SUCCESSFUL MAGNESIUM-SULFATE TOCOLYSIS - IS WEANING THE DRUG NECESSARY

OBJECTIVE: Magnesium sulfate is the most commonly used tocolytic agent for preterm labor. A common clinical practice is to slowly discontinu e the drug (wean) after successful tocolysis. Our objective was to det ermine the necessity of this practice. STUDY DESIGN: A prospective, ra ndomized clinical trial was performed from June 1993 to July 1996. Aft er successful magnesium sulfate tocolysis, patients with preterm labor were randomized to two groups: stopping the drug abruptly (no weaning ) or gradually weaning the drug(approximately 1 gm every 4 hours). Pre term labor was defined as documented cervical change with regular uter ine contractions or regular uterine contractions with a cervix of 2 cm and 75% effacement. The primary outcome variable was the necessity to reinstitute magnesium sulfate therapy within 24 hours of discontinuat ion of successful tocolysis. RESULTS: One hundred forty-one patients c ompleted the study. No patient in the no-wean group required retocolys is within 24 hours of magnesium discontinuation. However, eight patien ts in the wean group required retocolysis within 24 hours of magnesium discontinuation (p = 0.01). Significantly more patients in the wean g roup had retocolysis during pregnancy (3 vs 12, p = 0.03). Patients in the wean group were also in the labor and delivery unit longer and, a s would be anticipated, received magnesium sulfate significantly longe r. No differences in the neonatal outcomes were noted between the two groups. Seventy-seven percent of the patients in the study were delive red prematurely. CONCLUSION: This study demonstrated an increased need for retocolysis in the group weaned from magnesium sulfate. We also f ound that patients in the wean group had an increased labor and delive ry time and a longer administration time of magnesium sulfate. Thus we aning magnesium sulfate Increases health care cost. The practice of we aning magnesium sulfate does not appear beneficial.