Biomedical subjects

B Heintz

Publications and source records attributed to B Heintz.

At least 19 recordsLinked to original sources

PubMed2005

[Renovascular hypertension--diagnosis and therapy].

Atherosclerotic renal artery stenosis accounts for most cases of renovascular hypertension (RVH). Hypertensive patients with clinical features suggesting RVH should be submitted to further noninvasive evaluation including duplex Doppler ultrasonography, CT- or MR angiography. Invasive evaluation by contrast-enhanced angiography confirms the diagnosis of renal artery stenosis. However, neither diagnostic test reliably predicts the course of hypertension after revascularisation. The therapeutic approach in hypertensive patients with hemodynamically important renal artery stenosis includes medical or invasive therapy (renal percutaneous transluminal angioplasty, PTRA; renal arterial stent placement, PTRAS; surgical revascularisation). Randomized trials comparing invasive and conservative approaches demonstrated no differences in blood pressure control or renal function. Only patients with clear clinical indications should be submitted to interventional procedures as PTRA, PTRAS and surgical vascular intervention.

Angioplasty, Balloon↗

PubMed2005

Increased soluble VCAM-1 serum levels in preeclampsia are not correlated to urinary excretion or circadian blood pressure rhythm.

OBJECTIVE: Soluble vascular cell adhesion molecule-1 (VCAM-1) is known to be elevated in serum of patients with preeclampsia, but there are no data available on the significance of urinary VCAM-1 excretion in preeclampsia. The aim of our study was to uncover possible circadian rhythms of VCAM-1 plasma levels and urinary VCAM-1 excretion in uncomplicated and hypertensive pregnancies and to ascertain their relation to blood pressure. STUDY DESIGN: A total of 10 normotensive and 10 preeclamptic pregnant women were included in this study. Venous blood was collected hourly, and urine samples were taken every 2 h over a period of 24 h. VCAM-1 levels were determined by ELISA. We compared these results with the circadian blood pressure rhythm. RESULTS: The median VCAM-1 plasma levels were significantly (P < 0.01) increased in preeclamptic patients (851.5 ng/mL) in comparison to normotensive pregnant women (659.3 ng/mL) without any circadian rhythm being apparent; however, the urinary excretion of VCAM-1 showed a typical circadian rhythm, with a higher excretion rate during daytime. CONCLUSION: For the first time we have demonstrated that urinary VCAM-1 excretion in pregnancy shows a circadian rhythm without correlation to plasma levels or the circadian blood pressure rhythm. In contrast, VCAM-1 serum levels did not show a diurnal rhythm. We assume that VCAM-1 serum levels do not correlate with systemic blood pressure or urinary excretion.

Adult↗

PubMed2005

Influence of hemodialysis on the mean blood flow velocity in the middle cerebral artery.

BACKGROUND: Several effects of hemodialysis, including hemoconcentration, alterations of hemostasis or hemorheology and endothelial activation, could potentially interfere with cerebral blood flow (CBF) regulation. These treatment-specific changes may also be crucial for the enhanced incidence of stroke in uremic patients. Nevertheless, the influence of hemodialysis on CBF has not been yet adequately studied. PATIENTS AND METHODS: We registered mean blood flow velocity (MFV) in the middle cerebral artery (MCA) during hemodialysis treatment in order to evaluate its contribution on CBF changes. Transcranial Doppler ultrasonography (TCD) of the MCA was performed continuously during hemodialysis treatment in 18 stable patients (10 males and 8 females, mean age 62 +/- 11 years) with end-stage renal disease of various origin. Blood pressure (mmHg), heart rate (/min), ultrafiltration volume (ml), BV changes (deltaBV by hemoglobinometry, %), arterial blood gases (pO2, blood oxygen content, pCO2), hemostasis activation (thrombin-antithrombin III complex, ELISA) and fibrinogen (Clauss) were measured simultaneously at the beginning of treatment and every hour thereafter. RESULTS: Before the hemodialysis session the MFV in the MCA was within normal range (57.5 +/- 13.0 cm/s, ref. 60 +/- 12) and was mainly dependent on the patients' age (r = -0.697, p < 0.01). The blood flow velocity in the MCA decreased significantly from 57.5 +/- 13.0 cm/s before the beginning to 48.3 +/- 11.1 cm/s after four hours (n = 18, p < 0.05) and to 43.9 +/- 8.9 cm/s after five hours (n = 9, p < 0.05) of hemodialysis treatment. During hemodialysis treatment, the percentual changes of MFV in the MCA (delta%MFV) were interrelated to the ultrafiltration volume (r = -0.486, p < 0.01), the blood volume (BV%, r = 0.369, p < 0.01) and the percentual changes of the hematocrit (r = -0.358, p < 0.01), of the arterial blood oxygen content (delta%acO2, r = -0.420, p < 0.01) and of the plasma fibrinogen levels (delta%fibrinogen, r = 0.244, p < 0.05). CONCLUSION: A significant continuous decrease of the MFV in the MCA was observed during hemodialysis treatment, which inversely correlated both with ultrafiltration volume, BV changes and changes of plasma fibrinogen. The ultrafiltration-induced hemoconcentration with concomitant rise of hematocrit and oxygen transport capacity, may partly explain the alterations in the cerebral MFV observed during hemodialysis.

