Multiple effects of calcium entry blockers on renal function in hypertension

Hypertension in the Elderly

More than 50% of the U.S. population 65 years and older have elevated systolic pressure with or without elevated diastolic pressure--and thus in either case are at risk for cerebrovascular and cardiovascular sequelae. As therapy lowers diastolic pressure, however, mortality can increase, presumably when blood pressure is brought down to levels that compromise perfusion.

Advantages of new cardiovascular risk-assessment strategies in high-risk patients with hypertension

BACKGROUND

Accurate assessment of cardiovascular disease (CVD) risk in patients with hypertension is important when planning appropriate treatment of modifiable risk factors. The causes of CVD are multifactorial, and hypertension seldom exists as an isolated risk factor. Classic models of risk assessment are more accurate than a simple counting of risk factors, but they are not generalizable to all populations. In addition, the risk associated with hypertension is graded, continuous, and independent of other risk factors, and this is not reflected in classic models of risk assessment.

OBJECTIVE

This article is intended to review both classic and newer models of CVD risk assessment.

METHODS

MEDLINE was searched for articles published between 1990 and 2005 that contained the terms cardiovascular disease, hypertension, or risk assessment. Articles describing major clinical trials, new data about cardiovascular risk, or global risk stratification were selected for review.

RESULTS

Some patients at high long-term risk for CVD events (eg, patients aged <50 years with multiple risk factors) may go untreated because they do not meet the absolute risk-intervention threshold of 20% risk over 10 years with the classic model. Recognition of the limitations of classic risk-assessment models led to new guidelines, particularly those of the European Society of Hypertension-European Society of Cardiology. These guidelines view hypertension as one of many risk and disease factors that require treatment to decrease risk. These newer guidelines include a more comprehensive range of risk factors and more finely graded blood pressure ranges to stratify patients by degree of risk. Whether they accurately predict CVD risk in most populations is not known. Evidence from the Valsartan Antihypertensive Long-term Use Evaluation (VALUE) study, which stratified patients by several risk and disease factors, highlights the predictive value of some newer CVD risk assessments.

CONCLUSION

Modern risk assessments, which include blood pressure along with a wide array of modifiable risk factors, may be more accurate than classic models for CVD risk prediction.

Effects of nifedipine, verapamil and diltiazem on serum biochemical parameters and aortic composition of atherosclerotic chickens

Calcium appears to be involved in many of the cellular events, which are thought to be important in atherogenesis. In this study, we examine the effects of three calcium entry blockers (nifedipine, verapamil, and diltiazem at clinical and higher doses) on serum biochemical parameters and aortic calcium, cholesterol and triglyceride concentrations of atherosclerotic egg-fed chickens. All egg-fed chickens (treated and non-treated) showed an increase in serum total cholesterol, LDL-cholesterol and triglycerides without significant effect when calcium entry blockers were used. Increased HDL values were observed in clinical and high-dose nifedipine and clinical dose verapamil groups. The high-dose diltiazem group presented increased zinc values with respect to the clinical dose diltiazem and control groups. The sodium concentrations were significantly decreased in all the groups of animals treated with calcium entry blockers at high-doses and nifedipine at clinical doses. Measurements of aortic calcium concentration showed a significant decrease in the high-dose nifedipine and verapamil groups. Calcium channel blockers had a tendency to decrease total cholesterol in aortas. The values were statistically significant for the high-dose verapamil, and nifedipine groups. Only nifedipine showed a significant decrease for this parameter at clinical dosages. Triglyceride concentrations in aortas were significantly low in animals fed an atherogenic diet and treated with calcium channel blockers, without differences between drugs or dosages used in the experiment. In addition, the chicken atherosclerosis model has proved itself useful and very suitable for in vivo drug intervention studies.

Blood pressure management in the kidney transplant recipient

Hypertension is extremely common after kidney transplantation. It has been observed in up to 80% to 90% of patients. The etiologies are multifactorial but, in large part, rest with the native kidneys, concomitant immunosuppressant drugs, and behavioral factors that promote the development of higher levels of blood pressure, including obesity, salt intake, smoking, and alcohol consumption. There is a direct relationship between kidney allograft failure and level of systolic blood pressure during follow-up. Patients with a systolic blood pressure greater than 180 mmHg have 2-fold greater risk of loss of graft function compared with patients with systolics of less than 140 mmHg. A similar pattern exists for diastolic blood pressure. Some investigators have also demonstrated that higher levels of blood pressure also correlate with an increased risk of acute graft rejection, particularly in African Americans. What is not known is whether more effective control of arterial pressure in the transplant patient will reduce the likelihood of graft loss and improve survival. No prospective outcome trials have ever been performed. However, it is likely, given the marked success of better control of blood pressure in nontransplant patients in reducing cardiovascular death and the rate of progression of kidney disease, that similar benefits will be appreciated in the transplant patient. Given the greater cardiovascular burden in the kidney transplant recipient because of the presence, in many cases, of diabetes and hypertension, perhaps even more risk reduction may be realized with incremental reductions in blood pressure. Preferred treatment strategies for lowering blood pressure depends on the mechanism of action and medical comorbidity. Drugs that block the renin-angiotensin system should be preferentially considered because they may have similar advantages in delaying progressive loss of allograft function, much in the same way they have proven benefits in protecting native kidney function. Treating blood pressure in the kidney transplant recipient is a complicated process because patients are already on multiple medications and many will need 3 to 5 antihypertensive drugs to achieve optimal control of blood pressure, which should preferably be below 130/80 mmHg.

Monotherapy versus combination therapy as first line treatment of uncomplicated arterial hypertension

Mild to moderate hypertension still remains poorly controlled. This relates to multiple factors including low antihypertensive efficacy of single drug therapies reluctance of primary care physicians to modify/titrate initially chosen therapy to obtain target blood pressure, and poor compliance with medication. Several guidelines for the treatment of high blood pressure now include combination therapy with low doses of 2 drugs as one of the strategies for the initial management of mild/moderate arterial hypertension. Evidence discussed in this article points to superior control of blood pressure by combinations of low doses of 2 drugs as compared with monotherapy in regular doses. This superior effectiveness of combined therapy relates to a better antihypertensive efficacy and higher response rates in the low range of doses as the result of complementary mechanisms of antihypertensive effects, better tolerance as a result of a lower rate of adverse effects in the low dose range, improved compliance from better tolerance and simple drug regimen, and lower cost. Whether increased use of fixed low dose combination therapies would translate to better control of arterial hypertension in the population and thereby further reduction of cardiovascular/cerebrovascular morbidity and mortality caused by hypertension remains to be assessed.

