The effect of a single oral dose of prazosin on venous reflex response, blood pressure and pulse rate in normal volunteers.

Schapel, GJ; Betts, WH

doi:10.1111/j.1365-2125.1981.tb01324.x

Cited by 10 publications

(11 citation statements)

References 20 publications

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“…This study has demonstrated a highly significant reduction in the VRR in a group of healthy volunteers following a single oral 5 mg dose of alfuzosin in comparison with placebo. The inhibition of the VRR was strikingly evident at 1 h after the dose and persisted until the end of the experiment (6 h The inhibition of the VRR in our study is comparable with that obtained in a previously published study using prazosin 500 ,ug, in which every subject suffered from postural hypotension (Schapel & Betts, 1981). Suppression of the VRR in this latter study preceded the development of the postural fall in blood pressure.…”

Section: Discussionsupporting

confidence: 80%

“…The VRR was measured as previously described (Schapel & Betts, 1981 The transducer system was calibrated after each measurement, using a saline-filled column. With the subject supine, the hand and forearm were supported on a padded rest, such that the hand and pressure transducer diaphragm were level with the anterior axillary line.…”

Section: Venous Reflex Response (Vrr)mentioning

confidence: 99%

“…The venous reflex response (VRR) is considered to be an effective method for assessing noradrenergic systemic venoconstrictor tone (Samueloff et al, 1966;Epstein et al, 1968). Attenuation of the VRR has been shown to parallel the reduction in blood pressure during guanethidine therapy (Walter et al, 1975) and has been associated with postural hypotension and syncope ('first dose' phenomenon) following prazosin (Schapel & Betts, 1981 Time (min)…”

Section: Introductionmentioning

confidence: 99%

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Alfuzosin and the venous reflex response: studies in normal subjects.

Sinclair

Davies

Warrington

1989

Brit J Clinical Pharma

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1. Alfuzosin is a post‐synaptic alpha‐adrenoceptor antagonist with antihypertensive and peripheral vasodilator properties. 2. We measured the effect of alfuzosin, 5 mg, on sympathetically‐mediated venoconstriction by changes in the venous reflex response (VRR) in a randomised, double‐blind, placebo‐controlled, crossover study in a group of 10 healthy volunteers. 3. There was a significant inhibition of the VRR after alfuzosin compared with placebo (P less than 0.001) which was present 1 h after the dose and still evident at 6 h. 4. Supine blood pressure was significantly lower (P less than 0.01) and supine heart rate was significantly higher (P less than 0.001) after alfuzosin compared with placebo. 5. Inhibition of the VRR by alfuzosin was observed to precede the development of reflex tachycardia.

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Section: Discussionsupporting

confidence: 80%

Section: Venous Reflex Response (Vrr)mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alfuzosin and the venous reflex response: studies in normal subjects.

Sinclair

Davies

Warrington

1989

Brit J Clinical Pharma

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“…3,4 Therefore, it is interesting to investigate the effects of the drugs on vasoconstrictor reponse to sympathetic or adrenoceptor stimulations. In the present study, we examined whether the drugs have such effects or not in normal subjects using 2 noninvasive methods.…”

Section: Discussionmentioning

confidence: 99%

“…Orthostatic hypotension may be caused by failure of these responses, 3,4 and for the treatment it is important to select a drug considering its pharmacological properties and the pathophysiology of the disease. At present, vasoconsticting agents are often used for the treatment of orthostatic hypotension.…”

mentioning

confidence: 99%

Effect of Amezinium Metilsulfate on the Finger Skin Vasoconstrictor Response to Cold Stimulation and Venoconstrictor Response to Noradrenaline

