It seems to displace calcium from receptor sites within the uterine muscle, thereby increasing the amount of intercellular calcium and thus decreasing smooth muscle contraction. Magnesium is a plasma volume expander that causes a significant increase in osmolarity. It acts peripherally to produce vasodilatation. The body compensates by mobilizing fluid into the intravascular space which can produce pulmonary edema. Therefore, caution should be used when delivering Magnesium Sulfate to a woman with heart valve disease.
Neuromuscular toxicity is also a concern when Magnesium is used as a tocolytic.
As the plasma level rises, deep tendon reflexes decrease and eventually disappear. This particular side effect can be reversed with the administration of Calcium Gluconate. Managing premature labor can be an anxiety provoking experience for health care providers, since the well being of both mother and fetus are dependent upon the interventions made. Providence Seattle Medical Center Univ.