Influence of race and dietary salt on the antihypertensive efficacy of an angiotensin-converting enzyme inhibitor or a calcium channel antagonist in salt-sensitive hypertensives

Dietary salt restriction is a recommended adjunct with antihypertensive therapy. There may be racial differences in blood pressure response to salt restriction while on antihypertensive therapy. We performed a multicenter, randomized, double-blind, placebo-controlled, parallel-group clinical trial (black, n=96; Hispanic, n=63; white, n=232). Participants were initially preselected for stage I to III hypertension and then further selected for salt sensitivity (> or = 5 mm Hg increase in diastolic blood pressure after 3 weeks of low salt [< or = 88 mmol/d Na+] and high salt [>190 mmol/d Na+] diet). We compared the antihypertensive effect of an angiotensin-converting enzyme inhibitor (enalapril 5 or 20 mg BID) or a calcium channel antagonist (isradipine 5 or 10 mg BID) during alternating periods of high and low salt intake. The main outcome measure was blood pressure change and absolute blood pressure level achieved with therapy. During the high salt diet (314.7+/-107.5 mmol/d urinary Na+) there was greater downward change in blood pressure with both enalapril and isradipine compared with the low salt diet (90.1+/-50.8 mmol/d Na+); however, the absolute blood pressure achieved in all races was consistently lower on a low salt diet for both agents. Black, white, and Hispanic isradipine-treated salt-sensitive hypertensives demonstrated a smaller difference between high and low salt diets (black, -3.6/-1.6 mmHg; white, -6.2/-3.9 mmHg; Hispanic, -8.1/-5.3 mm Hg) than did enalapril-treated patients (black, -9.0/-5.3 mm Hg; white, -11.8/-7.0 mm Hg; Hispanic, -11.1/-5.6 mm Hg). On the low salt diet, blacks, whites, and Hispanics had similar blood pressure control with enalapril and isradipine. On the high salt diet, blacks had better blood pressure control with isradipine than with enalapril, whereas there was no difference in the blood pressure control in whites and Hispanics treated with either drug. Dietary salt reduction helps reduce blood pressure in salt-sensitive hypertensive blacks, whites, and Hispanics treated with enalapril or isradipine. These data demonstrate that controlling for salt sensitivity diminishes race-related differences in antihypertensive activity.

Renal effects of the calcium channel blocker aranidipine and its active metabolite in anesthetized dogs and conscious spontaneously hypertensive rats

The purpose of this study was to investigate the renal effects of aranidipine, a novel calcium channel blocker of the dihydropyridine type, and its active metabolite in anesthetized dogs and conscious spontaneously hypertensive rats (SHRs). When infused into the renal artery in anesthetized dogs, aranidipine (0.03 microg/kg/min) induced sustained increases in urine volume and urinary excretion of sodium and of potassium. This effect was greater than that elicited by nifedipine (0.1 microg/kg/min). The aranidipine metabolite, M-1 (0.1 microg/kg/min), also caused diuresis and natriuresis almost equal to those of nifedipine. The stop-flow experiment using the anesthetized dog showed that intrarenal infusion of aranidipine (0.03 microg/kg/min), as well as nifedipine (0.1 microg/kg/min), produced natriuresis at the distal tubular site rather than at the proximal site. Aranidipine (0.3, 1, and 3 mg/kg), when administered orally, dose-dependently increased urine volume and urinary excretion of electrolytes in conscious saline-loaded SHRs. M-1 (10 mg/kg, p.o.) also showed diuretic and natriuretic effects comparable to those of nifedipine (10 mg/kg) in SHRs. In addition, after repeated oral administration of aranidipine for 7 days, short-term tolerance was not found for its diuretic and natriuretic effects in SHRs. These results suggest that, apart from antihypertensive efficiency, aranidipine may offer a therapeutic advantage by producing diuresis and natriuresis in hypertensive patients. The metabolite of aranidipine may contribute, in part, to the diuretic, natriuretic, and antihypertensive effects of aranidipine.

Renal changes induced by nitric oxide and prostaglandin synthesis reduction: effects of trandolapril and verapamil

The benefits of the simultaneous administration of low doses of a calcium antagonist and a converting enzyme inhibitor in the treatment of hypertension and renal vasoconstriction are well established. The objective of this study was to evaluate whether the administration of low doses of a calcium antagonist and a converting-enzyme inhibitor have beneficial effects in treating the renal alterations induced by the acute administration of a cyclooxygenase inhibitor when nitric oxide synthesis is reduced. These effects were examined in anesthetized dogs before and during an acute sodium load. It was found that the intrarenal infusion of meclofenamate (5 microg x kg[-1] x min[-1]), simultaneously with a low dose of NG-nitro-L-arginine methyl ester (1 microg x kg[-1] x min[-1]), produced a 40% decrease of renal blood flow and glomerular filtration rate and a reduction in the renal excretory response to the sodium load. In a second group of dogs, intrarenal verapamil (0.5 microg x kg[-1] x min[-1]) was effective in blocking the effects of nitric oxide and prostaglandin synthesis inhibition on sodium excretion and glomerular filtration rate but did not modify the effects on renal blood flow. An intrarenal infusion of trandolapril (0.3 microg x kg[-1] x min[-1]) was effective in a third group of dogs in reducing the renal hemodynamic effects but not in preventing the antinatriuretic effect observed in the first group. Finally, in a fourth group, the simultaneous administration of verapamil and trandolapril was effective in treating all the renal changes induced by the cyclooxygenase inhibitor when nitric oxide synthesis was reduced. These results suggest that the combination of low doses of trandolapril and verapamil has additive effects in treating the renal vasoconstriction and antinatriuresis induced by the acute administration of a cyclooxygenase inhibitor, when nitric oxide synthesis is reduced.

A comparison of the effect of ramipril, felodipine and placebo on glomerular filtration rate, albuminuria, blood pressure and vasoactive hormones in chronic glomerulonephritis. A randomized, prospective, double-blind, placebo-controlled study over two years

The effects of an ACE-inhibitor (ramipril), a calcium antagonist (felodipine) and placebo on glomerular filtration rate (GFR), urinary albumin/creatinine ratio, blood pressure (BP) and vasoactive hormones were investigated in a randomized, prospective, double-blind, placebo-controlled study of patients with chronic glomerulonephritis and hypertension, with measurements at entrance and after 12 and 24 months. In total, 33 patients were included: 21 completed the study with 7 patients in each group. GFR was measured as 51Cr-EDTA clearance and the vasoactive hormones with radioimmunoassays. The reduction in GFR was significantly more pronounced in the felodipine group (-7 ml/min) than in the ramipril group (0 ml/min) but the same as in the placebo group (-6 ml/min). The urinary albumin/creatinine ratio was significantly more reduced in the ramipril group (-74 mg/mmol) than in the placebo group (-11 mg/mmol), which did not deviate from the felodipine group (-10 mg/mmol). BP was significantly reduced by ramipril and felodipine, but not by placebo. Angiotensin II and aldosterone in plasma increased or tended to increase in the felodipine and placebo groups, but were unchanged in the ramipril group. Endothelin increased only in the placebo group, and vasopressin, atrial natriuretic peptide, and brain natriuretic peptide were not significantly changed in any of the groups. It is concluded that ramipril seems to be superior to felodipine in chronic glomerulonephritis owing to better preservation of GFR.

The natriuretic effect of nifedipine gastrointestinal therapeutic system remains despite the presence of mild-to-moderate renal failure

BACKGROUND

Calcium channel blockers facilitate the renal excretion of sodium and this effect is maintained during chronic administration of these drugs. However, it is unknown whether this natriuretic effect remains despite the presence of a decreased renal function.

