<p>The action of dopamine hydrochloride is potentiated by monoamine oxidase inhibitors (MAOI&#39;s). The concurrent administration of cyclopropane or halogenated hydrocarbon anesthetics may cause ventricular arrhythmias. The cardiac effects of dopamine hydrochloride are antagonized by &beta; - adrenergic blocking agents such as Propranolol and Metoprolol. The ergot alkaloids should be avoided because of the possibility of excessive vasoconstriction. Tricyclic antidepressants and guanethidine may potentiate the pressor response to dopamine hydrochloride. Hypotension and bradycardia have been observed in patients receiving Phenytoin. Dopamine hydrochloride may increase the effect of diuretic agents. Peripheral vasoconstriction may be antagonized by &alpha; - adrenergic blocking agents, such as Phentolamine. Other vasodilators may also be useful in patients with heart failure, allowing greater inotropic and renal effects without the associated vasoconstriction. Care must be taken to avoid hypotension.</p>