Metabolic disturbances during intravenous use of ritodrine: increased insulin levels and hypokalemia.

The role played by insulin and the adrenergic system in the development of hypokalemia due to intravenous ritodrine has been evaluated. Fifteen women presenting with premature labor (group 1) were treated with ritodrine infusion, whereas seven pregnant women not in labor (group 2) were given 100 g glucose per os to induce hyperinsulinemia without participation of ritodrine. Serum glucose, insulin, potassium, sodium, chloride, and calcium were measured hourly. Whereas insulin levels were higher in group 2, potassium decreased markedly and significantly only in group 1. It is concluded that ritodrine-induced hypokalemia, that results partially from hyperinsulinemia, is mostly determined by other factors and is possibly a consequence of direct beta-adrenoceptor stimulation. Significant hypocalcemia of unexplained origin was observed with ritodrine.