Journal of cardiovascular pharmacology
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J. Cardiovasc. Pharmacol. · Jan 1988
ReviewVascular reactivity, adrenergic mechanisms, and arteriolar resistance in hypertension.
Hypertension, both essential and experimental is characterised by increased vascular resistance. This is in part structural, due to increases in the wall-to-lumen ratio secondary to vascular hypertrophy; however, functional increases in responses to neurohumoral stimuli also occur. The latter may be a consequence of hypertrophy or if a selective increase is observed, an indication of a primary underlying hypertensive mechanism. ⋯ However, in some experimental models, more selective increased responses have been reported. The mechanism of alpha-adrenoceptor-mediated vascular smooth muscle contraction is reviewed and the role of inositol phosphates and diacylglycerol as second messengers is discussed. The precise mechanism of increased vascular responses in hypertension is still uncertain.
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J. Cardiovasc. Pharmacol. · Jan 1988
Randomized Controlled Trial Clinical TrialTreatment of hypertensive urgencies and emergencies with nitrendipine, nifedipine, and clonidine: effect on blood pressure and heart rate.
Nitrendipine is a new calcium antagonist of the 1,4-dihydropyridine group with strong vasodilating properties. In a randomized trial involving 45 patients, whose mean blood pressure was 236 +/- 24/129 +/- 21 mm Hg, 5 mg nitrendipine (given sublingually via a phiole) was compared with 20 mg nifedipine (given sublingually via two pierced 10-mg capsules) and 0.15 mg clonidine (given intravenously). Blood pressure and heart rate were assessed for 8 h after intake of the antihypertensive agents. ⋯ Main side effects were observed in the nifedipine group (flush and reflex tachycardia) and in the clonidine group (dry mouth and drowsiness). In conclusion, nitrendipine, nifedipine, and clonidine show similar efficacy in the treatment of hypertensive urgencies and emergencies. However, sublingual application of the calcium antagonists is simple and safe; moreover, nitrendipine is better tolerated than nifedipine and clonidine.
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J. Cardiovasc. Pharmacol. · Jan 1988
24-hour noninvasive oscillometric blood pressure monitoring: evaluation of the antihypertensive circadian profile of nitrendipine.
The understanding of blood pressure (BP) and heart rate (HR) variation, circadian changes, and the responses to nonclinical situations has been improved by automated ambulatory recordings. The antihypertensive efficacy of a once-daily regimen (10/20 mg) of nitrendipine was evaluated in detail using the lightest available portable device equipped with an oscillometric blood pressure (BP) recorder (SpaceLabs 90202, weight 480 g) devoid of any electrode. A good antihypertensive effect throughout the day in 20 outpatients could be demonstrated. No significant change of BP could be found in early morning and wake-up period; HR was not significantly affected after 6 weeks of oral therapy.
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J. Cardiovasc. Pharmacol. · Nov 1987
Comparative StudyEffects of milrinone on systemic hemodynamics and regional circulations in dogs with congestive heart failure: comparison with dobutamine.
Milrinone is a new bipyridine inotropic agent with direct vasodilator properties. To determine the role of the vasodilator action in mediating systemic and regional hemodynamic responses to milrinone, we administered two equipotent inotropic doses of either milrinone or dobutamine to dogs with chronic congestive right heart failure produced by tricuspid avulsion and pulmonary artery stenosis. Similar increases in cardiac output, right and left ventricular dP/dt, and left ventricular dP/dt/P were produced by milrinone and dobutamine; however, heart rate increased and mean aortic pressure decreased only with milrinone infusion. ⋯ In contrast, milrinone infusion increased vascular resistance in quadriceps muscle and decreased it in renal and splanchnic beds. Thus, when milrinone was used in inotropic doses similar to those of dobutamine, the responses in systemic and regional hemodynamics in congestive heart failure differed. Milrinone produced a greater decline in total peripheral, renal, and splanchnic vascular resistances, probably resulting from its direct vasodilator action.
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J. Cardiovasc. Pharmacol. · May 1987
Comparative StudyCentral and regional vascular hemodynamics following intravenous milrinone in the conscious rat: comparison with dobutamine.
This study examined the hemodynamic and regional vascular profile of intravenous (i.v.) milrinone during increasing doses (3, 6, 12 micrograms/kg/min, n = 8) and by intraindividual comparison of milrinone and dobutamine (n = 10) in normal conscious rats. At 3 micrograms/kg/min, Milrinone increased coronary and cerebral blood flow (radioactive microspheres 15 +/- 5 microns) (7.7-9.8 and 1.05-1.27 ml/min/g respectively, both p less than 0.05) without significant changes in systemic hemodynamics. At 6 micrograms/kg/min milrinone increased skeletal muscle blood flow (0.19-0.24 ml/min/g, p less than 0.05) along with increases in cardiac output, stroke volume, and stroke work (all p less than 0.05), while systemic vascular resistance decreased (-51%, p less than 0.05). ⋯ At higher doses, milrinone causes a balanced increase in regional blood flow including enhanced flow to skeletal muscle. The hemodynamic (particularly as compared with dobutamine) and regional vascular profile of milrinone suggests a predominant vasodilating effect in the rat. Given a similar limited response of rat and diseased human myocardium to milrinone, these findings may have important clinical implications.