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Resolution of the enantiomers of racemic atenolol, metoprolol, propranolol, and labetalol, commonly used β-blockers, has been achieved by TLC on silica gel plates using vancomycin as chiral impregnating reagent or as chiral mobile phase additive. With vancomycin as impregnating agent, successful resolution of the enantiomers of atenolol, metoprolol, propranolol, and labetalol was achieved by use of the mobile phases acetonitrile-methanol-water-dichloromethane 7:1:1:1 ( v/v ), acetonitrile-methanol-water 6:1:1 ( v/v ), acetonitrile-methanol-water-dichloromethane-glacial acetic acid 7:1:1:1:0.5 ( v/v ), and acetonitrile-methanol-water 15:1:1 ( v/v ), respectively. With vancomycin as mobile phase additive, successful resolution of the enantiomers of metoprolol, propranolol, and labetalol was achieved by use of the mobile phases acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5) 6:1:1 ( v/v ), acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5) 15:1:2 ( v/v ), and acetonitrile-methanol-0.56 mM aqueous vancomycin (pH 5.5)-dichloromethane 9:1:1.5:1 ( v/v ), respectively. Spots were detected by use of iodine vapor. The detection limits were 1.3, 1.2, 1.5, and 1.4 μg for each enantiomer of atenolol, metoprolol, propranolol, and labetalol, respectively.

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Journal of Thermal Analysis and Calorimetry
Authors: J. Canotilho, R. Castro, M. Rosado, S. Nunes, M. Cruz, and J. Redinha

Abstract  

The growth of atenolol, pindolol and betaxolol hydrochloride from melt was investigated by differential scanning calorimetry (DSC) and polarized light thermal microscopy (PLTM). Phase transitions occurring on cooling and subsequent reheating runs performed between −160 °C and a temperature above the respective melting points were studied by DSC. The thermal cycles were also followed by PLTM. Details about the dynamic of the crystallization front taken from microscopic observations are given. An explanation of the results on the basis of molecular supramolecular recognition is advanced.

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The internal mammary artery (IMA) is currently the preferred conduit for myocardial revascularization. However, perioperative vasospasm and a hypoperfusion state during maximal exercise may limit its use as a bypass graft. The mechanism of spasm has not been clearly defined. Since beta-adrenoceptor activation plays a major role in vasorelaxation, the present study was carried out to investigate the beta-adrenoceptor responsiveness of human IMA smooth muscle. Isoproterenol produced a concentration-dependent relaxation in endothelium-denuded IMA segments, precontracted with phenylephrine (maximal relaxation 46.33....5.45%). Atenolol (10 –6 M) and propranolol (2×10 –7 M) inhibited isoproterenol-induced relaxation. While atenolol produced partial inhibition, propranolol caused a complete inhibition in a majority of the segments and a partial inhibition in a minority. BRL 37344, a selective beta 3-adrenoceptor agonist, produced a concentration-dependent relaxation in phenylephrine-precontracted rings of endothelium-denuded IMA (maximal relaxation 40.35....4.07%). Cyanopindolol, a beta-adrenoceptor partial agonist, produced a marked relaxation (58.65....6.2%) in endothelium-denuded IMA rings, precontracted with phenylephrine. Cyanopindolol-induced relaxation was resistant to blockade by propranolol (2×10 –7 M). Spontaneous contractions of IMA rings were also observed in some cases that were inhibited by isoproterenol and BRL 37344. This observation implies the important role of beta-adrenoceptor activation in prevention of human IMA spasm.

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Enantioresolution of three active pharmaceutical ingredients (APIs), namely, atenolol, betaxolol, and orciprenaline, marketed as racemic mixture, has been achieved in a direct mode using (S)-glutamic acid as chiral additive in thin-layer chromatography. Two different approaches were adopted: (1) (S)-glutamic acid was mixed in the silica gel slurry for making thin-layer plates, or (2) it was added in the mobile phase and plain plates without any chiral additive were used. Both (1) and (2) were capable of separating enantiomers of all the three racemates, but different combinations and proportions of solvents were found successful in the two cases. Good resolution was achieved in both cases, and the results are compared for these two sets of studies among themselves and with other literature reports. Iodine was used to locate the spots of the corresponding enantiomers. The detection limits for each enantiomer were found in the range of 1.4–1.9 μg (per spot).

