Drugs online research references
Anesthesiology. 1984 Jul;61(1):10-8.
Comparative cardiovascular effects of verapamil, nifedipine, and diltiazem during halothane anesthesia in swine.
Kates RA, Zaggy AP, Norfleet EA, Heath KR.
The cardiovascular effects of the calcium channel blockers verapamil (V), nifedipine (N) and diltiazem (D) were compared in halothane-anesthetized swine. Equipotent hypotensive doses of the three calcium channel blocking drugs were administered randomly by continuous infusion to three groups of six animals each to produce a uniform 25-30% reduction in mean systemic arterial blood pressure (BP). An additional group of six animals received sodium nitroprusside (S) to demonstrate the effects of lowering blood pressure with a pure vasodilator on this experimental preparation. Hemodynamic indices monitored before and after drug administration included ECG, mean systemic and pulmonary artery blood pressure, mean central venous and pulmonary capillary wedge pressure, thermodilution cardiac output, left ventricular pressure, and left ventricular dP/dt. All four study drug infusions reduced BP an average of 28%. V and D reduced BP by decreasing cardiac output (41% and 42%, respectively) without affecting systemic vascular resistance. N and S produced hypotension by decreasing systemic vascular resistance (36% and 21%, respectively) without affecting cardiac output. D reduced heart rate (18%) and both D and V increased the PR interval (60% and 40%, respectively). Calcium chloride (20 mg X kg-1 intravenous bolus) improved indices of myocardial contractility but did not affect drug-induced changes in cardiac electrophysiology. These data demonstrate that in this halothane-anesthetized swine model the administration of equihypotensive doses of verapamil or diltiazem has a more pronounced affect on cardiac conduction and myocardial contractility than does nifedipine, which predominantly reduces systemic vascular resistance with minimal effects on cardiac function.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6742468&dopt=Abstract
J Pharmacol Exp Ther. 1982 Jun;221(3):609-13.
Inotropic and chronotropic effects of vasodilators.
Perez JE, Borda L, Schuchleib R, Henry PD.
Although vasodilators are used with increasing frequency for the treatment of heart failure and myocardial ischemia, their direct effects on cardiac muscle have not been completely characterized. To delineate the action of vasodilators on mammalian myocardium, the chronotropic and inotropic effects of vasodilators on isolated guinea-pig atria (n = 163) have been determined. The spontaneous frequency and the peak rate of isometric force development at a fixed frequency of 200/min were used as indexes of chronotropy and inotropy. The potency series for negative chronotropy was diltiazem greater than D600 greater than verapamil greater than lidoflazine greater than bepridil greater than prenylamine greater than perhexiline greater than nifedipine. The potency series for negative inotropy differed substantially, exhibiting the sequence nifedipine greater than D600 greater than verapamil greater than bepridil greater than lidoflazine greater than prenylamine greater than perhexiline greater than diltiazem. Therefore, nifedipine acted as an "inoselective" and diltiazem as a "chrono-selective" depressant. Other vasodilators, including papaverine, nitroglycerin, nitroprusside, adenosine, dipyridamole, diazoxide and hydralazine exerted no or negligible negative chronotropic or inotropic effects even at high concentration (10(-5) M). Therefore, only vasodilators classified among the calcium antagonists proved to have appreciable direct myocardial effects. This supports the view that these drugs constitute a category of agents distinct from classical vasodilators.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=6806462&dopt=Abstract
Eur J Pharmacol. 1980 May 30;64(1):21-9.
Different antihypertensive effects of nifedipine in conscious experimental hypertensive and normotensive rats.
Ishii H, Itoh K, Nose T.
Antihypertensive effects of nifedipine and hydralazine were investigated in normotensive rats, spontaneously hypertensive rats (SHR), DOCA-NaCl hypertensive rats and renal hypertensive rats all in a conscious state. The blood pressure fall after nifedipine 5 mg/kg p.o. was 22% of the initial value in normotensive rats, 49% in SHR, 53% in DOCA-NaCl hypertensive rats and 44% in renal hypertensive rats. Hydralazine in the same dose decreased the blood pressure by 40% in normotensive rats, 52% in SHR, 33% in DOCA-NaCl hypertensive rats and 54% in renal hypertensive rats. The selective action of nifedipine in hypertensive rats in contrast to normotensive rats seemed to be attributable to the different affinity for calcium ion of vascular smooth muscle of hypertensive rats as compared with that of normotensive rats. Also, the heart rate of hypertensive rats or normotensive rats was increased with nifedipine but less than with hydralazine.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=7449813&dopt=Abstract
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