Adrenaline Hydralazine

The peripheral receptors activated by noradrenaline fall into at least two classes, a-receptors and /3-receptors, which differ in their function and in their response to drugs. The a-receptors cause constriction of blood vessels and compounds used to block them include indoramin (216), prazosin (217) and phentolamine (218). Another imidazoline, tolazoline (2-benzyl-2-imidazoline), is a useful vasodilator but is unsuitable for the treatment of hypertension since it stimulates the heart. Other drugs described as peripheral vasodilators are diazoxide (219), which is related to the thiazide diuretics, hydralazine (220) which also depresses the CNS, hydracarbazine (221) and minoxidil (222). The /3-receptors control the action of adrenaline on the heart (among other effects) and the agents that block them are mostly nonheterocyclic aromatic compounds with aminoethanol or 3-amino-2-hydroxypropoxy side-chains. They have proved effective in the treatment of hypertension. One heterocyclic compound of this class, timolol (223), is in use. 

Adrenaline, apomorphine, ascorbic acid, benserazide, dihydralazine, dobutamine, dodecyl gallate, dopamine, ethylnoradren-aline, hexoprenaline, hydralazine, iproniazid, isocarboxazid, isoetharine, isoniazid, isoprenaline, levodopa, meban-azine, methyldopa, methyldopate, nialamide, noradrenaline, phenelzine, procarbazine, protokylol, rimiterol... 

The manufacturers note that patients taking hydralazine who develop hypotension while undergoing surgery should not be treated with adrenaline (epinephrine). This is because hydralazine frequently causes tachycardia, and adrenaline would enhance this. ... 

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