Effect on interaction between clonidine and calcium channel blockers on vascular smooth muscles

ABSTRACT

The 2 alpha receptor triggered vasoconstriction appears to be largely dependent upon the influx of extracellular calcium ions. This study was conducted to study the interaction between calcium channel blockers [nifedipine and isradipine] and clonidine.Mongrel dogs were used to study this interaction on the blood pressure nifedipine and isradipine attenuated the effect of clonidine on the blood pressure. When dogs were subjected to bleeding, it was found that nifedipine and isradipine also attenuated the effect of clonidine on the blood pressure of dogs.Using Abino rat hind quarter preparations, it was found that nifedipine and isradipine produced significant increase in the vascular outflow rate. The effect of isradipine was more significant than that of nifedipine. Clonidine non- significantly decreased the vascular outflow rate nifedipine and isradipine significantly attenuated the vasoconstrictor response to clonidine and this should be taken in consideration if a subject under nifedipine or isradipine treatment needs alpha 2-stimulants for treatment of emergency hypotensive states