<prompt> In a patient on magnesium sulphate therapy, usually at what levels the patellar knee reflex disappears6-8mEqL10-12 mEqL12-14 mEqL15 mEqL  <response>: Ans. b 10-12 mEqL Ref. Williams Obstetrics 22nd ed., p 789; Dutta Obstetrics, 6th ed., p 249MAGNESIUM SULPHATE Magnesium sulphate is the treatment of choice for the prevention and treatment of eclamptic seizures. It reduces motor end plate sensitivity to acetylcholine. It induces cerebral vasodilatation, dilates uterine arteries, increases production of endothelial prostacyclin and inhibits platelet activation. Magnesium may prevent seizures by interacting with NMDA receptors in the CNS. The therapeutic level of serum magnesium is 4-7 mEqL. Eclamptic convulsions are almost always prevented by maintaining plasma magnesium levels between A--7 mEqL 2.0-3.5 mmolL. Repeat injections are given only if:- Knee jerks are present,- Urine output is 30 mLhour, and- Respiration rate is 12min. Loss of DTRs serves as the earliest warning sign of impending magnesium toxicity, because a further increase leads to respiratory depression.- Patellar reflex disappears when magnesium level reaches 10 mEqL 12 mgdL - curariform action.- Respiratory depression develops - when magnesium levels go 10 mEqL,- respiratory paralysis and arrest follows when levels 12 mEqL, . Rx:- With calcium gluconate 1 g IV and withholding magnesium sulphate reverses mild to moderate respiratory depression.- Usually magnesium sulphate is otherwise discontinued 24 hours after delivery.RegimenLoading doseMaintenance dosePritchard4 g IV over 3-4 min, 10 mg deep IM5 g IM in alternate buttockZuspan4 g IV over 5-10 min1-2 ghour IV infusionSibai6 g IV over 20 min2 ghour IV infusionRegimens for the administration of magnesium sulphate for seizure prophylaxis in women in labor with preeclampsia Intramuscular- 10 g 5 g IM deep in each buttock- 5 g IM deep q4h, alternating sides Intravenous- 6-g bolus over 15 min- 1-3 gh by continuous infusion pump- May be mixed in 100 mL crystalloid; if given by intravenous push, make up as 20 solution; push at maximum rate of 1 gmin- 40-g MgS04.7H,0 in 1000 mL Ringers lactate; run at 25-75 mLh 1-3 gh. 