OBJECTIVE

To compare the natriuretic capacity of nifedipine gastrointestinal therapeutic system (GITS) and lisinopril in patients with mild-to-moderate chronic renal failure.

METHODS

An open-label, randomized, comparative study was conducted to compare the natriuretic capacity of nifedipine GITS and lisinopril in the presence of mild-to-moderate renal failure (creatinine clearance 30-80 ml/min). After a wash-out period of 4 weeks an intravenous saline infusion (30 ml/kg of body weight of isotonic saline in 4 h) was performed and repeated after 4 weeks of active therapy. Two sex- and age-matched groups of hypertensive patients (n = 25) were included in the study. Renal failure was diagnosed as secondary to nephrosclerosis in all the patients.

RESULTS

A significant increase in the renal capacity to excrete the sodium load was observed in patients receiving nifedipine GITS (n = 11) but not in those taking lisinopril (n = 13). Both drugs controlled blood pressure to a similar extent. No changes were observed in body weight, glomerular filtration rate and renal plasma flow (measured as inulin and paraaminohippurate clearances). A significant drop was observed in urinary albumin excretion after lisinopril, but not after nifedipine. Heart rate was higher in nifedipine group.

CONCLUSION

The natriuretic capacity of nifedipine GITS remains despite the presence of mild-to-moderate chronic renal failure. Such an effect takes place in the absence of changes in renal hemodynamics, suggesting that it is caused by a direct tubular effect.

Antihypertensive and renal effects of isradipine in essential hypertension: focus on renin system activity

Calcium antagonists are known to exert various effects on the kidney that might modulate their antihypertensive potential. This study evaluated the renal effects, along with the efficacy, of isradipine in two subgroups of patients with mild to moderate essential hypertension (EH), defined according to plasma renin activity (PRA). Twenty-six patients were randomly assigned to receive 12-week treatment with slow-release isradipine (2.5-5 mg) or placebo. Assessment of PRA related to concurrent 24-hour sodium excretion was used to define patients with high/medium (n=16) and low renin profile (n=10). Urinary albumin excretion (UAE), serum creatinine and glomerular filtration rate (GFR, as endogenous creatinine clearance) were measured. Blood pressure (BP) decrease with isradipine was greater in the low PRA group as compared with the high/medium PRA group (P<0.05), and normalization of BP was achieved in all low-renin patients compared with 57% in the high/medium PRA group. BP reduction in the placebo group was statistically not significant. Isradipine, but not placebo, induced significant reduction in UAE (P<0.05); the decrease was similar in both PRA groups. Treatment did not cause any significant changes in GFR, PRA, urinary sodium or creatinine excretion, or serum aldosterone or creatinine concentrations. The decrease of BP in the whole isradipine-treated group was inversely correlated with pretreatment serum creatinine as well as with basal urinary creatinine excretion. In conclusion, the antihypertensive effect of isradipine was more pronounced in low-renin EH patients, despite similar effects on renal function and UAE in both PRA groups.

Effects of dietary docosahexaenoic acid on survival time and stroke-related behavior in stroke-prone spontaneously hypertensive rats

1. Dietary docosahexaenoic acid (DHA) suppressed the age-dependent increase in systolic blood pressure and prolonged the average survival time of stroke-prone spontaneously hypertensive rats (SHRSP). 2. Dietary DHA (1% and 5% in diets) altered the circadian rhythm of SHRSP, causing significant increases in ambulatory activity during the dark period. At the onset of stroke, desynchronization with light and dark phases and new biological rhythms were noted in all of the control SHRSP (DHA 0%). DHA treated SHRSP did not show such behavioral changes. 3. These effects were accompanied by the increase of DHA and the decrease of AA levels in plasma and brain cortex. 4. It was concluded that dietary DHA suppresses the development of hypertension and stroke-related behavioral changes, resulting in prolongation of the SHRSP's life span.

Efficacy, tolerability, and quality of life of losartan, alone or with hydrochlorothiazide, versus nifedipine GITS in patients with essential hypertension

A randomized, double-masked, parallel-group, multicenter clinical trial was conducted to compare the efficacy, tolerability, and effects on quality of life associated with the angiotensin II receptor antagonist losartan, alone or with hydrochlorothiazide (HCTZ), and the dihydropyridine calcium channel blocker nifedipine gastrointestinal therapeutic system (GITS) in patients whose sitting diastolic blood pressure measurements were between 95 and 115 mm Hg, inclusive, while receiving placebo. Patients were randomized to receive either losartan or nifedipine GITS in a double-masked, double-dummy fashion. A 4-week placebo washout period established baseline untreated blood pressure measurements and was followed by a 12-week active treatment period. Patients receiving losartan (n = 110) were initially given 50 mg once a day (QD) and could be titrated to losartan/HCTZ 50 mg/12.5 mg QD after 4 weeks followed by losartan/HCTZ 50 mg/25 mg QD after 8 weeks, as necessary. Patients in the nifedipine GITS group (n = 113) received 30 mg QD, which could titrated to 60 mg QD after 4 weeks followed by 90 mg QD after 8 weeks. Medication was titrated upward as necessary to achieve a sitting trough diastolic blood pressure < 90 mm Hg. Efficacy, tolerability, and quality-of-life scores were assessed after 12 weeks of each therapy. Trough sitting diastolic blood pressure reductions after 4, 8, and 12 weeks of therapy were clinically comparable: losartan, -8.9, -11.6, and -12.7 mm Hg, respectively, and nifedipine GITS, -9.3, -11.0, and -11.1 mm Hg, respectively, with the mean reduction in sitting diastolic blood pressure at 12 weeks in the losartan group 1.6 mm Hg lower (95% confidence interval, 3.4 mm Hg lower to 0.3 mm Hg Higher) than the mean reduction in sitting diastolic blood pressure in the nifedipine GITS group. Similarly, reductions in systolic blood pressure between the two treatment groups were comparable at all time points. The percentage of patients reaching the goal trough sitting diastolic blood pressure was comparable for the two treatment groups, with 74% of patients in the losartan regimen and 68% of patients in the nifedipine GITS regimen reaching the goal. Of patients reporting adverse events in the two groups (75 patients receiving losartan and 69 receiving nifedipine GITS), there was significantly more edema in the nifedipine GITS group (15% vs 4%; P = 0.005). Fourteen (12%) patients in the nifedipine GITS group were withdrawn due to an adverse event (eight of these were for edema). Six patients (5%) in the losartan group were withdrawn due to an adverse event (none of these patients had edema). There were significant differences in the patient-reported quality-of-life symptom bother inventory with respect to edema, with nifedipine GITS therapy causing significantly more bother due to edema in patients, regardless of whether that symptom was present at baseline (27% vs 9%; P = 0.0004). No statistically significant differences for bother due to the other symptoms in the inventory were noted. Of note, while the incidence of patient-reported symptom bother due to edema in the nifedipine GITS group was 27%, the incidence of physician-reported drug-related edema was 12%. This difference points to the need for improved physician-patient communication regarding adverse effects and their impact of patients' quality of life. In conclusion, a regimen of losartan, when compared with a regimen of nifedipine GITS, provides comparable efficacy, and with respect to edema, superior tolerability, less bother to patients, and fewer therapy dropouts.

