摘要:

Changes in plasma renin activity (PRA) were monitored in six mildly hypertensive men after intravenous doses, in seven separate experiments, of placebo, digoxin, potassium canrenoate, potassium canrenoate with digoxin, fur osemide, furo semide with digoxin, and potassium canrenoate with fur osemide and digoxin. Potassium canrenoate has been used as a rapid source of canrenone, which has been recently shown to be a competitive antagonist of ouabain at its Na‐K‐ATPase receptor site. Potassium canrenoate infusion reversed the hyporeninemic effect of digoxin. This result has been taken as evidence that: (1) antialdosteronic drugs can also reverse digoxin effects at extracardiac level and (2) the Na‐K‐ATPase system is involved in the renin secretory mechanism. A seemingly identical reversal of the hyporeninemic effect of digoxin was induced by fur osemide, which, when given alone, stimulated renin secretion. The simultaneous administration of potassium canrenoate, digoxin, and fur osemide induced an increase in PRA on the same order as that after furosemide alone. This result indicates that fur osemide stimulates renin release by affecting a biochemical system other than that affected by digoxin.Clinical Pharmacology and Therapeutics(1982)32,1–6; doi:10.1038/clp

ISSN:0009-9236    

DOI:10.1038/clpt.1982.118

年代:1982

数据来源: WILEY

摘要:

Immersion of the hand into ice water (cold‐pressor test) in nine hypertensive subjects induced elevation of mean blood pressure, increase of vascular resistance in the extremities, decrease of blood flow in the extremities, and increase in heart rate. The preejection phase of systole was not altered. Indoramin and propranolol, each alone and together, attenuated the pressor and other cardiovascular responses. Submaximal exercise increased heart rate during placebo treatment, a response only partially attenuated by indoramin, propranolol, and their combination, but it did not induce changes in mean blood pressure during any of the treatments.Clinical Pharmacology and Therapeutics(1982)32,7–11; doi:10.1038/clpt.1982

ISSN:0009-9236    

DOI:10.1038/clpt.1982.119

年代:1982

数据来源: WILEY

摘要:

Digoxin has been reported to induce feminizing effects in man. It does not compete for estradiol cytosol receptors in human breast carcinoma cells, however, and has no uterotrophic effect. We therefore investigated whether feminization might be due to digoxin action on plasma concentrations of sex steroids. Six healthy men (31.5 ±4 yr old) received therapeutic doses of digoxin for 43 days. We measured plasma concentrations of testosterone, androstenedione, dehydroepiandrosterone, estrone, estradiol, progesterone, 17‐hydroxyprogesterone, cortisol, and aldosterone. During 35 days on digoxin levels of these steroids remained in the normal range and there was no change from before‐drug values. Digoxin was in the therapeutic range of 1.9 ±3 nmol/l throughout. After stimulation by adrenocorticotropic hormone or human choriongonadotropin, the rise in plasma steroids was in the same range as when digoxin was given, as well as 16 wk after it had been discontinued. A normal rise in luteinizing hormone after luteinizing hormone‐releasing hormone showed that the hypothalamogonadal feedback was not altered by digoxin. Free testosterone, estradiol, and cortisol concentrations under basal conditions and after stimulation were also the same before and after drug. It is concluded that the estrogen‐like activity of digoxin cannot be explained by altered steroid availability from plasma. Feminizing effects attributed to digoxin may be caused by other conditions known to influence sex steroid hormones that are common in patients with heart disease. Our data suggest that digoxin may be the preferred digitalis therapy to avoid feminizing effects.Clinical Pharmacology and Therapeutics(1982)32,12–17; doi:10.1038/c

ISSN:0009-9236    

DOI:10.1038/clpt.1982.120

年代:1982

数据来源: WILEY

摘要:

Beta‐adrenoceptor blockade increases serum K, which may be related to renin inhibition, hypoaldosteronism, and exercise‐induced skeletal muscle release of serum K. We report on the dynamic and biochemical response to Clonidine (C) after single (S) 0.2‐mg and repeated (R) 0.1‐mg bid doses of C to six normal subjects at rest, 2 hr after dosing and immediately before dynamic physical activity (DPA) on a treadmill, and at peak activity and 2 hr after DPA. Blood pressure (BP), heart rate (HR), plasma renin concentration (PRC), aldosterone (ALD), serum K, epinephrine (E), and norepinephrine (NE) were measured in standing subjects before and 2 hr after placebo or C (S or R), at peak DPA, and 2 hr after exercise. K, BP, and HR were also determined during all stages of DPA. Results show a parallel rise in K at peak over rest after C (S or R) and after placebo. NE, E, and PRC decreased after 1 wk of C (P<0.01), but the fall of ALD was only slight. The fall in NE at rest suggested a relationship to the decrease in systolic BP and rate pressure product after 1 wk on C. With DPA there is a normal yet smaller increase in systolic BP and also a smaller rise in HR with S‐ and R‐dose C. There is no adverse rise in K in C‐treated subjects during DPA.Clinical Pharmacology and Therapeutics(1982)32,18–24; doi:10.10

