The influence of continuous venovenous haemodialysis on the pharmacokinetics of multiple oral moxifloxacin administration to patients with severe renal dysfunction

AIM

We investigated single dose and steady-state pharmacokinetics of moxifloxacin in eight venovenous haemodialysis patients.

METHODS

Plasma, dialysate and urine pharmacokinetic parameters for moxifloxacin and its main metabolites were calculated after single and multiple (7 days) dosing with 400 mg day(-1).

RESULTS

Moxifloxacin pharmacokinetics after a single dose and at steady state (multidose day 7) were comparable in patients with impaired renal function and healthy subjects (geometric mean/%CV AUC mg l(-1) h single dose 37.0/24.3 in haemodialysis patients vs. 29.8/22.6 in healthy subjects, 95% CI for ratio of haemodialysis patients to healthy subjects 99.34%, 154.60%; steady state 40.4/29.1 haemodialysis patients vs. 33.9/20.1 in healthy subjects, 95% CI for ratio of haemodialysis patients to healthy subjects 90/39%, 156.93%). In haemodialysis patients plasma concentrations of moxifloxacin at steady-state were elevated compared with those after a single 400 mg dose (AUC mg l(-1) h, geometric mean/%CV, 40.4/29.1) compared with 37.0/24.3; 95% CI for ratio of steady-state to single dose 87.29%, 136.52%, as were concentrations of metabolite M1 3.21/34.6 compared with 2.02/45.3, 95% CI for ratio of steady state to single dose 14.21%, 175.07%. Haemodialysis cleared about 9% of the dose as unchanged moxifloxacin.

CONCLUSIONS

No dose adjustments are required for venovenous haemodialysis patients on oral moxifloxacin therapy.

Exercise during hemodialysis

In patients with end-stage renal failure physical exercise has beneficial effects on functional capacity, anemia, cardiovascular risks factors and on psychosocial problems. However, only few patients are able or willing to participate in an exercise training which is organised on an outpatient basis. As a consequence, an exercise program was developed which can be performed during hemodialysis. This program consists of a low intensity endurance training with a bed bicycle ergometer, gymnastics to increase muscular strength, flexibility and co-ordination and of relaxation techniques. An increasing number of studies show that this type of exercise training has comparable beneficial effects as an outpatient exercise rehabilitation program. In addition, exercise during hemodialysis increases the solute removal and thereby the efficiency of dialysis probably by an increased perfusion of skeletal muscles. Since 1995 this type of exercise training was implemented in about 200 German dialysis centers. The participation rate is much higher than in supervised outpatient rehabilitation programs as also elderly patients and patients with severe additional medical problems participate. Even in very old patients functional capacity is improved by exercise during dialysis. As a consequence, some patients do not need any longer professional help for the activity of daily living. Up to now no serious adverse effects or complications were induced by exercise during dialysis. This could be achieved as the patients are instructed and supervised by physiotherapists who have special knowledge and skills in renal exercise rehabilitation. Almost all patients can do some exercise during dialysis and therefore this is the most favourable type of exercise training for hemodialysis patients today.

The T-allele of the C825T polymorphism is associated with higher arterial stiffness in young healthy males

Arterial stiffening is the major cause of increasing systolic blood pressure in arterial hypertension. Increased arterial stiffness is one major mechanism responsible for morbidity and mortality in hypertension. A C825T polymorphism was identified in the gene encoding the G-protein beta3 subunit (GNB3), and an association of the T-allele with hypertension was demonstrated in several studies. In order to identify a pathogenetic link between hypertension and arterial stiffness, we compared two indices of arterial stiffness, pulse wave velocity (PWV) and augmentation index, in young, healthy men with and without the 825T-allele under resting conditions. PWV was determined from pressure tracing over carotid and femoral arteries in 99 subjects (CC: n=43; CT&TT: n=56). Augmentation index was derived in 72 subjects (CC: n=30; CT&TT: n=42) by pulse wave analysis using radial applanation tonometry. Carriers of the 825T-allele exhibited a significantly higher PWV compared to subjects with the CC genotype (6.0+/-0.1 m/s (TC&TT) vs 5.7+/-0.1 m/s (CC); P=0.0251). There was also a significant difference (P = 0.0448) in augmentation index between carriers of the T-allele (CT&TT: 3.4+/-2.9%) and controls with the CC -genotype (-5.0+/-4.1 %). There was no difference in any other anthropometric (age, height, weight, body mass index) or haemodynamic (heart rate, peripheral and central blood pressure). In summary, the C825T polymorphism is associated with higher arterial stiffness in young, healthy males. Arterial stiffening may pathogenetically contribute to the development of hypertension in carriers of the T-allele.

Terlipressin and gelafundin: safe therapy of hepatorenal syndrome

BACKGROUND AND AIM

Hepatorenal syndrome (HRS) occurs in about 20 % of patients with liver cirrhosis and ascites and is characterized by intensive renal vasoconstriction, low glomerular filtration rate but preserved tubular function and normal renal histology. The potential of terlipressin and albumin to reverse HRS after a time period of 14 days has already been shown. However, intravenous albumin is expensive (approximately 25 per 50 ml 20% albumin in Germany) and has limited availability in some settings. Therefore we used an artificial plasma substitute, Gelatinepolysuccinat, which is less expensive (approximately 12 per 500 ml). The aim of our present study was to examine the effects of terlipressin and Gelatinepolysuccinat on renal function and hemodynamics in a time period of six days.

METHODS AND PATIENTS

Seven consecutive patients with cirrhosis and hepatorenal syndrome were included in a pilot study of terlipressin (6 mg /24 h iv) therapy associated with i.v. Gelatinepolysuccinat (Gelafundin 4% Infusionslösung, Company Braun, Mw: 30 000 D).

RESULTS

In five of the seven patients treatment was associated with a marked reduction of serum creatinine after six days (3.85 +/- 0.44 mg/dl vs.1.9 +/- 0.32 mg/dl; p< 0.018). Creatinine clearance improved (20 +/- 8.8 ml/min vs. 43 +/- 11.7 ml/min; p<0.12). There was a remarkable improvement in circulatory function in all patients, with an increase in mean arterial pressure (58+/-4.4 mmHg vs. 75 +/- 4.5 mmHg, p< 0.001). No patient developed signs of intestinal, myocardial or distal ischemia.

