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Different concepts in first-line treatment of essential hypertension. Comparison of a low-dose reserpine-thiazide combination with nitrendipine monotherapy. German Reserpine in Hypertension Study Group.

Low-dose combination therapy has been proposed as a rational first-line approach to hypertension treatment. We compared the efficacy and tolerability of the fixed combination of reserpine (0.1 mg) plus the thiazide clopamid (5 mg) with its single components and the calcium-antagonist nitrendipine (20 mg) in a randomized, double-blind, parallel study of 273 hypertensive patients with diastolic blood pressure (BP) between 100 and 114 mm Hg. The four groups did not differ regarding baseline characteristics (mean age, 58 years; 51% men; mean BP after a 2-week placebo period, 158 to 160/103 to 104 mm Hg). After 6 weeks of treatment with one capsule daily, mean reductions in sitting BP from baseline at 24 hours after dosing in the reserpine-clopamid combination, reserpine, clopamid, and nitrendipine groups were -23.0/-17.1, -14.0/-11.7, -13.6/-11.9, and -11.6/-12.3 mm Hg, respectively (2P < .01). The corresponding normalization rates (diastolic BP < 90 mm Hg) were 55%, 40%, 36%, and 33% (2P = .11). All patients whose BP had not been normalized at this point received two capsules of the respective medication once daily from weeks 7 to 12. At week 12, mean BP reductions were -25.7/-18.1, -14.6/-12.2, -17.7/-13.4, and -14.9/-15.3 mm Hg in the four groups, respectively (2P < .01). The respective normalization rates were 69%, 35%, 39%, and 45% (2P < .0001). Linear regression modeling indicated that reserpine and clopamid combined acted more than additively. As regards tolerability, adverse experiences were observed in 27%, 28%, 29%, and 48% of patients, respectively (2P < .05). The respective rates of premature discontinuation because of adverse effects were 3%, 3%, 7%, and 13% (2P = .06). In conclusion, a low-dose combination of reserpine and clopamid lowered BP significantly more than both the components alone and nitrendipine. Moreover, the combination was tolerated as well as its components and significantly better than nitrendipine. Thus, the use of this low-dose reserpine-thiazide combination appears to be a rational alternative to conventional monotherapy in the first-line treatment of hypertension.

Adolescent↗

Low-dose reserpine/thiazide combination in first-line treatment of hypertension: efficacy and safety compared to an ACE inhibitor.

The concept of initiating treatment of mild-to-moderate hypertension with a low-dose combination of reserpine and the thiazide clopamide in comparison to monotherapy with an ACE inhibitor was investigated. A total of 127 adult outpatients with diastolic blood pressure between 100 and 114 mmHg were randomized into this double-blind, parallel group study. After a 2-week wash-out period and a subsequent 2-week placebo run-in period, they were allocated to once-daily treatment with 0.1 mg reserpine plus 5 mg clopamide (R/C), or 5 mg enalapril. If diastolic blood pressure was not normalized after 3 weeks of therapy (i.e. DBP < 90 mmHg), the dosage was doubled from week 4 to 6. The primary efficacy variables were the change from baseline in mean sitting diastolic and systolic blood pressure (DBP/SBP) after 3 weeks of therapy. Secondary variables included the change in DBP and SBP after 6 weeks of therapy, the BP normalization rates at 3 and 6 weeks and, concerning tolerability, the rates of adverse events after 6 weeks of therapy. An intent-to-treat analysis was performed. The reserpine/ clopamide and enalapril groups did not differ with regard to demographic and baseline characteristics (mean age 57 or 58 years, respectively; 63% or 56% males, respectively; mean SBP/DBP after the 2-week placebo period = 156 mmHg/104 mmHg in both groups). After 3 weeks of treatment with one capsule daily, mean SBP/DBP reduction from baseline (24 h after last medication intake) in the R/C combination group was -19.6/ -17.0 mmHg, in the enalapril group -6.1/ -9.5 mmHg (between-group comparison: 2p < 0.01 for both parameters). The normalization rates for DBP (< 90 mmHg) were 64.1% (R/C) and 28.6% (enalapril) (2p < 0.01). Adverse events that were considered possibly or definitely drug-related by the investigator were noted in 11 patients (17.2%) in the R/C group and in 9 patients (14.3%) in the enalapril group (NS). Two patients in the enalapril group discontinued the study prematurely due to adverse events (cough; skin eruption). In the treatment of mild-to-moderate hypertension, a low-dose combination of reserpine and clopamide once a day is considerably more effective than, and as tolerable as, 5-10 mg of enalapril once a day. These findings suggest that treatment with a combination of different antihypertensives with different modes of action in low doses is a rational alternative to conventional monotherapy in the first-line treatment of hypertension. Besides, the "old" reserpine-diuretic regimen also in these days appears to be a rational alternative to "modern" monotherapies.

