Respiratory depression develops when magnesium sulphate concentration reaches:

During Magnesium toxicity, the first reflex to be lost is patellar reflex (loss of knee jerk) -While giving MgSO4 things should be monitored are as follows; Respiratory rate should be at least more than 12 Output should be more than 100 ml / 4hrs Knee jerks should be present Serum Mg2+ levels(meq/l) Clinical effects 4-7 Normal therapeutic level 8 - 10 Patellar reflex disappear 10-15 Respiratory depression 12-15 Respiratory paralysis 25 - 30 Cardiac arrest Treatment is with calcium gluconate 1 g IV