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There are many angles to consider in drug treatment of obese patients. On the one hand, some specific weight loss drugs are available, on the other, several drugs are associated with unintentional weight changes. When treating an obese patient for any given disease, several physiological changes may influence the pharmacokinetic properties of the drugs required. Thus, increased body weight may influence the efficacy and safety of some drug treatments. Even more complicated is the situation after weight reduction surgery. Due to the various changes to the gastrointestinal tract induced by the different surgical techniques used, and the dynamic changes in body composition thereafter, drug dosing has to be constantly reconsidered. Whereas all of these issues are of clinical importance, none of them have been investigated in the necessary depth and broadness to ensure safe and efficacious drug treatment of the massively obese patient. Individual considerations have to be based on comorbidities, concomitant medication, and on specific drug properties, for example, lipophilicity, volume of distribution, and metabolism. In this article we summarize the data available on different aspects of drug treatment in the obese patient with the hope of improving patient care.
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BACKGROUND: The immune response to seasonal influenza vaccines decreases with advancing age. Therefore, an adjuvanted inactivated trivalent influenza vaccine (Fluad®) exists for elderly individuals. Fluad® is more immunogenic and efficacious than conventional influenza vaccines. However, the immune response varies and may still result in high frequencies of poor responders. Therefore, we aimed to a) examine the prevalence of a weak response to Fluad® and b) identify potential risk factors. METHODS: A prospective population-based study among individuals 65-80 years old was conducted in 2015/2016 in Hannover, Germany (n = 200). Hemagglutination-inhibition titers 21 days after vaccination with Fluad® served as indicator of vaccine responsiveness. RESULTS: The percentage of vaccinees with an inadequate vaccine response varied depending on the influenza strain: it was lowest for H3N2 (13.5%; 95% CI, 9.4-18.9%), intermediate for B strain (37.0%; 30.6-43.9%), and highest for H1N1 (49.0%; 42.2-55.9%). The risk of a weak response to the influenza A H1N1 strain was independently associated with self-reported diabetes (AOR, 4.64; 95% CI, 1.16-18.54), a history of herpes zoster (2.27; 1.01-5.10) and, to a much lesser extent, increasing age (change per year, 1.08; 0.99-1.16). In addition, herpes zoster was the only risk factor for a weak response to the H3N2 antigen (AOR, 3.12; 1.18-8.23). We found no significant association between sex, Body Mass Index, cancer, hypertension, heart attack and CMV seropositivity and a weak response to these two influenza A antigens. Despite its occurence in over one third of vaccinees, none of the variables examined proved to be risk factors for a weak response to the B antigen. CONCLUSIONS: A considerable proportion of elderly individuals displayed a weak vaccine response to this adjuvanted seasonal influenza vaccine and further efforts are thus needed to improve immune responses to influenza vaccination among the elderly. Diabetes and herpes zoster were identified as potentially modifiable risk factors for a poor vaccine response against influenza A antigens, but the results also reveal the need for broader investigations to identify risk factors for inadequate responses to influenza B antigens. TRIAL REGISTRATION: No. NCT02362919 (ClinicalTrials.gov, date of registration: 09.02.2015).
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Diabetes Mellitus/imunologia , Herpes Zoster/imunologia , Imunidade Humoral , Vacinas contra Influenza/imunologia , Adjuvantes Imunológicos/farmacologia , Idoso , Idoso de 80 Anos ou mais , Antígenos Virais/imunologia , Feminino , Alemanha , Humanos , Vírus da Influenza A Subtipo H1N1/imunologia , Vírus da Influenza A Subtipo H3N2/imunologia , Vacinas contra Influenza/efeitos adversos , Vacinas contra Influenza/farmacologia , Influenza Humana/imunologia , Influenza Humana/prevenção & controle , Masculino , Estudos Prospectivos , Estações do Ano , AutorrelatoRESUMO
AIMS: The potential influence of angiotensin-receptor blockers (ARBs) on carcinogenesis is a much-debated topic. Both observational, as well as preclinical studies in rodent carcinogenic assays, suggest a major role of the Renin-Angiotensin-Aldosterone-System (RAAS) in cancer development. Therefore, a systematic review and meta-analysis with available study data on ARBs and carcinogenicity in general as primary outcome were conducted. Secondary outcomes were defined as tumour-specific mortality rates and the frequency of new cases of specific tumour types with particular emphasis on lung, breast, and prostate cancer. METHODS: A systematic literature research was performed in MEDLINE, EMBASE, Cochrane Library, and TOXLINE. We used a combination of MeSH terms, keywords and substance names of ARBs and searched between 1950 and 2016. At least 100 participants in each study arm and a minimum follow-up for one year were necessary for study inclusion. Odds ratios (OR) were calculated by a random-effects model. RESULTS: A total of 8818 potentially eligible publications were identified of whom seven randomised controlled trials, four case-control studies and one cohort study met our inclusion criteria. As a key result, we found no effect on carcinogenesis in randomised controlled trials for ARB usage. (OR 1.02, 95% CI 0.87-1.19; pâ¯=â¯.803). Conflicting results with observational studies could be explained by poor reporting- and study qualities. CONCLUSIONS: The results of our meta-analysis focusing only on high evidence levels and study designs (RCTs) did not reveal any relationship between pharmacotherapy with an ARB and an increased risk for cancer in general.
