From the Guidelines
For most patients with occasional constipation, Lax-A-Day (polyethylene glycol 3350 or PEG) is generally preferred over lactulose due to its more predictable action, fewer side effects, and better taste. Lactulose and Lax-A-Day are both effective laxatives, but they work differently and have distinct advantages. Lax-A-Day typically works within 24-48 hours by drawing water into the intestines to soften stool, with a standard dose of 17g (one heaping tablespoon) dissolved in water once daily 1. Lactulose is an osmotic laxative that works by being metabolized by gut bacteria to produce acids that draw water into the colon, usually dosed at 15-30mL once or twice daily. Lactulose may cause more bloating, gas, and abdominal discomfort than Lax-A-Day, and has a sweet taste that some find unpleasant 1. However, lactulose has specific advantages for hepatic encephalopathy patients as it reduces ammonia levels in the blood.
Some key points to consider when choosing between lactulose and Lax-A-Day include:
- The American Gastroenterological Association recommends the use of PEG (Lax-A-Day) over lactulose for the treatment of chronic idiopathic constipation, due to its more predictable action and fewer side effects 1.
- Lactulose may be considered for patients who do not respond to fiber and OTC laxatives, and do not experience significant bloating or abdominal pain with lactulose use 1.
- Both medications are generally safe for long-term use, but patients should start with the lowest effective dose and maintain adequate hydration while using either laxative.
- The use of lactulose in mildly constipated, non-insulin-dependent patients with diabetes mellitus type 2 may not lead to an increase in blood sugar levels 1.
Overall, while both lactulose and Lax-A-Day are effective laxatives, Lax-A-Day is generally preferred due to its more predictable action, fewer side effects, and better taste. However, lactulose may be considered for specific patient populations, such as those with hepatic encephalopathy or those who do not respond to other treatments.
From the Research
Comparison of Lactulose and Laxatives
- Lactulose is often compared to other laxatives in terms of efficacy and safety in treating constipation 2, 3, 4, 5, 6.
- A study comparing lactitol to lactulose found that lactitol was comparable to lactulose in terms of normal consistency of stool and number of bowel movements per week, but had better acceptance by patients and fewer adverse events 2.
- Another study found that a bulk laxative containing senna was more efficient than lactulose in treating constipation in geriatric patients 3.
- A meta-analysis of lactitol supplementation for adult constipation found that lactitol was well tolerated and improved symptoms of constipation, with similar efficacy and tolerance to lactulose 4.
- A study comparing lactulose to standardized senna in children found that lactulose was more effective and better tolerated than senna 5.
- A randomized controlled trial comparing lactulose to senna plus ispaghula husk in patients with pre-dialysis chronic kidney disease and constipation found that both treatments were similar in efficacy 6.
Efficacy of Lactulose
- Lactulose has been shown to be effective in increasing weekly stool frequency and improving stool consistency in adults with constipation 2, 4.
- Lactulose has also been found to be effective in treating constipation in children, with a significant difference in favor of lactulose in the number of days on which normal stools were passed 5.
- In patients with pre-dialysis chronic kidney disease and constipation, lactulose was found to increase complete spontaneous bowel movements weekly and improve stool appearance 6.
Safety of Lactulose
- Lactulose has been found to be safe and well tolerated in adults and children with constipation, with few adverse events reported 2, 4, 5.
- A study comparing lactulose to senna plus ispaghula husk found that no serious adverse events were reported in either group 6.
- Lactitol, a similar osmotic laxative to lactulose, has been found to have fewer adverse events than lactulose 2.