normal. In group 3, the immediate responses to the two drugs were similar (from an average of 208/130, pressure was lowered to an average of 170/95 mm Hg), and then it tended to rise again and recovery was faster with nifedipine. Although pressure was significantly reduced throughout the day by both preparations, normotension was never achieved in this group. Neither drug induced a tachycardia reaction, altered renal or cardiac function, or affected body weight or plasma renin activity. The tendency to produce dependent edema was less pronounced with nitrendipine. In conclusion, these calcium channel antagonists were equally effective in mild and moderate hypertension, while in the severe from the action of nitrendipine was more persistent. Within the limits of the drug regimens used in this study, it seems that both preparations as monotherapy may be satisfactory in mild, questionable in moderate, and inadequate for severe hypertension, although the action of nitrendipine is more lasting.

Effect of a calcium entry blocker on blood pressure, plasma renin activity, aldosterone and catecholamines in normotensive subjects

The effects of the calcium entry blocker nifedipine on blood pressure, heart rate, plasma renin activity, aldosterone, noradrenaline and adrenaline were studied in 23 normotensive subjects in the supine and upright positions. Nifedipine, 10 mg administered sublingually, lowered mean blood pressure and increased heart rate, plasma noradrenaline and renin activity without increasing plasma aldosterone in the supine position. The increase in plasma aldosterone in response to upright posture was inhibited by nifedipine, whereas the rise in plasma noradrenaline was augmented. These results suggest that intracellular calcium is important as a regulator of aldosterone secretion as well as of vascular tone in normotensive subjects.

Treatment of hypertensive urgencies and emergencies with nifedipine

The calcium channel blocker, nifedipine, is an effective antihypertensive agent for the treatment of hypertensive urgencies and emergencies. It produces a prompt, safe, predictable, and consistent reduction in systemic arterial pressure with minimal adverse effects. The reduction in blood pressure is inversely correlated with the pretreatment blood pressure level. Various nonparenteral administration forms (oral, sublingual, buccal, and rectal) permit a versatile, noninvasive, cost-effective alternative to parenteral antihypertensive therapy and continuous hemodynamic monitoring. The overall efficacy in reaching goal blood pressure approaches 98% with a 10 to 20 mg dose of nifedipine. Hemodynamic changes are favorable, and there is rarely any associated morbidity (severe hypotension) or mortality. The role of nifedipine in the treatment of hypertensive emergencies is promising, but further studies are needed to compare it to other approved emergency antihypertensive regimens.

Atenolol plus nifedipine for mild to moderate systemic hypertension after fixed doses of either agent alone

Three therapies were used to treat 35 patients with mild to moderate systemic hypertension: (1) the cardioselective beta-adrenoceptor blocker atenolol, (2) the calcium antagonist nifedipine and (3) combination therapy for those who failed to reach the target diastolic blood pressure (BP) of less than 90 mm Hg with monotherapy. After an initial run-in placebo period, when the mean supine diastolic BP was 102 +/- 1 mm Hg (mean +/- standard error of the mean), patients were randomized (double-blind) to atenolol, 100 mg as a single daily dose or nifedipine (slow-release form), 20 mg twice daily, then to a washout dummy placebo period before crossover. Each period lasted 4 weeks. Supine, erect and exercise BP were recorded. Atenolol and nifedipine, in the same fixed doses but in combination, were given to 20 patients in whom either supine or erect diastolic BP exceeded 90 mm Hg after the period of monotherapy. Atenolol monotherapy reduced the erect diastolic BP to less than 90 mm Hg in 14 patients (40%); of the remainder, 1 patient responded only to fixed-dose nifedipine and 11 to combination therapy, yielding a total success rate of 74%. The combination gave enhanced control, as shown by a further decrease in supine and erect BP and by better control of exercise BP; these effects were achieved without an increased incidence of adverse effects. The mean reductions in supine diastolic BP were: atenolol, 9 +/- 2 mm Hg; nifedipine, 6 +/- 2 mm Hg; and combination therapy, 16 +/- 2 mm Hg (p less than 0.05 vs atenolol or nifedipine).(ABSTRACT TRUNCATED AT 250 WORDS)