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A chromatographic-densitometric method has been established for identification and quantitation of selected beta-adrenergic-blocking agents in pharmaceutical preparations. Retention factors, R F , and characteristic absorption spectra of 11 drugs chromatographed on silica gel 60 F 254 HPTLC plates with six mobile phases were used for identification. Quantitation and validation of the method was performed for atenolol, acebutolol, propranolol, and bisoprolol using chloroform-methanol-ammonia, 15 + 7 + 0.2 ( v/v ), as mobile phase. UV densitometric measurements were performed at the wavelength of maximum absorption. Pharmaceutical preparations used in medicine and from a variety of manufacturers were analyzed and the method shown to be sufficiently sensitive for analysis of these samples. The limits of detection and determination ranged from 30 to 400 ng and recovery was from 97.14 to 102.18%. The precision of the method, described by the equation y = x mean ± 2 S , is good and the range of linearity is wide — from 0.020 to 0.250% for individual constituents.

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Summary

A simple, accurate, and sensitive reversed-phase HPLC method was developed for the simultaneous determination of celiprolol HCl (CE) and chlorthalidone (CT). Good chromatographic separation was achieved using a 250 mm × 4.6 mm i.d., 5 μm particle size Hypurity C8 column. Mobile phase containing a mixture of methanol and 0.04 M phosphate buffer (35:65, υ/υ) at pH 7.0 was pumped at a flow rate of 1.2 mL min−1 with UV detection at 225 nm. Lisinopril dihydrate (LIS) was used as internal standard. The method showed good linearity in the ranges 0.2–20 and 0.2–10 μg mL−1 with limits of detection 0.06 and 0.04 μg mL−1 and limits of quantification 0.20 and 0.14μg mL−1 for CE and CT, respectively. The suggested method was successfully applied to the simultaneous analysis of the studied drugs in their synthetic mixture and coformulated tablet. The method was further extended to the determination of CE in biological fluids. The proposed method was also applied to the determination of the studied drugs in presence of some coadministered or related drugs such as atenolol, propranolol, acetazolamide, enalapril, nicardipine, triamterene, and hydrochlorothiazide without any interference.

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The present studies were conducted: (1) to determine which β-adrenoceptor subtypes are involved in progesterone and oxytocin (OT) secretion, (2) to examine whether noradrenaline (NA) acts directly on the cytochrome P-450scc and 3β-hydroxysteroid dehydrogenase (3β-HSD), and (3) to study the effect of prostaglandin F, (PGF) on NA-stimulated steroidogenesis in luteal cells. The effect of NA on progesterone secretion from luteal slices of heifers on days 8–12 of the oestrous cycle was blocked by both atenolol (β1-antagonist) and ICI 118.551 hydrochloride (β2-antagonist). OT secretion was blocked only after treatment with ICI 118.551 hydrochloride (P < 0.05). Dobutamine (10−4−10−6), a selective β1 agonist and salbutamol (10−4−10−6), a selective β2 agonist, both increased progesterone production (P < 0.01) with an efficiency comparable to that produced by NA (P < 0.01). The increase of OT content in luteal slices was observed only after treatment with salbutamol at the dose of 10−5M (P < 0.01). Dobutamine had no effect on OT production at any dose. A stimulatory effect of NA on cytochrome P-450scc activity (P < 0.05) was demonstrated using 25-hydroxycholesterol as substrate. 3β-HSD activity also increased following NA (P < 0.01) or pregnenolone (P < 0.05) and in tissue treated with pregnenolone together with NA (P < 0.01). PGF decreased progesterone synthesis (P < 0.05) and 3β-HSD activity (P < 0.01) in tissue treated with NA. We conclude that NA stimulates progesterone secretion by luteal β1- and β2-adrenoceptors, while OT secretion is probably mediated only via the β2-receptor. NA also increases cytochrome P-450scc and 3β-HSD activity. PGF inhibits the luteotropic effect of NA on the luteal tissue.

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atenolol and metoprolol measured by heart rate variability during mental performance tasks, physical exercise, and daily life in stable postinfarct patients. Circulation 92, 3415-3423 (1995) Evaluation of importance of central

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, atenolol, betaxolol and ICI 118.551. J. Cardiovasc. Pharmacol. 12 ,208-217 (1988). Comparison or the beta-adrenoceptor affinity and selectivity of cetamolol, atenolol, betaxolol and ICI 118.551 J

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left ventricular function of nebivolol versus atenolol in patients with uncomplicated essential hypertension. Am. J. Cardiol., 2003, 92 (3), 344–348. Conti, V., Russomanno, G., Corbi, G., et al.: Adrenoreceptors

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