Adult↗

Inhibition of the Cl-/NaCO3- anion exchanger by xipamide in human red blood cells.

The mechanism of action of classical loop diuretics of the 2- or 3-amino-5-sulfamoylbenzoic acid and (aryloxy)acetic acid families involves competition with chloride for a common site on the (Na+, K+, 2Cl-) co-transport system. However this is not the mechanism of action of some high-ceiling diuretics like muzolimine, MK 473, xipamide, indapamide and clopamide, which are not carboxylic acids. We evaluated three of these latter diuretics (xipamide, muzolimine and clopamide) for their inhibitory effects on five ion transport systems in human red blood cells: (i) Cl(-)-dependent (Na+, K+) co-transport, (ii) (NaCO3-/Cl-) anion exchanger, (iii) (Cl-, K+) co-transport, (iv) Na+, K+ pump and (v) Na+: Li+ counter-transport; and on one ion channel the Ca2+-dependent, K+ channel. All erythrocyte transport pathways were resistant to the three diuretics studied (IC50 of 10(-3) M or higher) with one remarkable exception, the (NaCO3-/Cl-) anion exchanger. This transport system was inhibited by xipamide (IC50 of 2.5 +/- 0.4 X 10(-5) M, mean +/- S.D. of five experiments) and less potently by muzolimine (IC50 of 1.1 +/- 0.3 X 10(-4) M, mean +/- S.D. of three experiments). Clopamide only inhibited the anion exchanger at high concentrations (IC50 of about 10(-3) M). Xipamide, the most potent diuretic in this test, was at least one order of magnitude more active than furosemide, ethacrynic acid, hydrochlorothiazide and amiloride. Inhibition of the anion carrier could be involved in the diuretic action (inhibition of CO2-stimulated NaCl absorption in the TAL) and/or in the antihypertensive action (inhibition of net NaCO3- influx and secondarily of Ca2+ influx through Na+: Ca2+ exchange in vascular smooth muscle cells of xipamide).

Bicarbonates↗

Reversal of diuretic-induced increases in serum low-density-lipoprotein cholesterol by the betablocker pindolol.

Seventeen patients with mild to moderate essential hypertension received during three consecutive 4 wk periods a matched placebo, the thiazide-like diuretic, clopamide in a low dosage of 5 mg/day, or this diuretic combined with the betablocker, pindolol in a low dosage of 10 mg/day. Compared to placebo conditions, clopamide monotherapy significantly increased serum low-density lipoprotein cholesterol (LDL-C) by 13% (p less than 0.025). Following addition of pindolol, serum LDL-C was restored to control values. These variations in serum LDL-C were unrelated to concomitant changes in blood pressure, plasma potassium, renin activity or aldosterone levels. Blood pressure in the supine position was reduced from 152/99 +/- 13/9 mm Hg (+ SD) to 141/93 +/- 15/7 mm Hg following diuretic-monotherapy and to 139/90 +/- 12/9 mm Hg following diuretic-betablocker combination treatment. These findings suggest that antihypertensive combination treatment with low doses of clopamide and pindolol is not only effective and well tolerated, but may also avoid the increase in serum LDL-C levels occurring when the thiazide-like diuretic is given alone.

Adult↗

Interaction of cyclosporine-A with the renin-angiotensin system in canine veins.

