The absolute systemic availability of a new oral formulation of co-dergocrine in healthy subjects

We have studied the absolute systemic availability (f) of an oral formulation (Hydergin spezial = Hydergine FASR 4 mg per tablet) of co-dergocrine by three different methods. Twelve healthy volunteers received single doses of 0.9 mg co-dergocrine intravenously and 8.0 mg orally in a randomized crossover design. The pharmacological effect of co-dergocrine was monitored as a reduction in plasma prolactin. Maximal plasma concentrations of co-dergocrine after oral dosing ranged between 0.181 and 1.307 ng.ml-1. Maximal urinary excretion ranged between 4.7 and 9.9 micrograms.h-1 and between 0.3 and 2.3 micrograms.h-1 after intravenous and oral doses respectively. Clearance was measured as 90 +/- 22 l.h-1 and the absolute systemic availability (f) as 2.25 +/- 0.65% by using the areas under the plasma concentration-time curves extrapolated to infinity. Calculation of f by comparing areas up to 32 h or the fractions of the dose excreted in urine led to identical results. The intravenous and oral doses produced similar pharmacological effects (reduction of plasma prolactin concentrations) despite the small value of f.

[Bioavailability of heptaminol in healthy subjects]

In ten healthy volunteers the plasma and urine concentrations of heptaminol (Heptylon) were determined by high-performance liquid chromatography after intravenous administration of 250 mg heptaminol and oral intake of 2 x 150 mg heptaminol in tablet form, and the pharmacokinetic parameters were calculated. Heptaminol was rapidly and entirely absorbed following oral administration of heptaminol. Mean plasma peak concentrations of 1.6 mg/l were reached after 1.8 h, the area under the plasma concentration-time curve was equal to that after intravenous administration. The dominant terminal plasma half-life was 2.5-2.7 h. The total clearance amounted to 700 ml/min, and nearly all the dose given was recovered unchanged in urine within 24 h, indicating renal elimination by glomerular filtration and tubular secretion without metabolization.

[The bioavailability of midodrin and alpha-2,5-dimethoxyphenyl-beta-aminoethanol hydrochloride]

The pharmacokinetics of midodrin (alpha-2,5-dimethoxyphenyl-beta-glycinamidoethanol hydrochloride, ST 1085) and its main metabolite ST 1059 (alpha-2,5-dimethoxyphenyl-beta-aminoethanol hydrochloride) have been investigated in 12 male healthy volunteers. 2.5 mg midodrin hydrochloride were applied intravenously, as drinking solution or as tablet (Gutron) according to a randomized cross-over design. Plasma and urine samples collected up to 24 h after application were analyzed by high-performance liquid chromatography with fluorescence detection. The mean maximum concentration in plasma for midodrin was ca. 10 ng/ml 20-30 min after oral administration, for ST 1059 ca. 5 ng/ml after 1 h. Midodrin was eliminated with a terminal half-life of 0.5 h. The half-life of ST 1059 was determined to be 3 h. The mean area under the plasma-level vs. time curve (AUC) of ST 1059 after administration of 2.5 mg midodrin i.v. was 28.7 ng X h/ml, and as drinking solution or as tablet 25.7 and 25.6 ng X h/ml, respectively. The data of 10 volunteers could be used for the calculations of the bioavailability of ST 1059 by the AUC. Assuming an interval of equivalence of 0.75-1.25 because of the relatively small number of volunteers, the three galenical formulations are considered to be equivalent.