CONCLUSIONS

Terlipressin and Gelatinepolysuccinat appear to be a safe and effective treatment of hepatorenal syndrome.

Do effects on blood pressure contribute to improved clinical outcomes with metformin?

Hyperinsulinaemia and hypertension commonly coexist, and a large body of evidence points to a common pathogenesis based on the presence of underlying insulin resistance (the "insulin hypothesis" of hypertension). Metformin improves insulin sensitivity in liver and muscle as its primary antihyperglycaemic mechanism of action, and intensive glycaemic management with metformin significantly reduced the risk of macrovascular diabetic complications in the UK Prospective Diabetes Study. The clinical outcome benefits in the metformin group included a significant reduction in the risk of stroke (- 41% vs + 14% with sulphonylurea or insulin treatment, p=0.032), which is well known to be highly sensitive to changes in blood pressure. Furthermore, a placebo-controlled study has shown that metformin significantly improved endothelial function, a key regulator of vascular tone and blood pressure, in type 2 diabetic patients. However, clinical studies have shown that metformin treatment is not associated with clinically relevant reductions in blood pressure in man. These apparently conflicting observations are difficult to reconcile. Either the beneficial vascular actions of metformin involve physiological systems not involved in the control of blood pressure, or counter-regulatory mechanisms prevent beneficial effects of metformin on the vasculature being translated into a clinically meaningful antihypertensive effect. Further research will be required to resolve this paradox.

Diastolic blood pressure is an important determinant of augmentation index and pulse wave velocity in young, healthy males

Pulse wave velocity (PWV) and augmentation index are widely used measures of arterial stiffness. The purpose of this study was to evaluate the role of blood pressure as a determinant of both indices independent of potentially confounding factors including gender, age and cardiovascular disorders. A total of 77 young, healthy subjects were investigated under resting conditions. Augmentation index was derived by pulse wave analysis using carotid applanation tonometry. PWV was determined from pressure tracing over the carotid and femoral artery. The relations between stiffness markers and haemodynamic parameters were analysed by simple (r) and multiple (beta) regression analysis. Using simple regression analysis, augmentation index was correlated to age (r=0.292, P=0.0105), diastolic blood pressure (DBP, r=0.483, P<0.0001), mean arterial blood pressure (MAP, r=0.381, P=0.0007), pulse pressure (r=-0.414, P=0.0002) and total peripheral resistance (r=0.266, P=0.0204). After multiple regression analysis, augmentation index remained significantly correlated only to DBP (beta=0.347, P=0.0051). Using simple regression analysis, PWV was correlated to age (r=0.304, P=0.0067), systolic blood pressure (r=0.280, P=0.0129). DBP (r=0.455, P<0.0001), MAP (r=0.446, P&<0.0001) and heart rate (r=0.348, P=0.0018). After multiple regression analysis, PWV remained correlated only to age (beta=0.218, P=0.0422) and DBP (beta=0.4105, P=0.0316). In summary, DBP is an important determinant of augmentation index and PWV in young, healthy males. Further studies are needed to characterize the impact of blood pressure on arterial stiffness in other populations including females and older subjects.

A new system for regional citrate anticoagulation in continuous venovenous hemodialysis (CVVHD)

BACKGROUND

CVVHD is an established renal replacement therapy in hemodynamically unstable ICU patients. Various methods for regional citrate anticoagulation have been developed to minimize bleeding complications. Metabolic alkalosis, the risk of severe hypocalcemia and need for continuous calcium substitution as well as treatment-associated hypernatremia have limited the success of systems employed so far. We have developed a new technique for regional citrate anticoagulation in CVVHD to overcome these deficiencies and have performed a validation study.

METHODS

One hundred and thirty-three filters with an overall treatment duration of 3,324 hours were used in 19 critically ill patients with bleeding complications. We used a calcium-containing dialysate (1.81 mmol/l Ca) to avoid mandatory systemic calcium supplementation. Sodium bicarbonate was added to the dialysate in variable concentrations (13 - 34 mmol/l) to control acid-base status and prevent hypernatremia. The resulting dialysate sodium concentrations were between 121 and 140 mmol/l. Blood flow was set at 75 ml /min. Infusion of a solution containing trisodium citrate and citric acid with an overall citrate concentration of 113 mmol/l was started at 250 ml/h. Primary endpoints were pre- and post-filter ionized calcium (Ca(i)) concentrations, base excess and serum sodium. Filter life was assessed as a secondary end-point.

RESULTS

Control of electrolyte balance and azotemia was excellent (prefilter serum Ca(i) 1.06 +/- 0.012 mmol/l (+/- SEM), post-filter Ca(i) 0.23 +/- 0.01 mmol/l, base excess -0.39 +/- 0.4 mmol/l, serum sodium 137 +/- 4 mmol/l, mean serum creatinine 1.8 +/- 0.07 mg/dl). Normal base excess was achieved with a mean dialysate bicarbonate concentration of 26 mmol/l at a mean citrate infusion rate of 266 +/- 4 ml/h. After 48 hours, 25% of filters were still patent, mean filter life was 26 +/- 1.6 hours. No patient developed serious CVVHD-related adverse events.

CONCLUSION

The new regional citrate anticoagulation system for CVVHD is safe, feasible and can avoid major complications of previously described methods, especially hypocalcemia, alkalosis and hypernatremia.

Haemodynamic characterization of young normotensive men carrying the 825T-allele of the G-protein beta3 subunit

A C825T polymorphism was recently identified in the gene for the G-protein beta3 subunit, the T-allele being associated with hypertension. To better understand the underlying pathophysiological mechanisms, we compared the haemodynamics of young healthy males with and without the T-allele. In three studies, subjects were investigated with regard to cardiac and vascular function at rest and following intravenous administration of the beta-adrenoceptor antagonist, propranolol, and the alpha2-adrenoceptor agonist, alpha-methylnoradrenaline, and with regard to local venous vasoconstriction in the dorsal hand vein in situ following infusion of the alpha2-adrenoceptor agonist, azepexol. alpha2-Adrenoceptor agonists were chosen as vasoconstrictor drugs since alpha2-adrenoceptors couple to pertussis toxin (PTX)-sensitive G-proteins and since in-vitro studies have demonstrated enhanced signal transduction of PTX-dependent pathways in the presence of the T-allele. Total peripheral resistance was determined as a parameter of vasoconstrictor tone and heart rate, stroke volume and systolic time intervals for cardiac function. T-allele carriers had a significantly elevated stroke volume and lower total peripheral resistance at baseline. After propranolol, their fall in stroke volume was significantly greater. During alpha-methylnoradrenaline infusion, elevation of total peripheral resistance was not increased relative to controls. Similarly, the constriction response of the dorsal hand vein to azepexol was not different. Our study does not support the idea of increased vasoconstrictor tone in T-allele carriers either at rest or during stimulation of alpha2-adrenoceptors. However, this allele may be associated with elevated cardiac stroke volume.

