What is the equivalent dose of slow-release magnesium for 4 grams (GM) of magnesium?

Magnesium Dose Conversion

There is no direct pharmaceutical equivalent of "slow magnesium" as a standardized formulation, and the question cannot be answered as posed because "slow magnesium" is not a recognized medical term or specific product.

Understanding the Question

The term "slow magnesium" likely refers to one of the following:

• Slow-release or extended-release magnesium formulations - These are designed to release magnesium gradually over several hours rather than immediately 1
• Magnesium oxide given in divided doses - This is commonly used in clinical practice for conditions like short bowel syndrome, where 12-24 mmol daily (approximately 480-960 mg elemental magnesium) is administered, preferably at night when intestinal transit is slowest 2

Critical Clarification Needed

The conversion depends entirely on which specific product and salt form is being referenced:

If "4 GM of Magnesium" Refers to Elemental Magnesium:

• 4 grams (4000 mg) of elemental magnesium is an extremely high dose that far exceeds any standard clinical recommendation 2
• The recommended daily allowance is only 320 mg for women and 420 mg for men 2
• The tolerable upper intake level from supplements is 350 mg/day to avoid adverse effects 2
• This dose would be dangerous and is not appropriate for oral supplementation 2

If "4 GM" Refers to Magnesium Sulfate (MgSO4):

• 4 grams of magnesium sulfate contains approximately 325 mg of elemental magnesium (MgSO4 is about 8% elemental magnesium by weight)
• For acute IV administration in severe asthma or cardiac conditions, 2 g of MgSO4 is the standard dose, administered over 20 minutes 3
• There is no established conversion to oral "slow-release" formulations from IV magnesium sulfate because the routes of administration, bioavailability, and clinical indications are fundamentally different 4

Bioavailability Considerations

Different magnesium salts have dramatically different absorption rates:

• Magnesium oxide has poor bioavailability (only 4% fractional absorption) 4
• Magnesium chloride, lactate, and aspartate have significantly higher and equivalent bioavailability 4
• Slow-release formulations like magnesium chloride extended-release provide continuous release over 6 hours, improving absorption compared to immediate-release products 1

Clinical Algorithm for Magnesium Supplementation

To provide appropriate magnesium dosing, you must:

1. Identify the clinical indication - Is this for hypomagnesemia, constipation, short bowel syndrome, cardiac arrhythmia, or another condition? 2

2. Determine the route - IV magnesium is used for acute severe conditions (1-2 g over 15 minutes for cardiac arrest with hypomagnesemia), while oral is used for chronic supplementation 3

3. Select the appropriate salt form - Organic salts (citrate, lactate, aspartate) have better bioavailability than magnesium oxide 4

4. Start with standard doses - For chronic oral supplementation, begin with 320-420 mg elemental magnesium daily, not 4 grams 2

Common Pitfalls

• Confusing magnesium salt weight with elemental magnesium content - A 500 mg magnesium oxide tablet contains only about 300 mg of elemental magnesium 2
• Assuming IV and oral doses are interchangeable - They are not; bioavailability differs dramatically by route 4
• Using magnesium oxide for conditions requiring high bioavailability - Magnesium oxide is poorly absorbed and may worsen diarrhea 4, 2
• Failing to check renal function - Avoid magnesium supplementation if creatinine clearance is less than 20 mL/min due to hypermagnesemia risk 2

The question as stated cannot be answered without clarification of what "4 GM of Magnesium" specifically refers to (salt form vs. elemental) and what specific "slow magnesium" product is intended.