Search results for "β-Blocker"
showing 6 items of 6 documents
Submicellar and micellar reversed-phase liquid chromatographic modes applied to the separation of beta-blockers.
2009
The behaviour of a reversed-phase liquid chromatographic (RPLC) system (i.e. elution order, resolution and analysis time), used in the analysis of β-blockers with acetonitrile-water mobile phases, changes drastically upon addition of an anionic surfactant (sodium dodecyl sulphate, SDS). Surfactant monomers cover the alkyl-bonded phase in different extent depending on the concentration of both modifiers, in the ranges 1 × 10-3-0.15 M SDS and 5-50% acetonitrile. Meanwhile, the surfactant is dissolved in the mobile phase as free monomers, associated in small clusters or forming micelles. Four characteristic RPLC modes are yielded, with transition regions between them: hydro-organic, micellar, …
Performance of different C18 columns in reversed-phase liquid chromatography with hydro-organic and micellar-organic mobile phases
2014
Column selection in reversed-phase liquid chromatography (RPLC) can become a challenge if the target compounds interact with the silica-based packing. One of such interactions is the attraction of cationic solutes to the free silanols in silica-based columns, which is a slow sorption-desorption interaction process that gives rise to tailed and broad peaks. The effect of silanols is minimised by the addition of a competing agent in the mobile phase, such as the anionic surfactant sodium dodecyl sulphate (SDS). In micellar-organic RPLC, the adsorption of an approximately fixed amount of SDS monomers gives rise to a stable modified stationary phase, with properties remarkably different from th…
Peak half-width plots to study the effect of organic solvents on the peak performance of basic drugs in micellar liquid chromatography.
2009
The addition of the anionic surfactant sodium dodecyl sulphate (SDS) to hydro-organic mixtures of methanol, ethanol, propanol or acetonitrile with water yielded enhanced peak shape (i.e. increased efficiencies and symmetrical peaks) for a group of basic drugs (β-blockers) chromatographed with a Kromasil C18 column. The effect can be explained by the thin layer of surfactant associated to the hydrocarbon chain on the stationary phase in the presence of the organic solvents, which covers the free silanols on the siliceous support avoiding their interaction with the cationic basic drugs. These instead interact with the anionic head of the surfactant increasing their retention and allowing a mo…
Nontumorous portal vein thrombosis in liver cirrhosis: Possible role of β-blockers
2018
<b><i>Objective:</i></b> Nonselective β-blockers (NSBB) are used in liver cirrhosis (LC) to prevent variceal bleeding because they decrease portal pressure. A main risk factor for the development of portal vein thrombosis (PVT) in LC is decreased portal vein inflow velocity. The aim of our study was to examine retrospectively the incidence of PVT and its correlation with the use of β-blockers in a cohort of LC patients. <b><i>Subjects and Methods:</i></b> Data from 230 LC patients (90% Child-Pugh class A), who had been followed up for at least 5 years, were reviewed. The diagnosis of PVT was made by ultrasound. The presence of PVT was evaluate…
Oral Propranolol for Circumscribed Choroidal Hemangioma
2011
Introduction: Several therapeutic approaches have been developed to treat choroidal hemangioma. However, all these therapies are associated with a potential risk of damaging the overlying retina. Case Report: We report a case of circumscribed choroidal hemangioma (CCH) in a 59-year-old man refractory to laser treatment. Visual acuity was 20/200 and a serous macular detachment was present. The CCH was treated with oral propanolol, whereupon visual acuity improved to 20/20 and the macular detachment resolved without systemic or local adverse effects. Discussion: Propanolol is a β-blocker commonly used in cardiology that may induce endothelium vasoconstriction and inhibit endothelial prolifera…
Effect of β-Blocker Withdrawal on Functional Capacity in Heart Failure and Preserved Ejection Fraction
2021
BACKGROUND Chronotropic incompetence has shown to be associated with a decrease in exercise capacity in heart failure with preserved ejection fraction (HFpEF), yet b-blockers are commonly used in HFpEF despite the lack of robust evidence. OBJECTIVES This study aimed to evaluate the effect of b-blocker withdrawal on peak oxygen consumption (peak VO2) in patients with HFpEF and chronotropic incompetence. METHODS This is a multicenter, randomized, investigator-blinded, crossover clinical trial consisting of 2 treatment periods of 2 weeks separated by a washout period of 2 weeks. Patients with stable HFpEF, New York Heart Association functional classes II and III, previous treatment with b-bloc…