ISSN:0009-9236    

DOI:10.1038/clpt.1982.121

年代:1982

数据来源: WILEY

摘要:

The effect of oral sotalol on the heart rate‐corrected QT interval (QTC) was studied in 33 hypertensive patients. Sotalol given once daily in doses of 160 to 640 mg prolonged the QTCinterval in a concentration‐dependent manner by up to 150 msec (P<0.001) over presotalol levels. The prolongation did not correlate with the initial length of the QTCinterval. In seven patients with sotalol‐prolonged QTCinterval, the withdrawal of sotalol for 3 days shortened the interval to nearly its original length. The effect of sotalol on PQ and QRS times was minimal. Sotalol seems to differ from other beta antagonists in having clear amiodarone‐like effects on the action potential of the heart after short‐ and long‐term administration. The measuring of the QTCinterval is recommended if high sotalol concentrations are expected, since the risk of cardiac arrhythmias may increase.Clinical Pharmacology and Therapeutics(1982)32,25–32; doi:10.1038

ISSN:0009-9236    

DOI:10.1038/clpt.1982.122

年代:1982

数据来源: WILEY

摘要:

Pranolium chloride (dimethylpropranolol chloride) is a nonbeta blocking quaternary ammonium that has structural similarities to propranolol and bretylium that exerts antiarrhythmic effects in animals. In initial studies, eight patients with chronic ventricular arrhythmias were given gradually increasing intravenous doses of pranolium (up to 3 mg/kg) obtaining plasma concentrations up to 7 μg/ml without change in pulse, blood pressure, or arrhythmia frequency. We therefore evaluated the response to pranolium in seven similar patients at doses up to 10 mg/kg as an infusion of 100 μg/kg/min over 40 to 100 min. At plasma concentrations of 4.7 to 12.2 μg/ml, there was suppression of ventricular ectopic depolarizations (>90%) in three subjects and in two others there was partial suppression (49% and 82%). Arrhythmia frequency was unchanged in two. At plasma concentrations of 4.1 to 17.2 μg/ml four subjects developed nausea (two of these also vomited) and two experienced perioral numbness. There was no change in sinus heart rate, supine or standing blood pressure, venous reflex response (adrenergic reflex venoconstriction), or ECG intervals in any subject. Pranolium appeared to have antiarrhythmic efficacy in five of seven subjects, without evidence of beta‐adrenergic blockade or interference with sympathetic neuron function known to occur with its congeners, propranolol and bretylium. There is a narrow margin between pranolium efficacy and toxicity. It may, however, be a prototype for antiarrhythmic drugs that do not exert undesirable effects on the adrenergic nervous system.Clinical Pharmacology and Therapeutics(1982)32,33–40; doi:10.1038/clpt.

ISSN:0009-9236    

DOI:10.1038/clpt.1982.123

年代:1982

数据来源: WILEY

摘要:

The effect of oral prazosin on blood pressure and antagonism of phenylephrine‐induced blood pressure increase was investigated in six healthy subjects during a dosing interval after the first dose and 3 days after the first dose of the drug. Prazosin lowered standing blood pressure more after the first dose than after the same dose 3 days later, despite similar plasma levels. Blood pressure decrease correlated with plasma prazosin levels during the elimination phase at the first dose, but not after 3 days of therapy. The phenylephrine log dose‐response curves shifted to the right after prazosin, which indicates α‐receptor antagonism of the drug. On day 4, the phenylephrine curve before prazosin dose shifted to the right of the pretreatment curve on day 1, despite very low prazosin plasma levels. On day 4 after prazosin dosing the phenylephrine dose‐response curves were shifted to the left of that on day 1. Our data indicate tolerance to prazosin effect on blood pressure and to phenylephrine agonism after 3 days dosing. Our data suggest that this might be due to de sensitization of α1‐adrenoceptors with differential effects of agonists and antagonists.Clinical Pharmacology and Therapeutics(1982)32,41–47; doi:10.1038