Inhibition of monoamine oxidase by viloxazine in rats

Biochemical and pharmacological investigations about the effect of the antidepressant drug viloxazine (Vivalan) on catecholamine metabolism in rats led to the following results: Viloxazine exerts a dose and time dependent inhibition of monoamine oxidase activity of brain and liver mitochondrial fraction and tissue homogenates of hypothalamus, heart, liver, and adrenal glands, both in vitro and after oral and parenteral administration in vivo. Consequently, an increase in catecholamine concentrations in brain of rats could be observed after pretreatment with viloxazine. In addition brain serotonin concentrations rose and 5-hydroxy-indoleacetic acid was diminished. However, characterization of inhibition of monoamine oxidase activity by viloxazine in vitro revealed: Compared to the specific inhibitors clorgyline for MAO-A- and pargyline for MAO-B-activity, viloxazine was a very weak inhibitor both for MAO-A and MAO-B in vitro. The type of inhibition was competitive and reversible. From the presented results and the results obtained by other laboratories it is concluded that inhibition of monoamine oxidase activity by viloxazine, although clearly demonstrated in animal experiments, may not be the only mechanism for an antidepressant action of the drug in man.

Pharmacokinetics, in-vitro activity, therapeutic efficacy and clinical safety of aztreonam vs. cefotaxime in the treatment of complicated urinary tract infections

The minimal inhibitory concentrations (MICs) of aztreonam and cefotaxime were determined against 400 isolates from urological in-patients with complicated and/or hospital acquired urinary tract infections (UTI). Against the Gram-negative rods the activities of both antibiotics were comparable except for higher activity of aztreonam against Pseudomonas aeruginosa. The pharmacokinetic study in nine elderly patients showed a prolonged plasma half life of aztreonam (2.7 h) as compared to younger volunteers (1.6-1.9 h). In a prospective randomized study 39 urological patients with complicated and/or hospital acquired UTI were treated with 1 g aztreonam or cefotaxime iv twice daily for 4 to 15 days. Cure was obtained in 5 out of 18 patients in the aztreonam and 7 out of 20 patients in the cefotaxime group. There were 3 superinfections, 7 relapses and 3 reinfections in the aztreonam group and 1 failure, 1 superinfection, 6 relapses and 5 reinfections in the cefotaxime group. There was no significant difference in therapeutic efficacy between the two antibiotics. Both antibiotics were tolerated well and seem to be equally effective in the treatment of complicated UTI caused by sensitive organisms.

Circulating and tissue catecholamines in rats with chronic neurogenic hypertension

To study the role of peripheral catecholamines in plasma and different tissues in neurogenic hypertension we measured directly blood pressure, maximum rate of left ventricular pressure rise (dp/dtmax) and heart rate through an aortic catheter 5 weeks after total sino-aortic baroreceptor deafferentation in male Sprague-Dawley rats. Blood samples were collected through the same catheter to determine plasma catecholamine concentrations. Blood pressure and dp/dtmax were significantly higher in neurogenic-hypertensive rats when compared with sham operated rats. Plasma noradrenaline concentrations and plasma adrenaline concentrations reached significantly higher levels in neurogenic-hypertensive rats. In the heart noradrenaline content was lower (when calculated per g wet weight) and in the adrenal medulla adrenaline content was higher in neurogenic-hypertensive rats, when compared with sham operated controls. A significant positive correlation was found between dp/dtmax and plasma noradrenaline concentrations. It is concluded that sino-aortic baroreceptor deafferentation produces a significant chronic hypertension, probably supported by elevated plasma catecholamine concentrations and enhanced synthesis and release of adrenaline from adrenal medulla.

Changes in plasma catecholamine concentrations in patients with coronary heart disease during pacing and physical exercise

To study the difference in sympathetic activity during pacing the right atrium or during physical exercise in patients with coronary heart disease, we investigated circulating plasma catecholamine concentrations in the coronary sinus and brachial artery radioenzymatically in 11 male patients with well documented coronary artery disease. Heart rate was increased stepwise 20 beats/min from 90 beats/min up to 150 beats/min by pacing the right atrium and physical exercise was performed by increasing work load stepwise by 25 from 25 up to 100 W on an ergometric bicycle. Plasma noradrenaline and adrenaline concentrations were increased significantly only during physical exercise. In addition, there was an increase in arterial-coronary sinus noradrenaline difference during graded physical exercise, whereas no further release of noradrenaline from the myocardium occurred during pacing. An enhanced cardiac sympathetic tone in patients with coronary heart disease is discussed. It is suggested that atrial pacing is not an adequate stimulus evoking an overall increase of cardiac and peripheral sympathetic tone.