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Neoplasias/epidemiologia , Antagonistas de Receptores de Angiotensina/efeitos adversos , Antagonistas de Receptores de Angiotensina/uso terapêutico , Humanos , Hipertensão/tratamento farmacológico , Neoplasias/induzido quimicamente , Ensaios Clínicos Controlados Aleatórios como Assunto , Sistema Renina-Angiotensina/efeitos dos fármacos , RiscoRESUMO
In the original publication, the text in Table 2 stated 'Hypersensitivity to the active substance, to Ferinject, or to any of its excipients'.
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Increased adverse health effects in older subjects due to exposure to ambient air pollutants may be related to the inflammatory response induced by these contaminants. The aim of this study was to assess airway and systemic inflammatory responses in older healthy subjects to a controlled experimental exposure with spark-generated elemental carbon black ultrafine particles (cbUFPs) and ozone (O3). Twenty healthy subjects, age 52-75 years, were exposed on three occasions separated by at least 8 weeks. The exposures to filtered air (FA), to cbUFP (50 µg/m3), or to cbUFP in combination with 250 ppb ozone (cbUFP + O3) for 3 h with intermittent exercise were performed double blind, and in random order. Sputum and blood samples were collected 3.5 h after each exposure. Exposure to cbUFP + O3 significantly increased plasma club cell protein 16 (CC16), the number of sputum cells, the number and percent of sputum neutrophils, and sputum interleukin 6 and matrix metalloproteinase 9. Exposure to cbUFP alone exerted no marked effect, except for an elevation in sputum neutrophils in a subgroup of 13 subjects that displayed less than 65% sputum neutrophils after FA exposure. None of the inflammatory markers was correlated with age, and serum cardiovascular risk markers were not markedly affected by cbUFP or cbUFP + O3. Exposure to cbUFP+O3 induced a significant airway and systemic inflammatory response in older healthy volunteer subjects. The effects induced by cbUFP alone suggest that the inflammation was predominantly mediated by O3, although one cannot rule out that the interaction of cbUFP and O3 played a role.
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Poluentes Atmosféricos/efeitos adversos , Ozônio/efeitos adversos , Sistema Respiratório/efeitos dos fármacos , Fuligem/efeitos adversos , Sistema Nervoso Simpático/efeitos dos fármacos , Idoso , Estudos Cross-Over , Método Duplo-Cego , Feminino , Alemanha , Humanos , Inflamação/induzido quimicamente , Inflamação/imunologia , Masculino , Pessoa de Meia-Idade , Distribuição Aleatória , Sistema Respiratório/imunologia , Sistema Nervoso Simpático/fisiologiaRESUMO
Purpose To investigate the safety and clinical activity of comprehensive human epidermal growth factor receptor (HER) family receptor inhibition using lumretuzumab (anti-HER3) and pertuzumab (anti-HER2) in combination with paclitaxel in patients with metastatic breast cancer (MBC). Methods This phase Ib study enrolled 35 MBC patients (first line or higher) with HER3-positive and HER2-low (immunohistochemistry 1+ to 2+ and in-situ hybridization negative) tumors. Patients received lumretuzumab (1000 mg in Cohort 1; 500 mg in Cohorts 2 and 3) plus pertuzumab (840 mg loading dose [LD] followed by 420 mg in Cohorts 1 and 2; 420 mg without LD in Cohort 3) every 3 weeks, plus paclitaxel (80 mg/m2 weekly in all cohorts). Patients in Cohort 3 received prophylactic loperamide treatment. Results Diarrhea grade 3 was a dose-limiting toxicity of Cohort 1 defining the maximum tolerated dose of lumretuzumab when given in combination with pertuzumab and paclitaxel at 500 mg every three weeks. Grade 3 diarrhea decreased from 50% (Cohort 2) to 30.8% (Cohort 3) with prophylactic loperamide administration and omission of the pertuzumab LD, nonetheless, all patients still experienced diarrhea. In first-line MBC patients, the objective response rate in Cohorts 2 and 3 was 55% and 38.5%, respectively. No relationship between HER2 and HER3 expression or somatic mutations and clinical response was observed. Conclusions Combination treatment with lumretuzumab, pertuzumab and paclitaxel was associated with a high incidence of diarrhea. Despite the efforts to alter dosing, the therapeutic window remained too narrow to warrant further clinical development. TRIAL REGISTRATION: on ClinicalTrials.gov with the identifier NCT01918254 first registered on 3rd July 2013.
