Drugs online research references
Kidney Int. 1992 Apr;41(4):1041-8.
Compliance and reactivity of the peripheral venous system in chronic intermittent hemodialysis.
Kooman JP, Wijnen JA, Draaijer P, van Bortel LM, Gladziwa U, Peltenburg HG, Struyker-Boudier HA, van Hooff JP, Leunissen KM.
Department of Nephrology and Hypertension, University Hospital Maastricht, The Netherlands.
A reduced venous compliance and/or inadequate venoconstriction could impair hemodynamics during hemodialysis. Therefore, compliance and reactivity of the peripheral venous system were assessed in hemodialysis patients and controls using strain gauge plethysmography. Reactivity of the venous system towards an efferent sympathetic stimulus was assessed using a cold pressor test. Results showed that venous compliance was reduced in hypertensive hemodialysis patients compared to normotensive dialysis patients (P = 0.013) and normotensive controls (P = 0.004). After one dosage with a directly acting venodilator (nitroglycerin 5 mg s.l.) and 3 days of treatment with an alpha 1-sympathicolytic agent (Doxazosin 2 mg), venous compliance remained unaltered in hypertensive dialysis patients. During the cold pressor test, the blood pressure response, rise in noradrenaline levels and decline in venous compliance were normal in hemodialysis patients. However, their response to the Valsalva manoeuver was significantly impaired (P = 0.011) compared to healthy controls. We conclude that hypertension, not renal failure, causes the reduction of peripheral venous compliance in hemodialysis patients, for which structural factors might be responsible. Despite the existence of autonomous neuropathy, the reaction of the peripheral venous system towards an efferent sympathetic stimulus is intact in hemodialysis patients.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1355148&dopt=Abstract
Psychopharmacology (Berl). 1992;108(3):283-8.
Chronic infusion of clonidine does not alleviate spontaneous morphine withdrawal symptoms in rats.
van der Laan JW, Jansen van't Land C.
Laboratory for Medicines and Medical Devices, National Institute for Public Health and Environmental Protection, Bilthoven, The Netherlands.
Opiate withdrawal is associated with behavioural symptoms and a sympathetic hyperactivity, the latter being sensitive to clonidine. The central question is whether behavioural symptoms would be also sensitive to clonidine. A rat model was used in which the locomotor activity was measured 24 h a day during the morphine withdrawal phase. Spontaneous withdrawal of morphine reduced strongly the high nocturnal locomotor activity, concomitantly decreasing food intake and body weight. Chronic infusion of clonidine (30-120 micrograms/kg/day) using osmotic minipumps had no effect on the withdrawal symptoms. Higher dosages (250-1000 micrograms/kg/day) potentiated rather than alleviated the withdrawal symptoms, suggesting an alpha 1-adrenergic effect of clonidine rather than an alpha 2-action. Therefore, we studied the action of a more specific alpha 2-agonist UK-14.304. UK-14.304 was less potent than clonidine in naive animals. It slightly alleviates the decrease of nocturnal activity during spontaneous morphine withdrawal. Furthermore, we have tested whether the effects of high dosages of clonidine could be altered by a specific alpha 1-antagonist doxazosine. Doxazosine reduced only slightly the potentiation in the decrease in food intake by clonidine during morphine withdrawal. For the other symptoms no interaction between doxazosine and clonidine was found. The data suggest that the use of clonidine in the detoxification of opiate dependent people is based on the suppression of the sympathetic hyperactivity rather than on symptoms with a more behavioural character.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1355921&dopt=Abstract
Cardiovasc Res. 1992 Mar;26(3):279-84.
Transmural heterogeneity of postjunctional alpha 2 adrenergic coronary vasoconstriction in hypoperfused cat left ventricle.
Westby J, Birkeland S, Lekven J, Grong K.
Department of Surgery, University of Bergen, Haukeland Hospital, Norway.
OBJECTIVE: The aim was to analyse the influence of coronary postjunctional alpha 1 and alpha 2 adrenergic vasoconstriction in hypoperfused myocardium with special emphasis on transmural distribution of blood flow. METHODS: The left coronary artery was hypoperfused by means of a clamped shunt line. Sequential selective postjunctional alpha 1 (doxazosin) and alpha 2 (SK&F 104078) adrenergic antagonism was established following beta adrenergic antagonism with propranolol. Regional myocardial blood flow was measured with radiolabelled microspheres during equal coronary perfusion pressures. Experimental subjects were nine pentobarbitone anaesthetised open chest cats. RESULTS: Left coronary hypoperfusion decreased endocardial blood flow, whereas epicardial flow was unaltered. In this situation alpha 1 adrenergic antagonism did not affect myocardial blood flow. Subsequent alpha 2 antagonism impaired endocardial blood flow, whereas epicardial blood flow was augmented. Mean coronary vascular resistance declined following combined alpha 1 and alpha 2 adrenergic antagonism. CONCLUSIONS: Coronary alpha adrenergic vasoconstriction is localised mainly epicardially in hypoperfused myocardium and counteracts endocardial hypoperfusion distal to a fixed coronary stenosis. Furthermore, this vasoconstriction is of the postjunctional alpha 2 adrenergic subtype.
online pharmacy ref source: www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=1358445&dopt=Abstract
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