Similarities and differences in the antihypertensive effect of two calcium antagonist drugs, verapamil and nifedipine

The short- and long-term effects of two calcium channel blocking drugs, verapamil and nifedipine, on blood pressure, heart rate, plasma catecholamines, plasma renin activity, plasma volume and cardiac performance (echocardiography) were studied in essential hypertensive patients and in normal subjects. Verapamil, 160 mg orally, reduced blood pressure within 60 minutes in 22 hypertensive patients, but not in 12 normotensive subjects. Nifedipine, 10 mg sublingually, reduced blood pressure within 15 minutes in 19 hypertensive patients, but not in 7 normotensive subjects. Plasma noradrenaline was significantly increased both in normal subjects and in hypertensive patients only after nifedipine was administered. Verapamil (80 mg three times a day) first, and nifedipine (10 mg three times a day) thereafter, or vice versa, were given to 12 hospitalized hypertensive patients on a fixed sodium and potassium intake; the drugs produced similar blood pressure reductions, but heart rate and plasma catecholamines were increased only after nifedipine (p less than 0.05). Neither drug affected plasma volume, aldosterone or plasma renin activity. Long-term ambulatory treatment with verapamil (80 or 160 mg three times a day for 2 to 4 months) or nifedipine (10 mg three times a day for 2 months) produced changes in all variables that were similar to those observed in the hospital (controlled) study. Shortening fraction was significantly increased after nifedipine (p less than 0.05) but no change was observed after verapamil. In conclusion, blood pressure is effectively reduced by both verapamil and nifedipine; an appreciable adrenergic stimulation may be caused by nifedipine, but usually not by verapamil, and fluid retention, renin release or myocardial depression is not observed during verapamil or nifedipine treatment.

Evidence that prostacyclin modulates the vascular actions of calcium in man

Increases in extracellular calcium (Ca++) can alter vascular tone, and thus may result in increased blood pressure (Bp) and reduced renal blood flow (RBF). Ca++ can stimulate prostaglandin E2 (PGE2) and/or prostacyclin (PGI2) release in vitro, which may modulate Ca++ vascular effects. However, in man, the effect of Ca++ on PG release is not known. To study this, 14 volunteers received low-dose (2 mg/kg Ca++ gluconate) or high-dose (8 mg/kg) Ca++ infusions. The low-dose Ca++ infusion did not alter systemic or renal hemodynamics, but selectively stimulated PGI2, as reflected by the stable metabolite 6-keto-PGF1 alpha in urine (159 +/- 21-244 +/- 30 ng/g creatinine, P less than 0.02). The same Ca++ infusion given during cyclooxygenase blockade with indomethacin or ibuprofen was not associated with a rise in PGI2 and produced a rise in Bp and fall in RBF. However, sulindac, reported to be a weaker renal PG inhibitor, did not prevent the Ca++ -induced PGI2 stimulation (129 +/- 33-283 +/- 90, P less than 0.02), and RBF was maintained despite similar increases in Bp. The high-dose Ca++ infusion produced an increase in mean Bp without a change in cardiac output, and stimulated urinary 6-keto-PGF1 alpha to values greater than that produced by the 2-mg/kg Ca++ dose (330 +/- 45 vs. 244 +/- 30, P less than 0.05). In contrast, urinary PGE2 levels did not change. A Ca++ blocker, nifedipine, alone had no effect on Bp or urinary 6-keto-PGF1 alpha levels, but completely prevented the Ca++ -induced rise in Bp and 6-keto-PGF1 alpha excretion (158 +/- 30 vs. 182 +/- 38, P greater than 0.2). However, the rise in 6-keto-PGF1 alpha was not altered by the alpha 1 antagonist prazosin (159 +/- 21-258 +/- 23, P less than 0.02), suggesting that calcium entry and not alpha 1 receptor activation mediates Ca++ pressor and PGI2 stimulatory effects. These data indicate a new vascular regulatory system in which PGI2 modulates the systemic and renal vascular actions of calcium in man.

