Therapy with both magnesium sulfate and nifedipine does not increase the risk of serious magnesium-related maternal side effects in women with preeclampsia

Objective: Does the use of nifedipine and magnesium sulfate together increase serious magnesium-related effects? Study design: This was a retrospective chart review of women who were admitted to BC Women' s Hospital and Health Centre (1997-2001) and were given intravenous magnesium sulfate for preeclampsia. Serious magnesium-related effects were compared among 162 cases who received magnesium sulfate and contemporaneous nifedipine and 215 control subjects who received magnesium sulfate and either another antihypertensive (n = 32 women) or no antihypertensive (n = 183 women) medication. Chi-squared test, Fisher' s exact test, or the Student t test was used for data comparison between cases and each control group. A probability value of .05 was considered statistically significant. Results: The cases had more severe preeclampsia and a longer magnesium sulfate infusion. However, cases had no excess of neuromuscular weakness (53.1% ) versus control subjects who received antihypertensive medication (53.1% ; P = .99) or control subjects who received no antihypertensive medication (44.8% ; P = .13) or other serious magnesium-related effects. Cases versus control subjects who received antihypertensive medication had less neuromuscular blockade (odds ratio, 0.04; 95% CI, 0.002-0.80). Cases versus control subjects who received no antihypertensive medication had less maternal hypotension (41.4% vs 53.0% ; P = .04). Conclusion: The use of nifedipine and magnesium sulfate together does not increase the risk of serious magnesium-related effects.