Endothelin-A receptor antagonist inhibits angiotensin II and noradrenaline in man

AIMS

Endothelin-1 (ET-1) is a potent vasoconstrictor produced by the vascular endothelium. The interactions of ET with the mediators of the sympathetic nervous system and the renin-angiotensin-system in humans are unclear.

METHODS

We studied the effects of the ETA-selective antagonist BQ-123 and the ETB-selective antagonist BQ-788 (both 10(-10)-10(-8) M) on ET-1 (10(-16)-10(-10) M), angiotensin II (AT, 10(-16)-10(-10) M) and noradrenaline (NA, 10(-16)-10(-10) M) induced vasoconstriction in the human skin microcirculation in vivo in 25 healthy male volunteers using laser Doppler flowmetry and double injection technique.

RESULTS

BQ-123 caused a dose-dependent vasodilatation (maximum effect: + 949 +/- 84 AUC-PU, P < 0.001), whereas BQ-788 induced mild vasoconstriction (maximum effect: -388 +/- 96 AUC-PU, P < 0.01). In the presence of BQ-123, but not BQ-788, ET-1, AT and NA caused markedly less vasoconstriction at any tested agonist dose; the effect was most pronounced on ET-1 (maximum effect at 10(-14) M: + 814 +/- 93 AUC-PU vs ET alone, P < 0.001), followed by noradrenaline (maximum effect at 10(-16) M: +580 +/- 107 AUC-PU vs NA alone, P < 0.01) and angiotensin II (maximum effect at 10(-14) M: + 493 +/- 111 AUC-PU vs AT alone, P < 0.001).

CONCLUSIONS

ETA-selective antagonism inhibits vasoconstriction to AT and NA in vivo in healthy subjects. This beneficial effect may be useful for the treatment of patients with cardiovascular disease including hypertension especially in combination therapy with sympatholytic agents and inhibitors of the renin-angiotensin system.

Antihypertensive drugs and the sympathetic nervous system

The sympathetic nervous system (SNS) plays an important role in the regulation of blood pressure homeostasis and cardiac function. Furthermore, the increased SNS activity is a predictor of mortality in patients with hypertension, coronary artery disease and congestive heart failure. Experimental data and a few clinical trials suggest that there are important interactions between the main pressor systems, i.e. the SNS, the renin-angiotensin system and the vascular endothelium with the strongest vasoconstrictor, endothelin. The main methods for the assessment of SNS activity are described. Cardiovascular drugs of different classes interfere differently with the SNS and the other pressor systems. Pure vasodilators including nitrates, alpha-blockers and dihydropyridine (DHP)-calcium channel blockers increase SNS activity. Finally, central sympatholytics and possibly phenylalkylamine-type calcium channel blockers reduce SNS activity. The effects of angiotensin-II receptor antagonists on SNS activity in humans is not clear; experimental data are discussed in this review. There are important interactions between the pressor systems under experimental conditions. Recent studies in humans suggest that an activation of the SNS with pure vasodilators in parallel increases plasma endothelin. It can be assumed that, in cardiovascular diseases with already enhanced SNS activity, drugs which do not increase SNS activity or even lower it are preferable. Whether this reflects in lower mortality needs to be investigated in intervention trials.

The nitric oxide synthase inhibitor L-NMMA potentiates noradrenaline-induced vasoconstriction: effects of the alpha2-receptor antagonist yohimbine

OBJECTIVE

Alpha2-adrenoceptors can be found both on vascular smooth muscle cells and on the endothelium, where they exert opposing effects on vascular tone. In vitro, the stimulation of alpha2-adrenoceptors on endothelial cells leads to the release of vasodilating substances like nitric oxide (NO) and prostanoids. Little is known of this mechanism in vivo.

DESIGN AND METHODS

We investigated the effects of the NO-synthase inhibitor L-NMMA (10(-6) mol) and the alpha2-adrenoceptor antagonist yohimbine (YO, 10(-10)-10(-6) mol) on noradrenaline (NA, 10(-12)-10(-8) mol)-induced vasoconstriction in the forearm skin microcirculation of 16 healthy volunteers using double injection technique and laser Doppler flowmetry. Results are expressed in perfusion units (PU) as differences from baseline and control in mean +/- SEM; the area under the time-response-curve was calculated (AUC).

RESULTS

NA (10(-8)- 10(-12) mol) caused a marked, dose-dependent reduction in blood flow (mean effect -745 +/- 84 AUC PU; P< 0.001 versus saline). NA-induced vasoconstriction was enhanced by L-NMMA (mean effect -916 +/- 72 AUC PU; P< 0.001 versus NA). YO (10(-6)-10(-10) mol) induced a significant, dose-dependent vasodilation (mean effect +/- 446 +/- 110 AUC PU; P < 0.05 versus control); high doses of YO (10(-6) mol) inhibited NA constriction (P < 0.001 versus NA), whereas lower doses of YO (10(-8)/10(-10) mol) had no effect or even increased NA-induced constriction. In the presence of L-NMMA, YO (10(-8) and 10(-10) mol) further potentiated NA-induced vasoconstriction (mean effect -1165 +/- 108 AUC PU; NS versus NA).

CONCLUSION

These data demonstrate, that in humans in vivo, endogenous NO attenuates noradrenergic constriction. The effects of YO suggest that endothelial alpha2-adrenoceptors are involved in the release of NO and other vasodilating substances. Furthermore, there is an additive NO-independent vasodilation, which can be unmasked by L-NMMA.

Do saw palmetto extracts block human alpha1-adrenoceptor subtypes in vivo?

BACKGROUND

To test whether saw palmetto extracts, which act as alpha1-adrenoceptor antagonists in vitro, also do so in vivo in man.