Renal effects of nicardipine in patients with mild-to-moderate essential hypertension

We studied the renal effects of nicardipine, a calcium entry blocker, in seven patients with mild-to-moderate essential hypertension. Glomerular filtration rate (GFR) and renal blood flow (RBF) were measured by means of thiosulfate and para-aminohippurate, respectively. Intravenous administration of nicardipine hydrochloride (0.5 mg) increased RBF by 26.8 +/- 5.8% (mean +/- SEM, p less than 0.01), GFR by 35.4 +/- 12.4% (p less than 0.05), and urinary excretion of sodium by 56.4 +/- 10.7% (p less than 0.05) with a significant (p less than 0.01) reduction in systolic and diastolic blood pressure as compared to control values. Nicardipine decreased total renal vascular resistance by 30.0 +/- 3.2% (p less than 0.05) from the control value, while filtration fraction remained unchanged. Our results indicate that nicardipine has several favorable renal effects with a concomitant hypotensive action in patients with mild-to-moderate essential hypertension.

Calcium channel blockers and treatment of hypertension

Over the past years, research efforts have been focused on the pathophysiologic role of calcium ions, and the implication for the potential role of calcium channel blockers in the management of essential hypertension. Numerous studies have shown that nifedipine and verapamil are effective antihypertensive agents, initial experience with diltiazem is also encouraging. The magnitude of blood pressure reduction with these drugs is related to the pre-treatment blood pressure. In refractory hypertension, combination with other antihypertensive agents provide additive effect. In the elderly population and in patients with ischemic heart disease, supraventricular arrhythmia, bronchospastic disease, peripheral vascular disease or diabetes mellitus, the calcium channel blockers offer potential advantages over other antihypertensive agents. Experimental studies also suggest that these drugs may reverse ventricular hypertrophy. When long-term safety with these drugs is documented from well-controlled clinical trials, the calcium channel blockers may be our first line of therapy for the management of hypertension.

Acute effect of nifedipine on blood pressure and left ventricular ejection fraction in severely hypertensive outpatients: predictive effects of acute therapy and prolonged efficacy when added to existing therapy

Nifedipine is known to reduce blood pressure both acutely and chronically. However, the following questions remain to be answered: can nifedipine be given acutely and safety to patients with severe hypertension in an outpatient setting, would its efficacy be retained with long-term therapy, and is nifedipine safe in the presence of cardiomegaly? Nifedipine (10 mg capsule sublingually) was given to 46 outpatients with severe or apparently refractory hypertension; 19 were followed-up for 18 months and 18 for 24 months. Nifedipine reduced blood pressure acutely and safely in 43 of 46 outpatients (mean control diastolic pressure 137 mm Hg), irrespective of prior treatment regimen. Blood pressure levels after 2 to 24 months of twice daily oral nifedipine (10 mg) were similar to 20-minutes levels, showing that tolerance did not occur. In a separate series of 37 patients, who had radiologic cardiomegaly in addition to hypertension, the control ejection fraction was 62%. Nifedipine, when used acutely, slightly increased the ejection fraction to 65% (p less than 0.005). Our studies show that in outpatients with severe hypertension, sublingual nifedipine is an antihypertensive agent which acts swiftly and safely, without causing a decrease in the ejection fraction when it is used for acute blood pressure reduction, and that subsequent therapy with oral nifedipine results in a predictive long-term hypotensive effect.

