What is the accepted therapeutic serum magnesium concentration for seizure prophylaxis and treatment in eclampsia?

• A 2.0 to 4.0 mg/dL
• B 4.8 to 8.4 mg/dL ✓
• C 9.0 to 12.0 mg/dL
• D 13.0 to 16.0 mg/dL

Explanation

The therapeutic window for magnesium sulfate in eclampsia is 4.8 to 8.4 mg/dL. Loss of the patellar reflex occurs around 9 to 10 mg/dL, respiratory paralysis above roughly 10 to 12 mg/dL, and cardiac arrest at much higher concentrations near 25 to 30 mg/dL. This ladder explains why reflex monitoring is the bedside safety check: absent reflexes signal the drug must be stopped before respiration fails. Levels below 4.8 mg/dL are subtherapeutic and leave the patient unprotected against recurrent seizures.

Reference: DC Dutta's Textbook of Obstetrics, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.