Blood Flow Velocity↗

PubMed2004

Tacrolimus- (FK 506) based immunosuppression in severe systemic lupus erythematosus.

In a 30-year-old male patient systemic lupus erythematosus was diagnosed based on the presence of 8 out of 11 ARA criteria. Disease onset was acute and included renal function impairment with biopsy-proven lupus nephritis (WHO class IV) requiring renal replacement therapy. Although conventional immunosuppressive therapy regimens proved effective in controlling disease activity, all of the administered drugs were accompanied by serious side effects: bilateral femur head necrosis with corticosteroids, allergic skin reaction in response to azathioprine, nephrotoxicity with cyclosporine, nausea and abdominal pain with mycophenolate mofetil and life-threatening septicemia with cyclophosphamide treatment. In search for alternative treatment options, tacrolimus (FK506, trough serum levels 3-6 ng/ml) was started. FK506 was well-tolerated and lupus activity completely resolved within 7 months after initiation of therapy. During 36 months of follow-up no arthritic complaints occurred and renal function stabilized at a serum creatinine of 2.1 mg/dl with negative anti-ds-DNA antibodies and ANA titers. In conclusion, FK506 may be considered as alternative immunosuppressive for maintenance treatment in patients with severe lupus erythematosus and side effects to conventional regimens.

Adult↗

PubMed2003

[Therapy and prophylaxis of renal failure].

The number of patients with end-stage renal disease is constantly growing. If patients at risk are identified early enough, currently available therapeutic options allow a potent primary and secondary prevention of progressive renal failure. If the underlying disease can not be eliminated, the mainstay of the therapy are supportive measures such as antihypertensive and, in case of an underlying diabetes mellitus, antidiabetic therapy, dietary restrictions as well as avoidance of additional nephrotoxic agents. Furthermore, even a mild renal insufficiency has been identified as a potent cardiovascular risk factor. The second major goal of supportive therapy therefore is a reduction of the markedly increased cardiovascular morbidity of these patients. This can be achieved through treatment of various consequences of renal failure, such as hyperparathyroidism, renal anemia etc. Supportive therapy thus represents a highly complex and interdisciplinary treatment, which should prompt an early inclusion of a nephrologist into the therapeutic strategy.

Diabetes Complications↗

PubMed2001

Pharmacokinetics of tilidine in terminal renal failure.