Calcium-channel blockers for combined angina pectoris and systemic hypertension

Calcium-channel blockers have been successfully used in the treatment of angina of effort and systemic hypertension. Many patients present with concomitant angina pectoris and hypertension. Controlled clinical trials demonstrate that the calcium-channel blockers are safe and effective as monotherapy in the treatment of these patients, and that their use compares favorably with that of propranolol. The effectiveness of these agents in hypertension appears to be primarily due to their ability to induce systemic vasodilation. Calcium-channel blockers have several therapeutic effects in angina pectoris. Beneficial actions on the major determinants of oxygen consumption, i.e. heart rate, blood pressure and contractility, are generally seen. The potent coronary vasodilating actions of these agents allow for increased coronary blood flow. Improvements in ventricular compliance, regression of left ventricular hypertrophy and cardioprotection appear to be additional effects of the calcium-channel blockers; their contribution to the drugs' overall therapeutic efficacy is presently being evaluated. Calcium-channel blockers are a welcome addition to drug regimens available for the management of patients with coexisting angina pectoris and hypertension.

[Prevention of hypertensive attacks after carotid surgery. The value of nifedipine and diltiazem]

A randomized study was carried out to determine whether postoperative administration of either intranasal nifedipine or intravenous diltiazem was effective in preventing hypertensive episodes after carotid endarterectomy. Sixty-three consecutive patients undergoing this surgery were randomly assigned to three groups (n = 21): control (C), nifedipine (N) and diltiazem (D). Anaesthesia was induced with flunitrazepam (0.02 mg X kg-1), fentanyl 6 micrograms X kg-1 and pancuronium (0.1 mg X kg-1), and maintained by N2O/O2 (50%), additional fentanyl and halothane or enflurane when warranted. Postoperatively, patients were warned whilst under mechanical ventilation in a recovery room. Upon arrival in the recovery room, intranasal nifedipine (10 mg) was given to patients included in group N, while patients from group D received an intravenous dose of 0.3 mg X kg-1 of diltiazem, followed by a continuous infusion of 3 micrograms X kg-1 X min-1 until 15 min after extubation. No preventive treatment was given to patients in group C. If postoperative systolic blood pressure rose to more than 180 mmHg, 10 mg of nifedipine were administered intranasally. During the postoperative period, 13 patients from group C, 5 from group N and 4 from group D exhibited hypertensive episodes (systolic blood pressure greater than 180 mmHg or diastolic blood pressure greater than 100 mmHg). Intranasal administration of 10 mg nifedipine led to the normalization of blood pressure in 20 out of these 22 patients. This study confirmed the high incidence of hypertensive attacks after carotid endarterectomy, and showed that prophylactic administration of nifedipine or intravenous diltiazem was highly effective in preventing such hypertensive episodes.

Relative potency of a beta-blocking and a calcium entry blocking agent as antihypertensive drugs in black patients

The short-term efficacy of nitrendipine (N) as a first stage antihypertensive drug in black patients has been assessed and compared with acebutolol (A) in a double-blind study. Forty patients were randomized and after a 4 week run-in period on placebo, the active treatment was administered for 6 weeks starting with 20 mg N or 200 mg A once daily. The dose was increased up to 60 mg N or 600 mg A as needed. Nitrendipine appeared to be more efficient than acebutolol in reducing blood pressure and the N-induced fall in blood pressure was achieved after 2 weeks. After 2 and 6 weeks on N, the recumbent blood pressure was decreased by 13% and 12% for the systolic and by 14% and 11% for the diastolic pressure. The concurrent decreases in the A group averaged 4% and 5% for the systolic and 5% and 10% for the diastolic pressure after 2 and 6 weeks. Pulse rate and plasma renin activity in the N group were slightly increased and body weight was decreased at the end of the active treatment period.

Blood pressure and hormonal responses to sublingual nifedipine in acute childhood hypertension

Twelve infants and children were treated with sublingual application of the calcium antagonist nifedipine. Blood pressure fell within 1 h following administration of nifedipine to age-related normal values. Whereas plasma renin activity, plasma concentrations of aldosterone and arginine vasopressin did not change within 1 h after drug application, plasma noradrenaline rose (p less than 0.05), probably in response to vasodilatation. Plasma concentration of nifedipine at 30 and 60 min after application correlated positively with the fall in mean arterial pressure. Nifedipine was well tolerated and appeared to be an effective and safe drug in the treatment of acute rises of blood pressure in infants and children.

