RESUMEN
OBJECTIVE: To evaluate the tolerability and safety of intravenous magnesium sulfate use for tocolysis in a center that uses a "high-dose" regimen. STUDY DESIGN: We conducted a retrospective cohort study of patients treated with magnesium sulfate for preterm labor from December 2006 to June 2010. Data were abstracted from review of individual patient electronic medical records. RESULTS: The cohort consisted of 456 women. Of these, 417 (91.4%) experienced side effects. Severe side effects (pulmonary edema, respiratory arrest, intensive care unit transfer, cardiac arrest, or death) occurred in 24 (5.3%) cases, all but one due to pulmonary edema. No cases of respiratory arrest, cardiac arrest, or death occurred. Those with severe side effects were less likely to have a singleton and more likely to have a higher order multifetal gestation (p < 0.001), received more magnesium, and more often were given multiple concurrent tocolytics (p = 0.04). CONCLUSION: "High-dose" magnesium tocolysis results in side effects for 9 of every 10 patients treated, and severe side effects occur in 1 of every 20 patients. When used for tocolysis, magnesium should be used as a single agent, for less than 48 hours, and with great caution in multifetal gestations.