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  • 1
    ISSN: 1432-1041
    Keywords: verapamil ; renal failure ; norverapamil ; pharmacokinetics ; haemodialysis ; ECG ; blood pressure ; heart rate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics of verapamil was studied in patients with end-stage chronic renal failure and in normal subjects after i.v. injection of 3 mg and a single oral dose of 80 mg. Plasma levels of verapamil and its active metabolite norverapamil were measured by HPLC. After i.v. injection, the terminal phase half-life and total plasma clearance of verapamil in both groups were similar. Haemodialysis did not change the time course of plasma verapamil levels after i.v. administration. After a single oral dose, the plasma levels of verapamil and norverapamil in both groups of subjects were similar. Subsequently, normal volunteers and patients with renal failure were treated for 5 days with oral verapamil 80 mg t.d.s. There was no difference between the 2 groups of subjects in the trough and peak levels of verapamil or of norverapamil. Intravenous and oral administration of the calcium channel blocking agent had similar effects on blood pressure, heart rate and the PR-interval in the electrocardiogram in both groups. The study demonstrated that the disposition of verapamil was similar in normal subjects and in patients with renal failure.
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  • 2
    ISSN: 1432-1041
    Keywords: Benserazide ; decarboxylase inhibition ; alpha-methyldopa ; essential hypertension
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In a single-blind study, the dopa-decarboxylase inhibitor benserazide (375 mg/day for 3 days and 750 mg/day for further 3 days) and a placebo were given orally in combination with individually effective doses of alpha-methyldopa (mean 1.5 g/day) to 3 hospitalized patients with essential hypertension. Alpha-methyldopa (α-MD) alone lowered blood pressure from 165/107 to 136/93 mm Hg (P〈0.05). Benserazide did not alter the hypotensive effect of α-MD, although the decarboxylation of α-MD was markedly reduced, as shown by the urinary excretion of alpha-methyldopamine (α-MDA). During administration of α-MD alone, the ratio α-MD/α-MDA in urine of the 3 patients was 8:1, 7:1 and 22:1, respectively. When benserazide 375 mg/day was added the ratio rose to 31:1, 31:1 and 35:1; the ratio was 37:1, 18:1 and 46:1 at the higher dose of inhibitor. In a double-blind crossover study the effect on blood pressure of 3 weeks of treatment with α-MD (mean 1.75 mg/day), benserazide (375 mg/day), placebo and their combinations were compared in 5 hypertensive subjects. Again, benserazide did not influence the antihypertensive action of α-MD. To study whether benserazide entered the CNS, a single oral dose of14C-benserazide of 125 mg was given to 2 patients who were to undergo diagnostic lumbar puncture. Two hours after intake of the labelled drug, when radioactivity in blood had reached a maximum, the concentration of radioactivity in spinal fluid was less than 1% of the plasma level. Thus, the antihypertensive action of α-MD was not influenced by oral doses of the decarboxylase inhibitor benserazide. The results suggest that benserazide in doses up to 750 mg/day does not affect central decarboxylation of α-MD and that this antihypertensive agent lowers blood pressure by a central action.
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  • 3
    ISSN: 1432-1041
    Keywords: ramipril (HOE 498) ; hypertension ; angiotensin converting inhibition ; dose-response relationship ; time course
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The time course of the blood pressure lowering effect and the dose-response relationship of the new angiotensin converting enzyme inhibitor ramipril (HOE 498) were studied in 8 patients with essential hypertension. As compared with placebo, a single oral dose of 2.5 mg ramipril lowered systolic and diastolic blood pressure. The antihypertensive action of single oral doses of 5, 7.5 and 10 mg ramipril was more pronounced. No change in heart rate occurred. Angiotensin converting enzyme activity was suppressed after all doses of ramipril studied. Plasma renin activity increased after 2.5 mg and 5 mg ramipril. Plasma aldosterone was not affected by 2.5 mg, but it fell after 5 mg ramipril. Thus, ramipril produced prolonged inhibition (more than 12 hours) of angiotensin converting enzyme activity and lowered blood pressure in patients with essential hypertension.