The aim of the present study was to investigate the pharmacokinetics of tilidine and its metabolites during the dialysis procedure and in the dialysis-free interval. Tilidine is a prodrug that is metabolized presystemically into the active metabolite nortilidine. Nortilidine is degraded thereafter to bisnortilidine and several polar metabolites. Nine patients with a creatinine clearance < 5 ml/min were treated in a crossover design with single oral doses of 1.5 mg/kg on the day of dialysis (dialysis performed from 3 to 6 hours after drug administration) and on a day in the dialysis-free interval. Blood samples were taken frequently and analyzed for tilidine, nortilidine, and bisnortilidine. Drug and metabolite concentrations were also measured in aliquots of dialysate collected during dialysis. Only negligible amounts of tilidine, nortilidine, and bisnortilidine (about 0.9% of the dose) were recovered from the dialysate. The pharmacokinetics of nortilidine and its inactive metabolite bisnortilidine was not affected by dialysis. The presystemic apparent clearance of the prodrug tilidine was decreased significantly during the dialysis-free interval. A significant decrease of the rate of elimination and an increase of the AUC of bisnortilidine were observed if these parameters were compared with data obtained from healthy volunteers. The plasma concentrations of nortilidine were comparable in patients and normal volunteers. Thus, a reduction of the dose of tilidine in patients with severely impaired kidney function seems not to be required. Tilidine and its metabolites cannot be removed from the body by dialysis.

Adult↗

PubMed2001

Influence of recombinant human erythropoietin therapy on plasma endothelin-1 levels during hemodialysis.

The correction of anemia with human recombinant erythropoietin (rHuEPO) in end stage renal disease is associated with hypertension in about one third of hemodialysis patients. The pathogenesis of the rHuEPO-induced hypertension is still uncertain, though evidence of the involvement of endothelial cells has emerged. The aim of this study was to determine plasma endothelin-1 during hemodialysis and to compare the endothelin-1 levels in hemodialysis patients with and without rHuEPO substitution. Nineteen stable patients (13 male and 6 female, mean age 62 +/- 11 years) with end stage renal disease were studied. Cuprophan dialysers (GFS 12, Gambro, Lund, Sweden) were used for hemodialysis in all cases. rHuEPO (40 U/kg s.c.) was administered to 10 patients. Blood pressure (BP; RR mmHg) and blood volume changes (deltaBV; hemoglobinometry %) were serially measured. Samples were taken before and every hour during hemodialysis. Plasma endothelin-1 was measured by ELISA (R&D Systems, Minneapolis, USA) and corrected for hemoconcentration. Endothelin-1 concentration was elevated before commencement of hemodialysis (1.16 +/- 0.36 pg/ml) when compared to healthy controls (ref. 0.3-0.9) and increased to 1.47 +/- 0.51 pg/ml by the end of the session (p<0.05). In patients under rHuEPO-substitution plasma endothelin-1 was higher when compared to patients without substitution before (1.25 +/- 0.3 vs. 1.05 +/- 0.3 pg/ml) and at the end of HD (1.62 +/- 0.5 vs. 1.28 +/- 0.3 pg/ml, p<0.05). There was no difference in BP and deltaBV between the two groups during treatment. Plasma endothelin-1 was higher in hemodialysis patients and there was a continuous rise in plasma endothelin-1 during a session. Comparison of two groups of hemodialysis patients with and without s.c. rHuEPO-replacement treatment revealed a significantly higher plasma endothelin-1 concentration in patients with s.c. rHuEPO treatment. However, the elevated endothelin-1 levels were not accompanied by arterial hypertension.

Anemia↗

PubMed2000

Urinary thymidine glycol as a biomarker for oxidative stress after kidney transplantation.

