Which constipation treatment should be used with extreme caution in patients with chronic renal insufficiency?

• A. Milk of Magnesia
• B. Psyllium (Metamucil)
• C. Docusate Sodium (Colace)
• D. Lactulose (Chronulac)

Answer: (A)

In chronic renal insufficiency, the kidneys can’t clear magnesium efficiently, so magnesium-containing laxatives pose a real danger. Milk of Magnesia (magnesium hydroxide) delivers magnesium that can accumulate and lead to hypermagnesemia, with symptoms ranging from nausea and hypotension to bradycardia, reduced reflexes, and even respiratory depression in severe cases. Because of that, it should be used with extreme caution or avoided in these patients.

The other options don’t carry this magnesium risk. Psyllium is a bulk-forming fiber that increases stool water content and mass without significant electrolyte disturbance. Docusate sodium is a stool softener that helps with easier passage and is generally safe in CKD. Lactulose is an osmotic laxative that isn’t absorbed and is also used in CKD (and in hepatic encephalopathy), though it can cause gas and electrolyte shifts; it does not introduce magnesium.

So the laxative to watch closely or avoid in chronic renal insufficiency is the magnesium-containing Milk of Magnesia.