Effects of nicotine and its major metabolites on blood pressure in anaesthetized rats

Blood pressure and heart rate in anaesthetized rats has been determined after i.v. injection of increasing doses of nicotine (NI) and its major metabolites, i.e. continine (CO), nornicotine (NOR), metanicotine (MN) and dihydrometanicotine (DMN). NI and MN elicited similar dose response curves, increasing blood pressure according to the dose injected. However, the dose response curve of MN was shifted to the right. Furthermore DMN caused similar pressor effects than MN and the pressor effects of NOR was even weaker. Only after injection of CO was a dose-dependent depressor effect observed and this was reversed after very high doses. CO also reduced heart rate in a dose-dependent manner, whereas NI and its other metabolites did not significantly change heart rate.

Sympathoadrenal dysfunction in rats with chronic neurogenic hypertension

Compared to sham-operated controls 5 weeks after surgery neurogenic hypertensive rats with sino-aortic baroreceptor deafferentation had higher blood pressure, higher plasma noradrenaline and adrenaline levels, lower heart noradrenaline concentrations, higher adrenomedullary adrenaline levels and increased cardiac intraventricular pressure (dp/dtmax).

High-performance liquid chromatographic analysis of cefotetan epimers in human plasma and urine

Cefotetan, a new broad-spectrum 7 alpha-methoxycephalosporin antibiotic, was assayed in plasma and urine by means of reversed-phase high-performance liquid chromatography. Commercially available cefotetan exists in two epimeric forms. The procedure described allows the separation and quantitation of both epimers. For the first time a different pharmacokinetic behaviour (t1/2 = 3 h versus 4 h) for each epimer after intravenous injection to healthy volunteers is demonstrated. It is assumed that one epimer is bound to a greater extent to serum proteins and is therefore responsible for the differences observed. As both epimers exhibit similar antibacterial activity, it seems doubtful whether these differences would have clinical significance. Iothalamic acid was determined simultaneously as a marker of kidney function.

Changes in peripheral and central catecholaminergic and serotoninergic neurons of rats after acute and subacute administration of nicotine

To establish dose-response relationships for nicotine (acute and subacute administration), we measured hemodynamic parameters as well as circulating and tissue catecholamines in sympathetically innervated organs in rats. We also investigated nicotines's influence on adrenoceptor binding sites of the heart and on serotonin metabolism. In conscious and anesthetized rats, we found a dose-dependent increase in circulating catecholamines after acute injection of nicotine. At low doses nicotine released norepinephrine, resulting in a decrease of blood flow and heart rate, whereas high doses of nicotine released epinephrine, resulting in a reversal of the cardiovascular parameters investigated. In the heart norepinephrine concentration increased after nicotine application. In the lung epinephrine rose markedly, whereas serotonin and 5-hydroxyindolacetic acid were diminished. After subacute administration of nicotine the number of binding sites for 3H-Dihydroalprenolol in the heart was significantly reduced, whereas norepinephrine content was increased. Dopamine, serotonin, and 5-hydroxyindolacetic acid were increased in the hypothalamus. Our findings show that nicotine not only affects peripheral and central catecholaminergic neurons, but also central serotoninergic neurons, thus enhancing turnover of these amines.

