(-)Doxazosin is a necessary component for the hypotensive effect of (±)doxazosin during long-term administration in conscious rats
Aim: Doxazosin is a racemic mixture of (–)doxazosin and (+)doxazosin that is currently used as an add-on therapy for hypertension. In this study we investigated the contribution of each enantiomer to the hypotensive action of long-term administration of (±)doxazosin in conscious rats. Methods: Blood...
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Published in | Acta pharmacologica Sinica Vol. 35; no. 1; pp. 48 - 57 |
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Main Authors | , , , , , , , |
Format | Journal Article |
Language | English |
Published |
United States
Nature Publishing Group
01.01.2014
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Subjects | |
Online Access | Get full text |
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Summary: | Aim: Doxazosin is a racemic mixture of (–)doxazosin and (+)doxazosin that is currently used as an add-on therapy for hypertension. In this study we investigated the contribution of each enantiomer to the hypotensive action of long-term administration of (±)doxazosin in conscious rats.
Methods: Blood pressure of conscious SD rats was measured using a volume pressure recording system. The rats were orally administered (–)doxazosin, (+)doxazosin, or (±)doxazosin (8 mg·kg-1·d-1) for 12 weeks. Plasma concentrations of the agents were analyzed with HPLC. The effect of the agents on α1-adrenoceptor was examined in isolated rat caudal artery preparations.
Results: Treatment of conscious rats with a single dose of (±)doxazosin (8 mg/kg) did not affected DBP and MBP, but significantly decreased SBP by 11.9% 4 h after the administration. Long-term treatment of conscious rats with (±)doxazosin significantly decreased SBP, DBP and MBP with a maximal decrease of SBP by 29.3% 8 h after the last administration. The rank order of the hypotensive actions caused by long-term treatment in conscious rats was (±)doxazosin〉(+)doxazosin〉〉(–)doxazosin. However, the pKB values for inhibiting NA-induced contraction of isolated rat caudal artery were (+)doxazosin (8.995)〉(±)doxazosin (8.694)〉(–)doxazosin (8.032). The plasma concentrations of (–)doxazosin, (+)doxazosin, and (±)doxazosin were 18.26±3.55, 177.11±20.66, and 113.18±13.21 ng/mL, respectively, 8 h after the last administration of these agents.
Conclusion: Long-term treatment with (±)doxazosin produces potent hypotensive action in conscious rats that seems to result from synergic interaction of the two enantiomers. |
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Bibliography: | doxazosin; enantiomer; blood pressure; hypotension; plasma drug concentration; α1-adrenoceptor; noradrenaline; tail artery; conscious rat Aim: Doxazosin is a racemic mixture of (–)doxazosin and (+)doxazosin that is currently used as an add-on therapy for hypertension. In this study we investigated the contribution of each enantiomer to the hypotensive action of long-term administration of (±)doxazosin in conscious rats. Methods: Blood pressure of conscious SD rats was measured using a volume pressure recording system. The rats were orally administered (–)doxazosin, (+)doxazosin, or (±)doxazosin (8 mg·kg-1·d-1) for 12 weeks. Plasma concentrations of the agents were analyzed with HPLC. The effect of the agents on α1-adrenoceptor was examined in isolated rat caudal artery preparations. Results: Treatment of conscious rats with a single dose of (±)doxazosin (8 mg/kg) did not affected DBP and MBP, but significantly decreased SBP by 11.9% 4 h after the administration. Long-term treatment of conscious rats with (±)doxazosin significantly decreased SBP, DBP and MBP with a maximal decrease of SBP by 29.3% 8 h after the last administration. The rank order of the hypotensive actions caused by long-term treatment in conscious rats was (±)doxazosin〉(+)doxazosin〉〉(–)doxazosin. However, the pKB values for inhibiting NA-induced contraction of isolated rat caudal artery were (+)doxazosin (8.995)〉(±)doxazosin (8.694)〉(–)doxazosin (8.032). The plasma concentrations of (–)doxazosin, (+)doxazosin, and (±)doxazosin were 18.26±3.55, 177.11±20.66, and 113.18±13.21 ng/mL, respectively, 8 h after the last administration of these agents. Conclusion: Long-term treatment with (±)doxazosin produces potent hypotensive action in conscious rats that seems to result from synergic interaction of the two enantiomers. 31-1347/R ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 These authors contribute equally to this work. |
ISSN: | 1671-4083 1745-7254 |
DOI: | 10.1038/aps.2013.154 |