Effect of magnesium on plasma cholinesterase activity.

Plasma cholinesterase activity levels were studied in 15 pregnant patients with preeclampsia before and after the administration of therapeutic doses of magnesium sulfate. Plasma cholinesterase activity was also studied in 15 healthy nonpregnant and 15 healthy pregnant women. The mean plasma cholinesterase activity level in pregnant patients with preeclampsia before and after the administration of magnesium sulfate was 179 +/- 26 and 176 +/- 39 units/ml, respectively. The healthy nonpregnant patients and healthy pregnant patients had a plasma cholinesterase activity level of 426 +/- 85 and 264 +/- 24 units/ml, respectively. Our data demonstrated that magnesium has no significant effect on plasma cholinesterase activity. Our data also confirm that there is a significant reduction in plasma cholinesterase activity in pregnant patients with preeclampsia compared with either healthy nonpregnant or healthy pregnant patients. We conclude that the low level of plasma cholinesterase activity is probably responsible for the prolonged action of succinylcholine in pregnant patients with preeclampsia receiving magnesium sulfate.