[Clinical observation of prophylactic lactulose for prevention of oral morphine-induced constipation].

Objective: To evaluate the effects of different doses of lactulose on preventing oral morphine-induced constipation.
Methods: From January 2011 to May 2012, a total of 112 patients received oral lactulose solution to prevent morphine-induced constipation at our hospital and their clinical data were retrospectively analyzed. The doses of morphine were adjusted according to the pain scores and lactulose was taken simultaneously. There were 52 males and 60 females. They were randomized into Group 30 ml/d (n = 40), Group 60 ml/d (n = 43) and Group 90 ml/d (n = 29). The incidences of constipation and adverse reactions were obtained at 1 week after the start of medicine. The measurement data were analyzed with analysis of variance. And the enumeration data were analyzed with χ(2), Kruskal-Wallis and Mann-Whitney U tests.
Results: The incidence of constipation was 67.5% (27/40) in Group 30 ml/d, 46.5% (20/43) in Group 60 ml/d, and 37.9% (11/29) in Group 90 ml/d. And there were statistical differences (P = 0.036). The incidence of constipation in Group 30 ml was significantly higher than Group 90 ml/d (P = 0.015). No statistical difference existed in the incidence of constipation between Groups 30 ml/d and 60 ml/d (P = 0.054) or Groups 60 ml/d and 90 ml/d (P = 0.471). The incidence of vomiting was 34.5% (10/29) in Group 90 ml/d and it was significantly higher than 10.0% (4/40) in Group 30 ml/d (P = 0.013) and 9.3% (4/43) in Group 60 ml/d (P = 0.009). No statistical difference existed in the incidence of vomiting between Groups 30 ml/d and 60 ml/d (P = 0.915). The incidence of diarrhea was 17.2% (5/29) in Group 90 ml/d and it was significantly higher than 0 (0/40) in Group 30 ml/d (P = 0.007). No statistical difference existed in the incidence of diarrhea between Groups 30 ml/d and 60 ml/d (4.7% (2/43), P = 0.170) or Groups 60 ml/d and 90 ml/d (P = 0.072).
Conclusion: The correct dosage of lactulose for the prevention of oral morphine-induced constipation is 60 ml/d.