Dietary docosahexaenoic acid (22: 6n-3) prevents the development of hypertension in SHRSP

1. We previously reported that hypertension in stroke-prone spontaneously hypertensive rats (SHRSP) caused renal membrane phospholipid degradation. Renal phospholipase A2 activity increased and membranous phospholipids decreased along with age in SHRSP. Membranous abnormalities induced by membrane fluidity and calcium permeability changes may contribute to the elevation of blood pressure in SHRSP. DHA, a major component of fish oil, constitutes a part of membrane phospholipid acylchains. 2. The purpose of this study was to clarify the effect of DHA on the relationship between the renal function and the development of hypertension in SHRSP. 3. Six week old male SHRSP were fed a semi-purified diet supplemented with DHA (0, 1 and 5%) for 14 weeks. 4. The systolic blood pressure of control SHRSP (DHA 0%) significantly increased from 120.2 mmHg to 202.9 mmHg. This increase in systolic blood pressure was significantly inhibited in a dose-dependent manner by 1 and 5% DHA diet to 167.8 to 149.8 mmHg, respectively. 5. Serum creatinine concentration and blood urea nitrogen (BUN) were significantly lower in DHA (5%)-treated SHRSP than in the control SHRSP. 6. These results indicate that DHA prevents the development of hypertension in SHRSP, which is associated with changes in renal function.

Effect of captopril and angiotensin II receptor blockade on pressure natriuresis in transgenic TGR(mRen-2)27 rats

The pressure-natriuresis curve of transgenic rats harboring an extra mouse renin gene [TGR(mRen-2)27] is shifted rightward compared with controls; however, whether intrarenal angiotensin II effects are responsible for the rightward shift is unknown. To clarify this issue we infused the converting enzyme inhibitor captopril or the angiotensin II receptor blocker CV 11974 into transgenic and normotensive Sprague-Dawley Hannover control rats. We eliminated any other neural or endocrine regulatory differences between transgenic and control rats by renal denervation and infusion of vasopressin, aldosterone, corticosterone, and norepinephrine in sufficient quantities to occupy all receptors. Sodium excretion increased from 3.4 +/- 1.2 to 10.1 +/- 0.5 mumol/min per gram kidney weight in transgenic rats when renal perfusion pressure was increased from 158 to 201 mm Hg. Captopril (4 mg/kg) and CV 11974 (0.1 mg/kg) shifted the pressure-natriuresis curve of transgenic rats leftward, so that sodium excretion was threefold higher at similar renal perfusion pressures (150 to 160 mm Hg). Similarly, fractional sodium and water excretion curves were shifted leftward, so that values for transgenic and control rats were no longer different. Over the pressure range, renal blood flow in transgenic rats ranged from 3.1 +/- 0.7 to 4.4 +/- 0.5 mL/min per gram kidney weight and increased (P < .05) with both captopril and CV 11974 to ranges from 4.8 +/- 0.9 to 6.8 +/- 0.6 or from 4.5 +/- 0.7 to 6.9 +/- 1.0 mL/min per gram kidney weight, respectively. Glomerular filtration rate in transgenic rats, on the other hand, was not increased. Transgenic kidneys showed severe hypertension-induced nephrosclerosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Diltiazem: ten years of clinical experience in the treatment of hypertension

Diltiazem hydrochloride is a benzothiazepine derivative calcium-channel blocker with proven antianginal and antihypertensive capabilities. Its primary mechanism of action is vasodilatation, which results in diminished vascular resistance and improved perfusion to various vascular beds and target organs. The antihypertensive efficacy of diltiazem in various demographic groups has been studied and compared with diuretics, beta-blockers, angiotensin-converting enzyme inhibitors, and other calcium-channel blockers. These studies have shown that the antihypertensive effect of diltiazem is similar to that of the other therapies. Diltiazem does not adversely affect electrolytes or carbohydrate or lipid metabolism, and it may have beneficial effects on the heart and kidneys. Diltiazem reduces myocardial hypertrophy and exerts antianginal effects on the heart through coronary vasodilation and reduction in the blood pressure double product. Diltiazem improves renal perfusion and attenuates proteinuria. These effects may be helpful in limiting the progression of renal injury. Overall, the efficacy and tolerability of diltiazem, as well as its salutary effects on the heart and kidneys, make it an important therapeutic consideration for patients with hypertensive disease.

Protection from hypoxemic renal dysfunction by verapamil and manganese in the rabbit

The ability of calcium channel blockers to prevent and/or to reverse the hypoxemia-induced renal dysfunction was studied in anesthetized and mechanically-ventilated rabbits. Renal blood flow (RBF) and glomerular filtration rate (GFR) were determined by para-aminohippuric acid and inulin clearance, respectively. Each animal was considered as its own control. In 9 rabbits (group 1), verapamil infusion, 1 microgram.kg-1.min-1, did not change basal renal hemodynamics. In a second group (n = 9), hypoxemia induced marked significant decreases in GFR, RBF and urine flow rate (-22 +/- 5%, -18 +/- 6% and -34 +/- 7% respectively). The administration of verapamil partially reversed the hypoxemia-induced renal dysfunction. Likewise, hypoxemia did not induce any change in renal function in verapamil pretreated rabbits (n = 8). This study shows that verapamil is able to prevent and to partially reverse the adverse effects of hypoxemia on renal hemodynamics. The intrarenal infusion of manganese chloride, another calcium channel blocker, was also effective in blunting the hypoxemia-induced changes in the left infused kidney, but not in the contralateral kidney. The overall results demonstrate that a significant protection from hypoxemic renal dysfunction can be achieved by inhibitors of calcium ion transport.

Acute effects of nifedipine in renal transplant recipients treated with cyclosporine or azathioprine

Cyclosporine (CsA) impairs renal function, probably by preglomerular vasoconstriction. Vasodilating substances may therefore be of benefit to ameliorate CsA-induced renal dysfunction. We studied the acute effects on blood pressure and renal function of the dihydropyridine calcium antagonist nifedipine (10 mg orally) in 20 CsA-treated renal transplant patients. In addition, we compared the effects of nifedipine when given immediately before and 4 weeks after elective conversion from CsA to azathioprine. Compared with placebo (n = 14), administration of nifedipine led to a significant decrease in blood pressure and a strong natriuretic and diuretic response. Despite the reduction in blood pressure, glomerular filtration rate improved from 60 +/- 20 (mean +/- SD) to 69 +/- 24 mL/min/1.73 m2 (P < 0.001) and renal plasma flow (RPF) increased from 260 +/- 87 to 338 +/- 120 mL/min/1.73 m2 (P < 0.001). The combination of a decreased blood pressure with an increased RPF was reflected in a sharp decrease in renal vascular resistance (0.34 +/- 0.18 units v 0.23 +/- 0.10 units; P < 0.001). The conversion from CsA to azathioprine by itself led to significant increases in glomerular filtration rate (62 +/- 15 mL/min/1.73 m2 v 76 +/- 18 mL/min/1.73 m2; P < 0.05) and RPF (280 +/- 86 mL/min/1.73 m2 v 334 +/- 66 mL/min/1.73 m2; P < 0.05). During treatment with azathioprine an effect of nifedipine on glomerular filtration rate and RPF was no longer observed, although the natriuretic effect was similar on both occasions. The decrease in renal vascular resistance was larger during treatment with CsA than during treatment with azathioprine (P < 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Pharmacokinetics and pharmacodynamics of a slow-release formulation of diltiazem after the administration of a single and repeated doses to healthy volunteers

