Magnesium sulfate and beta-mimetic dual-agent tocolysis in preterm labor after single-agent failure.

Twenty-three patients in preterm labor failed to respond to single-agent tocolytic therapy or could not tolerate the dosage necessary to inhibit contractions. A combination of magnesium sulfate and ritodrine or terbutaline was used to inhibit labor in these patients. Fourteen patients (60.9%) responded to dual-agent tocolysis by delaying delivery for 48 hours or more. Six patients had delivery delayed for more than one week. Five patients had multiple gestations; three of them had delivery delayed more than 48 hours. Five patients developed pulmonary edema under treatment with dual-agent tocolysis; all responded to diuretic and/or oxygen therapy after the termination of tocolysis. Dual-agent tocolysis may significantly prolong some pregnancies complicated by preterm labor, but only at some risk to maternal well-being.