et al. 1998

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hen a person assumes an upright posture, an increase of sympathetic outflow and an inhibition of parasympathetic activity occur reflexly, 1,2 which increases the heart rate and vascular resistance in order to maintain systemic blood pressure. Orthostatic hypotension may be caused by failure of these responses, 3,4 and for the treatment it is important to select a drug considering its pharmacological properties and the pathophysiology of the disease. At present, vasoconsticting agents are often used for the treatment of orthostatic hypotension. To understand the mechanism of these drugs, their effects not only on systemic blood pressure but also on the vasoconstrictor response to sympathetic stimulation should be examined. However, to our knowledge, such information is limited.Amezinium metilsulfate (amezinium) is one of the most popular drugs in Japan for the treatment of orthostatic hypotension. Amezinium has a unique mechanism of vasoconstriction; that is, it inhibits monoamine oxidase (MAO) activity and uptake of noradrenaline, 5,6 which prompted us to examine whether it influences the vasoconstrictor response to sympathetic stimulation and to -adrenoceptor stimulation by noradrenaline in humans.To examine the effects of the drug, the following 2 methods were thought to be suitable and were used in the present study, because they are sensitive and noninvasive and are used for the evaluation of autonomic disturbances or orthostatic hypotension. First, the finger-tip vasoconstrictor response to cold stimulation on the contralateral hand was examined using a laser Doppler flowmeter, which is an appropriate means for the study of the vasomotor response mediated by -adrenoceptor stimulation. 7,8 Second, the venoconstrictor response to locally infused noradrenaline was examined using a linear variable differential transformer (LVDT), which provides a sensitive and easy reproducible means of assessing the effect of a drug on peripheral veins. 9 As the decrease in venous blood return to the heart is involved in the pathogenesis of orthostatic hypotension, 3 it is interesting to also examine the effect of these drugs on veins.In the present study, we examined, using these methods, the effects of amezinium on the vasoconstrictor responses, and compared them in healthy subjects with those of midodrine hydrochloride (midodrine), an 1-adrenoceptor agonist, 10 which is also a popular drug for orthostatic hypotention. Methods SubjectsEight healthy Japanese males (21-26 years, 64-78 kg) were selected. They were normotensive and nonsmokers, without concomitant medication for at least 2 weeks before the study. The study was approved by the Ethical Committee of Jichi Medical School and all subjects gave their informed consent.Jpn Circ J 1998; 62: 824 -828 (Received April 10, 1998; revised manuscript received July 9, 1998; accepted July 14, 1998 Orthostatic hypotension can be caused by an inadequate vasoconstrictor response. The effects of amezinium on vasoconstrictor response to sympathetic stimulation and to exogenous noradre...

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Antihypertensive Action of Nifedipine: Effects on Arteries and Veins

Masotti

Morettini

Galanti

et al. 1985

The Journal of Clinical Pharma

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Nifedipine is a calcium-channel antagonist with effective antihypertensive activity and has been suggested for the treatment of high blood pressure as an alternative to vasodilators. The aim of this study was to define the acute effect of nifedipine and in particular the dose-effect relationship, effects on veins, influence on adrenergic reflexes, and effectiveness on hypertension according to severity and etiologic type. The effects of nifedipine on blood pressure, heart rate, forearm blood flow, peripheral vascular resistance, orthostatic and cold reflexes, and venous tone were examined in 45 patients with hypertension of different etiologies (essential, renovascular, and renal parenchymal) and different World Health Organization grades. The antihypertensive effect was dose dependent, but a dose of 20 mg has nearly maximal activity with acceptable side effects. The drug acts by lowering peripheral vascular resistance, and this lowering is directly related to baseline values; therefore, the antihypertensive effect increases with severity of the hypertension. Nifedipine had the same effect in all three etiologic groups of hypertension studied. The drug seems to increase venous tone, since it caused venoconstriction when locally injected in hand veins. Nifedipine did not alter adrenergic reflexes induced by both cold application and standing and was well tolerated. In conclusion, the calcium antagonist nifedipine for its characteristics of action, at least in acute administration, seems to be a useful alternative in the treatment of various forms of hypertension.

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The effect of a single oral dose of prazosin on venous reflex response, blood pressure and pulse rate in normal volunteers.

Cited by 10 publications

References 20 publications

Alfuzosin and the venous reflex response: studies in normal subjects.

Alfuzosin and the venous reflex response: studies in normal subjects.

Effect of Amezinium Metilsulfate on the Finger Skin Vasoconstrictor Response to Cold Stimulation and Venoconstrictor Response to Noradrenaline

Antihypertensive Action of Nifedipine: Effects on Arteries and Veins

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