A woman receiving intramuscular magnesium sulfate therapy for eclampsia has a serum magnesium level measured during steady state. Within which range is seizure prophylaxis considered adequate?

• A 14 to 18 mg/dL
• B 9 to 11 mg/dL
• C 4.8 to 8.4 mg/dL ✓
• D 2 to 4 mg/dL

Explanation

The therapeutic range for magnesium sulfate is 4.8 to 8.4 mg/dL (roughly 4 to 7 mEq/L). Patellar reflexes disappear at around 9 to 12 mg/dL, respiratory paralysis develops above roughly 12 mg/dL, and cardiac conduction disturbance and arrest occur at much higher levels. Monitoring deep tendon reflexes, respiratory rate, and urine output clinically substitutes for routine serum levels in most settings.

Reference: Williams Obstetrics, 26th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.