Dose response and length of action of nifedipine capsules and tablets in patients with essential hypertension: a randomised crossover study

Twelve patients with essential hypertension on no other drug treatment were entered into a randomised crossover study of 5, 10 and 20 mg capsules of nifedipine given 3 times a day and 20 mg tablets given twice a day. Each dose was given for 2 weeks in a random order. All forms of nifedipine were effective in lowering blood pressure. However, 5 mg capsules were less effective than the 10 and 20 mg capsules or 20 mg tablets. There was little to choose between the latter. All doses of nifedipine were more effective 1 and 3 h after the dose compared to subsequent times afterwards. Indeed, as time elapsed after the last dose up to 12 h, there was a gradual increase in blood pressure. However, even at 12 h the 10, 20 mg capsules and 20 mg tablets were still causing an approximate 10% reduction in blood pressure. Nifedipine tablets are as effective as capsules though they might be longer acting, particularly around 6 h after the last dose.

Management of urgent hypertension: a comparison of oral treatment regimens in the emergency department

Urgent hypertension is defined by severe elevations of blood pressure without associated end-organ damage. The use of parenteral agents for this entity entails intensive monitoring and the potential for significant hemodynamic complications. Therefore, various oral regimens have been studied. Herein described are mechanisms of action, pharmacokinetics, clinical efficacy, and side effects of oral agents used in the treatment of urgent hypertension.

Nifedipine in combination therapy for chronic hypertension. A review

Results are presented from a study conducted in twelve male patients with hypertension who were treated during alternating one-month periods with a calcium channel blocker, a beta blocker, or a combination of both drugs. After one month of placebo therapy, the patients received 10 mg of nifedipine three times daily, 100 mg of metoprolol twice daily plus 10 mg of nifedipine three times daily, or 100 mg of metoprolol twice daily during successive periods. Nifedipine monotherapy resulted in a significant decrease in both systolic and diastolic blood pressures at rest and in systolic blood pressure during exercise. Monotherapy with metoprolol also significantly reduced systolic blood pressure during exercise. Combination therapy with the calcium channel blocker and the beta blocker produced a significantly greater decrease in both resting and exercise blood pressures than with either drug alone, with achievement of adequate blood pressure control in all patients.

Body sodium-blood volume state, aldosterone, and cardiovascular responsiveness after calcium entry blockade with nifedipine

Exchangeable sodium, blood volume, plasma norepinephrine (NE), epinephrine, renin and aldosterone levels, and pressor responses to infused NE or angiotensin II (AII) were assessed in ten patients with essential hypertension on placebo, following 6 to 8 weeks of calcium-antagonist nifedipine (NIF), 3 X 10 to 20 mg/day, and after 6 to 8 weeks on NIF combined with the diuretic chlorthalidone (CHLOR), 25 to 50 mg/day. Pressor effects of infused calcium also were evaluated on placebo and NIF. Supine blood pressure was decreased from 151/97 +/- 5/2 (SEM) to 132/88 +/- 6/2 mm Hg after NIF alone (P less than 0.05) and to 124/83 +/- 7/3 mm Hg after NIF + CHLOR (P less than 0.01). Body wt was increased from 72.7 to 73.9 kg on NIF alone (P less than 0.05), but decreased to 72.1 (P less than 0.05 compared with placebo) after adding CHLOR. Exchangeable sodium also rose from 2642 +/- 237 to 3360 +/- 266 mmoles on NIF (+ 27%; P less than 0.01) and returned to control values (2638 +/- 248 mmoles) after addition of CHLOR. Plasma volume was only slightly modified on NIF (from 2621 +/- 193 to 2751 +/- 160 ml; + 5%), but was reduced to 2232 +/- 231 ml on NIF + CHLOR (P less than 0.05). Responses of circulating aldosterone to AII were similarly diminished (P less than 0.01) during both conditions. Heart rate, supine and upright plasma renin, aldosterone and catecholamine levels, and pressor responses to NE, AII, or calcium were not consistently changed.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of the new calcium antagonist nisoldipine (BAY k-5552) on myocardial infarct size limitation in conscious dogs