Ceftazidime: pharmacokinetics in young volunteers versus elderly patients and therapeutic efficacy with complicated urinary tract infections

Thirty-six urological patients (21 male, 15 female) aged 21 to 83 years with complicated and/or hospital-acquired urinary tract infections due to sensitive bacteria were treated with ceftazidime intravenously with a daily dose of 2 g bd over 5 to 17 days. Twenty-seven patients were followed for 1 to 4 weeks after therapy. Cure was observed in 41%, reinfection in 33% and relapse in 26% of the patients. Eradication of the original pathogen occurred in 74%. Five patients showed minor side effects: diarrhoea (2), nausea (1), rash (1), headache (1). No signs of renal, hepatic or haematological toxicity were observed. A pharmacokinetic study was performed in 13 elderly patients aged 63 to 83 years on day 1 of treatment and in 6 volunteers aged 24 to 32 years following administration of 2 g of ceftazidime as short intravenous infusion. The mean serum half life in 12 patients 2.9 h significantly higher than in volunteers (1.75 h). Serum concentrations in patients on day 7 of treatment, however, showed no accumulation when treated with a dosage of 2 g bd.

Transmitter-peptide coexistence in the central nervous system

In this minireview about transmitter coexistence situations in central nervous system and peripheral sympathetically innervated tissues, the classical transmitters, dopamine, noradrenaline, adrenaline and serotonin, together with peptides such as substance P, cholecystokinin and avian pancreatic polypeptide, have been considered. The specificity of an immunohistochemical reaction for the identification of peptides and functional aspects of central transmitter peptide coexistence are discussed. In conclusion, in several experimental models it has been demonstrated that peptides, which are known to coexist with monoamines, exert specific effects in those regions where coexistence situations have been reported. In general, the effect of the co-stored peptides seems to be enhancement of the response caused by monoamines, indicating that two coexisting neuroactive substances cooperate in causing a certain physiological response.

Induction of anesthesia with halothane increases plasma norepinephrine concentrations

In seven unstimulated, unmedicated patients given halothane/O2 via face mask, plasma norepinephrine concentration increased 15 min after induction and returned to control at 45 to 60 min. Changes in plasma norepinephrine levels did not correlate with changes in cardiovascular variables. In 10 additional awake, unpremedicated patients, plasma norepinephrine concentration did not change during 5 min of application of 100 per cent oxygen via face mask, but rose with subsequent administration of halothane and nitrous oxide. Again, changes in plasma norepinephrine did not correlate with changes in cardiovascular variables. The authors perfused seven isolated cat spleens with a Krebs-Ringer's lactate solution. Addition of 0.01 atm halothane to the perfusate initially increased release of norepinephrine into the effluent. The authors conclude that halothane or halothane-nitrous oxide initially increases plasma norepinephrine during induction of anesthesia. This increase is not due to the placement of a face mask, but may relate to an effect of halothane at sympathetic nerve endings.

Elevated plasma catecholamines in young hypertensive and hyperkinetic patients: effect of pindolol

1 The sympathetic nervous system plays an important role in the regulation of blood pressure. Plasma catecholamine concentrations are considered to be reliable indices of sympatho-neuronal (noradrenaline) and sympatho-adrenal (adrenaline) activity and reactivity in man.

2 Sympathetic and adrenal activity and reactivity in young patients with essential hypertension or hyperkinetic heart syndrome were compared with an appropriate control group matched for age. The groups of hypertensive patients and patients with hyperkinetic heart syndrome could be clearly distinguished from control subjects on the basis of circulating catecholamine levels at rest.

3 A clear-cut increase in circulating noradrenaline and adrenaline was observed in young patients with essential hypertension and hyperkinetic heart syndrome at rest. Clinically, hypertensive patients were characterized by elevated systolic and diastolic blood pressure and increased heart rate, whereas patients with hyperkinetic heart syndrome had increased heart rate and increased systolic blood pressure, whereas diastolic blood pressure was normal. At rest, there was a significant positive correlation between heart rate and circulating catecholamines in both groups of patients. In hypertensives a positive correlation between heart rate and plasma adrenaline concentrations, in patients with hyperkinetic heart syndrome a positive correlation between heart rate and plasma noradrenaline concentrations could be observed. In addition a positive correlation between plasma noradrenaline concentrations and systolic blood pressure in all groups of patients studied, was obtained.

