Mechanism of Ergotamine-induced Decrease of Peripheral Systolic Blood Pressure in Man

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Abstract
We have previously reported a consistent decrease of peripheral‐central systolic blood pressure (SBP) gradients after ergotamine. SBP was measured with cuffs and it is unknown whether measured values reflect changes of intra‐arterial SBP or increase of vessel wall tone beneath the cuffs. We hence studied the effect of ergotamine tartrate 0.5 mg intravenously on finger‐arm systolic gradients after the following procedures: Infiltration around finger arteries with papaverine (n = 2) and dihydralazine (n=3), occlusion of blood supply to a finger by an inflated cuff before and 2 hours after ergotamine (n = 6). A normal reduction in finger‐arm systolic gradients was seen. The ergotamine‐induced decrease of peripheral SBP must therefore be due to a fall in peripheral intra‐arterial SBP i.e. to contraction of arteries proximal to the digital arteries. Intra‐arterial injection of 10 μg ergotamine tartrate caused similar decrease in finger‐arm systolic gradients as intravenous administration of 0.5 mg (n= 1) indicating a peripheral site of action.