Reactive oxygen species are generated during ischemia-reperfusion tissue injury. Oxidation of thymidine by hydroxyl radicals (HO*) causes formation of 5,6-dihydroxy-5,6-dihydrothymidine (thymidine glycol). Thymidine glycol excreted in urine can be used as a biomarker of oxidative DNA damage. The aim of this study was to investigate the oxidative DNA damage in patients showing immediate allograft function after kidney transplantation, and to find out whether this damage correlates with glomerular and tubular lesions. Time dependent changes in urinary excretion rates of thymidine glycol, but also of total protein, albumin, low molecular weight (alpha1-microglobulin, beta2-microglobulin) and high molecular weight proteins (transferrin, IgG, alpha2-macroglobulin) were analyzed quantitatively and by polyacrylamide-gel electrophoresis in six patients. Urinary thymidine glycol was determined by a fluorimetric assay in combination with affinity chromatography and HPLC. After kidney transplantation the urinary excretion rate of thymidine glycol increased gradually reaching a maximum within the first 48 hours (16.56+/-11.3 nmol/m mol creatinine, ref. 4.3+/-0.97). Severe proteinuria with an excretion rate of up to 7.2 g/mmol creatinine was observed and declined within the first 24 hours of allograft function (0.35+/-0.26 g/mmol creatinine). The gel-electrophoretic pattern showed a nonselective glomerular and tubular proteinuria. The initial nonselective glomerular proteinuria disappeared within 48 hours, changing to a mild selective glomerular proteinuria. In this period (12-48 hours) higher levels of thymidine glycol excretion were observed, when compared to the initial posttransplant phase (13.66+/-9.76 vs. 4.31+/-3.61 nmol/mmol creatinine; p<0.05). An increased excretion of thymidine glycol is seen after kidney transplantation and is explained by the ischemia-reperfusion induced oxidative DNA damage in the kidney. In the second phase higher levels of excretion were observed parallel to the change from a nonselective to a selective glomerular and tubular proteinuria. An explanation may be sought in the repair process of DNA in the glomerular and tubular epithelial cells, appearing simultaneously with functional recovery.

Adult↗

PubMed2000

The heterogeneous and delayed course of blood pressure normalization in hypertensive patients after bilateral nephrectomy with and without subsequent renal transplantation.

BACKGROUND: Controversy exists about the time course of blood pressure normalization following bilateral nephrectomy. We sought to evaluate the time course of blood pressure normalization following bilateral nephrectomy and after subsequent kidney transplantation. METHODS AND RESULTS: Clinical data from 14 hypertensive patients were retrospectively assessed. Baseline blood pressure was 175 +/- 33/109 +/- 9 mmHg. Ten patients firstly underwent unilateral nephrectomy, which resulted in a slight increase of blood pressure (185 +/- 22/110 +/- 5 mmHg). One month following bilateral nephrectomy, blood pressure was 167 +/- 23/104 +/- 17 mmHg, at 3 months 159 +/- 42/104 +/- 25 mmHg, and at 6 months 149 +/- 41/96 +/- 30 mmHg. Antihypertensive medication was necessary in 9/14 patients at a 2 year follow-up. Eight patients remained anephric (group I), 6 patients had subsequent kidney transplantation (group II). In group I, blood pressure was 159 +/- 42/93 +/- 17 mmHg and 129 +/- 34/75 +/- 14 mmHg at 3 and 6 months, respectively (p< 0.05 vs. baseline). In group II, blood pressure decreased from 188 +/- 42/ 128 +/- 46 mmHg to 167 +/- 48/113 +/- 32 mmHg at 3 months, but increased after transplantation to 186 +/- 39/118 +/- 33 mmHg. Antihypertensive medication was still necessary in 5 transplanted patients (83%) and in 3 anephric patients (38%). CONCLUSION: Adaptation of the blood pressure response following bilateral nephrectomy is a time requiring process, and long-term antihypertensive medication may still be necessary.

Adolescent↗

PubMed1999

VCAM-1, ICAM-1, and E-selectin in IgA nephropathy and Schönlein-Henoch syndrome: differences between tissue expression and serum concentration.

The tissue expressions of vascular cell adhesion molecule 1 (VCAM-1), intercellular adhesion molecule 1 (ICAM-1) and endothelial leukocyte adhesion molecule 1 (E-selectin-1) were investigated in biopsy specimens from 28 patients with different stages of IgA nephropathy (IgAN) and 20 patients with acute renal failure (ARF) or chronic renal diseases (amyloidosis, Alport's glomerulopathy) by immunohistochemistry. The results were compared with the serum levels of the three adhesion molecules. VCAM-1 expression was significantly increased on parietal/tubular epithelial cells in IgAN and ARF. Significantly elevated circulating VCAM-1 levels were measured in IgAN and amyloidosis, but did not correlate with renal function (creatinine clearance). Significantly increased glomerular endothelial/epithelial ICAM-1 expression was found in IgAN and ARF. Intense mesangial ICAM-1 expression was found in mild stages of IgAN and in Schönlein-Henoch syndrome. Circulating ICAM-1 was not significantly elevated in IgAN and different renal diseases. VCAM-1 and ICAM-1 expressions of interstitial infiltrating cells were significantly higher in severe than in mild IgAN and associated with an increased infiltration of inflammatory leukocytes. Patients with IgAN and different renal diseases had decreased mesangial and almost absent interstitial E-selectin expression as compared with controls. The circulating E-selectin levels were significantly elevated in ARF. In conclusion, the tissue expression of adhesion molecules in IgAN reflects a continuous inflammatory renal activity. However, only increased circulating VCAM-1 serum levels correlated significantly with the histological state of renal inflammation and could be used as a disease marker.