4 Sympatho-neuronal and sympatho-adrenal reactivity during mental stress or physical exercise increased in both groups of patients, mirrored by an increase in blood pressure and heart rate.

5 Pindolol, a potent non-selective β-adrenoceptor blocking drug with intrinsic sympathomimetic activity and minimal membrane stabilizing properties, administered in a single oral dose of 10 mg, diminished the exaggerated sympathetic tone in both groups of patients by attenuating circulating catecholamine levels at rest or during mental stress, but not during physical exercise.

Plasma noradrenaline correlates to sympathetic muscle nerve activity in normotensive man

Recordings of multiunit sympathetic activity were made in muscle branches of the peroneal nerve in 22 healthy subjects at rest in recumbent position. Nerve activity was quantitated in terms of burst incidence (number of pulse synchronous sympathetic bursts per 100 heart beats or per min). In a separate session, 4-45 months later, blood was drawn from an antecubital vein for noradrenaline analysis. Both sympathetic activity and plasma concentrations of noradrenaline varied widely between subjects and both parameters increased with age. There was a significant positive correlation between a subject's level of sympathetic activity and his plasma concentration of noradrenaline. It is suggested that overflow of transmitter from sympathetic terminals in muscles contributes significantly to plasma levels of noradrenaline at rest.

[Effects of acute beta-adrenoceptor blockage (metoprolol i.v.) on plasma norepinephrine concentration and hemodynamics in postmyocardial infarction patients]

The effect of acute beta-adrenoceptor blockage (Metoprolol) (M), 0.1 mg/kg i.v.) on left ventricular performance has been investigated at rest and during exercise in 15 patients with 2--3 months old transmural myocardial infarctions. Coronary venous and arterial norepinephrine (NE) concentrations were determined. There was no significant change in arterial and coronary venous NE concentrations (0.27 and 0.22 ng/ml, respectively) after blockage of beta-adrenoceptors (0.36 vs 0.26 ng/ml), which caused a fall of stroke volume from 79 to 68 ml, a reduction of ejection fraction from 62 to 55% and of circumferential fibre shortening form 1.2 to 0.9 circ/sec. During physical exercise the plasma NE concentration in the arterial (0.51 ng/ml) and coronary venous (0.6 ng/ml) blood increased significantly and increased even further to 0.65 and 0.76 ng/ml, respectively, following administration of Metoprolol. The arterio-coronary sinus difference in NE concentrations demonstrate a release of NE from the myocardium. As compared to control values, heart rate following Metoprolol was lower (116 vs 106/min), mean PCV pressure was slightly increased (from 21 to 23 mm Hg) and there was a fall of cardiac index from 6.3 to 5.2 l/min X m2. It is likely that the increased sympathetic activity after Metoprolol and during exercise is a compensatory reaction due to the hemodynamic effects of blockade of beta-adrenoceptors. Further studies are in preparation in order to find out if this is only a transient phenomenon during the early adaptation phase after blockade of beta-adrenoceptors.

Changes in central catecholaminergic neurons in the spontaneously (genetic) hypertensive rat

Catecholamines and catecholamine-synthesizing enzymes have been examined in specific brain areas during the development of spontaneously (genetic) hypertensive (SH) rats. Changes in catecholamine metabolism were localized to regions of the brain implicated in the regulation of blood pressure. Norepinephrine levels and dopamine-beta-hydroxylase (DBH) activities were decreased in specific nuclei of the hypothalamus and in the nucleus interstitialis striae terminalis ventralis, in both young and adult rats. The decrease in the formation of norepinephrine can result in a reduced activation of central alpha-adrenergic receptors which may be related causally to the onset of hypertension. The activity of the epinephrine-forming enzyme, phenylethanolamine-N-methyltransferase (PNMT), was increased in the A1 and A2 areas of the brainstem in young SH rats, but it was normal in adult hypertensive animals. These results implicate adrenergic neurons in the brainstem and noradrenergic neurons in the hypothalamus in the development of spontaneous (genetic) hypertension in rats.