Diltiazem is a calcium antagonist used in angina pectoris and hypertension. There is little information concerning the slow-release (SR) formulation in the literature. The pharmacokinetics of diltiazem SR (120 mg) have been assessed over a 36h period in healthy volunteers after single- (SD) and multiple-dose (MD) administrations. Cmax, AUC0-36, and AUC0-infinity were significantly increased at steady state compared to the extrapolated SD values, suggesting accumulation of the drug. Renal and cardiovascular parameters have also been assessed at intervals of 3-6h during baseline (B) and following single and multiple doses of diltiazem SR. Diuresis over a 24 h period was increased, but not significantly, by the administration of diltiazem SR i.e. 1782 ml (MD) and 1915 ml (SD), versus 1626 ml (B). Natriuresis and creatinine clearance were slightly decreased by diltiazem SR, compared to B values; this might be due to the relatively short period over which steady state was maintained (five days) and the effects of norepinephrine and angiotensine II on renal vasculature and the pharmacokinetics of diltiazem SR. No increase in the systolic blood pressure occurred after the administration of diltiazem SR; diastolic blood pressure and PR interval were decreased and increased respectively by diltiazem SR. These results do not appear to be clinically significant. Finally, no relation was found between the pharmacokinetics and pharmacodynamics of diltiazem. This may be attributed to the absence of clinically significant effects in healthy volunteers, the presence of active metabolites, the pharmacokinetics of the SR formulation and/or the accumulation of the drug at steady state.

Are renal hemodynamics a key factor in the development and maintenance of arterial hypertension in humans?

The kidney plays a key role in the control of body fluids and blood pressure. Evidence has shown that impairment of renal function can lead to the development of arterial hypertension. The regulation of renal blood flow appears to be a key element in the pathophysiology of the hypertensive process, because multiple evidence suggests the existence of a functional enhancement of renal vascular tone in this disorder. The existence of renal vasoconstriction and of an inherited defect in the regulation of renal blood flow has been proposed in the prehypertensive stage. The mechanisms responsible for this alteration include a lack of modulation of the renal vasculature to angiotensin II, increased sympathetic activity, or suppressed renal dopaminergic activity. Established hypertension is characterized by elevated renal vascular resistance, decreased renal blood flow, sustained glomerular filtration rate, and increased filtration fraction. The increase in renal vascular resistance is initially due to elevations in renal vascular tone and is reversible, whereas later it becomes irreversible because of structural changes involved in nephrosclerosis. Antihypertensive drugs are able to decrease blood pressure and to prevent the development of further renal vascular damage independently of variable effects on renal hemodynamics.

Effects of a calcium channel blocker, nicardipine, on pressure-natriuresis in Dahl salt-sensitive rats

The effects of a calcium channel blocker, nicardipine, on pressure-natriuresis responses were studied in Dahl salt sensitive (DS) and resistant (DR) rats. Differences in the neural and endocrine background were minimized by renal denervation and by holding plasma vasopressin, aldosterone, corticosterone, and norepinephrine levels constant by intravenous infusion. The renal plasma flow (RPF) and glomerular filtration rate (GFR) of DS rats were disautoregulated in the low renal perfusion pressure range, while those of DR rats were autoregulated. Administration of nicardipine (0.3 microgram/kg/min) into the renal artery significantly increased RPF and GFR and abolished the autoregulation in both strains of rats. Nicardipine also sharpened the pressure-natriuresis responses in both strains without changes in fractional excretion of sodium. These findings suggest that nicardipine increased GFR and thereby improved the pressure-natriuresis responses of DS rats.

Effects of a continuous diltiazem infusion on renal function during cardiac surgery

Thirty-five male patients undergoing coronary artery surgery were studied to investigate renal function during a continuous infusion of the calcium channel blocker diltiazem. All patients had preoperative renal function within normal limits (serum creatinine below 0.133 mmol/L) and were randomly divided into three groups: Control (C), Diltiazem 1 (D1), and Diltiazem 2 (D2). Diltiazem was infused in D1 (1 microgram/kg/min) and D2 (2 micrograms/kg/min) patients throughout surgery and during the following 36 hours. Glomerular function was investigated using the endogenous creatinine clearance while tubular function was assessed by means of water and sodium reabsorption tests, as well as urinary enzyme activity measurements. Hemodynamic monitoring was performed using a pulmonary artery catheter. The glomerular filtration rate of C and D1 patients showed a significant fall during cardiopulmonary bypass (CPB) with respect to the prebypass period and returned to the baseline values only in the postoperative period. A similar change was not observed in D2 patients. The analysis of variance demonstrated that the glomerular filtration rate was significantly higher in Group D2 versus Group C during and after CPB (P = 0.03 and P = 0.04, respectively). Furthermore, after CPB, urinary output was significantly improved in D2 patients, both versus C and D1 patients (P = 0.003), notwithstanding a lower mean arterial pressure in the D2 Group (P = 0.04 v C Group). Tubular function was not influenced by diltiazem infusion. It is concluded that a continuous diltiazem infusion, at a dose of 2 micrograms/kg/min during cardiac surgery, may be useful to prevent a decrease in glomerular function secondary to cardiopulmonary bypass.

The role of atrial natriuretic peptide in the diuretic effect of Ca2+ entry blockers

The effect of three calcium entry blockers--verapamil, nifedipine and felodipine--on diuresis, natriuresis, the renin-aldosterone axis, and atrial natriuretic peptide (ANP) levels was studied in 30 previously untreated patients with mild to moderate essential hypertension. All three blockers produced significant antihypertensive effects after 2 and after 24 h. Heart rate tended to decrease, but did not change significantly after verapamil, but increased significantly 1-2 h after nifedipine and felodipine. Plasma renin activity (PRA) did not change significantly with any treatment, and plasma aldosterone decreased with all three agents. ANP levels did not change significantly after verapamil, but increased significantly after nifedipine and felodipine. There was a significant positive correlation between the maximal change in ANP level and urinary sodium after nifedipine and felodipine. The increase in urinary sodium after verapamil was not significant. The role of the direct renal effect of calcium entry blockers in their persistent natriuretic action is discussed, as well as their short-term enhancement of ANP levels, which may account for the initial diuretic and natriuretic effects seen with this class of dihydropiridines.

Pharmacologic management of childhood hypertension

Antihypertensive drug therapy is used in children primarily to treat secondary forms of hypertension, because the prevalence of essential hypertension in the first decade of life is considerably less than 1% of the childhood population. This prevalence increases during the second decade of life, but the percentage of teenagers with essential hypertension continues to be low. Pharmaceutical companies have been able to target drug development to specific physiologic and biochemical systems. The converting enzyme inhibitors and calcium-channel blockers have greatly improved the success of therapy concomitant with a reduction in the incidence of adverse effects. The result has been a major change during the past decade in the recommendations for antihypertensive drug therapy.

