From the Guidelines
The recommended dose of lactulose for treating constipation is 10–20 g (15–30 mL or 1–2 packets) daily, with the option to increase to 40 g (60 mL or 2–4 packets) daily if needed. This dosage is based on the most recent clinical practice guideline from the American Gastroenterological Association-American College of Gastroenterology, published in 2023 1. The guideline suggests that lactulose can be considered for patients who have failed to improve with fiber and over-the-counter laxatives, and who do not experience significant bloating or abdominal pain with lactulose use.
Some key points to consider when prescribing lactulose include:
- The dose may need to be adjusted based on individual response, with some patients requiring higher or lower doses to achieve desired bowel movements.
- Lactulose works as an osmotic laxative, drawing water into the intestines and softening stool, while also being fermented by gut bacteria to produce acids that stimulate bowel movements.
- Common side effects of lactulose include bloating, gas, and abdominal cramps, especially when starting treatment, but these are generally dose-dependent and may decrease over time.
- Patients should be advised to take lactulose with a full glass of water and maintain adequate fluid intake throughout treatment to minimize the risk of side effects.
It's also important to note that lactulose has been shown to be effective in reducing impactions and the need for enemas in patients with constipation, as demonstrated in a study published in the Netherlands, although the demographics of the patient population were not reported 1. Overall, lactulose is a viable treatment option for patients with constipation, particularly those who have not responded to other treatments, and its use should be guided by the most recent clinical evidence and individual patient needs.
From the FDA Drug Label
The usual adult, oral dosage is 2 to 3 tablespoonfuls (30 mL to 45 mL, containing 20 grams to 30 grams of lactulose) three or four times daily. The dosage may be adjusted every day or two to produce 2 or 3 soft stools daily
The recommended dose of lactulose for treating constipation is 2 to 3 tablespoonfuls (30 mL to 45 mL), containing 20 grams to 30 grams of lactulose, taken three or four times daily. The dose may be adjusted to produce 2 or 3 soft stools daily 2.
- Key considerations:
- Dosage adjustment: every day or two
- Target stool frequency: 2 or 3 soft stools daily
- Initial dose for infants: 2.5 mL to 10 mL in divided doses
- Initial dose for older children and adolescents: 40 mL to 90 mL daily
From the Research
Lactulose Dosage for Constipation
The recommended dose of lactulose for treating constipation varies across different studies. Here are some key findings:
- A study published in 2006 found that lactulose doses of 10-20 g per day are commonly used to treat constipation 3.
- Another study from 1978 used a dosage of 30 ml daily of 50% lactulose syrup, which was reduced to 15 ml if the initial dosage produced two or more bowel movements daily 4.
- A 1981 study compared lactulose syrup to a placebo and used dose levels of 30 and 60 ml/day in normal subjects, and 60 ml/day in constipated subjects 5.
- A more recent study from 2016 used a dose of 15 ml once a day, with a maintenance dose of 5-15 ml/time according to the defecation condition of patients 6.
- A 1993 study used daily doses of 20.1 g of lactulose to treat chronic constipation in geriatric patients 7.
Key Findings
Some key findings from these studies include:
- Lactulose is an effective laxative that can increase the frequency, weight, volume, and water content of stools, and produce stools of softer consistency 3, 5.
- The laxative effects of lactulose are dose-related, with higher doses producing greater effects 5.
- Lactulose is safe to use and can be effective in treating constipation in various patient populations, including elderly and postpartum patients 4, 6, 7.