Responses of canine saphenous veins to bradykinin and angiotensin and the effect of cyclosporine-A were investigated both in conscious dogs in vivo and on ring preparations from canine saphenous veins in vitro. In vivo local infusion of bradykinin into the saphenous vein elicited dose-dependent reduction in compliance, i.e., venoconstriction, whereas local infusion of angiotensin elicited dose-dependent venodilatation, which was markedly enhanced during blockade of endogenous thromboxane A2 synthesis by dazoxiben (2.5 mg/kg i.v.). The venoconstrictor response to bradykinin was attenuated after oral administration of both the thiazide-like diuretic clopamide (0.5 mg/kg) or cyclosporine-A (30 mg/kg), and by concomitant local infusion of cyclosporine-A (1-10 micrograms/min). Systemic i.v. infusion of the renin inhibitor H-77 (0.1 mg/kg/h) reversed the inhibition of bradykinin by both clopamide and cyclosporine-A. In vitro bradykinin elicited relaxation at low (0.1-10 nmol/l) but constriction at higher concentrations. The venoconstrictor response to bradykinin was resistant to blockade of thromboxane A2 synthesis and only partially attenuated after selective blockade of cyclooxygenase or lipoxygenase. Concomitant blockade of both lipoxygenase and cyclooxygenase activity by nordihydroguaiaretic acid (NDGA 10-30 mumol/l) nearly abolished the contractile response thereby enhancing the relaxant component of the bradykinin effect. Angiotensin II also elicited biphasic responses of partially contracted venous rings. Concomitant blockade of both lipoxygenase and cyclooxygenase by NDGA (10 mumol/l) again attenuated the contractile component of the angiotensin effect thereby unmasking the venodilator activity which could be inhibited by the angiotensin II receptor blocker saralasin (0.01-1 mumol/l).(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II↗

[Combined uni- and multicenter double-blind studies in hypertensive patients. Comparison of blood pressure measurements].

In a double-blind study to investigate the antihypertensive effect of a fixed triple combination with 0.05 mg reserpine, 2.5 mg clopamide and 0.4 mg dihydroergocristine in comparison to a fixed double combination with 0.05 mg reserpine and 2.5 mg clopamide, a patient subgroup of 34 patients followed a unicenter (central unit, 'institute') as well as a multicenter (established physicians) study design. The patients visited both investigation units on the day of admission to the study (week 0), after four weeks and after eight weeks of therapy (after the morning intake of the drugs). The paper in hand looks at the results of this subgroup with respect to the conformity of blood pressure values in the two investigative units. The analyses confirm the already published results of the entire study: Both combinations proved to be highly effective antihypertensive drugs. The triple combination showed therapeutical advantages for systolic blood pressure after four weeks, for diastolic pressure after eight weeks of therapy at the 'institute' as well as, although less distinct, in the medical offices. A comparison of the individual values did not show a convincing coherence of the measurements between institute and offices. All investigated possible systematic sources of error (different methods of measurement, days or times of measurement) could be excluded by correlation statistics as a reason for the divergences. The results show the necessity--particularly in multicenter studies--of a careful documentation of all accompanying data (e.g. method or time of measurement) as well as a greatest possible standardization of investigation (e.g. identical measuring apparatus and investigator.)

Antihypertensive Agents↗

Renal excretory actions of antihypertensive agents. Effects of rilmenidine.

The acute renal excretory actions of several antihypertensive agents were assessed in healthy volunteers. Rilmenidine (1 mg) did not affect water and electrolyte balance. Beta-adrenergic blockers had little effect upon urinary composition, whereas diuretics caused significant urinary losses of fluid, sodium, potassium, and magnesium as expected. The vasodilators ketanserin and flosequinan did not affect water and electrolyte excretion. Ketanserin increased urate output in common with angiotensin-converting enzyme inhibitors, which may act as facultative diuretics. Combining the angiotensin-converting enzyme inhibitor captopril (100 mg) or rilmenidine (1 mg) with hydrochlorothiazide (25 mg) had little influence upon the known actions of the diuretic. When the beta-blocker pindolol (10 mg) was given with the diuretic clopamide (5 mg), beneficial effects were noted; potassium and magnesium losses were markedly reduced, whereas the natriuretic and diuretic effects of clopamide were unchanged. These short-term studies in healthy volunteers provide useful pointers to some possible pharmacodynamic effects of antihypertensive drugs in patients.

Adolescent↗

In vitro and ex vivo inhibition of the modification of low-density lipoprotein by indapamide.