The effect of the new calcium antagonist nisoldipine (BAY k-5552) on myocardial infarct size was studied in four groups of conscious dogs undergoing acute left anterior descending coronary artery occlusion. Group I received placebo for 48 hours before and for 24 hours after occlusion; group II received placebo before and nisoldipine (0.3 mg/kg orally every 6 hours) after occlusion; group III received nisoldipine before and placebo after occlusion; and group IV received nisoldipine before and after occlusion. Infarct size was quantified with the tetrazolium red staining technique. Infarcted ventricular mass was 24.5 +/- 6.6% (mean +/- SD) for group I (control), 21.4 +/- 4.4% for group II (p = NS against control), 13.9 +/- 4.5% for group III (p less than 0.05), and 14.1 +/- 4.0% for group IV (p less than 0.05). Post occlusion sudden death was 30% in non-pretreated dogs and 0% in pretreated dogs (p less than 0.001). We conclude that prophylactic oral treatment with nisoldipine decreases infarct size and lowers the incidence of sudden death in conscious dogs undergoing acute coronary occlusion.

Syncope and conduction disturbances following sublingual nifedipine for hypertension

We present a case of a 79-year-old woman with periods of syncope, complete heart block (CHB), and ventricular standstill during periods of increased vagal tone following sublingual nifedipine for hypertension. The syncopal episodes were associated with periods of elevated vagal tone (micturition and vomiting) with one monitored episode showing a clear time course of emesis; CHB then ensued, progressing to ventricular standstill with loss of consciousness that resolved over several minutes. Although nifedipine is not thought to affect conduction at current clinical dosages, it seems likely that the additive effects of nifedipine and elevated vagal tone produced the observed conduction abnormalities. This is the first case report of nifedipine administration followed by syncope and conduction disturbances.

Nifedipine in the treatment of essential hypertension

The antihypertensive efficacy of nifedipine as a second-step drug in 24 patients, uncontrolled by a diuretic alone, was studied according to a double-blind placebo-controlled protocol. A significant blood pressure lowering was observed in nine out of 12 patients receiving the active drug and four out of 12 receiving placebo. Average mean blood pressure decreased by 13 +/- 1 mm Hg in the active drug group versus 5 +/- 3 mm Hg in the placebo group (P less than .02). There were no consistent changes or significant differences in heart rate or in the levels of plasma renin activity and plasma catecholamines between the two groups. In conclusion, nifedipine appears to be a safe and effective antihypertensive agent when used in conjunction with a diuretic for the treatment of moderately severe hypertension.

Hemodynamic effects of a new alpha- and beta-adrenergic receptor inhibitor with calcium entry blocking effects (CGS 10078B) in WKY and SHR rats

The immediate acute hemodynamic effects of CGS 10078B, a new agent with combined alpha- and beta-adrenergic antagonist with slow channel calcium entry blocking effects, were studied in normotensive Wistar-Kyoto (WKY) and spontaneously hypertensive (SHR) rats. Heart rate (HR), mean arterial pressure (MAP), cardiac index (CI), total peripheral resistance index (TPRI), and regional hemodynamic measurements were determined before and two hours after its administration (10 mg/kg, gavage) using the combined radioactive reference sample and microsphere techniques (85SR and 141Ce). The agent significantly reduced MAP (168 +/- 5 to 158 +/- 5 mm Hg; p less than 0.02) after 20 minutes without changing HR in SHR. After two hours MAP, HR, and Cl were significantly reduced without change in TPRI. Only Cl decreased (p less than 0.05) in WKY, presumably from its beta receptor antagonist effects. Blood flow to the major organs (eg, heart, brain, and kidneys) was maintained in both groups of rats. These hemodynamic effects reflect the combined actions of this new agent and suggest its potential value for the treatment of hypertension.