METHODS

In a placebo-controlled, double-blind, four-way cross-over study 12 healthy young men were treated with three different saw palmetto extract preparations (320 mg o.d.) for 8 days each. On the last day, before and 2, 4 and 6 hr after drug intake blood pressure and heart rate were determined and blood samples obtained, which were used in an ex vivo radioreceptor assay with cloned human alpha1-adrenoceptor subtypes.

RESULTS

Saw palmetto extract treatment did not result in alpha1-adrenoceptor subtype occupancy in the radioreceptor assay. Although the saw palmetto extracts caused minor reductions of supine blood pressure, they did not affect blood pressure during orthostatic stress testing and did not alter heart rate under either condition. Moreover, plasma catecholamines remained largely unaltered.

CONCLUSIONS

Despite their alpha1-adrenoceptor antagonist effects in vitro, therapeutically used doses of saw palmetto extracts do not cause alpha1-adrenoceptor antagonism in man in vivo.

Modulation of noradrenaline-induced microvascular constriction by protein kinase inhibitors

We have tested the role of various protein kinases in noradrenaline-induced, alpha1A-adrenoceptor-mediated constriction of mesenteric and intrarenal rat microvessels. The protein kinase C inhibitors, H7 and staurosporine, inhibited constriction in both vessel types in concentrations which also inhibit myosin light chain kinase. The more selective protein kinase C inhibitors, bisindolylmaleimide I and Gö 6976, did not inhibit microvessel constriction in concentrations selective for protein kinase C. Moreover, the protein kinase C-activating phorbol ester, phorbol-12-myristate-13-acetate, did not cause constriction. The tyrosine kinase inhibitors, genistein and tyrphostin 23, inhibited constriction in concentrations compatible with tyrosine kinase inhibition. An inhibitor of the extracellular signal-regulated kinase cascade, PD 98059, also caused concentration-dependent inhibition. While chelation of extracellular Ca2+ abolished noradrenaline-induced constrictions, the Ca2+-ATPase inhibitor, thapsigargin, had no effects. We conclude that tyrosine kinases and extracellular signal-regulated kinase (but not protein kinase C) may be involved in noradrenaline-induced rat mesenteric and intrarenal microvessel constriction but this appears to occur independently of an effect on sarcoplasmic Ca2+ storage.

[Diuretic therapy of hypertensives with Type 2 diabetes; rational therapy or malpractice?]

There is overwhelming evidence that effective antihypertensive therapy with diuretics reduces total mortality and cardiovascular morbidity. Therefore, diuretics have a well established place in the pharmacotherapy of hypertension. However, their role in the treatment of hypertensives with type-II-diabetes is a matter of controversy due to their potentially adverse effects on glucose-, lipid- and electrolyte metabolism which--in type-II-diabetics--may potentially offset the beneficial effects of blood pressure lowering. However, results of large-scale, prospective, randomised intervention trials demonstrate that in type-II-diabetics the beneficial effects of blood pressure reduction per se are more important than any potentially adverse effects on metabolic surrogate parameters. The reduction in total mortality and cardiovascular morbidity as a result of effective antihypertensive therapy is more pronounced in type-II-diabetics than in non-diabetics. This holds also true for a diuretic based antihypertensive therapy in type-II-diabetics. Clearly their effects on glucose-, lipid- and electrolyte metabolism are of minor, if any, clinical relevance. The hypertensive type-II-diabetic benefits from diuretics--they prolong life and improve its quality. Therefore, antihypertensive therapy with diuretics constitutes a rational pharmacotherapy founded on the principles of evidence based medicine and must not be considered as malpractice.

[Heart failure as a cardiac symptom of sarcoidosis. Successful treatment of heart failure with steroids, digitalis and an angiotensin-1-receptor antagonist in sarcoidosis]

BACKGROUND

Sarcoidosis is a multisystemic disorder that may involve every organ. A symptomatic manifestation of the myocardium is possible, in these cases arrhythmias are the most common symptoms.

CASE REPORT

This case report presents a 26-year-old female with the recurrence of Boeck's sarcoid. Fever, chill and a severe reduction in stress tolerance were the first symptoms. At the time of admission she complained of Grade III dyspnea according to the NYHA classification. The echocardiogram showed a severe impairment of the global and left ventricular function. The left ventricular ejection fraction was reduced to 30% and the Tei index was elevated to 1.0. A specimen taken from a mediastinal tumor confirmed the hypothesis of the recurrence of the sarcoidosis. Myocardial perfusion scintigraphy showed typical lesions for myocardial sarcoidosis. There were signs of an old anteroseptal infarction in the resting ECG without evidence of myocardial ischemia during a stress test. Repeated Holter-ECGs were without signs of severe arrhythmias whereas ventricular late potentials were positive. After the combined therapy with steroids, digitalis and an angiotensin-1 receptor antagonist, mediastinal mass and Tei index were reduced and the ejection fraction moved to 56%. Dyspnoea was classified with Grade II according to the NYHA classification.

CONCLUSION

Treatment of asymptomatic sarcoidosis is still controversial, whereas the treatment of life-threatening sarcoidosis, eye involvement or severe hypercalcemia is accepted. This case report presents the successful treatment of severe heart failure with prednisone, glycosides and an angiotensin-1 receptor antagonist. With this combined therapy an improvement of subjective and objective parameters was possible.

Disodium cromoglycate does not prevent terbutaline-induced desensitization of beta 2-adrenoceptor-mediated cardiovascular in vivo functions in human volunteers