The effect of an antihypertensive drug, indapamide, on copper- and endothelial cell-induced peroxidation of human low-density lipoprotein (LDL) was studied and compared with that of drugs previously shown to protect LDL against peroxidation: probucol and vitamin E and other thiazidic and nonthiazidic diuretics (clopamide, hydrochlorothiazide, and furosemide). Incubation with indapamide inhibited in a dose-dependent manner LDL peroxidation induced either by copper ions or by cultured endothelial cells. Both electrophoretic mobility and thiobarbituric acid-reactive substances (TBARS) content of LDL returned to almost normal values in the presence of 1 microM indapamide. This drug was at least 10 times more potent than probucol and vitamin E in inhibiting LDL peroxidation. No inhibitory effect has been observed with clopamide, hydrochlorothiazide, and furosemide in the same experimental conditions. Homozygote Watanabe rabbits were treated orally with indapamide (10 mg/kg/d for 3 days) to evaluate the potential protective effect of the compound on LDL peroxidation in vivo. Purified LDL from placebo and treated rabbits were submitted to peroxidation induced by copper ions, and indapamide was effectively able to protect LDL in these experimental conditions. This effect was especially obvious 6 and 8 h after the start of the incubation when LDL of the placebo-treated animals were modified. The mechanism of action of these drugs was examined in vitro using the 1,1-diphenyl-2-picryl-hydrazyl (DPPH) test and in kinetic studies of arachidonic acid photoperoxidation. Indapamide as well as vitamin E and probucol were effective free radical scavengers, but the other diuretic molecules were not.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

Effects of indapamide and various diuretics alone or combined with beta-blockers on serum lipoproteins.

A prospective evaluation was started in 1976 to study the influence of diuretics alone or combined with beta-blockers on serum lipoproteins in normal or hypertensive subjects. Compared to placebo conditions, 4 or 6-weeks' monotherapy with various diuretics significantly (p less than 0.05) increased the beta-lipoprotein fraction (furosemide, 80 mg/day or chlorthalidone, 100 mg/day; n = 16) or low-density lipoprotein-cholesterol (LDL-C) (chlorthalidone, 100 mg/day, n = 27 men; tienilic acid, 250 mg/day, n = 16 men, clopamide, 5 mg/day, n = 17 men; or muzolimine, 20 to 40 mg/day, n = 13 men or post-menopausal women). No increase in LDL-C was noted in 43 men (32 normal, 11 with mild hypertension) treated with indapamide, 2.5 mg/day. Serum high-density lipoprotein-cholesterol and apoproteins A1, A2 and B were not consistently changed by any of these agents. In women, chlorthalidone (100 mg/day) significantly increased LDL-C in the (100 mg/day) significantly increased LDL-C in the post-menopausal (n = 18) but not in the pre-menopausal (n = 22) state. Increases in LDL-C caused by chlorthalidone monotherapy were prevented or reversed by the addition of a beta-blocker, usually propranolol or atenolol (n = 18); increases in LDL-C during clopamide monotherapy were reversed after the addition of the beta-blocker pindolol (10 mg/day, n = 17). In all studies, variations in beta-lipoprotein or LDL-C levels could not be explained by changes in blood volume, serum glucose or insulin and did not correlate with alterations in blood pressure, plasma potassium, renin, aldosterone, adrenaline or noradrenaline. These observations indicate that various diuretics may increase serum LDL-C in men or post-menopausal women. Pre-menopausal women may often be protected from this side-effect. Long-term studies are now needed to clarify the pathogenic and prognostic relevance of lipoprotein changes induced by diuretics. In the meantime, it is of clinical interest that indapamide had no significant effect on serum lipoproteins and that certain beta-blockers appear to prevent or reverse increases in LDL-C during diuretic treatment in men and post-menopausal women.

Adrenergic beta-Antagonists↗

The effect of diuretics and vasopressin on the osmotic permeability of the frog urinary bladder.

1. Large concentrations (in mM) of ethacrynic acid (0.1), furosemide (1.0), theophylline (5.0) and osmotic diuretics (100.0) sharply increased the flux of water along an osmotic gradient through the frog urinary bladder wall. Spironolactone (0.1), and hydrochlorothiazide (5.0) showed only a weak action on osmotic permeability. MercusalR, clopamide and triamterene did not affect water transport. 2. The presence of 0.2--1.0 mU/ml vasopressin (ADH) after pretreatment with a diuretic did not result in summation of the effects of both drugs used. 0.01--0.1 mM ethacrynic acid and 0.01 mM MercusalR significantly decreased the reaction to ADH. 1.0 mM furosemide, 0.1 mM spironolactone, 0.01 mM clopamide and 0.8 mM acetazolamide did not change the reaction to ADH. A reduction in the cellular response to ADH and a decrease in the osmotic permeability of the tubular wall may be responsible in part for the diuretic action of ethacrynic acid and MercusalR.

