From the Guidelines
The preferred treatment for constipation is magnesium-based laxatives, such as magnesium hydroxide or magnesium citrate, due to their faster onset of action, lower cost, and fewer side effects compared to lactulose. According to the American Gastroenterological Association-American College of Gastroenterology clinical practice guideline 1, magnesium oxide is recommended as a first-line option for individuals with chronic idiopathic constipation (CIC) due to its efficacy, tolerability, and low cost. The guideline suggests starting with a lower dose of magnesium oxide, which may be increased if necessary, and avoiding its use in patients with significant renal impairment to prevent hypermagnesemia 1.
Key Considerations
- Magnesium hydroxide (Milk of Magnesia) can be taken as 30-60 mL or 2-4 tablespoons once daily, while magnesium citrate is typically used as 200-300 mL of the solution as a single dose.
- Lactulose is often reserved for more chronic constipation or specific conditions like hepatic encephalopathy, as it works more slowly (24-48 hours) and frequently causes bloating and gas 1.
- Magnesium laxatives are generally more affordable and cause fewer uncomfortable side effects than lactulose, but should be used cautiously in patients with kidney disease as it can accumulate in the body.
Recommendations
- For occasional constipation, starting with magnesium-based products is reasonable, but persistent constipation should prompt medical evaluation to determine the underlying cause and most appropriate treatment.
- The combination of efficacy, tolerability, availability of OTC, and low cost make magnesium oxide an attractive first-line option for individuals with CIC, as stated in the guideline 1.
From the Research
Comparison of Lactulose and Magnesium for Constipation
- Lactulose is a commonly used osmotic laxative for the treatment of chronic constipation, as seen in studies comparing it to other laxatives such as Polyethylene Glycol 2 and lactitol 3.
- Magnesium, in the form of magnesium hydroxide or citrate, is also used as an osmotic laxative to treat constipation, with its mechanism of action involving the retention of water in the intestinal lumen 4.
- There is no direct comparison between lactulose and magnesium in the provided studies, making it difficult to determine a preferred treatment.
- Lactulose has been shown to be effective in treating postpartum constipation 5 and chronic constipation in various patient populations, but its efficacy compared to magnesium is unknown.
- Other laxatives, such as bulk laxatives containing senna, have been compared to lactulose and shown to be more efficient in treating constipation in certain patient populations, such as geriatric patients 6.
Efficacy and Safety of Lactulose
- Lactulose has been found to be effective in treating chronic constipation, but its efficacy may vary depending on the patient population and comparison laxative 2, 3, 5.
- Lactulose has been shown to be safe to use in various patient populations, including geriatric patients and postpartum women 5, 6.