Current issues of ACP Journal Club are published in Annals of Internal Medicine


Sorbitol was as effective as lactulose in constipation in elderly men

ACP J Club. 1991 May-June;114:66. doi:10.7326/ACPJC-1991-114-3-066

Source Citation

Lederle FA, Busch DL, Mattox KM, West MJ, Aske DM. Cost-effective treatment of constipation in the elderly: a randomized double-blind comparison of sorbitol and lactulose. Am J Med. 1990;89:597-601.



To evaluate the effectiveness of sorbitol as an inexpensive alternative to lactulose for treating constipation in men age 65 or older.


Randomized, double-blind, crossover study of 4 weeks duration.


The Minneapolis Veterans Affairs Medical Center.


Men, aged 65 years or older, were included if they had a history of constipation for at least 1 year and were able to walk to the toilet unassisted. Patients were excluded if they had diabetes mellitus requiring drug treatment, a history of diarrhea alternating with constipation, known colorectal disease other than diverticulosis or hemorrhoids, were taking codeine or other narcotics, or were intolerant of lactulose. Of 31 patients randomly assigned, 30 completed the study.


Patients received either lactulose or 70% sorbitol for 4 weeks, followed by a 2-week washout period. They then received the other treatment. The initial dose of each drug was 30 mL before bed, to be adjusted by the patient from 0 to 60 mL, as needed. Patients were instructed to maintain high-fiber diets and to avoid sources of free fructose, such as apples and pears.

Main outcome measure

Frequency of bowel movements.

Main results

The average number of bowel movements per week was 6.71 with sorbitol and 7.02 with lactulose (95% CI -0.43 to 1.06, P > 0.3). The average number of days per week with bowel movements was 5.23 with sorbitol and 5.31 with lactulose (CI -0.32 to 0.48, P > 0.3). No outcome measured, except for nausea, differed significantly between the treatment groups. The score for nausea was higher during treatment with lactulose (P < 0.05).


Sorbitol and lactulose were equally effective in treating constipation in men aged 65 years or older. Sorbitol caused less nausea and was less expensive than lactulose.

Source of funding: Not stated.

Address for article reprint: Dr. F.A. Lederle, Division of General Internal Medicine (III-O), Department of Medicine, Minneapolis Veterans Affairs Medical Center, One Veterans Drive, Minneapolis, MN 55417, USA.


Constipation can usually be satisfactorily treated by increasing dietary fiber and fluids or by using a bulk-forming agent, such as psyllium. A few patients need additional laxative therapy. Lactulose, a nonabsorbable disaccharide that acts as an osmotic laxative, is often recommended for treatment of chronic constipation in the elderly. Lederle and colleagues hypothesized that sorbitol, another nonabsorbable sugar, might be as effective as lactulose.

Although the study design was strong, it had 2 methodologic flaws. First, during the 2 weeks before randomization, patients were given lactulose, and 9 of 40 patients dropped out because of lactulose intolerance. The results of the randomized trial thus underestimate the frequency of adverse effects with lactulose and may distort the relative frequency in comparison with sorbitol. Second, although eligible patients had three or fewer spontaneous bowel movements per week and, with their current laxative regimen, had fewer than one a day, the baseline severity of constipation was not actually measured.

Nevertheless, this study convincingly shows that sorbitol and lactulose have similar effects on chronic constipation in the elderly. Only 6 patients reported nausea during the study, so the slightly higher average nausea score for lactulose is hard to interpret. However, the fairly high level of prerandomization intolerance to lactulose must be considered. Interestingly, 11 patients preferred sorbitol, 12 preferred lactulose, and 7 had no preference.

Based on this trial, I would recommend that patients with chronic constipation who did not respond to treatment with high dietary fiber and psyllium agents use 70% sorbitol, 30 mL before bedtime. Patients should be counseled that nausea and bloating are side effects to monitor.

Eric B. Larson, MD, MPH
University of Washington School of MedicineSeattle, Washington, USA