Acute Kidney Injury↗

PubMed1999

Influence of hematocrit on hemostasis in continuous venovenous hemofiltration during acute renal failure.

BACKGROUND: Hematocrit plays a major role in primary hemostasis by influencing blood viscosity and platelet adhesion. During continuous venovenous hemofiltration (CVVH), it is suspected that an increased hematocrit is accompanied by an activation of hemostasis and frequently leads to thromboses in the extracorporeal system. In order to examine this hypothesis, we studied the influence of hematocrit on hemostasis during CVVH. METHODS: Fourteen patients (8 men and 6 women, mean age 65+/-10 years) with acute renal failure undergoing CVVH were prospectively enrolled. Polysulfone hemofilters (AV 600; Fresenius, Oberursel, Germany) were used in all of the patients; blood flow rates were adjusted to 120 ml/min. No blood products and coagulation-related medication, except unfractionated heparin, were applied. Study exclusion criteria included a history of thromboembolism and artificial heart valves. Hemostasis activation markers (fibrinopeptide A, thrombin-antithrombin III complex, beta-thromboglobulin, platelet retention) and hematocrit values were determined before and at three-day intervals during the course of CVVH treatment. RESULTS: The mean hematocrit value (mean +/- SEM) was 29+/-1% (range, 22 to 35%). Patients with hematocrit values of less than 30% (N = 7) were compared with patients with higher hematocrit values (>30%, N = 7). The patients with a lower hematocrit (<30%) showed a stronger activation of hemostasis during CVVH when compared with those with a higher hematocrit (>30%), as indicated by a tendency toward higher values for fibrinopeptide A (25+/-8 vs. 14+/-5 ng/ml, P = 0.35), thrombin-antithrombin III complex (15+/-4 vs. 10+/-2 ng/ml, P = 0.66), and a higher beta-thromboglobulin/creatinine ratio (0.62+/-0.17 vs. 0.48+/-0.12, P = 0.8). CONCLUSION: Contrary to our hypothesis, hematocrit values of more than 30% are not accompanied by an increased hemostasis activation during CVVH. Concerning hemostasis activation, hematocrit values between 30 and 35% may be suitable for patients on CVVH.

Acute Kidney Injury↗

PubMed1999

Is dialysis membrane type responsible for increased circulating adhesion molecules during chronic hemodialysis?

BACKGROUND: Patients with chronic renal failure under maintenance hemodialysis (HD) present with numerous adverse effects including immunologic alterations. Serious abnormalities of neutrophil function have been reported to be associated with disturbed cell adhesiveness. These adhesion processes are mediated by cytokines and different adhesion molecules. PATIENTS AND METHODS: In this study, serum concentrations of the intercellular adhesion molecule ICAM-1, vascular cell adhesion molecule VCAM-1 and endothelial leukocyte adhesion molecule E-selectin were investigated during employment of different dialysis membranes (cuprophane: n = 23, cellulose: 8, polysulfone: 26, acrylonitrile: 7). These adhesion parameters from 64 patients before and after a hemodialysis session were investigated parallel to the serum levels of circulating cytokines and their inhibitors. RESULTS: Circulating ICAM-1 levels were not elevated in low-flux membranes and most of the high-flux HD membranes, except for one high-flux polysulfone membrane. cVCAM-1 levels were significantly elevated both in low- and high-flux dialysis membranes, whereas cE-selectin was not increased. cICAM-1 levels were not different before and after hemodialysis in the entire study group. In contrast, cVCAM-1 and cE-selectin levels increased significantly during HD in the entire study group (both p < 0.001). Serum levels did not correlate with the duration of end-stage renal failure and hemodialysis. Levels of circulating cytokine antagonists/inhibitors (Il-lra, Il-2R, TNFsRp55/75) were significantly increased in all patients before and after HD, whereas the serum concentrations of the corresponding circulating cytokines (I1-1beta, Il-1, TNF-alpha) were within normal ranges. CONCLUSION: Increased levels of cVCAM-1 which suggest an important role for immunological alterations in HD and cytokine-independent changes during HD sessions in all membranes without alterations of cICAM-1 in most membranes and unchanged cE-selectin indicate that processes such as uremia are responsible for these effects rather than membrane characteristics. The level of circulating adhesion molecules does not serve as an appropriate marker of membrane biocompatibility.