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Anticorpos Monoclonais Humanizados/administração & dosagem , Protocolos de Quimioterapia Combinada Antineoplásica/administração & dosagem , Neoplasias da Mama/tratamento farmacológico , Paclitaxel/administração & dosagem , Receptor ErbB-2/antagonistas & inibidores , Adulto , Idoso , Anticorpos Monoclonais Humanizados/efeitos adversos , Anticorpos Monoclonais Humanizados/farmacocinética , Antineoplásicos/administração & dosagem , Antineoplásicos/efeitos adversos , Antineoplásicos/farmacocinética , Protocolos de Quimioterapia Combinada Antineoplásica/efeitos adversos , Neoplasias da Mama/genética , Neoplasias da Mama/metabolismo , Diarreia/induzido quimicamente , Feminino , Humanos , Hipopotassemia/induzido quimicamente , Masculino , Pessoa de Meia-Idade , Paclitaxel/efeitos adversos , Polimorfismo de Nucleotídeo Único , Receptor ErbB-2/genética , Receptor ErbB-2/metabolismo , Receptor ErbB-3/antagonistas & inibidores , Receptor ErbB-3/genética , Receptor ErbB-3/metabolismoRESUMO
INTRODUCTION: HbA1c is the gold standard for glycemic control in pre-diabetes and diabetes. However, its validity has been questioned, especially in the presence of imbalanced iron homeostasis. The CLEVER trial aims to evaluate the relationship between iron deficiency and HbA1c (a biomarker for the diagnosis and therapeutic monitoring of type 2 diabetes) in a randomized, placebo-controlled, multicenter clinical trial. METHODS: The CLEVER (intravenous ferric CarboxymaLtosE for improVement of mEtabolic parameters in type 2 diabetes patients with iRon deficiency) trial is a randomized, single-blind, proof-of-concept study with two treatment arms. 140 men and women diagnosed with type 2 diabetes and iron deficiency will receive either placebo or ferric carboxymaltose (500 or 1000 mg) as intravenous infusions. The primary outcome measure is the change in HbA1c level between baseline and after 12 weeks of treatment. Secondary endpoints include change of iron status and metabolic markers as well as treatment safety and tolerability. Furthermore, the potential clinical improvement in quality of life and the reliability of HbA1c measurement in patients with type 2 diabetes and iron deficiency will be investigated. RESULTS: Both excessive iron and iron deficiency are associated with metabolic disorders; excessive iron is a risk factor for the development of diabetes, whereas iron deficiency is associated with obesity and insulin resistance. It has been suggested that iron increases insulin secretion in pancreatic beta-cells. CLEVER is the first study to investigate the hypothesis that intravenous substitution with ferric carboxymaltose reduces HbA1c levels in patients with type 2 diabetes and iron deficiency, thereby improving metabolic status and quality of life. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov (NCT01513369). FUNDING: GWT-TUD GmbH acts as sponsor of the clinical trial. Financial support is provided by Vifor Pharma.
