Am Fam Physician. 2006;74(5):715-716
to the editor: The article, “Treatment of Constipation in Older Adults,”1 by Dr. Hsieh that appeared in the December 1, 2005, issue of American Family Physician provided a nice overview of the treatment of chronic constipation in older adults. However, I believe several points warrant clarification.
My first point is that constipation should not be defined only by stool frequency. Several studies have clearly demonstrated a significant disconnect between patients and physicians with regard to defining constipation. For example, patients use a variety of terms (e.g., straining, bloating, abdominal discomfort, incomplete evacuation) to define constipation,2 whereas physicians primarily focus on stool frequency.3 Defining constipation using stool frequency alone maximizes the potential to underdiagnose a significant number of patients who suffer from chronic constipation.
Second, irritable bowel syndrome is generally considered a primary cause of constipation rather than a secondary cause, because its precise etiology is still under investigation. Third, it is important to remember that fiber therapy is effective only in patients who are fiber deficient. For patients who already consume the recommended 25 to 30 g of fiber per day, having them increase their fiber intake will likely not improve symptoms and may worsen bloating and discomfort. Fourth, Dr. Hsieh classifies misoprostol (Cytotec) and colchicine as prokinetic agents when neither is a true prokinetic agent. Misoprostol results in mild, transient, dose-related diarrhea and increased colon transit time, total stool weight, and frequency of stools, because of its prostaglandin side effects. Misoprostol has been shown to be a short-term treatment for constipation, but its role in the treatment of chronic constipation remains unclear. The mechanism by which colchicine loosens stool is unknown, and long-term use is not encouraged because of potential toxic effects.
Finally, Dr. Hsieh does not cite the most recent position statement and systematic review on the management of chronic constipation published by the American College of Gastroenterology (ACG)4 or discuss the most recent evidence on the efficacy of tegaserod (Zelnorm),5,6 which was approved by the U.S. Food and Drug Administration in 2004 for the treatment of patients younger than 65 years with chronic idiopathic constipation. In a systematic review,4 the ACG Chronic Constipation Task Force analyzed all published clinical trial data for patients with chronic constipation who were treated with a variety of over-the-counter and prescription medications available in the United States and made recommendations for use based on the quality of the evidence. For many agents, such as calcium polycarbophil, methylcellulose (Citrucel), bran, magnesium hydroxide (Milk of Magnesia), stool softeners, and stimulant laxatives, the Task Force concluded that there was insufficient evidence to make a recommendation.4 In contrast, the Task Force concluded that tegaserod is effective in improving the frequency of complete spontaneous bowel movements, straining, stool frequency, and stool consistency in patients with chronic constipation and gave tegaserod a grade A recommendation based on its high-quality clinical trial evidence.
in reply: I would like to thank Dr. Lacy for his insightful comments. I agree that constipation should not be defined only by stool frequency. As addressed in my review,1 a consensus definition for constipation known as the Rome II criteria2 is based on multiple symptoms including hard, lumpy stools; straining; a sense of incomplete evacuation; sense of anorectal obstruction; the use of manual maneuvers to pass stool; and/or less than three bowel movements a week, with no evidence of organic disease. At least two symptoms must be present for at least 12 weeks to make the diagnosis of chronic functional constipation.2 Although these criteria may not be practical to use in the office setting, they emphasize the need to look at a variety of symptoms when diagnosing constipation.
Irritable bowel syndrome (IBS) is listed as “other” causes of secondary constipation because its etiology is still unclear. Constipation is a predominant symptom in many patients with IBS, and many symptoms of chronic constipation and IBS may overlap. I agree that fiber therapy is only effective in patients who are fiber deficient, but many Americans consume less than the recommended fiber intake. A dietary diary may be helpful to quantify whether there is a need for the patient to increase fiber intake. Misoprostol (Cytotec) and colchicine are not true prokinetic agents and should have been listed as miscellaneous agents.
The most recent position statement and systematic review on the management of chronic constipation published by the American College of Gastroenterology3 was not available when my review article1 went to press. The systematic review3 made recommendations based on the quality of evidence from clinical trials. Specifically, the Task Force gave a grade A recommendation for polyethylene glycol 3350 (Miralax) and lactulose for their effectiveness at improving stool frequency and consistency in patients with chronic constipation. Tegaserod (Zelnorm) also was given a grade A recommendation for improving frequency of complete spontaneous bowel movements, straining, stool frequency, and stool consistency in patients with chronic constipation. Psyllium (Metamucil) received a grade B recommendation for its effects in increasing stool frequency. However, there were insufficient data to make recommendations about the effectiveness of stimulant laxatives, stool softeners, and other bulking agents.