Early manifestations may include painful muscle cramps, nausea, vomiting, and lethargy. Mental status changes may become evident and include irritability, disorientation, depression, and psychosis. Reversible respiratory muscle failure may occur in severe hypomagnesemia. Severe magnesium deficiency may cause PR prolongation or widened QRS complexes. Little is understood about the uptake kinetics at the cell membrane level, so the optimal dosage to produce an effective intracellular uptake is unknown.
Dosage also varies from patient to patient.
With renal impairment, reduce these doses by at least half. Base magnesium replacement in children on the child's weight. Rapid IV administration can be life threatening. Risks involved with IV magnesium therapy include hypermagnesemia, hypocalcemia, and sudden hypotension. IV infusion rates should not exceed 67 mEq over 8 hours.