In humans, prolonged administration of the beta 2-adrenoceptor agonist terbutaline leads to a desensitization of beta 2-adrenoceptor-mediated cardiovascular responses, which can be blunted by concomitant administration of the antianaphylactic drug ketotifen. This study investigated the effect of disodium cromoglycate, another antiallergic drug, on terbutaline-induced desensitization of beta-adrenoceptor-mediated cardiovascular and noncardiovascular responses. In a double-blind, placebo-controlled, randomized design, nine healthy male volunteers received disodium cromoglycate (4 x 200 mg/day, p.o.) or placebo for 3 weeks with terbutaline (3 x 5 mg/day, p.o.) administered concomitantly during the last 2 weeks. beta 2-Adrenoceptor cardiovascular function was assessed by the increase in heart rate and reduction of diastolic blood pressure induced by an incremental intravenous infusion of the unselective beta-adrenoceptor agonist isoprenaline; beta 1-adrenoceptor cardiovascular function was assessed by exercise-induced tachycardia. Tremulousness was monitored as a beta 2-adrenoceptor-mediated noncardiovascular effect. After 2 weeks' administration of terbutaline, there was a marked and significant (p < 0.001) attenuation of isoprenaline-induced tachycardia (mean percentage attenuation, 53.3%) and of the isoprenaline-induced decrease in diastolic blood pressure (mean percentage attenuation, 55.6%). Exercise-induced tachycardia also was significantly (p < 0.001) blunted, but the magnitude of this attenuation was only very small (mean attenuation, 5.6%). Disodium cromoglycate affected neither the rightward shift of beta 2-adrenoceptor-mediated responses nor the small rightward shift in beta 1-adrenoceptor-mediated exercise tachycardia after 2 weeks' administration of terbutaline. Tremulousness observed during the first few days of terbutaline administration disappeared after 4 to 8 days, indicating development of desensitization of beta 2-adrenoceptor-mediated noncardiovascular responses. This was not prevented by disodium cromoglycate. These results confirm that long-term beta 2-adrenoceptor agonist therapy leads to a desensitization of beta 2-adrenoceptor-mediated cardiovascular and noncardiovascular effects in humans in vivo. However, unlike ketotifen, cromolyn sodium is not able to attenuate this desensitization.

Adrenoceptors mediating the cardiovascular and metabolic effects of alpha-methylnoradrenaline in humans

alpha-Methylnoradrenaline is a widely used tool to study alpha2-adrenoceptor function, but its selectivity for this receptor has not been validated in humans in vivo. To characterize the adrenoceptors mediating cardiovascular and metabolic effects of alpha-methylnoradrenaline in humans, we have performed graded i.v. infusions of alpha-methylnoradrenaline in a randomized, placebo-controlled crossover study in six young, healthy males in the absence and presence of the beta-adrenoceptor antagonist propranolol, the alpha1-adrenoceptor antagonist doxazosin, and the alpha2-adrenoceptor antagonist yohimbine. alpha-Methylnoradrenaline dose-dependently increased heart rate, systolic blood pressure, cardiac output, blood glucose, serum insulin, free fatty acids, and gastrin, shortened the duration of heart rate-corrected electromechanical systole, and decreased diastolic blood pressure, total peripheral resistance, and plasma noradrenaline. Propranolol completely reversed the rise in heart rate and cardiac output, the fall in peripheral resistance, the shortening of electromechanical systole, and the rise in insulin; it blunted the increase in free fatty acids and gastrin. Yohimbine did not significantly influence most parameters but significantly potentiated the rise in insulin, blunted the increase in glucose, and prevented the fall in noradrenaline. Doxazosin was largely without effect on any of these parameters. We conclude that i.v. administered alpha-methylnoradrenaline primarily acts on beta-adrenoceptors in the human cardiovascular and metabolic system, but an alpha2-adrenergic component of the response is detectable for changes of plasma noradrenaline, blood glucose, and serum insulin. Whereas alpha-methylnoradrenaline is selective for alpha2- over alpha1-adrenoceptors, beta-adrenoceptor blockade is required to unmask alpha-adrenoceptor-mediated vasoconstriction.

Ketotifen and cardiovascular effects of xamoterol following single and chronic dosing in healthy volunteers

AIMS

To study whether desensitization occurs after long-term administration of the 1-adrenoceptor partial agonist xamoterol and, if so, whether this can be influenced by ketotifen.

METHODS

In a double-blind, randomized design 10 young, healthy males received ketotifen (2 x 1 mg day(-1) p.o.) or placebo for 3 weeks with xamoterol (2 x 200 mg day(-1) p.o.) administered concomitantly during the last 2 weeks. 'l1-adrenoceptor mediated responses were assessed as exercise-induced tachycardia and isoprenaline-induced shortening of heart rate corrected electromechanical systole (QS2c); isoprenaline-induced tachycardia was measured as a mixed beta1-/beta2-adrenoceptor-mediated effect.

RESULTS

The first dose of xamoterol significantly increased resting heart rate and systolic blood pressure and significantly shortened QS2c. The last dose of xamoterol after 2 weeks of treatment still produced the same responses. Ketotifen did not influence these effects of xamoterol on resting haemodynamics. The first dose of xamoterol caused a rightward shift of the exercise- and isoprenaline-induced tachycardia (mean dose ratios+/-s.e.mean: 1.20+/-0.05 and 2.46+/-0.23) and the isoprenaline-evoked shortening of QS2c (dose ratio 3.59+/-0.68). This rightward shift was even more pronounced after 2 weeks xamoterol treatment. This additional rightward shift after 2 weeks of xamoterol was not affected by ketotifen (mean difference (95% CI) of log transformed dose ratios between placebo and ketotifen: exercise tachycardia 0.001 (-0.03; 0.04); isoprenaline tachycardia 0.03 (-0.15; 0.21); isoprenaline induced shortening of QS2c 0.13 (-0.22; 0.48)).

CONCLUSIONS

In humans xamoterol is a partial beta1-adrenoceptor agonist with positive chrono- and inotropic effects at rest and antagonistic properties under conditions of beta-adrenoceptor stimulation. These effects were well maintained after chronic dosing with no signs of beta1-adrenoceptor desensitization. Ketotifen does not change the beta-adrenoceptor mediated responses of xamoterol after chronic dosing.

Differential vascular alpha1-adrenoceptor antagonism by tamsulosin and terazosin

AIMS

In patients with lower urinary tract symptoms suggestive of benign prostatic obstruction the alpha1-adrenoceptor antagonist terazosin lowers blood pressure whereas only very small if any alterations were reported with the alpha1-adrenoceptor antagonist tamsulosin. Therefore, we have compared the vascular alpha1-adrenoceptor antagonism of tamsulosin and terazosin directly.

METHODS

Ten healthy subjects were investigated in a randomized, single-blind, three-way cross-over design and received a single dose of 0.4 mg tamsulosin, 5 mg terazosin or placebo on 3 study days at least 1 week apart. Before and 1, 3, 5, 7, 10 and 23.5 h after drug intake, alterations of diastolic blood pressure and other haemodynamic parameters in response to a graded infusion of the alpha1-adrenoceptor agonist phenylephrine were determined non-invasively.