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OBJECTIVE: To study the effect of exercise on hemodynamic profiles and red blood cell (RBC) concentrations of adenosine-5'-triphosphate (ATP). METHODS: Male Sprague-Dawley (SD) rats (n = 9) were exercised on a treadmill for 15 min at a speed of 10 m/min with a 5% gradient after an hour settling down in a restrainer. Blood samples were collected via an indwelling carotid artery catheter using a 'Stopping Solution' from each rat before, during and after exercise. Hemodynamic recordings were collected continuously throughout the experiment. Concentrations of ATP and other purine nucleotides in the RBCs were determined by a validated high-performance liquid chromatography (HPLC) assay. A control group (n = 12) was treated the same way except without the exercise. Data between groups were analyzed by analysis of variance (ANOVA) and Student's t-test, and differences were considered significant when p < 0.05. RESULTS: Exercise increased systolic blood pressure (SBP; 141±23 vs. 132±17 mmHg) and heart rate (HR; 420±33 vs. 397±41 bpm), but decreased diastolic blood pressure (DBP; 105±18 vs. 110±14 mmHg). This was followed by a postexercise condition when SBP, DBP, and HR were decreased for the remainder of the experiment. RBC concentrations of ATP and guanosine-5'-triphosphate (GTP) increased significantly during exercise and continued to increase for 5 hours postexercise (1.5±0.75 vs. 0.96 vs. 0.36 mM for ATP; and 0.14±0.061 vs. 0.058±0.030 mM) (p < 0.05). CONCLUSION: Exercise increased RBC ATP concentrations in a rodent model, which was correlated with the decrease in BP and HR postexercise.
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Trifosfato de Adenosina/metabolismo , Eritrócitos/metabolismo , Condicionamento Físico Animal/fisiologia , Análise de Variância , Animais , Pressão Sanguínea/fisiologia , Cromatografia Líquida de Alta Pressão , Guanosina Trifosfato/metabolismo , Frequência Cardíaca/fisiologia , Masculino , Nucleotídeos de Purina/metabolismo , Ratos , Ratos Sprague-DawleyRESUMO
Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease characterized by loss of motor neurons in the cerebral cortex, brain stem, and spinal cord. Most cases (90%) are classified as sporadic ALS (sALS). The remainder 10% are inherited and referred to as familial ALS, and 2% of instances are due to mutations in Cu/Zn superoxide dismutase (SOD1). Using cDNA microarray on postmortem spinal cord specimens of four sALS patients compared to four age-matched nonneurological controls, we found major changes in the expression of mRNA in 60 genes including increase of cathepsin B and cathepsin D (by the factors 2 and 2.3, respectively), apolipoprotein E (Apo E; factor 4.2), epidermal growth factor receptor (factor 10), ferritin (factor 2), and lysosomal trafficking regulator (factor 10). The increase in the expression of these genes was verified by quantitative reverse transcriptase polymerase chain reaction. Further analysis of these genes in hSOD1-G93A transgenic mice revealed increase in the expression in parallel with the deterioration of motor functions quantified by means of rotorod performance. The comparability of the findings in sALS patients and in the hSOD1-G93A transgenic mouse model suggests that the examined genes may play a specific role in the pathogenesis of ALS.
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Esclerose Lateral Amiotrófica , RNA Mensageiro/metabolismo , Medula Espinal , Superóxido Dismutase , Idoso , Idoso de 80 Anos ou mais , Esclerose Lateral Amiotrófica/enzimologia , Esclerose Lateral Amiotrófica/genética , Esclerose Lateral Amiotrófica/patologia , Animais , Catepsina B/genética , Catepsina B/metabolismo , Catepsina D/genética , Catepsina D/metabolismo , Modelos Animais de Doenças , Receptores ErbB/genética , Receptores ErbB/metabolismo , Feminino , Ferritinas/genética , Ferritinas/metabolismo , Perfilação da Expressão Gênica , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Masculino , Camundongos , Camundongos Transgênicos , Pessoa de Meia-Idade , Dados de Sequência Molecular , Análise de Sequência com Séries de Oligonucleotídeos , Proteínas/genética , Proteínas/metabolismo , RNA Mensageiro/genética , Medula Espinal/citologia , Medula Espinal/enzimologia , Medula Espinal/fisiologia , Superóxido Dismutase/genética , Superóxido Dismutase/metabolismo , Superóxido Dismutase-1 , Proteínas de Transporte VesicularRESUMO
