Effects of Calcium Antagonists on Adrenaline-induced Hypokalaemia

Long term treatment with nifedipine and nitrendipine, but not verapamil and diltiazem, may reduce plasma potassium levels in hypertensive patients. To test the hypothesis that this effect is related to adrenaline-mediated influx of potassium from the extracellular space, the effect of adrenaline infusions (12.5, 25 and 50 ng/kg/min) on plasma potassium levels was assessed in normotensive subjects after administration of placebo for 4 days, and after administration of nitrendipine, verapamil or diltiazem for 4 days. The adrenaline-induced decrease in plasma potassium levels was enhanced in subjects receiving nitrendipine, but was unaffected in those subjects receiving verapamil or diltiazem. The effects of adrenaline on blood glucose levels, heart rate and blood pressure were uninfluenced in subjects receiving nitrendipine or verapamil, and were blunted in subjects receiving diltiazem. These results suggest that enhancement of the adrenaline-induced intracellular transfer of potassium from the extracellular space is relatively specific to dihydropyridine calcium antagonists.