Document Detail

The hypotensive effect of trimazosin is not caused solely by alpha 1-adrenoceptor blockade.
MedLine Citation:
PMID:  6199597     Owner:  NLM     Status:  MEDLINE    
Trimazosin is a quinazoline antihypertensive agent structurally related to the selective alpha 1-adrenoceptor blocker prazosin. Trimazosin has been shown previously to have less affinity for alpha 1-adrenoceptors than prazosin. In the present study we compared the hypotensive potency and efficacy of the two agents, and their effects on pressor responses to phenylephrine in anesthetized dogs. We also determined the effect of trimazosin administered during a maximum hypotensive response to prazosin, and of sodium nitroprusside administered after trimazosin or prazosin. Compared with prazosin, trimazosin was a less potent but more efficacious hypotensive agent. At doses which caused equal or even greater hypotensive effects than those caused by prazosin, trimazosin caused less inhibition of pressor responses to phenylephrine. When administered during a maximum hypotensive response to prazosin, trimazosin caused an additional fall in pressure. These results clearly demonstrate an additional action of trimazosin beyond blockade of alpha 1-adrenoceptors. Both trimazosin and prazosin augmented the hypotensive effect of sodium nitroprusside, but only trimazosin enhanced its relaxant effect on isolated rat aorta. Thus we conclude that in addition to alpha 1-adrenoceptor blockade, another mechanism contributes to the hypotensive effect of trimazosin, and we speculate that elevation of cyclic GMP levels in vascular smooth muscle may be related to this additional mechanism.
J W Constantine; W Lebel; R Weeks
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Publication Detail:
Type:  Comparative Study; In Vitro; Journal Article    
Journal Detail:
Title:  Journal of cardiovascular pharmacology     Volume:  6     ISSN:  0160-2446     ISO Abbreviation:  J. Cardiovasc. Pharmacol.     Publication Date:    1984 Jan-Feb
Date Detail:
Created Date:  1984-03-29     Completed Date:  1984-03-29     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  7902492     Medline TA:  J Cardiovasc Pharmacol     Country:  UNITED STATES    
Other Details:
Languages:  eng     Pagination:  142-50     Citation Subset:  IM    
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MeSH Terms
Adrenergic alpha-Antagonists / pharmacology*
Antihypertensive Agents / pharmacology*
Blood Pressure / drug effects
Cyclic GMP / metabolism
Heart Rate / drug effects
Muscle Contraction / drug effects
Muscle, Smooth, Vascular / drug effects
Nitroprusside / pharmacology
Phenylephrine / pharmacology
Piperazines / pharmacology*
Prazosin / pharmacology
Pressoreceptors / drug effects
Rats, Inbred Strains
Receptors, Adrenergic, alpha / drug effects
Reg. No./Substance:
0/Adrenergic alpha-Antagonists; 0/Antihypertensive Agents; 0/Piperazines; 0/Receptors, Adrenergic, alpha; 15078-28-1/Nitroprusside; 19216-56-9/Prazosin; 35795-16-5/trimazosin; 59-42-7/Phenylephrine; 7665-99-8/Cyclic GMP

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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