I received an email from AARP (am a member) listing 10 medications I should be cautious about. There is only one that stood out, the laxative, Magnesium Citrate:

10 Over-the-Counter Medications That Can Become Risky After 50

8. Magnesium citrate, milk of magnesia
Gershman recommends older adults be careful with the over-the-counter laxative magnesium citrate. It can cause changes in electrolytes, like potassium and sodium, potentially leading to irregular heartbeat. Magnesium citrate is sometimes used for bowel preparation before colonoscopies.

Though it also contains magnesium, milk of magnesia is a “safer option” to magnesium citrate, Gershman says. However, she cautions that even milk of magnesia poses risks with long-term use. This is especially concerning for older adults as magnesium can build up to toxic levels in people whose kidneys are not functioning well.

Many of us on this forum take Magnesium Citrate pills for our Afib. Is there a concern continuing with the pills for older people (says it can cause an irregular heart beat??)? Is there more of a concern if you are over 80 years old?

I've personally taken a lot (>4 or 5 grams/day) of magnesium in many different forms for several decades.

Here is what ChatGPT 4 says, with references:

Magnesium intake, especially in excess, can indeed affect the balance of other electrolytes such as potassium and sodium, though the mechanism can be complex. Here’s how magnesium impacts potassium and sodium concentrations, along with related risks:

### 1. **Magnesium and Potassium Relationship**:
- **Magnesium’s role in potassium balance**: Magnesium is essential for the proper function of sodium-potassium pumps (Na+/K+ ATPase) in cells, which maintain the correct intracellular and extracellular concentrations of potassium and sodium. Low magnesium levels impair this pump’s activity, leading to a potential decrease in potassium (hypokalemia).
- **Excess magnesium and potassium**: High magnesium levels, particularly from supplementation, can interfere with potassium handling by the kidneys. This could lead to either potassium loss (hypokalemia) or retention (hyperkalemia), depending on the individual’s renal function.
- **Clinical example**: Studies have shown that magnesium deficiency can lead to refractory hypokalemia, meaning low potassium levels that are hard to correct without addressing magnesium deficiency first (Whang & Ryder, *Journal of the American College of Nutrition*, 1990).

### 2. **Magnesium and Sodium Relationship**:
- **Sodium retention and magnesium deficiency**: There is evidence suggesting that magnesium deficiency may lead to increased sodium retention in the kidneys. Magnesium modulates the activity of certain sodium transporters in the kidney, and insufficient magnesium could lead to an imbalance, causing higher sodium levels (hypernatremia) (Eck et al., *Magnesium Research*, 1997).
- **Excess magnesium and sodium loss**: High magnesium intake, particularly from supplements or intravenous magnesium administration, can promote sodium excretion (natriuresis). This might be beneficial in conditions like hypertension but could lead to a risk of hyponatremia (low sodium levels) if excessive sodium loss occurs.

### 3. **Magnesium and Renal Function**:
- **Kidney function’s role**: The kidneys play a crucial role in balancing magnesium, potassium, and sodium. People with impaired renal function are at a greater risk of electrolyte imbalances. For example, excessive magnesium intake can overwhelm the kidneys’ ability to excrete the surplus, leading to hypermagnesemia, which can subsequently cause dysregulation of potassium and sodium levels.
- **Risk in healthy individuals**: In those with normal kidney function, moderate magnesium supplementation typically doesn’t cause significant imbalances in potassium or sodium. However, very high doses of magnesium can lead to side effects, including electrolyte disturbances (hyperkalemia or hyponatremia), due to the interdependent nature of electrolyte regulation.

### 4. **Clinical Cases**:
- **Hypermagnesemia**: A condition where excessive magnesium can lead to electrolyte disturbances, including low sodium (hyponatremia) and high potassium (hyperkalemia). In one clinical case, a patient with renal insufficiency who received high doses of magnesium developed both hyperkalemia and hyponatremia, highlighting the interrelatedness of these electrolytes (*Clinical Nephrology*, 2007).
- **Hypokalemia due to Magnesium Deficiency**: Patients with magnesium deficiency often exhibit low potassium levels, even if they have adequate potassium intake. This is because magnesium is crucial for maintaining the balance of potassium in cells. Correcting the magnesium deficiency often helps resolve the potassium imbalance (Ryan MP, *New England Journal of Medicine*, 1981).

### Summary:
- **Excess magnesium intake** can lead to **sodium and potassium imbalances**, particularly in those with renal impairment. It may cause:
- **Hypokalemia** (low potassium) by impairing potassium reabsorption in cells.
- **Hyperkalemia** (high potassium) in cases of excess magnesium intake, especially if the kidneys are unable to excrete it.
- **Hyponatremia** (low sodium) or **hypernatremia** (high sodium) depending on the magnesium’s effect on sodium transporters and kidney function.
- **Magnesium deficiency** is more commonly associated with **hypokalemia** and sodium retention, as magnesium is needed to support potassium balance and prevent sodium retention.

### References:
1. Whang R, Ryder KW. *Frequency of hypomagnesemia and hypokalemia in hospitalized patients*. J Am Coll Nutr. 1990.
2. Eck P, Baran DT, Kukreja SC, et al. *Magnesium deficiency increases sodium retention*. Magnesium Research. 1997.
3. Ryan MP. *The role of magnesium in the renal handling of potassium*. N Engl J Med. 1981.
4. Norman PE, Powell JT. *Magnesium and health outcomes: a systematic review*. Clin Nephrol. 2007.