Document Detail


Comparative effects of clonidine and dihydroergotamine on venomotor tone and orthostatic tolerance in patients with severe hypoadrenergic orthostatic hypotension.
MedLine Citation:
PMID:  11904110     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
PURPOSE: Clonidine, an alpha(2)-adrenergic agonist, raises blood pressure in patients with autonomic failure, in whom failure of reflex neurogenic venoconstriction leads to severe orthostatic hypotension. Because animal studies suggest that postjunctional alpha(2)-adrenoreceptors are located mainly on venous capacitance rather than arterial resistance vessels, we tested the hypothesis that venoconstriction is the main mechanism by which clonidine raises blood pressure in patients with autonomic failure. SUBJECTS AND METHODS: We measured forearm venous and arterial tone using plethysmography in 4 patients with autonomic failure before and after acute administration of clonidine (0.4 mg orally) or dihydroergotamine (0.15 mg intravenously), a known venoconstrictor agent. We also recorded supine intraarterial pressure at rest and during graded orthostatic stress with lower body negative pressure. RESULTS: Clonidine and dihydroergotamine caused similar increases in supine (mean +/- SD) arterial pressure (+23 +/- 11 mm Hg vs. and +27 +/- 5 mm Hg) and forearm vascular resistance (+36% +/- 13% vs. +28% +/- 9%). However, the drugs had different effects on forearm venous tone, which increased by 38% +/- 9% with dihydroergotamine (P = 0.01 vs. control) but was unaffected by clonidine (change = 0% +/- 14%). A single dose of clonidine was less effective than a single dose of dihydroergotamine in maintaining arterial pressure during graded orthostatic stress. CONCLUSION: In contrast with what has been hypothesized, clonidine appears to function mainly as an arterial constrictor in patients with hypoadrenergic orthostatic hypotension. Further studies are needed to determine if venoconstrictor agents are of greater therapeutic benefit in this condition than are pure arterial vasoconstrictors.
Authors:
Ronald G Victor; William T Talman
Publication Detail:
Type:  Comparative Study; Journal Article; Research Support, U.S. Gov't, Non-P.H.S.; Research Support, U.S. Gov't, P.H.S.    
Journal Detail:
Title:  The American journal of medicine     Volume:  112     ISSN:  0002-9343     ISO Abbreviation:  Am. J. Med.     Publication Date:  2002 Apr 
Date Detail:
Created Date:  2002-03-20     Completed Date:  2002-04-02     Revised Date:  2007-11-14    
Medline Journal Info:
Nlm Unique ID:  0267200     Medline TA:  Am J Med     Country:  United States    
Other Details:
Languages:  eng     Pagination:  361-8     Citation Subset:  AIM; IM    
Affiliation:
Donald W. Reynolds Clinical Cardiovascular Research Center, Department of Internal Medicine, Hypertension Division, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Boulevard, Dallas, TX 75235-8586, USA.
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MeSH Terms
Descriptor/Qualifier:
Adrenergic alpha-Agonists / therapeutic use*
Aged
Autonomic Nervous System Diseases / complications
Blood Pressure / drug effects*
Clonidine / therapeutic use*
Dihydroergotamine / therapeutic use*
Female
Forearm
Humans
Hypotension, Orthostatic / drug therapy*,  etiology
Male
Middle Aged
Plethysmography
Vascular Resistance
Vasoconstrictor Agents / therapeutic use*
Grant Support
ID/Acronym/Agency:
HL 01362/HL/NHLBI NIH HHS; HL 14388/HL/NHLBI NIH HHS; HL 32205/HL/NHLBI NIH HHS; NS 24621/NS/NINDS NIH HHS
Chemical
Reg. No./Substance:
0/Adrenergic alpha-Agonists; 0/Vasoconstrictor Agents; 4205-90-7/Clonidine; 511-12-6/Dihydroergotamine
Comments/Corrections
Comment In:
Am J Med. 2002 Apr 1;112(5):419-21   [PMID:  11904120 ]

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