Effect of prolonged treatment with adrenergic neuron blocking drugs on sympathoadrenal reactivity in rats

The effects of repeated high doses of the adrenergic neuron blocking drug guanethidine or a hexahydropyrazinoindole compound (2-guanyl-1,2,3,10,10a, hexahydro-1,2,a-pyrazinoindole, EMD 21192) (30 mg/kg i.p., 21.5 mg/kg i.p. respectively, equimolar doses) on sympathoadrenal activity were investigated in normotensive adult rats. During treatment for 5 weeks with either guanethidine or EMD 21192 the systemic blood pressure fell steadily. Noradrenaline content in the heart and vas deferens were decreased markedly by guanethidine and to a much less degree by EMD 21192. EMD 21192 markedly lowers the catecholamine content of the adrenal medulla, presumably as a result of inhibition of dopamine-beta-hydroxylase. The plasma catecholamine concentrations reflected the different sites of action of the drugs in the sympathoadrenal system, i.e. guanethidine mainly reduced circulating norepinephrine and dopamine-beta-hydroxylase by more than 50%, whereas EMD 21192 decreased considerably by the total catecholamines (mainly epinephrine) without altering significantly in the plasma norepinephrine. Disappearance or reduction of fluorescent nerve endings in the iris and the heart and a decrease of the intensity of fluorescence in chromaffin cells of the adrenal gland caused by the drugs were consistent with the biochemical alteration. Whereas the repeated doses of guanethidine caused degeneration of sympathetic nerves, destruction of adrenergic neurons was not found after prolonged treatment with EMD 21192.

Biochemical and morphologic study of catecholamine metabolism in spontaneously hypertensive rats

Catecholamines and catecholamine-synthesizing enzymes have been studied quantitatively in specific brain areas of spontaneously (genetically) hypertensive rats by means of a combination of sensitive enzymatic-isotopic methods and a microdissecting technique. Changes in catecholamine metabolism were found to be localized to regions of the brain implicated in the regulation of blood pressure. Noradrenaline levels were decreased in specific nuclei of the anterior hypothalamus and in the nucleus interstitialis striae terminalis ventralis. The activity of the adrenaline-forming enzyme, phenyl-ethanolamine-N-methyl transferase, was increased in the A1 and A2 areas of the brain stem. These results implicate catecholamine-forming neurons in the hypothalamus and brain stem in the development of spontaneous hypertension in rats.

Peripheral and central catecholaminergic neurons in genetic and experimental hypertension in rats

1. Activity of peripheral and central catecholaminergic neurons was studied in spontaneously hypertensive rats (SHR) and deoxycorticosterone (DOCA)-salt hypertensive rats. 2. In young SHR (4 weeks) the plasma values of bpth noradrenaline and dopamine-beta-hydroxylase activity were increased compared with those of normotensive rats of the Wistar/Kyoto strain. Total catecholamines (mostly adrenaline) were not significantly different. 3. In the adrenal glands of 2-weeks-old and 4-weeks-old SHR activities of tyrosine hydroxylase, dopamine-beta-hydroxylase, phenylethanolamine-N-methyl transferase were decreased, compared to Wistar/Kyoto rats. 4. The adrenaline-forming enzyme was elevated in the A1 and A2 regions of the brain stem of 4-weeks-old SHR and in the A1 region of adult DOCA-salt hypertensive rats. 5. In the adrenal glands of adult DOCA-salt hypertensive rats tyrosine hydroxylase activity was increased. 6. These results implicate peripheral noradrenaline-containing neurons and central adrenaline-containing neurons in the development of genetic and experimental hypertension in rats.