ISSN:0009-9236    

DOI:10.1038/clpt.1982.124

年代:1982

数据来源: WILEY

摘要:

The new angiotensin converting enzyme inhibitor enalapril maleate was given in single oral doses of 2.5, 5, and 10 mg to 11 hospitalized patients with uncomplicated essential hypertension who were on a 150‐mEq sodium diet. All doses of enalapril induced reduction of mean seated diastolic blood pressure (SDBP). The magnitude of the initial SDBP reduction was not dose related, but the duration of effect was longer (>12 hr) after the 5 and 10 mg. After dosing, mean plasma angiotensin converting enzyme activity (ACE) and aldosterone concentration (PAC) fell, while plasma renin activity (PRA) rose. Serum concentrations of the active diacid form of enalapril increased linearly with dosage; ACE was inhibited maximally at concentrations above 10 ng/ml. During repeated dosing in the outpatient trial there was attenuation of the antihypertensive effect (12 to 24 hr after dosing) in eight of 10 patients. Despite dose increases only two patients achieved SDBP control (≤90 mm Hg). In the five patients in whom 50 mg/day hydrochlorothiazide was added near the end of the trial mean SDBP was further reduced. Enalapril was well tolerated. Further studies of the drug, especially in combination with diuretic, are needed.Clinical Pharmacology and Therapeutics(1982)32,48–53; doi:10.1038/clpt.19

ISSN:0009-9236    

DOI:10.1038/clpt.1982.125

年代:1982

数据来源: WILEY

摘要:

The effects of dipyridamole, a coronary and peripheral vasodilator drug, on cardiac performance were investigated in nine patients with severe chronic heart failure. Dipyridamole (30 to 80 mg IV) increased cardiac index (1.63 to 2.65 l/min/m2) and decreased systemic vascular resistance (2097 to 1124 dyn/sec/cm−5). Left ventricular filling pressure decreased (23.7 to 20.7 mm Hg) without significant changes in mean right atrial pressure or heart rate. These effects were similar to the hemodynamic responses after 100 mg hydralazine in the same patients, but they were of shorter duration (<90 min). In contrast, oral dipyridamole induced only modest responses in three of eight patients despite large single doses of the drug (150 to 300 mg). Dipyridamole is a rapid‐acting short‐lived vasodilator, which exerts predominantly arterial vasodilator actions similar to those of hydralazine. Due to inconsistent response after oral doses, however, the therapeutic application of dipyridamole in long‐term management of chronic heart failure appears to be limited.Clinical Pharmacology and Therapeutics(1982)32,54–61; doi:10.1038/clp

ISSN:0009-9236    

DOI:10.1038/clpt.1982.126

年代:1982

数据来源: WILEY

摘要:

Nitroprusside and furosemide are both used to treat acute left ventricular failure, but their hemodynamic effects have not been compared in the same patients. In 13 patients with acutely decompensated chronic left ventricular failure, we infused nitroprusside to reduce pulmonary wedge pressure to normal without inducing hypotension. When hemodynamics returned to control after stopping nitroprusside, furosemide was given as a 200‐mg rapid infusion. Control hemodynamic values before each drug were in the same range. Mean arterial pressure fell from 99.9 ± 16.7(SD) to 74.8 ±10.5 mm Hg on nitroprusside (P<0.001) and was unchanged after furosemide. Nitroprusside reduced pulmonary wedge pressure from 30.5 ±6.9 to 15.9 ±6.0 mm Hg (P<0.001), while furosemide reduced it to 27.5 ±8.5 mm Hg (P<0.05). Cardiac index rose from 2.33 ±0.78 l/min/m2to 3.62 ±0.93 l/min/m2(P<0.001) on nitroprusside and remained unchanged at 2.32 ±0.64 l/min/m2after furosemide. At the same pulmonary wedge pressure on each drug (24 mm Hg), cardiac index was increased by nitroprusside (+0.6 ± 0.5 l/min/m2, P<0.01) and unchanged by furosemide. Thus, furosemide reduces only preload without changing cardiac output in patients with left heart failure, whereas nitroprusside at similar or lower preload in the same patients reduces afterload and raises cardiac output and improves left ventricular performance. Nitroprusside appears preferable for the immediate treatment of left ventricular failure.Clinical Pharmacology and Therapeutics(1982)32,62–69; doi:10.1038/

ISSN:0009-9236    

DOI:10.1038/clpt.1982.127

年代:1982

数据来源: WILEY