Milk of Magnesia in Dialysis Patients: Absolute Contraindication
Patients on chronic dialysis should never use milk of magnesia (magnesium hydroxide) for constipation or acid reflux due to the high risk of life-threatening hypermagnesemia. 1, 2, 3
Why This Is Dangerous
The kidneys are responsible for nearly all magnesium excretion from the body. 4 In end-stage renal disease (ESRD), the limited ability to excrete magnesium can result in toxic serum concentrations, even with normal therapeutic doses. 4, 5
Life-threatening complications documented in dialysis patients taking milk of magnesia include: 6, 7
- Severe bradycardia and cardiac arrest
- Asystole requiring resuscitation
- Metabolic encephalopathy
- Hypothermia and respiratory failure requiring intubation
- Shock mimicking sepsis or cardiogenic shock
- Death despite emergency dialysis
Clear Guideline Recommendations
The American Gastroenterological Association explicitly states to avoid magnesium oxide (and by extension, all magnesium-containing laxatives including milk of magnesia) in patients with renal insufficiency due to risk of hypermagnesemia. 1, 2
The FDA drug label for magnesium hydroxide warns patients to "ask a doctor before use if you have kidney disease." 3 This warning exists precisely because of the documented fatalities in renal failure patients. 6, 7
When creatinine clearance is <20 mL/min (which includes all dialysis patients), magnesium supplementation is absolutely contraindicated. 2, 8
Documented Fatal Cases
A 50-year-old woman with normal renal function developed a magnesium level of 11.0 mg/dL from taking milk of magnesia for constipation, experienced cardiac arrest, and died despite continuous renal replacement therapy. 7
An 82-year-old woman with ESRD taking 3,000 mg daily of magnesium hydroxide developed metabolic encephalopathy with a magnesium level of 9.9 mg/dL. 7
A male patient with ESRD developed severe bradycardia, asystole, atrial fibrillation with QRS widening, hypothermia, hypotension, and apnea requiring intubation after using milk of magnesia, with serum magnesium >4.1 mmol/L (>10 mg/dL). 6
Safer Alternatives for Constipation in Dialysis Patients
First-line recommendation: Polyethylene glycol (PEG) 17g daily 2
- Strong recommendation with moderate-quality evidence 1
- No systemic absorption concerns 2
- Durable 6-month response demonstrated 1
- Side effects limited to abdominal distension, loose stool, flatulence, and nausea 1
- Psyllium fiber (if dietary fiber intake is low and constipation is mild) 1
- Lactulose (for patients who fail or are intolerant to PEG) 1
- Bisacodyl or sodium picosulfate (short-term or rescue therapy) 1, 2
All of these alternatives are safe in renal failure because they are not systemically absorbed or do not accumulate in kidney disease. 2
Critical Clinical Pitfall
The most dangerous mistake is assuming "just one dose" or "occasional use" of milk of magnesia is safe in dialysis patients. Even single doses can cause life-threatening hypermagnesemia because these patients cannot excrete the magnesium load. 6, 7, 4
Magnesium accumulation in ESRD patients occurs rapidly, and toxic concentrations develop even when the kidney attempts compensatory mechanisms. 4, 5 The use of magnesium-containing antacids as phosphate binders was largely discontinued two decades ago after reports of toxic magnesium levels. 5, 9
For Acid Reflux in Dialysis Patients
If the patient was considering milk of magnesia for acid reflux rather than constipation, safer alternatives include:
- Calcium carbonate (also serves as phosphate binder)
- Proton pump inhibitors
- H2-receptor antagonists
Never use magnesium-containing antacids in dialysis patients. 5, 9