Antihypertensive effect of nitrendipine in the hypertensive patient with renal impairment

Calcium antagonists exert several characteristic effects on the kidney that potentiate their antihypertensive effect. The objective of the present study was to investigate the effectiveness of nitrendipine in the presence of different degrees of renal impairment. Two groups of hypertensive patients were included in the study. Group 1:10 patients with arterial hypertension secondary to chronic renal parenchymatous disease and adequately controlled with a diuretic and/or a beta-blocker who were switched to nitrendipine. These patients were then followed monthly for 1 year. Group 2:24 patients diagnosed as having essential hypertension who presented values of urinary albumin excretion above 30 mg/day after a minimum of 3 years of adequate blood pressure control with a diuretic and/or a beta-blocker. Patients were randomly assigned to continue with the same therapy or to switch to nitrendipine for 1 year. In both groups nitrendipine was as efficacious as standard therapy for controlling blood pressure and did not induce changes in renal hemodynamics. Nitrendipine did not modify the level of proteinuria in group 1, nor the urinary excretion of albumin in group 2. These results seem to indicate that nitrendipine can be safely used in patients with arterial hypertension and different degrees of renal function impairment.

Inhibition of sodium pump by bepridil. An in vitro and microcalorimetric study

The effects of diltiazem, verapamil, bepridil, nicardipine and nifedipine were studied in vitro on Na+,K(+)-ATPase from dog kidney (EC 3.6.1.37). Except diltiazem, all the drugs tested showed an inhibitory effect on Na+,K(+)-ATPase activity in a dose-dependent manner. Among these drugs bepridil is far more effective than the others (IC50 approximately 10(-4) M). Competition studies showed that bepridil acted in a non-competitive manner with the ATP-Mg2+ complex and in a partially competitive manner with K+. Since ouabain acted similarly under the same experimental conditions, we tested the interaction of bepridil and ouabain on Na+,K(+)-ATPase. With low doses of ouabain, the enzyme inhibition corresponded to a potentiated synergy of the two drugs. We then studied the action of bepridil on the sodium pump activity of intact red blood cells by an ex vivo microcalorimetric technique. At 10(-5) M bepridil caused a significant decrease in sodium pump activity (33 +/- 8%).

Hypertensive nephropathy: is a more physiologic approach to blood pressure control an important concern for the preservation of renal function?

During the past 2 decades, there have been important reductions in stroke-related morbidity and mortality due to better control of hypertension. However, there has been a lesser effect on the reduction of coronary mortality and far less of an impact on all other forms of noncardiovascular disorders such as renal disease. This suggests that our ability to prevent hypertensive nephrosclerosis through traditional methods of lowering blood pressure may not be as effective as was once thought, particularly in high-risk patients such as blacks, diabetics, the elderly, and patients with preexisting renal disease. One reason that may partially explain the difficulty in protecting the renal circulation from hypertensive damage is the interaction between antihypertensive medications and the aged-related decline in renal perfusion. Depending on their mechanism of action, antihypertensive agents may impair renal blood flow (through plasma volume contraction or reduction) and further aggravate the age-related decline in renal perfusion. A worsening of renal perfusion may activate counterregulatory neurohormonal mechanisms, such as the renin-angiotensin-aldosterone system, which in turn may place the patient at increased risk for the development of glomerulosclerosis through promotion of vascular or mesangial hypertrophic changes or increased intraglomerular pressure, despite an associated reduction in systemic blood pressure. Since antihypertensive agents have such varied effects on systemic and renal hemodynamics, an understanding of the antihypertensive actions in a given patient may have significant influence on renal function. Thus, an improved understanding about the effects of aging and hypertension on the renal microcirculation will hopefully facilitate a more physiologically appropriate antihypertensive medication selection with the expectation that renal function will be benefitted over the long term.

Calcium antagonists for the treatment of systemic hypertension

As shown by large-scale clinical trials, the antihypertensive effectiveness of diuretics has been associated with a dramatic decrease in the incidence of stroke. This decrease, however, has not been accompanied by a similar reduction in atherosclerotic complications of hypertension, perhaps because other risk factors are important contributors to cardiovascular disease. In particular, a pathophysiologic relationship appears to exist between high blood pressure, left ventricular hypertrophy, diabetes and dyslipidemia. Thus, metabolically neutral antihypertensive agents such as calcium antagonists, which have no adverse effects on serum lipids and insulin sensitivity and can reduce left ventricular mass, are particularly suitable for the treatment of hypertension and attendant cardiovascular complications.

Renal abnormalities in normotensive insulin-dependent diabetic offspring of hypertensive parents

To assess the effects of genetic predisposition of essential hypertension on early renal function in recent insulin-dependent diabetics, we studied inulin, para-aminohippuric, sodium, and lithium clearances in 69 unselected diabetics with (n = 20) and without (n = 49) a family history of essential hypertension. Despite similar metabolic control, glomerular filtration rate and mean arterial pressure were significantly higher in diabetics with than in those without a family history of hypertension. However, no difference was found between the two groups regarding renal vascular resistance, sodium excretion, or fractional proximal and distal sodium reabsorption. Renal responses to acute captopril (75 mg) administration were evaluated in 27 patients (six with family history of hypertension). Captopril decreased filtration fraction and mean arterial pressure similarly in both groups, whereas glomerular filtration rate and renal vascular resistance decreased more dramatically in diabetics with family history of hypertension. These findings indirectly suggest an abnormal response to angiotensin of vascular tone in recent diabetics with familial predisposition to hypertension. Renal response to acute nicardipine (2.5 mg i.v.) administration was analyzed in 24 patients (five with family history of hypertension). In both groups, nicardipine similarly decreased mean arterial pressure and renal vascular resistance and induced a marked natriuretic effect due to a predominant reduction in proximal reabsorption of sodium. However, the increase in sodium excretion was twofold to threefold more pronounced in diabetics with a family history of hypertension. Whether these early renal abnormalities may contribute to the risk of diabetic nephropathy, as suggested by retrospective studies, remains to be determined.

Normalization of pressure-natriuresis by nisoldipine in spontaneously hypertensive rats

This study examined whether the calcium antagonist nisoldipine can shift the relations between sodium excretion, papillary blood flow, renal interstitial pressure, and renal perfusion pressure toward lower pressures in spontaneously hypertensive rats. Mean arterial pressure decreased similarly by 9% and 12% in Wistar-Kyoto and spontaneously hypertensive rats after nisoldipine (0.5 microgram/kg bolus + 0.017 microgram/kg/min). Urine flow and sodium excretion increased by 35% and 24% in Wistar-Kyoto rats after nisoldipine. In contrast, urine flow and sodium excretion rose by 121% and 132% in spontaneously hypertensive rats, and fractional sodium excretion rose from 1.9 +/- 0.3 to 4.2 +/- 0.4%. Control sodium excretion, papillary blood flow, and renal interstitial pressure were significantly lower in spontaneously hypertensive rats than in Wistar-Kyoto rats when compared at similar renal perfusion pressures. Sodium excretion, papillary blood flow, and renal interstitial pressure all increased in spontaneously hypertensive rats after nisoldipine, whereas it had no effect on papillary blood flow or renal interstitial pressure in Wistar-Kyoto rats. The relations among sodium excretion, papillary blood flow, renal interstitial pressure, and renal perfusion pressure were shifted toward lower pressures in spontaneously hypertensive rats given nisoldipine and became similar to those seen in Wistar-Kyoto rats. These results indicate that nisoldipine normalizes the relations among sodium excretion, renal interstitial pressure, papillary blood flow, and renal perfusion pressure in spontaneously hypertensive rats perhaps by correcting the defect in renal medullary perfusion associated with resetting of pressure natriuresis in this model of hypertension.