Risk factors for the development of cardiovascular disease, in particular myocardial infarction, are smoking, high body weight, sedentary lifestyle, unfavorable diet, high blood pressure, elevated fasting glucose or diabetes, and dyslipidemia (Tables 1 and 2). If the risk for cardiovascular mortality of 5% (using the SCORE Score) or for nonfatal cardiovascular events of 20% (PROCAM Score) within the next 10 years is exceeded or overt atherosclerosis or type 2 diabetes mellitus is present, the use of (poly)pharmacotherapy is indicated and lifestyle intervention (diet, physical activity) alone is not sufficient at that point (Figure 1). A new therapeutic option, able to modify a number of cardiovascular risk factors at a time, is the blockade of the so-called endocannabinoid system (Figure 2). For rimonabant not only a reduction of body weight and waist circumference was shown in clinical trials, its use was also accompanied by an increase of HDL cholesterol, a decrease in triglycerides, and a reduction in HbA1c and fasting blood glucose (Table 4). Together with preliminary data on the efficacy in smoking cessation, rimonabant has a therapeutic impact on four out of eight relevant risk factors in order to prevent myocardial infarction as promoted by the American College of Cardiology/American Heart Association. Currently, a large clinical study program is ongoing to further investigate the role of rimonabant in managing cardiovascular risk (Table 3). Published clinical trial results have revealed, that rimonabant is generally well tolerated (most frequent side effect: nausea) and the data are promising with regard to the potential future role of rimonabant in managing cardiovascular risk.
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Canabinoides/antagonistas & inibidores , Doenças Cardiovasculares/tratamento farmacológico , Doenças Cardiovasculares/epidemiologia , Ensaios Clínicos como Assunto/estatística & dados numéricos , Piperidinas/uso terapêutico , Pirazóis/uso terapêutico , Humanos , Prevalência , Rimonabanto , Resultado do TratamentoRESUMO
BACKGROUND: In the literature, surveys of malignant intracerebral nerve sheath tumors are very rare (Table 1). Therapeutic guidelines do not exist. CASE REPORT: A 28-year-old female patient presented with a tumor in the postcentral region of the left parietal lobe (Figures 1 and 2). The specimen could not be categorized into a common tumor entity and was classified as sarcoma NOS. Shortly after surgery, a recurrence occurred (Figures 3 to 5) followed by a further excision. Due to the rapid tumor growth irradiation with CT-aided treatment planning (Figure 6) has been started immediately afterwards. A dose of 5,400 cGy in 22 fractions was administered. RESULT: 2 weeks after treatment, the patient presented with a noticeable tumor regression (magnetic resonance imaging; Figures 7 to 9). She developed pulmonary metastases. A partial remission could be achieved by systemic chemotherapy. Unfortunately, the patient died because of an exacerbation of a hepatic encephalopathy. CONCLUSION: In cases of intracerebrally localized sarcomas NOS, the earliest possible start of radiotherapy after surgery seems useful because of the noticed radiosensitivity of these tumors. In regard of the local control, this tumor entity shows a documented excellent response to radiotherapy. Expectedly, distant metastases cannot be influenced. Interdisciplinary cooperation is mandatory to enhance the diagnostic process, the treatment decisions, and the results.
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Neoplasias Encefálicas/radioterapia , Irradiação Craniana , Neoplasias Primárias Múltiplas/radioterapia , Neurofibrossarcoma/radioterapia , Lobo Parietal , Equipe de Assistência ao Paciente , Adulto , Neoplasias Encefálicas/patologia , Neoplasias Encefálicas/cirurgia , Terapia Combinada , Comportamento Cooperativo , Evolução Fatal , Feminino , Humanos , Neoplasias Pulmonares/patologia , Neoplasias Pulmonares/secundário , Imageamento por Ressonância Magnética , Recidiva Local de Neoplasia/patologia , Recidiva Local de Neoplasia/radioterapia , Recidiva Local de Neoplasia/cirurgia , Neoplasias Primárias Múltiplas/patologia , Neoplasias Primárias Múltiplas/cirurgia , Neurofibrossarcoma/patologia , Neurofibrossarcoma/secundário , Neurofibrossarcoma/cirurgia , Planejamento da Radioterapia Assistida por Computador , Radioterapia Adjuvante , RetratamentoAssuntos
Antidepressivos de Segunda Geração/administração & dosagem , Bupropiona/administração & dosagem , Cognição/efeitos dos fármacos , Adulto , Antidepressivos de Segunda Geração/sangue , Bupropiona/sangue , Cromatografia Líquida/métodos , Estudos Cross-Over , Método Duplo-Cego , Esquema de Medicação , Eletroencefalografia/métodos , Olho/efeitos dos fármacos , Humanos , Masculino , Espectrometria de Massas/métodosRESUMO
May 2004: We present the case of a male newborn (38th week of gestation) with a 3-week history of a sonographically detected parietal mass of 5-cm diameter. The entire mass was removed at surgery. Surprisingly, microscopy revealed an intracerebral hemorrhage and nests of glycophorin-A immunoreactive blasts and nucleated erythrocytes in the surrounding parenchyma. The final diagnosis was chronic intracerebral hemorrhage of unknown etiology with reactive changes of the surrounding brain tissue and perifocal extramedullary erythropoiesis. This case is unique because, to date, intracranial extramedullary erythropoiesis has only been described in chronic subdural hemorrhage.
