What outcome indicates that lactulose is effective?

Lactulose is a synthetic sugar commonly used to treat constipation and hepatic encephalopathy. Its primary function in treating constipation is to draw water into the bowel, which softens the stool and facilitates bowel movements. An effective outcome when using lactulose is characterized by achieving two to three soft stools per day. This outcome indicates that the drug is functioning as intended by promoting bowel regularity without causing excessive urgency or diarrhea.

The other outcomes do not reflect the main goal of lactulose when used for constipation. An increase in urine output is typically not a specific indicator of laxative effectiveness. Watery, diarrhea stools could suggest an overuse of the laxative or an adverse effect rather than a desired therapeutic effect. Lastly, increased serum bilirubin would be concerning and may indicate worsening liver function, which would not be an effective indicator of lactulose's intended outcomes. Thus, having two to three soft stools per day is the most appropriate measure of efficacy for lactulose in this context.