Abnormal renal hemodynamics in black salt-sensitive patients with hypertension

African-Americans with essential hypertension are more prone to the development of renal failure and are frequently salt-sensitive as well. Because alterations of intrarenal hemodynamics are important in the progression of renal disease and because salt-sensitive animal models with hypertension manifest a greater propensity to develop glomerulosclerosis in association with a rise in glomerular capillary pressure, we tested whether the renal hemodynamic adaptation to high dietary Na+ intake differs in salt-sensitive and salt-resistant hypertensive patients. We studied 17 black and nine white patients with essential hypertension who were placed on a low Na+ diet (20 meq/day) for 9 days, followed by a high Na+ diet (200 meq/day) for 14 days. During the last 4 days of each diet regimen, they received 30 mg/day of slow-release nifedipine. Eleven blacks were salt-sensitive, and all whites were salt-resistant. During the low Na+ diet period, salt-sensitive and salt-resistant patients had similar mean arterial pressure, glomerular filtration rate, effective renal plasma flow, and filtration fraction.(ABSTRACT TRUNCATED AT 250 WORDS)

Calcium channel blockade inhibits platelet activating factor production by human umbilical vein endothelial cells

An increase in intracellular calcium level is an important signal in the regulation of cellular responses under normal and pathological conditions. Because two key enzymes in the synthetic pathway of platelet activating factor (PAF), phospholipase A2 and acetyltransferase, are calcium dependent, we hypothesized that calcium channel blockade may inhibit agonist-induced PAF synthesis. Primary cultures of human umbilical vein endothelial cells (EC), pre-incubated with [3H]acetate, were exposed to thrombin (5 U/mL) and PAF production was quantitated by incorporation of radiolabel into the EC lipid fraction co-migrating with exogenous PAF in thin-layer chromatography. The effect of pre-incubation with calcium channel blockers (verapamil, diltiazem, 10(-4) M) or buffer was determined. Results (triplicate experiments, * P less than 0.05 vs buffer, P less than 0.05 vs thrombin) demonstrate that pre-incubation with calcium channel blocker markedly inhibits thrombin-induced PAF production (verapamil:buffer 273 +/- 122, thrombin 10,735 +/- 1524*, thrombin + verapamil 178 +/- 91 cpm/plate; diltiazem:buffer 1097 +/- 581, thrombin 15,283 +/- 2661*, thrombin + diltiazem 280 +/- 56 cpm/plate). The effect of diltiazem was dose-dependent (% inhibition: 10(-7) M, 46%; 10(-5) M, 60%; 10(-4) M, 98%). Diltiazem also inhibited bradykinin (10(-8) M) induced PAF synthesis. In calcium-free medium or in the presence of LaCl3 (10(-3) M), the PAF response of EC to thrombin was blunted (buffer 582 +/- 360, thrombin 5394 +/- 1069, thrombin + calcium free medium 1055 +/- 571, thrombin + LaCl3 1271 +/- 58 cpm/plate). We conclude that calcium channel blockers prevent agonist-induced PAF synthesis, possibly by preventing cellular calcium influx and activation of PAF synthetic enzymes. We speculate that this mechanism may underlie, at least in part, the beneficial effect of calcium channel blockade under various pathological conditions.

Effects of nifedipine GITS and atenolol monotherapy on serum lipids, blood pressure, heart rate, and weight in mild to moderate hypertension

Forty-nine patients, with ages ranging from eighteen to seventy years and with mild to moderate primary hypertension (sitting diastolic blood pressure of greater than or equal to 95 mmgH and less than or equal to 115 mmHg) were randomized into a twenty-one-week, double-blind, prospective study to determine the effects of monotherapy of nifedipine GITS (gastrointestinal therapeutic system) versus atenolol on serum lipids, lipid subfractions, apolipoproteins, (apo), and blood pressure (BP). Nifedipine GITS and atenolol significantly reduced blood pressure, but nifedipine GITS reduced sitting and standing systolic BP significantly more than atenolol (p = .001). Sitting and standing heart rate decreased significantly (p = 0.001) during atenolol therapy but did not change significantly during nifedipine GITS therapy. Atenolol increased weight (mean change + 2.2 lb; p = 0.011), but nifedipine GITS decreased weight (mean change - 2.4 lb; p = 0.07). Nifedipine GITS had a more favorable effect on the lipid profile. High density lipoprotein cholesterol (HDL-C) and HDL2 subfractions were increased significantly (p = .001) as were apo A1 (p = 0.037) and apo A2 (p = 0.025). Nifedipine GITS increased HDL3 (NS), reduced triglycerides (TG) (NS), and had no significant effect on total cholesterol (TC) low density lipoprotein cholesterol (LDL-C) and apo B. Atenolol significantly increased serum total cholesterol (p = 0.039) and HDL-C and HDL2 (p = 0.049 and 0.048 respectively). Atenolol increased TG (NS) and apo B (NS) with little change in apo A1 and apo A2. It is concluded that nifedipine GITS had equal or better antihypertensive efficacy than atenolol and had a more favorable effect on the lipid profile. These effects may offer advantages in reducing CHD risk.

The relationship of sodium balance and concomitant diuretic therapy to blood pressure response with calcium channel entry blockers

Marked heterogeneity exists in the response of blood pressure to specific antihypertensive agents. In general, a single therapeutic agent can be expected to provide an adequate blood pressure response in 40% to 60% of hypertensive patients. The addition of a second agent usually extends the response rate to over 85%. The addition of a diuretic to nondiuretic regimens often produces an additive blood pressure-lowering effect. However, calcium channel entry blockers (CCBs) may be an exception, as diuretics do not appear to improve these agents' efficacy. CCBs have a dual mechanism for blood pressure reduction. In addition to their vasodilatory actions, they also promote diuresis and natriuresis. These features account for the striking efficacy of these agents when used as monotherapy in hypertensive patients. Studies have shown that dietary sodium restriction does not appear to improve the efficacy of CCBs, nor is a high-salt diet predictive of a better therapeutic outcome. Recent studies also indicate that the addition of a diuretic to a CCB does not produce a significant or consistent additive antihypertensive effect. Because CCBs do not produce the typical responses of the renin-angiotensin-aldosterone (RAA) system to sodium/volume depletion, their diuretic and natriuretic effects do not result in the same adverse metabolic consequences as experienced with traditional diuretic therapy.