RESULTS

At most time points tamsulosin inhibited phenylephrine-induced diastolic blood pressure elevations significantly less than terazosin (5 h time point: median difference in inhibition 35%, 95% CI: 18.7-50.3%). On the other hand, phenylephrine-induced changes of cardiac output, heart rate and stroke volume were similar during both active treatments.

CONCLUSIONS

In doses equi-effective for treatment of lower urinary tract symptoms tamsulosin causes less inhibition of vasoconstriction than terazosin.

Tamsulosin treatment of 19,365 patients with lower urinary tract symptoms: does co-morbidity alter tolerability?

PURPOSE

We compare the tolerability and blood pressure effects of 0.4 mg. tamsulosin once daily in patients with lower urinary symptoms suggestive of benign prostatic obstruction with or without concomitant disease and/or antihypertensive medication.

MATERIALS AND METHODS

Data from 2 open label, observational studies (study 1, 9,507 patients treated for 4 weeks and study 2, 9,858 patients treated for 12 weeks) were analyzed for global tolerability and effects on blood pressure stratifying for co-morbidity (none, diabetes, hypertension, other cardiovascular disease) and co-medication (diuretics, beta-blockers, calcium channel blockers, angiotensin converting enzyme inhibitors).

RESULTS

Overall 90 and 95% of patients in studies 1 and 2, respectively, reported good or very good tolerability. While global tolerability was slightly reduced in patients with concomitant disease or some forms of medication (p < 0.05), it was rated as good or very good by more than 90 and 95% of patients even in those groups. In control patients, that is those with neither co-morbidity nor co-medication, the tamsulosin induced blood pressure reductions were similar to those previously reported for placebo treatment but were statistically significant (p < 0.05). Mean additional blood pressure reductions in patients with concomitant disease or medication were not more than 2 mm. Hg.

CONCLUSIONS

Tamsulosin is well tolerated and has marginal effects on blood pressure in the majority of patients. It largely maintains its good global tolerability and minimal blood pressure effects in patients with cardiovascular co-morbidity or diabetes, or those on co-medication with antihypertensive agents.

Tamsulosin treatment of 19,365 patients with lower urinary tract symptoms: does co-morbidity alter tolerability?

PURPOSE

We compare the tolerability and blood pressure effects of 0.4 mg. tamsulosin once daily in patients with lower urinary symptoms suggestive of benign prostatic obstruction with or without concomitant disease and/or antihypertensive medication.

MATERIALS AND METHODS

Data from 2 open label, observational studies (study 1, 9,507 patients treated for 4 weeks and study 2, 9,858 patients treated for 12 weeks) were analyzed for global tolerability and effects on blood pressure stratifying for co-morbidity (none, diabetes, hypertension, other cardiovascular disease) and co-medication (diuretics, beta-blockers, calcium channel blockers, angiotensin converting enzyme inhibitors).

RESULTS

Overall 90 and 95% of patients in studies 1 and 2, respectively, reported good or very good tolerability. While global tolerability was slightly reduced in patients with concomitant disease or some forms of medication (p < 0.05), it was rated as good or very good by more than 90 and 95% of patients even in those groups. In control patients, that is those with neither co-morbidity nor co-medication, the tamsulosin induced blood pressure reductions were similar to those previously reported for placebo treatment but were statistically significant (p < 0.05). Mean additional blood pressure reductions in patients with concomitant disease or medication were not more than 2 mm. Hg.

CONCLUSIONS

Tamsulosin is well tolerated and has marginal effects on blood pressure in the majority of patients. It largely maintains its good global tolerability and minimal blood pressure effects in patients with cardiovascular co-morbidity or diabetes, or those on co-medication with antihypertensive agents.

Radioreceptor assay analysis of tamsulosin and terazosin pharmacokinetics

AIMS

A radioreceptor assay has been developed for alpha1-adrenoceptor subtypes and applied to a pharmacokinetic analysis of tamsulosin and terazosin.

METHODS

Young, male, healthy volunteers received 0.4 mg tamsulosin (as Omnic modified release capsules) or 5 mg terazosin (as Flotrin tablets) in a randomized, cross-over design. Before and after 1, 3, 5, 7, 10 and 23.5 h plasma was analyzed by radioreceptor assay using cloned human alpha1A-, alpha1B- and alpha1D-adrenoceptors and specific h.p.l.c. analysis.

RESULTS

Following ingestion of tamsulosin median peak plasma levels of 16 ng ml(-1) were reached after 5 h and declined to 2 ng ml(-1) at 23.5 h. The time course in the radioreceptor assay was similar, and at most time points binding to alpha1A-adrenoceptors was significantly greater than to alpha1B- and alpha1D-adrenoceptors. Following ingestion of terazosin median peak plasma levels of 91 ng ml(-1) were reached after 1 h and declined to 11 ng ml(-1) at 23.5 h. In the radioreceptor assay binding also peaked at 1 h and declined thereafter, but even after 23.5 h considerable binding activity remained detectable at all three subtypes. At most time points binding to the alpha1A- and alpha1D-adrenoceptor was significantly greater than to the alpha1B-adrenoceptor.

CONCLUSIONS

We conclude that alpha1-adrenoceptor antagonist pharmacokinetics can be monitored by radioreceptor assays in a subtype-selective manner. Tamsulosin and terazosin exhibit subtype selective receptor binding ex vivo. The discordance between terazosin blood levels as determined by h.p.l.c. and radioreceptor assay at late time points indicates the possible involvement of metabolites in in vivo terazosin effects.