Acrylonitrile↗

PubMed1998

Cerebral tuberculoma 11 years after renal transplantation.

A case of cerebral tuberculoma in a 39-year-old patient who had received a renal graft from a living related donor 11 years previously is reported. The patient had a major seizure, progressive psychiatric signs and fever 5 days prior to admission. The clinical history suggested a neurological cause and rapid diagnosis of a cerebral tuberculoma was made by a computed tomography-guided stereotactic puncture of a space-occupying cerebral lesion. The aspirated pus contained Mycobacterium tuberculosis. Anti-tuberculous therapy with isoniacid, rifampicin, ethambutol and pyracinamide was administered. Transplant function deteriorated and the patient died due to intractable septicemia with multiorgan failure from pulmonary infection dissemination and additional urinary tract infection with atypical mycobacteria. The chance for a benign clinical course necessitates vigorous procedures for an early diagnosis of cerebral infections in renal transplant recipients with neurological/psychiatric signs.

Adult↗

PubMed1998

Long-term extracorporeal bilirubin elimination: A case report on cascade resin plasmaperfusion.

Acute hepatic failure develops as a disease entity of rather diverse origin. With disease progression, toxic bilirubin levels may cause severe complications which include AV-nodal blockage, cardiac arrhythmia, impaired consciousness, generalized seizures, and status epilepticus. Treatment choices to prevent clinical deterioration comprise of costly and limited available orthotopic liver transplantation, utilization of extracorporeal bioartificial liver support devices and haemoperfusion/plasmaperfusion treatment with activated charcoal/anion exchange filters. Here, we present a patient with acute drug-induced cholestatic hepatitis. Excessively elevated bilirubin levels were accompanied by cardiac and cerebral complications. Extracorporeal resin perfusion treatment (Plasorba, BR-350) was successfully performed over a 50-day period without activation of the coagulation system or side effects. Bilirubin levels were lowered to a minimum of 225 micromol/l, with concurrent clinical improvement. In conclusion, extracorporeal anion exchange plasmaperfusion may be a viable long-term treatment for hyperbilirubinaemic side effects in overt cholestatic hepatitis.

Acute Kidney Injury↗

PubMed1998

Pressure oscillation regulates human mesangial cell growth and collagen synthesis.

Experimental renal disease models establish glomerular hypertension as a crucial determinant in glomerulosclerosis progression and demonstrate that glomerular capillary pressure reduction delays sclerosis development. An oscillating pressure (OP) chamber was constructed as an in vitro model to study human mesangial cells. Cell cultures were grown under atmospheric pressure (AP) and a controlled OP corresponding to intraglomerular capillary pressure. We show that OP significantly decreases mesangial cell proliferation within 24 hours and attenuates DNA synthesis throughout a 7-day period. To explore the effects of OP on cell metabolism, cell-associated and medium-secreted extracellular (CA and EC, respectively) collagen synthesis were measured by [3H]proline incorporation. In subconfluent cultures, total CA and EC collagen synthesis was unaffected by OP, while in confluent cultures total EC collagen [3H]proline incorporation was increased. To determine whether OP influenced mesangial cell growth induction, the effects of increasing glucose in the cell culture media were investigated. Our data show that the high glucose growth stimulatory effect on cell number and DNA synthesis was suppressed by OP. Under high glucose conditions, total CA collagen synthesis was increased in confluent cultures, whereas the EC collagen fraction remained unchanged. In these cultures, OP caused an additional increase in CA collagen synthesis. This study shows that mesangial cell growth and collagen synthesis are influenced by hyperbaric OP, supporting the hypothesis that glomerular capillary pressure plays a role in progressive glomerulosclerosis development.

