Profound hypotension complicating magnesium therapy.

Two preeclamptic women became profoundly hypotensive while receiving magnesium sulfate. No evidence of toxic levels was present in either. In both, preeclampsia-induced hypovolemia was extreme. That nontoxic magnesium levels can cause severe hypotension is an alarming possibility. Acknowledgment of this complication and expeditious reversal of the problem is essential.