Animals↗

Serum potassium and body weight during treatment with two fixed combinations of beta-blockers and diuretics in hypertensive patients: a controlled study.

Two fixed combinations of beta-blockers and diuretics, penbutolol plus furosemide and pindolol plus clopamide, were compared with respect to efficacy, safety, and tolerability in hypertensive out-patients. The two preparations were equally effective in reducing blood pressure when given as a single daily dose. Doubling the dosage for those patients who responded poorly did not improve therapeutic response. The group treated with pindolol-clopamide had a significant increase in mean body weight and a substantial decrease in serum potassium concentrations. No direct relationship between these findings could be demonstrated, but the loss of potassium would be an important consideration when treating patients who are particularly vulnerable to the consequences of hypokalemia.

Adrenergic beta-Antagonists↗

Sensitive high-performance liquid chromatographic determination of famotidine in plasma. Application to pharmacokinetic study.

A sensitive high-performance liquid chromatographic (HPLC) method for the quantitation of famotidine in human plasma is described. Clopamide was used as the internal standard. Plasma samples were extracted with diethyl ether to eliminate endogenous interferences. Plasma samples were then extracted at alkaline pH with ethyl acetate. Famotidine and the internal standard were readily extracted into the organic solvent. After evaporation of ethyl acetate, the residue was analysed by HPLC. The chromatographic separation was accomplished with an isocratic mobile phase consisting of acetonitrile-water (12:88, v/v) containing 20 mM disodium hydrogenphosphate and 50 mM sodium dodecyl sulphate, adjusted to pH 3. The HPLC microbore column was packed with 5 microns ODS Hypersil. Using ultraviolet detection at 267 nm, the detection limit for plasma famotidine was 5 ng/ml. The calibration curve was linear over the concentration range 5-500 ng/ml. The inter- and intra-assay coefficients of variation were found to be less than 10%. Applicability of the method was demonstrated by a bioavailability/pharmacokinetic study in normal volunteers who received 80 mg famotidine orally.

Biological Availability↗

[Potassium metabolism during antihypertensive treatment with beta-receptor blocker and diuretic treatment].

In a controlled, prospective, cross-over study 15 patients with essential hypertension received for four weeks either a combination of beta-receptor blocker and diuretic (twice 10 mg pindolol and 5 mg clopamide daily) or of three drugs: beta-receptor blocker, diuretic and sodium-preserving diuretic (twice daily 10 mg timolol, 25 mg hydrochlorothiazide and 2.5 mg amiloride). Both drug combinations produced quantitatively comparable and definite blood pressure lowering from 162/102 mmHg to 128/82 and 130/82, or 130/84 and 127/82, respectively, after two and four weeks. A significant fall in serum potassium from 4.24 to 3.77 and 3.92 mmol/l occurred with the combined two drugs but not the combination of three. With the two-drug combination renal potassium excretion was significantly raised at one of two control points in time. Heart rate remained constant with the two-drug treatment but fell significantly on three-drug administration. There were more side effects with the two-drug preparation. Combinations of beta-receptor blockers and diuretics are thus by no means potassium neutral but can cause renal potassium loss, fall in serum potassium and hypokalaemia. For this reason combining potassium-sparing diuretic with beta-receptor blocker and diuretics is reasonable and justified.

Adrenergic beta-Antagonists↗

The effect of once daily beta-adrenoceptor blocker-thiazide diuretic combination on the ambulatory blood pressure.

1 We have assessed the efficacy of Viskaldix, a combination of pindolol 10 mg and clopamide 5 mg using continuous intra-arterial ambulatory blood pressure monitoring. 2 Fourteen of the sixteen patients entered were studied on no therapy and following a minimum of 6 weeks at a constant dosage of Viskaldix. 3 Viskaldix produced a marked and consistent reduction of the blood pressure over the 24 h. The diurnal variation in the heart rate was decreased. 4 The results were compared with those of a similar study with once-daily pindolol where there was control during the day but not in the early morning when the blood pressures rose rapidly.

Adrenergic beta-Antagonists↗