Drugs online research references
Circ Res. 1977 May;40(5 Suppl 1):I89-93.
Effect of beta-blocking agents and angiotensin II on isoproterenol-stimulated renin release from rat kidney slices.
Capponi AM, Gourjon M, Vallotton MB.
Mechanisms by which beta-blocking agents decrease blood pressure and suppress renin release are incompletely understood. We previously demonstrated that renin release by kidney slices may be increased by beta-adrenergic agonists, and the present communication contains our results on the effects of 15 beta-blocking agents and angiotensin II on isoproterenol-stimulated renin release. None of the beta-blocking compounds inhibited basal renin release. Each agent was evaluated at concentrations ranging from 10-8 to 10-5 m and three different dose-response curve patterns were observed: (1) Metoprolol, acebutolol, labetalol, and d-propranolol had no effect on isoproterenol-stimulated renin release at any concentration, whereas pindolol and bufuralol demonstrated minimal inhibition at 10-5 m only. (2) Isoproterenol stimulation was completely inhibited when dl- or l-propranolol, alprenolol, and sotalol were administered at doses ranging between 5 x 10-6 and 10-6 m; but greater concentration of these agents resulted in reappearance of the isoproterenol response. (3) Dose-related inhibition was observed with practolol, oxprenolol, timolol, nadolol, and atenolol at concentrations ranging from 10-8 to 10-5 m. Basal renin release was significantly (P is less than 0.01) inhibited by angiotensin II at 10-6 m, which also inhibited isoproterenol-stimulated renin release in a dose-related fashion. [Sar1, Ala8] angiotensin II had no direct effects on either basal or isoproterenol-stimulated renin release, but blocked the inhibitory action of angiotensin II on these parameters. Conclusions: There are three different effects of beta-blocking agents on isoproterenol-stimulated renin release which can only partially be explained by their presently ascribed pharmacological properties. (Beta 1- and beta2-agonists, intrinsic sympathomimetic activity, membrane-stabilizing actions). Angiotensin II inhibition of renin release appears to be functionally related to adrenergic pathways.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=15737&dopt=Abstract
Life Sci. 1994;55(4):269-81.
Methylphenidate-induced hepatotoxicity in mice and its potentiation by beta-adrenergic agonist drugs.
Roberts SM, Harbison RD, Roth L, James RC.
Center for Environmental and Human Toxicology, University of Florida, Alachua 32615.
Methylphenidate hydrochloride, when administered as a single 75 to 100 mg/kg i.p. dose, was found to produce hepatic necrosis in male ICR mice. Peak hepatotoxicity, as measured by serum ALT elevations, occurred 16 hours post-treatment while maximal histopathological evidence of hepatotoxicity occurred 24-48 hours after the methylphenidate dose. Liver injury measured by either method was essentially nonexistent for dosages < or = 50 mg/kg in male mice, and was only minimally evident in female mice at the highest dosage testable. Co-treatment of mice with either alpha 1- or alpha 2-adrenergic agonist drugs had no meaningful effect on methylphenidate-induced hepatotoxicity. In contrast, the beta-adrenergic agonist drug isoproterenol produced a striking potentiation of the liver injury, and shifted the apparent threshold for toxicity approximately 5- to 10-fold. Co-administration of methylphenidate with the mixed alpha/beta-adrenergic agonist dobutamine or with the beta 2-selective agonists metaproterenol, ritodrine or terbutaline produced a similar potentiation of toxicity. Parallel tests with beta-adrenergic antagonists revealed that the potentiation by isoproterenol could be significantly diminished by a single dose of the non-selective beta-adrenoreceptor blocking drug nadolol or the beta 2-selective antagonist ICI-118,551, but not the beta 1-selective antagonist metoprolol. Collectively, these observations suggest that potentiation of methylphenidate hepatotoxicity occurs through stimulation of beta 2-adrenoreceptors. Mice co-treated with isoproterenol were found to have substantially higher serum and liver methylphenidate levels following the methylphenidate dose, and significant increases were also observed in the area-under-the-curve (AUC) for methylphenidate in both tissues of isoproterenol co-treated mice. The results of this study suggest that beta 2-adrenergic agonist drugs are capable of potentiating methylphenidate-induced hepatotoxicity in mice by increasing hepatic methylphenidate concentrations.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7913199&dopt=Abstract
J Chromatogr. 1992 Sep 2;579(2):361-5.
Stereospecific high-performance liquid chromatographic assay of metoprolol.
Bhatti MM, Foster RT.
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Canada.
A valid, sensitive high-performance liquid chromatographic technique is reported for the separation of the two enantiomers of metoprolol in human plasma. The procedure involves pre-column derivatization with the homochiral reagent S-(+)-1-(1-naphthyl)ethyl isocyanate. Once formed, the diastereomers are separated using normal-phase high-performance liquid chromatography. Fluorescence detection (220 nm excitation; no emission filter) was utilized, resulting in baseline resolution (Rs greater than 1.5). The peaks corresponding to metoprolol enantiomers were free from interference throughout the examined range of 5-500 ng/ml; accuracy and precision were within approximately 10%. Analysis of a plasma sample collected from a healthy volunteer demonstrated that the assay is applicable to clinical studies.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1429986&dopt=Abstract
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