Magnesium toxicity secondary to catharsis during management of theophylline poisoning

Multiple doses of oral activated charcoal are used increasingly to promote elimination of toxins that have already reached the bloodstream; this is often referred to as gastrointestinal dialysis. Cathartics usually are used in conjunction to hasten transit of the charcoal-adsorbed toxin. In the present case, a regimen of activated charcoal and magnesium citrate was used to treat a patient with theophylline poisoning. It was effective in lowering the patient's serum theophylline concentration but produced an elevated magnesium level associated with decreased responsiveness, confusion, and diminished deep tendon reflexes. Magnesium citrate may not be the optimal cathartic for use in gastrointestinal dialysis, at least in selected patients. Sorbitol has been shown to produce a more rapid catharsis without disturbing magnesium serum concentrations. Therefore, the use of sorbitol in place of magnesium citrate, at least in selected patients, may be preferred.