Cell Division↗

PubMed1998

Clinical pharmacokinetics of vasodilators. Part I.

Understanding the mechanism of action and the pharmacokinetic properties of vasodilatory drugs facilitates optimal use in clinical practice. It should be kept in mind that a drug belongs to a class but is a distinct entity, sometimes derived from a prototype to achieve a specific effect. The most common pharmacokinetic drug improvement is the development of a drug with a half-life sufficiently long to allow an adequate once-daily dosage. Developing a controlled release preparation can increase the apparent half-life of a drug. Altering the molecular structure may also increase the half-life of a prototype drug. Another desirable improvement is increasing the specificity of a drug, which may result in fewer adverse effects, or more efficacy at the target site. This is especially important for vasodilatory drugs which may be administered over decades for the treatment of hypertension, which usually does not interfere with subjective well-being. Compliance is greatly increased with once-daily dosing. Vasodilatory agents cause relaxation by either a decrease in cytoplasmic calcium, an increase in nitric oxide (NO) or by inhibiting myosin light chain kinase. They are divided into 9 classes: calcium antagonists, potassium channel openers, ACE inhibitors, angiotensin-II receptor antagonists, alpha-adrenergic and imidazole receptor antagonists, beta 1-adrenergic agonist, phosphodiesterase inhibitors, eicosanoids and NO donors. Despite chemical differences, the pharmacokinetic properties of calcium antagonists are similar. Absorption from the gastrointestinal tract is high, with all substances undergoing considerable first-pass metabolism by the liver, resulting in low bioavailability and pronounced individual variation in pharmacokinetics. Renal impairment has little effect on pharmacokinetics since renal elimination of these agents is minimal. Except for the newer drugs of the dihydropyridine type, amlodipine, felodipine, isradipine, nilvadipine, nisoldipine and nitrendipine, the half-life of calcium antagonists is short. Maintaining an effective drug concentration for the remainder of these agents requires multiple daily dosing, in some cases even with controlled release formulations. However, a coat-core preparation of nifedipine has been developed to allow once-daily administration. Adverse effects are directly correlated to the potency of the individual calcium antagonists. Treatment with the potassium channel opener minoxidil is reserved for patients with moderately severe to severe hypertension which is refractory to other treatment. Diazoxide and hydralazine are chiefly used to treat severe hypertensive emergencies, primary pulmonary and malignant hypertension and in severe preeclampsia. ACE inhibitors prevent conversion of angiotensin-I to angiotensin-II and are most effective when renin production is increased. Since ACE is identical to kininase-II, which inactivates the potent endogenous vasodilator bradykinin, ACE inhibition causes a reduction in bradykinin degradation. ACE inhibitors exert cardioprotective and cardioreparative effects by preventing and reversing cardiac fibrosis and ventricular hypertrophy in animal models. The predominant elimination pathway of most ACE inhibitors is via renal excretion. Therefore, renal impairment is associated with reduced elimination and a dosage reduction of 25 to 50% is recommended in patients with moderate to severe renal impairment. Separating angiotensin-II inhibition from bradykinin potentiation has been the goal in developing angiotensin-II receptor antagonists. The incidence of adverse effects of such an agent, losartan, is comparable to that encountered with placebo treatment, and the troublesome cough associated with ACE inhibitors is absent.

Angiotensin II↗

PubMed1998

Clinical pharmacokinetics of vasodilators. Part II.