Working ability and exercise tolerance during treatment of a mild hypertension. I. Comparison between a beta-adreno-receptor blocking drug and a calcium antagonist

A randomized cross-over trial was undertaken on 21 occupationally active persons who had a stable mild or moderate hypertension with the purpose of comparing the effect of a beta-adreno-receptor blocking agent (atenolol) with that of a calcium channel inhibitor (nifedipine). The doses recommended by the manufactures were used. Atenolol (100 mg) given once a day resulted in a marked hypotensive effect at rest as well as during exercise, the compliance was satisfactory, and the hemodynamic changes were not reflected in unfavourable side effects during muscular exercise or in the subjects own personal assessment of fatigue during the exercise tests which ranged in energy expenditure from about three to six times the resting level. However, unfavourable, modest side effects occurred in two subjects during atenolol medication to the extent that they wanted to terminate the study. Nifedipine therapy with doses of 10 mg, three times a day, resulted in a modest, but statistically insignificant reduction in arterial blood pressure, which contrasts with previous published results. It is suggested that the modest effect is caused or related to the poor compliance and a daily dose that was quantitatively too small. No unfavourable side effects were seen during muscular efforts when the subjects were on nifedipine medication.

Calcium-entry blocking agents in the treatment of systemic hypertension

Calcium-entry blocking agents resemble established dilators such as diazoxide, minoxidil and hydralazine in that they act predominantly on the arterial resistance vessels and have little or no effect upon the veins. They have therefore been evaluated in the treatment of hypertension. Controlled studies have shown that verapamil and nifedipine are effective in decreasing blood pressure when given as sole agents. The antihypertensive effect of nifedipine is additive with that of a beta blocker, and nifedipine is also effective when given as a "third step" agent in combination with a beta blocker (or alpha methyldopa) and a diuretic. In contrast to other directly acting dilators, nifedipine causes, at most, only moderate stimulation of renin secretion and verapamil does not increase renin release at all; neither drug induces sodium retention. Both verapamil and nifedipine produce a moderate incidence of unwanted effects; these are mostly subjective in nature, but verapamil may cause constipation that is occasionally severe and nifedipine sometimes causes ankle swelling. Calcium-entry blockers should be considered as initial therapy when some contraindication exists to the use of other standard drugs. Nifedipine appears preferable to hydralazine for use in combination with a beta blocker and a diuretic: it is at least as effective as hydralazine and has a lower incidence of serious adverse effects.

Acute haemodynamic effects of felodipine in congestive heart failure

The haemodynamic effects of felodipine 0.1 mg/kg p.o., a new arteriolar dilator, were studied in 7 patients with severe congestive heart failure of NYHA Class IV (Group A) and in 3 patients in Class II-III (Group B). In Group A, measurements were made before and 1 and 4 h after felodipine administration. There was a substantial fall in systemic arterial pressure, which was not associated with a compensatory tachycardia. In fact, there was a fall in heart rate from 92 to 82 beats/min 1 h after drug administration. The pulmonary capillary wedge pressure was reduced from 22 to 14 mm Hg and the cardiac index and stroke volume index rose significantly. Consequently, there was a marked reduction in systemic vascular resistance. In Group B measurements were performed at rest and during exercise before and 1 h after felodipine. The pulmonary wedge capillary pressure during exercise was lower than in the control situation. Coronary sinus flow was increased and there was a pronounced fall in coronary vascular resistance. The results would suggest that felodipine, by virtue of its ventricular unloading potency, might be a valuable drug in the treatment of congestive heart failure.

Slow-release nifedipine as a single or additional agent in the treatment of essential hypertension--a placebo-controlled crossover study