Influence of atropine on the cardiovascular effects of noradrenaline and tyramine in elder volunteers

The aim of this study, carried out in six elder healthy volunteers (mean age: 61 years), was to determine the influence of muscarinic receptor blockade with atropine (15 microg/kg i.v. loading dose followed by 0.15 microg/kg/min by i.v. infusion) on the effects of i.v. infusions of noradrenaline (5 incremental doses of 10-120 ng/kg/min) or tyramine, that releases endogenous noradrenaline (4 incremental doses of 5-20 microg/kg/min), on blood pressure, heart rate and systolic time intervals (STI's, as a measure of positive inotropism). These results were compared with those recently published for young healthy volunteers (mean age: 26 years; Schäfers et al. 1997). Noradrenaline caused increases in systolic and diastolic blood pressure, decreases in heart rate and a shortening of STI's that were not different from those in young volunteers. Atropine did not significantly affect these hemodynamic responses to noradrenaline, while in young volunteers it significantly enhanced noradrenaline-induced blood pressure increases and converted the heart rate decrease into an increase. In the present study in elder volunteers, tyramine caused a smaller increase in systolic blood pressure than in the previous study in young volunteers; in addition, it slightly increased diastolic blood pressure while it decreased diastolic blood pressure in young volunteers. Atropine did not significantly affect the hemodynamic effects of tyramine in the elder volunteers, while in the young volunteers it enhanced the increase in systolic blood pressure and converted the decreases in diastolic blood pressure and heart rate into increases. These results indicate a) that ageing is accompanied by a blunted baroreflex-mediated parasympathetic activation resulting in reduced cholinergic vasodilation and decreases in heart rate, and b) that ageing is associated with a decreased responsiveness of (cardiac) beta-adrenoceptors and (vascular) alpha1-adrenoceptors which is only unmasked when the counterregulatory action of parasympathetic activation is removed.

Vasoconstriction of rat renal interlobar arteries by noradrenaline and neuropeptide Y

1. We have studied the contractile effects of noradrenaline and neuropeptide Y given alone and in combination on isolated rat renal interlobar arteries. 2. Noradrenaline contracted proximal and distal intrarenal microvessels in a concentration dependent manner, with similar potency (EC50 approximately equal to 550 nM), but maximal effects were greater in the proximal than in the distal vessel segments (approximately equal to 10 and 6 nM, respectively). 3. The noradrenaline-induced contraction was inhibited by low prazosin concentrations (3-10 nM) but not by 1 microM yohimbine indicating involvement of alpha(1)-but not alpha(2)-adrenoceptors. The alpha(1)A-adrenoceptor-selective antagonist, 5-methylurapidil and tamsulosin, had high potency (apparent affinities of approximately equal to 8 nM and 57 pM, respectively) while the alpha(1)D-adrenoceptor-selective antagonist, BMY 7378, had only low potency (apparent affinity approximately equal to 300 nM). The alpha(1)B-adrenoceptor-alkylating agent, chloroethylclonidine (10 microM for 30 min at 37 degrees C), had no inhibitory effects. The Ca2+ entry blocker, nitrendipine (300 nM), reduced the potency and maximal effects of noradrenaline. 4. Neuropeptide Y (1-100 nM) also contracted interlobar arteries in a concentration dependent manner, with greater effects in the proximal than in the distal segments, but maximal effects were only small in either segment (< 2 mN). In addition, neuropeptide Y also potentiated the response to noradrenaline, i.e. lowered its EC50 but this enhancement was also small. 5. We conclude that noradrenaline contracts rat interlobar arteries by an alpha(1)A-adrenoceptor; its co-transmitter, neuropeptide Y, affects the response only marginally in this vascular bed.

Influence of adrenoceptor and muscarinic receptor blockade on the cardiovascular effects of exogenous noradrenaline and of endogenous noradrenaline released by infused tyramine

This study aimed firstly to compare the in vivo cardiovascular effects of exogenously administered and of endogenously released noradrenaline; secondly to characterize the adrenoceptors mediating these responses; thirdly to assess the influence of parasympathetic tone on the cardiovascular effects of noradrenaline. In two randomised placebo-controlled studies, healthy, young, male volunteers received intravenous (i.v.) infusions of noradrenaline at six incremental doses of 10-160 ng/kg/min and-in order to release endogenous noradrenaline-tyramine at four incremental doses of 5-20 micrograms/kg/min. Noradrenaline and tyramine were administered in the absence and presence of alpha 1-adrenoceptor blockade with doxazosin (2 mg p.o.), alpha 2-adrenoceptor blockade with yohimbine (15 mg p.o.), selective beta 1-adrenoceptor blockade with bisoprolol (15 mg p.o.) and muscarinic receptor blockade with atropine (1.5 micrograms/kg i.v. loading dose followed by 0.15 microgram/kg/min by i.v. infusion). Vasoconstrictor effects were assessed by measurement of diastolic blood pressure (Pdiast) and myocardial effects by measurement of systolic time intervals, namely the duration of electromechanical systole corrected for heart rate (QS2c). I.v. noradrenaline increased Pdiast (delta max 17 mmHg) and this was nearly completely suppressed by doxazosin but only slightly blunted by yohimbine. Noradrenaline also slightly shortened QS2c (delta max -22 ms), and this was potentiated by both doxazosin and yohimbine and completely blocked by biosprolol. I.v. tyramine reduced Pdiast (delta max -7 mmHg), which was not affected by alpha 1-adrenoceptor blockade, and profoundly shortened QS2c (delta max -104 ms) which was significantly correlated with a marked increase in systolic blood pressure (Psyst) (delta max 57 mmHg). The shortening of QS2c and the rise in Psyst were not influenced by alpha-adrenoceptor blockade but were antagonized by bisoprolol. Atropine potentiated the blood pressure rise and the shortening of QS2c induced by i.v. noradrenaline and converted the fall in Pdiast induced by i.v. tyramine into an increase. Thus the cardiovascular effects of exogenous noradrenaline are mainly characterized by alpha 1-adrenoceptor-mediated vasoconstriction and the actions of endogenous noradrenaline (released by i.v. tyramine) by beta 1-adrenoceptor-mediated positive inotropic effects. The rise in Psyst with i.v. tyramine most likely reflects positive inotropism and not a vascular "pressor' response.

Effects of noradrenaline and neuropeptide Y on rat mesenteric microvessel contraction

We have studied the contractile effects of the sympathetic transmitter noradrenaline and its cotransmitter neuropeptide Y (NPY) given alone and in combination on isolated rat mesenteric resistance vessels (200-300 microns diameter). Noradrenaline and NPY each concentration-dependently contracted rat mesenteric microvessels (EC50 approximately equal to 800 nM and 10 nM, respectively), but noradrenaline caused considerably greater maximal effects than NPY (14.3 mN vs. 3.5 mN). A low antagonistic potency of yohimbine indicated that the response to noradrenaline did not involve alpha 2-adrenoceptors, and the subtype-selective antagonists 5-methylurapidil, tamsulosin and chloroethylclonidine indicated mediation via an alpha 1A-adrenoceptor. Shallow Schild regressions for prazosin and 5-methylurapidil indicated that an alpha 1-adrenoceptor subtype with relatively low prazosin affinity might additionally be involved. Studies with the NPY analogues PYY, [Leu31, Pro34] NPY and NPY18-36 demonstrated that NPY acted via a Y1 NPY receptor. In addition to its direct vasoconstricting effects NPY also lowered the noradrenaline EC50 but did not appreciably affect maximal noradrenaline responses indicating possible potentiation. The potentiating NPY response occurred with similar agonist potency as the direct contractile NPY effects and also via a Y1 NPY receptor. The Ca2+ entry blocker nitrendipine (300 nM) reduced direct contractile responses to noradrenaline and NPY but did not affect the potentiation response to NPY.