Stimulating cardiac beta 1-adrenoceptors with oxyfedrine causes dilatation of coronary vessels and positive inotropic effects on the myocardium. beta 1-adrenergic agonists increase coronary blood flow in nonstenotic and stenotic vessels. The main indication for the use of the phosphodiesterase inhibitors pamrinone, mirinone, enoximone and piroximone is acute treatment of severe congestive heart failure. Theophylline is indicated for the treatment of asthma, chronic obstructive pulmonary disease, apnea in preterm infants ans sleep apnea syndrome. Severe arterial occlusive disease associated with atherosclerosis can be beneficially affected by elcosanoids. These drugs must be administered parenterally and have a half-life of only a few minutes. Sublingual or buccal preparations of nitrates are the only prompt method (within 1 or 2 min) of terminating anginal pain, except for biting nifedipine capsules. The short half-life (about 2.5 min) of nitroglycerin (glyceryl trinitrate) makes long term therapy impossible. Tolerance is a problem encountered with longer-acting nitric oxide donors. Knowledge of the pharmacokinetic properties of vasodilating drugs can prevent a too sudden and severe blood pressure decrease in patients with chronic hypertension. In considering the administration of a second dose, or another drug, the time necessary for the initially administered drug to reach maximal efficacy should be taken into account. In hypertensive emergencies urapidil, sodium nitroprusside, nitroglycerin, hydralazine and phentolamine are the drugs of choice, with the addition of beta-blockers during catecholamine crisis or dissecting aortic aneurysm. Childhood hypertension is most often treated with angiotensin-converting enzyme (ACE) inhibitors or calcium antagonists, primarily nifedipine. Because of the teratogenic risk involved with ACE inhibitors, extreme caution must be exercised when prescribing for adolescent females. The propagation of health benefits to breast-fed infants, combined with more women delaying pregnancy until their fourth decade, has entailed an increase in the need for hypertension management during lactation. Low dose hydrochlorothiazide, propranolol, nifedipine and enalapril or captopril do not pose enough of a risk of preclude breastfeeding in this group. The most frequently used antihypertensive agents during pregnancy are methyldopa, labetalol and calcium channel antagonists. Methyldopa and beta-blockers are the drugs of choice for treating mild to moderate hypertension. Prazosin and hydralazine are used to treat moderate to severe hypertension and hydralazine, urapidil or labetalol are used to treat hypertensive emergencies. The use of overly aggressive antihypertensive therapy during pregnancy should be avoided so that adequate uteroplacental blood flow is maintained. Methyldopa is the only drug accepted for use during the first trimester of pregnancy.

Adrenergic alpha-Antagonists↗

PubMed1997

Permeability of the blood-retinal barrier in healthy humans. European Concerted Action on Ocular Fluorometry.

BACKGROUND: The aim of this study was to compare the inward permeability of the blood-retinal barrier in healthy subjects from six European cities. METHODS: Seventy-two healthy subjects (age 20-70 years) were selected. At 30 min and 60 min after fluorescein injection, fluorescein mass in vitreous was calculated from the concentrations measured along the optical axis of the eye. Non-protein-bound fluorescein (NPBF) concentrations were measured in plasma prepared from blood samples taken 7, 15 and 55 min after injection. Blood-retinal barrier permeability (PBRB) was calculated from the vitreous fluorescein mass and the time integral of NPBF and was corrected for the autofluorescence of ocular tissue and for lenticular light transmittance. RESULTS: Mean PBRB values +/- SD (nm.s-1) were 2.07 +/- 0.54 (Coimbra), 2.01 +/- 0.43 (Frankfurt), 2.24 +/- 0.50 (Ghent), 2.37 +/- 0.56 (Herlev), 1.89 +/- 0.44 (Leiden) and 1.74 +/- 0.38 (Porto). Differences between centers were not significant (P > 0.35). Measurements were reproducible and independent of the time after fluorescein injection (P > 0.50). A PBRB higher than 3.16 nm.s-1 or a value which had increased by 32% was considered abnormal (P < 0.05). CONCLUSION: PBRB values were similar in all centers. The results demonstrate that this is a highly sensitive and reliable method for measuring the permeability of the blood-retinal barrier.

Adult↗