The efficacy and safety of a new slow-release formulation of nifedipine ("Adalat Retard") were assessed in a double-blind cross-over trial in 19 subjects with essential hypertension (14 male, 5 female--ages: 34-72 years), 14 of whom continued previous antihypertensive medication. There were two 6 week treatment phases in which nifedipine 20 mg twice daily and placebo tablets twice daily were administered in random order. Supine mean blood pressure was 115 +/- 2 mm Hg during the placebo phase and 105 +/- 2 mm Hg during the nifedipine phase (p less than 0.001); and standing mean blood pressure was 121 +/- 2 mm Hg after placebo and 110 +/- 2 mm Hg after nifedipine (p less than 0.001). The magnitude of the blood pressure difference between the two phases was not related either to age or to the placebo phase blood pressure. The hypotensive effect of nifedipine was observed when administered as a single agent or in combination with diuretic and/or beta blocker. Heart rate was increased after nifedipine--75 +/- 2 beats/minute compared with 71 +/- 2 beats/minute after placebo (p less than 0.01). In this dose nifedipine (as "Adalat Retard") is an effective hypotensive agent which is a useful addition to presently available therapy.

The acute haemodynamic effects of oral nicardipine

The haemodynamic effects of oral nicardipine at two different doses were assessed in fifteen patients at rest following diagnostic cardiac catheterisation. Six patients received four doses of 20 mg nicardipine hydrochloride orally every 8 h, and nine patients received four doses of 30 mg orally every 8 h. No side effects were encountered with either dose. At both dose levels, there was a significant fall in systemic vascular resistance, significant increases in heart rate and cardiac output, and no change in stroke volume index. No changes were seen in pulmonary vascular haemodynamics, and there were no significant changes in mean arterial pressure. Plasma levels of nicardipine reached a peak within 1 h. In parallel with the haemodynamic effects, the plasma concentrations achieved after the third and fourth doses were higher than after the first dose. These haemodynamic changes are consistent with a vasodilator effect, which produces a decrease in peripheral vascular resistance. It would appear that the 30 mg dose has a more potent vasodilator action than the 20 mg dose and, in the patients studied, this larger dose was not associated with any side effects.

Treatment of normotensive and hypertensive patients with preterm labor using oral nifedipine, a calcium antagonist

The calcium antagonist nifedipine was tried on 28 patients with preterm labor. In eight patients the disorder was also accompanied by hypertension. In 80% of the patients delivery could be postponed for more than 3 days during which time corticosteroids were given to accelerate fetal lung maturation. On average, delivery occurred 12 days after start of treatment (delay beyond 36 weeks gestation not being included in the calculations). All patients with increased blood pressure were normotensive within 12 h of the start of treatment. There were no serious maternal or fetal side effects and no perinatal deaths. At 2 and 6 months after delivery all women were normotensive and all children were alive and well.

Calcium channel blockers as antihypertensive agents

Because of their unique action on the cardiovascular system, the calcium channel blockers have generated a great deal of excitement among pharmacologists, physiologists, and clinicians. One obvious potential application for these drugs is in antihypertensive therapy and, although experience with these agents for this indication is limited in the United States, it is considerable in Europe and Japan. These agents' ultimate role in antihypertensive therapy, however, has not been established. Since the available calcium channel blockers are structurally diverse, it is uncertain whether they will have comparable effects in hypertension. The rationale for the use of calcium channel blockers in treating hypertension and the relevant pharmacologic actions of these agents is discussed, along with a summary of some of the clinical trials, observations from our own experience with these drugs, and speculation about their future role in antihypertensive therapy.

Calcium channel blockers in emergency medicine

Diltiazem, nifedipine, and verapamil inhibit calcium entry into cells via different mechanisms with different pharmacologies. They display different relative effects on different cardiovascular functions, a complex interplay of direct actions and adrenergic reflexes. Peripheral arterial vasorelaxation causes adrenergic reflex activity which opposes their direct negative chronotropic, dromotropic, inotropic, and hypotensive actions. Verapamil's most potent activity is electrophysiologic, and nifedipine's effects are hemodynamic; diltiazem acts like a less-potent combination of verapamil and nifedipine. All three drugs are efficacious in angina. These three drugs may not be interchangeable in all patients, but individualization of therapy is possible. Future indications for calcium channel blocker therapy may include hypertrophic cardiomyopathy, cerebral vasospasm, migraine headaches, pulmonary hypertension, asthma, esophageal spasm, intestinal ischemia, Raynaud's phenomenon, dysmenorrhea, and premature labor.