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  • 4
    ISSN: 1432-1041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Description / Table of Contents: Zusammenfassung An 13 Hypertonikern wurde die Harnausscheidung von α-Methyldopa, α-Methyldopamin und Katecholammen während einer Dauerbehandlung oder nach einer Einzeldosis von α-Methyldopa untersucht. Die im Harn enthaltenen Substanzen werden durch Ionenaustausch- und Papierchromatographie voneinander getrennt und fluorometrisch oder biologisch bestimmt. — Von alien Patienten wurde außer freiem und konjugiertem α-Methyldopa und α-Methyldopamin auch α-Methylnoradrenalin ausgeschieden. Gleichzeitig nahm die Ausscheidung von Noradrenalin gegenüber der Vor-und Nachperiode bei fast allen Patienten ab. Es kann ausgeschlossen werden, daß die bei der Behandlung durch die Nieren ausgeschiedenen Mengen von α-Methyldopa, α-Methyldopamin oder α-Methylnoradrenalin die renale Ausscheidung von Noradrenalin herabsetzten. Die während der Behandlung ausgeschiedene Menge von Noradrenalin, Adrenalin und α-Methylnoradrenalin zusammengenommen unterschied sich nicht von der Katecholamin-Ausscheidung vor und nach der Behandlung. — Das biosynthetisch vom Menschen gebildete α-Methylnoradrenalin verhielt sich nach dem Ergebnis chemischer und pharmakologischer Tests wie Corbadrin, welches die Erythro-Konfiguration aufweist; α-Methylnoradrenalin ließ sich eindeutig von dem Diastereomeren von Corbadrin differenzieren, welches die Threo-Konfiguration besitzt. Im Harn der Patienten konnte α-Methyladrenalin nicht nachgewiesen werden. Gegen eine Beteiligung von α-Methyladrenalin, welches nach Tierversuchen durch Erregung von adrenergen β-Receptoren blutdrucksenkend wirkt, an der hypotensiven Wirkung von α-Methyldopa spricht ferner, daß die Blutdruckabnahme nach α-Methyldopa durch Propranolol nicht aufgehoben, sondern eher sogar verstärkt wurde. — Die systolische Blutdrucksenkung war sowohl der Abnahme der renalen Ausscheidung von Noradrenalin als auch dem Prozentsatz von α-Methylnoradrenalin an der gesamten Katecholamin-Ausscheidung significant korreliert; auch im Zeitverlauf ergab sich bei drei Patienten nach einer Einzeldosis von α-Methyldopa eine Korrelation zwischen hypotensivem Effekt einerseits und Abnahme der Noradrenalin- bzw. Zunahme der α-Methylnoradrenalin-Ausscheidung andererseits. — Die Ergebnisse machen es wahrscheinlich, daß der früher in Tierversuchen nach Verabreichung von α-Methyldopa nachgewiesene teilweise Ersatz des sympathischen Überträgerstoffs Noradrenalin durch α-Methylnoradrenalin auch unter therapeutischer Dosierung am Menschen stattfindet. Die Korrelationen von hypotensiven Effekten und Veränderungen im Aminstoffwechsel lassen den SchluB zu, daß α-Methyldopa den Blutdruek von Hypertonikern durch Freisetzung von α-Methylnoradrenalin als „falscher” Überträgersubstanz und entsprechende Verminderung der Noradrenalin-Freisetzung aus sympathischen Nervenfasern herabsetzt.
    Notes: Summary In 13 hypertensive patients the urinary excretion of α-methyldopa, α-methyldopamine und catechol amines was analyzed either during continuous administration or after a single dose of α-methyldopa. The compounds contained in the urine samples were separated by ion exchange and paper chromatography and determined fluorimetrically and biologically. — All patients excreted both free and conjugated α-methyldopa, α-methyldopamine, and small amounts of α-methylnoradrenaline. Compared with the pre- and postdrug period, in nearly all patients the noradrenaline excretion was decreased while α-methyldopa was administered. The experimental data obtained exclude the possibility that the noradrenaline excretion was diminished by the simultaneous excretion of α-methylnoradrenaline or of excessive amounts of α-methyldopa and α-methyldopamine. The combined quantities of noradrenaline, adrenaline and α-methylnoradrenaline excreted daily during administration of α-methyldopa did not differ significantly from the amount of noradrenaline and adrenaline excreted daily before drug treatment was started and after it was discontinued. —Evidence was obtained that α-methylnoradrenaline isolated from urine of patients given α-methyldopa behaved chemically and biologically in a way similar to (−)-corbadrine (erythro-configuration) but differed markedly from the diastereomer of corbadrine (threo-configuration). Hence, biosynthesis of α-methylnoradrenaline leads to the levorotatory erythro-isomer. — In animal experiments carried out previously α-methyladrenaline was found as another metabolite of α-methyldopa which decreased blood pressure by activation of adrenergic β-receptors. The patients given α-methyldopa did not excrete α-methyladrenaline. The method employed was sensitive enough to detect amounts of α-methyladrenaline less than 3 per cent of the α-methylnoradrenaline present. Furthermore, involvement of a β-adrenergic component in the response of the blood pressure to α-methyldopa in hypertensive patients was made unlikely by the observation that propranolol did not antagonize but rather enhanced the hypotensive effect of α-methyldopa. — There was a significant correlation between the fall of systolic blood pressure and both the decrease in urinary excretion of noradrenaline and the increase in the percentage of α-methylnoradrenaline of the total catecholamine output. Likewise, the time course of the depressor response to a single dose of α-methyldopa closely corresponded to the decrease in noradrenaline and the increase in α-methylnoradrenaline excretion. Conversely, the return of the blood pressure to the initial level was reflected by an increase in noradrenaline and a decrease in α-methylnoradrenaline excretion. — In animal experiments it was previously found that administration of α-methyldopa caused a partial displacement of noradrenaline by α-methylnoradrenaline which subsequently was released by sympathetic nerve stimulation. The present findings demonstrate that α-methylnoradrenaline is formed in man as well. It is concluded that α-methyldopa lowers the blood pressure of hypertensive patients by the release of α-methylnoradrenaline as a “false” neurotransmitter and the concomitant decrease in noradrenaline liberation from sympathetic nerve fibres.
