A client diagnosed with severe preeclampsia is receiving magnesium sulfate by IV infusion. Which magnesium level is within the therapeutic range?

A client diagnosed with severe preeclampsia is receiving magnesium sulfate by IV infusion. Which magnesium level is within the therapeutic range?

• A. 1 mEq/L (0.5 mmol/L)
• B. 3 mEq/L (1.5 mmol/L)
• C. 5 mEq/L (2.5 mmol/L)
• D. 10 mEq/L (5 mmol/L)

Answer: (C)

Magnesium sulfate is used in severe preeclampsia to prevent seizures by raising the seizure threshold; its effectiveness depends on keeping serum levels within a therapeutic window. The typical therapeutic range for seizure prophylaxis is about 4–7 mEq/L (roughly 2–3.5 mmol/L). A level of 5 mEq/L, which is 2.5 mmol/L, falls squarely inside that range. Levels lower than this may not provide adequate protection, while much higher levels increase the risk of magnesium toxicity, presenting with loss of deep tendon reflexes, respiratory depression, hypotension, and potential cardiac arrest—addressed emergently with calcium gluconate. Continuous monitoring of reflexes, respiratory rate, and urine output, along with periodic magnesium level checks, guides safe dosing.

Magnesium sulfate is used in severe preeclampsia to prevent seizures by raising the seizure threshold; its effectiveness depends on keeping serum levels within a therapeutic window. The typical therapeutic range for seizure prophylaxis is about 4–7 mEq/L (roughly 2–3.5 mmol/L). A level of 5 mEq/L, which is 2.5 mmol/L, falls squarely inside that range. Levels lower than this may not provide adequate protection, while much higher levels increase the risk of magnesium toxicity, presenting with loss of deep tendon reflexes, respiratory depression, hypotension, and potential cardiac arrest—addressed emergently with calcium gluconate. Continuous monitoring of reflexes, respiratory rate, and urine output, along with periodic magnesium level checks, guides safe dosing.