The beta-adrenoceptor subtype(s) mediating adrenaline- and dobutamine-induced blood pressure and heart rate changes in healthy volunteers

In order to characterize the beta-adrenoceptor subtype(s) mediating blood pressure and heart rate changes induced by adrenaline and dobutamine, we compared the effects in healthy male volunteers of propranolol (5 mg i.v.) and of the beta 1-adrenoceptor selective antagonist bisoprolol (15 mg p.o.) on adrenaline- and dobutamine-infusion induced changes in systolic (P(syst)) and diastolic blood pressure (P(diast)) and heart rate with those on blood pressure and heart rate (HR) changes induced by "pure" alpha- or beta-adrenoceptor agonists (phenylephrine, selective alpha, terbutaline, selective beta 2, isoprenaline, non-selective beta 1 and beta 2). Both beta-adrenoceptor antagonists did not affect phenylephrine (0.25 -1.0 microgram/kg/min for 10 min) infusion induced P(syst)- and P(diast)-increases and HR-decreases. On the other hand, propranolol completely suppressed terbutaline (25-150 ng/kg/min for 15 min) and isoprenaline (3.5-35 ng/kg/min for 8 min) infusion induced P(syst)- and HR-increases and P(diast)-decreases while bisoprolol significantly attenuated only isoprenaline-effects but had nearly no effect on terbutaline effects. Thus, in these doses bisoprolol antagonized only beta 1-adrenoceptor mediated effects, propranolol both beta 1- and beta 2-adrenoceptor mediated effects, but both antagonists had no alpha-adrenoceptor antagonistic effects. Dobutamine (1.0-6.0 micrograms/kg/min for 15 min) infusion significantly increased P(syst), but did not significantly affect P(diast) and HR; bisoprolol markedly reduced dobutamine-induced P(syst)-increase. In the presence of propranolol, however, dobutamine caused P(syst)- and P(diast)-increases and HR-decreases. Adrenaline (20-120 ng/kg/min for 15 min) infusion increased P(syst) and HR and decreased P(diast). Bisoprolol did not affect P(syst)- and HR-increases, but significantly attenuated P(diast)-decreases.(ABSTRACT TRUNCATED AT 250 WORDS)

[Acute hemolysis with subsequent life-threatening pancreatitis in hemodialysis. A complication which is not preventable with current dialysis equipment]

A retrospective study was undertaken of 14 patients (eleven men, three women; mean age 52 [33-68] years in whom haemolysis had occurred during chronic haemodialysis (n = 12) or haemofiltration (n = 2). The haemolysis was of mechanical cause in eight patients, by an osmotic mechanism in one, and of unknown cause in five. Cardinal symptoms were nausea in 14 patients, abdominal pain in nine, vomiting in eight and raised blood pressure in ten. The plasma was discoloured in all patients and there was also an increase in free haemoglobin (110-2400 mg/dl) and (or) lactate dehydrogenase (311-7403 U/l). In all of eleven patients in whom it was measured the activity of serum amylase and (or) lipase was more than doubled (to 73-2400 U/l and 473-16,740 U/l, respectively). All patients were treated symptomatically, three had a blood exchange, two others plasma separation. Eight patients recovered within a few days, but necrotizing pancreatitis developed in six, three of whom died while two had permanent sequelae. This series shows that dialysis-induced acute haemolysis can cause life-threatening pancreatitis. Narrowings within the extracorporeal circuit, not always recognized in current dialysis equipment, are the most frequent cause of the mechanical haemolysis.

Positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in the human heart: effects of long-term beta 1-adrenoceptor antagonist treatment

OBJECTIVES

This study was conducted to determine whether activation of cardiac beta 2-adrenoceptors increases contractility in humans and whether this is affected by long-term beta 1-adrenoceptor antagonist treatment.

BACKGROUND

Coexistence of beta 1- and beta 2-adrenoceptors in the human heart is generally accepted. The functional importance of cardiac beta 2-adrenoceptors for increases in contractility in humans, however, has not been completely established.

METHODS

We studied 1) the beta-adrenoceptor subtype mediating positive inotropic effects of the beta 2-adrenoceptor agonist terbutaline in vitro (on right atrial and left ventricular preparations from nonfailing human hearts) and increases in contractility (by measurement of systolic time intervals) in vivo in seven healthy male volunteers; and 2) in vivo whether long-term treatment of volunteers with the beta 1-adrenoceptor antagonist bisoprolol affects terbutaline-induced increases in contractility.

RESULTS

In vitro terbutaline caused a concentration-dependent increase in atrial and ventricular adenylate cyclase activity and force of contraction. Terbutaline effects were antagonized only by the beta 2-adrenoceptor antagonist ICI 118,551, indicating that they were mediated by beta 2-adrenoceptor stimulation. In vivo intravenous infusions of terbutaline (dose range 25 to 300 ng/kg body weight per min for 15 min) dose dependently increased heart rate and shortened the pre-ejection period and heart rate-corrected electromechanical systole (QS2) time. These effects are mediated predominantly by beta 2-adrenoceptor stimulation because they were only marginally affected by the beta 1-adrenoceptor antagonist bisoprolol (1 x 10 mg orally), either given 2 h before infusion or long term for 3 weeks.

CONCLUSIONS

Stimulation of cardiac beta 2-adrenoceptors in humans causes not only in vitro but also in vivo positive inotropic effects. Long-term beta 1-adrenoceptor antagonist treatment does not considerably affect beta 2-adrenoceptor-mediated in vivo increases in contractility. Thus, it may be possible to treat patients with chronic heart failure and long-term beta 1-adrenoceptor antagonist therapy with beta 2-adrenoceptor agonists if immediate inotropic support is needed.