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Doenças do Sistema Nervoso Central/patologia , Hemorragia Cerebral/patologia , Doenças do Sistema Nervoso Central/metabolismo , Hemorragia Cerebral/metabolismo , Proteína Glial Fibrilar Ácida/metabolismo , Humanos , Imuno-Histoquímica/métodos , Recém-Nascido , Imageamento por Ressonância Magnética/métodos , Masculino , Sinaptofisina/metabolismoRESUMO
OBJECTIVES: Recent studies suggest that stimulation of beta-adrenergic receptors results in both endothelium-dependent and endothelium-independent venodilation, but results of former studies are inconsistent. This study was designed to elucidate the underlying mechanisms of isoproterenol (INN, isoprenaline)-induced venodilation by investigation of dorsal hand vein responses. METHODS: In phenylephrine-constricted veins, isoproterenol (2-514 ng/min) was infused with and without oral pretreatment with 1 g acetylsalicylic acid (n = 7) or 5 mg of the selective beta(1)-adrenergic receptor antagonist bisoprolol (n = 7). In addition, isoproterenol was coinfused with the nitric oxide inhibitor N(G)-monomethyl-l-arginine (l-NMMA) (6.3 micromol/min [n = 6]), with selective blockers of calcium (Ca(++))-dependent potassium (K(+)) channels (tetraethylammonium, 300 microg/min [n = 6]) and adenosine triphosphate (ATP)-sensitive K(+) channels (glyburide [INN, glibenclamide], 20 microg/min [n = 6]) or with the cyclic guanosine monophosphate inhibitor methylene blue (13 microg/min [n = 6]). Finally, L-NMMA was coinfused with potassium chloride (20 mmol/L) to inhibit hyperpolarization (n = 6). RESULTS: Isoproterenol induced dose-dependent venodilation to 67.4% +/- 6.8%. Oral pretreatment with bisoprolol (P =.340) or acetylsalicylic acid (P =.760) did not affect isoproterenol-induced venodilation. Coinfusion of isoproterenol and L-NMMA relaxed the veins to the same extent as in the presence of isoproterenol alone. Neither inhibition of ATP-sensitive K(+) channels (P =.196) nor blockade of Ca(++)-dependent K(+) channels (P =.640) modulated isoproterenol-induced venodilation. In contrast, methylene blue reduced the maximum response to isoproterenol by about one third (68.5% +/- 4.3% versus 41.7% +/- 5.5%, P =.001). Infusion of L-NMMA alone raised vein size to 38.8% +/- 6.5%, yielding an L-NMMA-sensitive increase of 20% (P =.001), which was antagonized by coinfusion of potassium chloride to 17.1% +/- 6.7% (P =.02). CONCLUSIONS: Isoproterenol dilates human hand veins exclusively via beta(2)-adrenergic receptors without involvement of endothelium-derived epoprostenol. Although a contribution of endothelium-derived nitric oxide appears unlikely, the venodilating effect of L-NMMA could have obscured the nitric oxide component of isoproterenol. beta(2)-Adrenergic receptor-mediated dilation is mediated in part by cyclic guanosine monophosphate-dependent mechanisms, whereas ATP- and Ca(++)-dependent K(+) channels are not involved, excluding a significant contribution of smooth muscle cell hyperpolarization. In addition, high concentrations of the nitric oxide synthase blocker L-NMMA dilate human hand veins via activation of endothelium-derived hyperpolarizing factors.