In the ambulatory care and geriatrics space, I see magnesium supplements used on a fairly frequent basis in practice. Here are a few magnesium clinical pearls that I’ve picked up along the way.
Drugs That Cause Magnesium Deficiency
There are a few no doubters that you need to remember when it comes to hypomagnesemia. In patients taking chronic diuretics, PPIs, or immunosuppressive agents like cyclosporine or tacrolimus, you have to ensure that patients are not magnesium deficient. If a patient is taking one or more of these agents and displays signs and symptoms of deficiency, be sure to address the possibility of a medication-related deficiency. There are a few oddball drugs that may contribute to deficiency as well. The chemotherapy agent cisplatin, aminoglycosides, and amphotericin B are all associated with magnesium deficiency.
Prescription Versus OTC Magnesium
There is a difference in most situations between prescription and OTC magnesium supplements. Prescribed magnesium supplements are often due to a known deficiency due to lab monitoring. Patient-driven OTC magnesium use is often due to a recommendation by a friend or started by Dr. Google. In my experience, the most common situation where patients begin to take magnesium on their own is when they are experiencing leg cramps. If this is the case, you have to look at their medications and see if they are on a diuretic which is one of the most common causes of cramping and electrolyte deficiencies.
One of the most important disease states that you should remember with magnesium deficiency is alcohol use disorder. Patients with excessive drinking habits can have magnesium deficiency and may require ongoing supplementation. Conditions like Crohn’s or Ulcerative colitis may cause diarrhea which can lead to fluid and electrolyte loss (including magnesium).
Magnesium can lead to the prescribing cascade and the most common adverse effects are GI-related. Diarrhea is the one that I have seen the most in practice. I have seen situations where the magnesium has lead to the prescribing cascade (i.e. anti-diarrheal agents were necessary to manage the adverse effect of diarrhea).
If you are looking for more magnesium clinical pearls, I talk in-depth about it on this episode of the Real Life Pharmacology podcast.