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  • 5
    ISSN: 1432-1041
    Keywords: nifedipine ; renal failure ; pharmacokinetics ; protein binding ; blood pressure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The total and free steady-state plasma levels of nifedipine in patients with renal failure have been compared with those in subjects with normal renal function. Studies were done after administration of nifedipine 10 mg t.d.s. p.o. for 5 days, after i.v. infusion of 4·4 mg, and after a single 10 mg oral dose. The systemic clearance of nifedipine after a single i.v.-dose was higher in subjects with renal insufficiency (854 ml/min) than in those with normal renal function (468 ml/min). After the single oral dose the AUC (6100 ng·min·ml−1) and maximum plasma concentration (75.0 ng·ml−1) were lower than in subjects with normal renal function (19300 ng·ml−1; 122 ng·ml−1). The plasma protein binding of nifedipine averaged 95.5% in normal subjects and 94.8% in patients with renal failure. Although free and total steady-state plasma levels of nifedipine tended to be somewhat lower than normal in renal failure, the changes in pharmacokinetics and decreased protein binding of nifedipine did not result in a significantly different steady-state plasma level of the drug. The blood pressure response to a given plasma nifedipine level appeared to be enhanced in renal failure.
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  • 6
    ISSN: 1432-1041
    Keywords: nitrendipine ; renal failure ; pharmacokinetics ; protein binding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The pharmacokinetics and plasma protein binding of nitrendipine in patients with terminal renal failure have been compared with those in subjects with normal renal function. Kinetic parameters were calculated after a single 40 mg oral dose, an i.v. injection of 3 mg and after a 15 mg i.v. infusion of nitrendipine. Steady-state plasma levels were determined after 5 days of oral treatment with 20 mg b.d. Pharmacokinetic parameters and steady-state plasma levels in patients with renal failure did not differ from those in subjects with normal renal function. Nitrendipine was as highly bound to plasma proteins in patients with renal failure, as in subjects with normal renal function. The plasma protein did not differ between the two. The dosage of nitrendipine need not be modified for kinetic reasons in patients with renal failure.
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  • 7
    ISSN: 1432-1041
    Keywords: Dopamine-β-hydroxylase ; dopamine infusion ; blood pressure ; plasma ; man ; inter-individual variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In order to study the function of dopamine-β-hydroxylase (DBH) in human plasma, dopamine, its natural substrate, was infused intravenously in 22 healthy volunteers. Their plasma DBH activities showed great interindividual variations (31–301 units/ml). The infusion rates of dopamine required to increase systolic blood pressure (BP) by 30 mm Hg differed considerably between the subjects, and ranged from 3,0 to 11,6 µg/kg/min. No correlation could be shown between the various dopamine doses and individual plasma levels of DBH. It was concluded, therefore, that plasma DBH in the blood stream was enzymatically inactive. Experiments with human plasma DBH in vitro also support this interpretation. Consequently, interindividual differences in the effects on BP during dopamine infusion cannot be due to pressor effects of noradrenaline synthesized by plasma DBH.
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  • 8
    ISSN: 1432-1041
    Keywords: dobutamine ; dopamine ; myocardial infarction ; haemodynamics ; plasma noradrenaline ; plasma renin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The comparative hemodynamic effects of dobutamine and dopamine were studied in 6 patients with low cardiac output resulting from acute myocardial infarction. Plasma levels of noradrenaline and renin were measured before and during a 5 µg/kg/min infusion of each of the drugs. Dobutamine had a more pronounced chronotropic effect, increased the systolic arterial pressure more and decreased the systemic vascular resistance less than dopamine at doses which had comparable effects on cardiac output. Dobutamine stimulated renin release, which might partly be the cause of the increased systolic arterial pressure. The drug reduced the plasma level of noradrenaline, which might be explained as a reflex reduction in sympathetic tone. Dopamine, however, did not stimulate renin release but it did enhance the plasma level of noradrenaline, which might be due mainly to the release of endogenous noradrenaline.
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  • 9
    ISSN: 1432-1041
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary In hypertensive patients, the effect of propranolol and of the optical isomers of N-isopropyl-p-nitrophenylethanolamine (INPEA) on blood pressure was studied. Single oral doses of 40 mg propranolol, 700 mg (−)-INPEA and 700 mg (+)-INPEA decreased supine systolic as well as standing systolic and diastolic blood pressure. Single intravenous doses of 75 mg (−)-INPEA and 75 mg (+)-INPEA lowered supine systolic and diastolic blood pressure. The antihypertensive action of the beta adrenergic blocking levorotatory isomer of INPEA and of the dextrorotatory isomer, which is devoid of beta adrenergic blocking activity, did not differ. It is concluded from these results that the antihypertensive action of beta adrenergic blocking agents is not related to their beta receptor blocking effect.
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  • 10
    ISSN: 1432-1041
    Keywords: dopamine infusion ; plasma noradrenaline
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
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