CARDIAC GLYCOSIDES MAY ENHANCE OR PRECIPITATE BRADYCARDIA, A.V. BLOCK OR ARRHYTHMIA ON CONCOMITANT USE. THE USE OF DRUGS THAT STIMULATE ALPHA-ADRENERGIC RECEPTORS (E.G., PHENYLEPHRINE, PSEUDOEPHEDRINE, EPHEDRINE, PHENYLPROPANOLAMINE OR DIHYDROERGOTAMINE) MAY ENHANCE OR POTENTIATE THE PRESSOR EFFECTS OF PROAMATINE. ALPHA-ADRENERGIC BLOCKING AGENTS, SUCH AS PRAZOSIN, TERAZOSIN, AND DOXAZOSIN, CAN ANTAGONIZE THE EFFECTS OF MIDODRINE.