Drugs online research references
G Ital Cardiol. 1994 Apr;24(4):361-6.
[Protection by blockers against human low density lipoprotein peroxidation induced by oxygen free radicals]
[Article in Italian]
Napoli C, Ambrosio G, Chiariello P, Palumbo G, Chiariello M.
Cattedra di Cardiologia, Universita di Napoli Federico II.
Previous studies in other systems have shown that beta-receptor blockers may effectively inhibit oxygen radical-induced lipid peroxidation. On the other hand, it has been recently proposed that oxygen free radicals can induce peroxidation of human low density lipoproteins (LDL), and that peroxidized LDL may be an atherogenic stimulus. Chemically modified LDL are internalized by macrophages via a specific cell surface receptor that was termed the scavenger receptor. This phenomenon may induce foam cells transformation in vivo. In the present study we investigated whether beta-blockers may reduce oxygen radical-mediated LDL peroxidation. Purified human LDL were oxidized by exposure to oxygen free radicals generated by xanthine (0.2 mM) and xanthine oxidase (100 mU) at 37 degrees C after a pre-incubation (30 min) in presence of different concentrations (from 1 to 30 microM) of acebutolol, metoprolol or propranolol, three agents with a different degree of lipophilicity. Peroxidation was measured from malonyldihaldehyde (MDA) production. Data have shown a significant percent inhibition of MDA formation in presence of beta-blockers (from 33 to 85%). Thus, beta-blockers reduced peroxidation of human LDL in vitro at clinically relevant concentrations. The order of potency appears to follow the degree of lipophilicity. These data suggest that, although beta-blockers are known to adversely effect lipid metabolism, these agents might on the other hand prevent atherogenesis via a mechanism of inhibition of LDL peroxidation in vivo and reduced foam cells formation.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7914499&dopt=Abstract
Br J Clin Pharmacol. 1985;19 Suppl 2:231S-238S.
Oros controlled-release formulations of metoprolol: an approach to the development of a system for once daily administration.
Good W, Leeson LJ, Zak SL, Wagner WE, Meeker JB, Arnold JD.
A combined biopharmaceutical and haemodynamic approach to the development of a metoprolol Oros controlled-release delivery system for once daily administration is reported. Two studies, each involving 18 healthy volunteers, were performed in which twice daily administration of 100 mg conventional metoprolol tartrate tablets was compared with once daily administration of Oros systems containing 190 mg metoprolol fumarate but with different drug release rates. Plasma drug concentrations and beta-adrenoceptor blocking effects were measured over 24 h on days 1 and 5 of each treatment, and pre-dose in the interval between the main study days. The results of the first study with a 19 mg/h Oros system indicated that this rate was too rapid to provide the required response under steady-state dosing conditions. Theoretical calculations based on a one-compartment pharmacokinetic model and input functions for hypothetical Oros systems were then performed to define the optimal release rate for a once daily preparation. The results of the second study confirmed that a 14 mg/h system possessed the required characteristics in that it maintained more uniform beta-adrenoceptor blockade throughout 24 h, and produced pre-dosing plasma concentrations and haemodynamic effects which were identical to those for the conventional tablet twice daily regimen.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4005128&dopt=Abstract
Jpn J Pharmacol. 1989 Jun;50(2):93-100.
Selectivity of bunitrolol for beta 1- and beta 2-adrenergic receptors and 5HT1B-receptors: assessment by biphasic Scatchard plots and biphasic displacement curve analysis with 125I-iodocyanopindolol and 3H-CGP12177.
Tsuchihashi H, Nagotomo T, Imai S.
Department of Pharmacology, Niigata College of Pharmacy, Japan.
The preference by bunitrolol for beta 1- and beta 2-adrenoceptors of the rat brain, heart and/or lung was assessed by the radioligand binding assay method with 125I-iodocyanopindolol (125I-ICYP) or 3H-CGP12177. Scatchard plots of 125I-ICYP binding in the presence of bunitrolol were found to be non-linear. The inhibition constants (Ki) of bunitrolol for high (beta 2-) and low affinity sites (beta 1-) were: 0.42 +/- 0.16 nM for beta 1 and 3.55 +/- 1.61 nM for beta 2 (beta 1 greater than beta 2), respectively. Displacement experiments conducted with the preparations of the rat brain using 125I-ICYP or with the preparations of the rat heart using 3H-CGP12177 yielded Ki values for bunitrolol of 0.53 +/- 0.20 (beta 1) and 2.37 +/- 0.78 (beta 2) nM for 125I-ICYP binding and 2.01 +/- 0.38 (beta 1) and 12.67 +/- 6.54 (beta 2) nM for 3H-CGP12177 binding. In addition, the Ki value for 5HT1B-receptors assessed in displacement experiments conducted with 125I-ICYP in the presence of 30 microM I-metoprolol in the rat brain was 10.54 +/- 5.92 nM. Thus, bunitrolol is a beta 1-selective antagonist.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=2570175&dopt=Abstract
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