Overdose : מינון יתר

4.9 Overdose
Signs:
Clinical signs of overdose will be those of hypermagnesaemia - see Section 4.8.
Patients with renal failure and metabolic derangements develop toxicity at lower doses.
Magnesium intoxication is manifested by a sharp drop in blood pressure and respiratory paralysis. Disappearance of the patellar reflex is a useful clinical sign to detect the onset of magnesium intoxication.

Mg plasma concentration (mmol/L)                       Symptoms and undesirable effects  2 to 3                                                 nausea, flushing, headache, lethargy, drowsiness,
diminished deep tendon reflexes, platelet disaggregation

3 to 5                                                 somnolence, hypocalcemia, absent deep tendon reflexes, hypotension, bradycardia, and ECG changes
>5                                                     muscle paralysis, respiratory paralysis, coma. In most cases, respiratory failure precedes cardiac collapse
>7.0                                                   Complete heart block and cardiac arrest 

Treatment:
Appropriate action should be taken to reduce the blood level of magnesium. In the event of overdosage, artificial ventilation must be provided until a calcium salt can be injected IV to antagonize the effects of magnesium.

Neuromuscular blockade associated with hypermagnesaemia may be reversed with calcium salts, such as calcium gluconate, which should be administered intravenously in a dose equivalent to 2.5 to 5 mmol of calcium.