The effect of nifedipine GITS on renal function in hypertensive patients with renal insufficiency

Twelve hypertensive patients with moderately severe renal dysfunction were entered into a protocol to assess the blood pressure and renal effects of the sustained release calcium antagonist, nifedipine GITS (30-180 mg/d given once a day) administered for 5 weeks. Nifedipine GITS monotherapy effectively lowered blood pressure in 50% of the patients. Glomerular filtration rate and effective renal plasma flow were increased 18% and 20%, respectively. The filtration fraction and urinary protein excretion remained unchanged. Changes that were observed in renal function were independent of the blood pressure responses of the patients; there was no correlation between the systemic and renal effect of nifedipine GITS monotherapy. Patients who had a poor systemic blood pressure response exhibited an increase in glomerular filtration rate (+11%) but had a decrease in effective renal plasma flow (-6%); patients who achieved a goal blood pressure response showed increases in both glomerular filtration rate (+35%) and effective renal plasma flow (+40%). These results show that nifedipine GITS monotherapy has the potential to improve renal function abnormalities that are encountered in hypertensive patients with renal disease; the improvement in renal function may be independent of their effect on systemic blood pressure.

Contrasting effects of lisinopril and nifedipine on albuminuria and tubular transport functions in insulin dependent diabetics with nephropathy

An open, randomized, cross-over study was undertaken to assess the effects of lisinopril and nifedipine on albumin excretion, renal haemodynamics and segmental tubular reabsorption in overt diabetic nephropathy. The study consisted of a 4-week run-in period, a 3-week active treatment period, a 4-week wash-out period and a second 3-week active treatment period. Twelve patients with type 1 diabetes with albuminuria, mild to moderate hypertension and a serum creatinine level of less than 200 mumol l-1 were included. Lisinopril reduced albumin excretion from 1343 +/- 337 micrograms min-1 to 879 +/- 299 micrograms min-1 (P less than 0.01), whereas nifedipine was without effect, 1436 +/- 336 micrograms min-1 vs. 1319 +/- 342 micrograms min-1. Glomerular filtration rate (GFR) was unchanged by either drug. Both drugs increased effective renal plasma flow (ERPF) by about 20%. No differences between the drugs were observed with regard to their effect on renal haemodynamic parameters. By contrast, nifedipine exerted an inhibitory effect on several proximal tubular transport markers, whereas lisinopril was without effect. The different actions on tubular transport mechanisms exerted by lisinopril and nifedipine may contribute to the observed effect on albumin excretion.

Effect of a calcium-entry blocker, nicardipine, on intrarenal hemodynamics in essential hypertension

The effects of a calcium-entry blocker, nicardipine, on intrarenal hemodynamics were studied in essential hypertension. A 4-week study was performed in eight patients with essential hypertension who were given a regular sodium diet in the first and third weeks, and a sodium-restricted diet in the second and fourth weeks. Nicardipine, 60 mg/d, was administered in the third and fourth weeks. The urinary sodium excretion rate (UNaV) was plotted on the y-axis against the mean arterial pressure (MAP) on the x-axis before and after the administration of nicardipine. Assuming the difference between MAP and the x-intercept of this renal function curve represents the effective filtration pressure across the glomerular capillaries, the intrarenal hemodynamics such as afferent arteriolar resistance (RA) and efferent arteriolar resistances (RE), glomerular pressure (PG), and gross filtration coefficient (KFG) were calculated. Although the MAP on regular salt diet was lowered from 125 +/- 3 to 109 +/- 2 mm Hg by nicardipine, neither the renal blood flow rate (RBF) (670 +/- 40 mL/min) nor the glomerular filtration rate (GFR) (79 +/- 2 mL/min) was altered. The RA was estimated to be reduced from 9,300 +/- 900 to 7,400 +/- 700 dyne.s.cm-5 (P less than 0.01), while no changes were noted in RE (4,900 +/- 400 dyne.s.cm-5), PG (50 +/- 1 mm Hg), or KFG (0.180 +/- 0.041 [mL/s]/mm Hg). Essential hypertension has been characterized by a prominent increase in RA, resulting in maintenance of normal PG. This Ca-entry blocker worked to normalize intrarenal hemodynamics in essential hypertension by dilating afferent arterioles alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of calcium antagonists on the hypertensive kidney

This review focuses on the effects of calcium antagonists on renal function in hypertensive human subjects. Specifically assessed are the acute and chronic effects of diltiazem, verapamil, amlodipine, felodipine, isradipine, nicardipine, nifedipine, and nitrendipine on glomerular filtration rate; effective renal plasma flow/renal blood flow; renal vascular resistance; and urinary protein excretion. Among the calcium antagonists, only the dihydropyridine derivatives have been demonstrated consistently to acutely increase effective renal plasma flow/renal blood flow. The acute effects on glomerular filtration rate are variable. With respect to chronic therapy, many of the calcium antagonists have been reported to produce sustained increases in the effective renal plasma flow/renal blood flow and/or the glomerular filtration rate. Renal vascular resistance is reduced. Although calcium antagonists preserve or improve renal perfusion and glomerular filtration, long-term clinical trials are required to determine their potential therapeutic benefit to modify the natural course of hypertensive renal disease.

Renal effects of calcium entry blockers

Calcium entry blockers exert several characteristic effects on renal function that contribute to their blood-pressure lowering capacity. They are able to dilate renal vasculature and, in certain circumstances, can increase the glomerular filtration rate, both effects being dependent on the preexisting vascular tone. Calcium blockers are also able to increase renal sodium excretion, mainly through a direct tubular effect that remains during the chronic administration of these drugs. These effects clearly differentiate calcium entry blockers from nonspecific vasodilators and contribute to their effectiveness when they are used as first-step drugs in the therapy of arterial hypertension.

Felodipine in the treatment of patients with severe hypertension and impaired renal function

Twenty-three patients with severe hypertension and impaired renal function were included in an open study of the efficacy and tolerance of felodipine treatment over 6 months. All patients were previously treated with a diuretic, a beta blocker, and a vasodilator, and eight of them also received an ACE inhibitor. At the start of felodipine treatment the previously used vasodilator was withdrawn. In nine patients the concomitant antihypertensive treatment was reduced during the study. The glomerular filtration rate (GFR), as 51Cr EDTA clearance, was determined before and at the end of the study. The blood pressure (BP) and heart rate (HR) were recorded at all clinical visits in the morning 12 hours after the evening dose of felodipine and 2 hours after the morning dose. Plasma concentrations of felodipine were measured at every visit before the morning dose and 2 hours after dose. The BP was reduced after felodipine was substituted for the previously used vasodilator. A significant additional anti-hypertensive effect was recorded 2 hours after the dose and amounted to -37 +/- 22/-15 +/- 12 mmHg (p = 0.0001/p = 0.0002) at 6 months. The effect measured 12 hours after the dose was less pronounced and was -11 +/- 28/-6 +/- 10 mmHg (p = 0.15/p = 0.03). Mean GFR was unchanged during the study, 38 +/- 19 versus 38 +/- 19 ml/min (n = 16). There was a sixfold interindividual variation in the trough plasma concentrations at steady state at the same drug dosage. Higher plasma concentrations seemed to be required to achieve the same antihypertensive effects as in patients with less severe hypertension and normal renal function.(ABSTRACT TRUNCATED AT 250 WORDS)